US 7,852,017 B1Grant

Ballast for light emitting diode light sources

Issue Date:2010-12-14

•22 Claims

•14 Drawing Sheets

Abstract

A lighting source ballast utilizes switching and control technology to convert an alternating current (AC) phase modulated dimmer input voltage into an approximately constant drive current to illuminate one or more light emitting diodes (LED(s)). In at least one embodiment, the state of the drive current conforms to a phase delay of the input voltage to facilitate, for example, dimming. The phase delay of the input voltage indicates a particular dimming level. The drive current varies for different dimming levels. However, the light source ballast controls drive current so that the drive current is approximately constant for each dimming level. In at least one embodiment, the ballast emulates a resistive load and, thus, the ballast has an approximately unity power factor. The switching frequency of one or more switches can be modified to spread the spectrum of electromagnetic radiation generated by the ballast.

Metadata

Assignee

Cirrus Logic, Inc.

Inventor

John L. Melanson

Application Information

Application Number:US 12/047,249

Filing Date:2008-03-12

Priority Date:2007-03-12

Art Unit:2821

Classifications

IPC:

G05F1/00

Patent Drawings (14 sheets)

Description

Cross Reference to Related Applications

[0001] This application claims the benefit under 35 U.S.C. §119(e) and 37 C.F.R. §1.78 of U.S. Provisional Application No. 60/894,295, filed Mar. 12, 2007 and entitled “Lighting Fixture.” U.S. Provisional Application No. 60/894,295 includes exemplary systems and methods and is incorporated by reference in its entirety.

[0002] This application claims the benefit under 35 U.S.C. §119(e) and 37 C.F.R. §1.78 of U.S. Provisional Application No. 60/909,458, entitled “Ballast for Light Emitting Diode Light Sources,” inventor John L. Melanson, and filed on Apr. 1, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety.

[0003] U.S. patent application Ser. No. 11/926,864, entitled “Color Variations in a Dimmable Lighting Device with Stable Color Temperature Light Sources,” inventor John L. Melanson, and filed on Mar. 31, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety.

[0004] U.S. Provisional Application No. 60/909,457, entitled “Multi-Function Duty Cycle Modifier,” inventors John L. Melanson and John Paulos, and filed on Mar. 31, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson I.

[0005] U.S. patent application Ser. No. 12/047,258, entitled “Multi-Function Duty Cycle Modifier,” inventors John L. Melanson and John Paulos, and filed on Mar. 12, 2008 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson II.

[0006] U.S. patent application Ser. No. 11/695,024, entitled “Lighting System with Lighting Dimmer Output Mapping,” inventors John L. Melanson and John Paulos, and filed on Mar. 31, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson III.

[0007] U.S. patent application Ser. No. 11/864,366, entitled “Time-Based Control of a System having Integration Response,” inventor John L. Melanson, and filed on Sep. 28, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson IV.

[0008] U.S. patent application Ser. No. 11/967,269, entitled “Power Control System Using a Nonlinear Delta-Sigma Modulator with Nonlinear Power Conversion Process Modeling,” inventor John L. Melanson, and filed on Dec. 31, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson V.

[0009] U.S. patent application Ser. No. 11/967,275, entitled “Programmable Power Control System,” inventor John L. Melanson, and filed on Dec. 31, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety. Referred to herein as Melanson VI.

[0010] U.S. patent application Ser. No. 12/047,262, entitled “Power Control System for Voltage Regulated Light Sources,” inventor John L. Melanson, and filed on Mar. 12, 2007 describes exemplary methods and systems and is incorporated by reference in its entirety.

Background of the Invention

[0011] 1. Field of the Invention

[0012] The present invention relates in general to the field of electronics and lighting, and more specifically to a system and method for providing ballast for light sources, such as light emitting diode light sources.

[0013] 2. Description of the Related Art

[0014] Commercially practical incandescent light bulbs have been available for over 100 years. However, other light sources show promise as commercially viable alternatives to the incandescent light bulb. Light Emitting Diodes (“LEDs”) are becoming particularly attractive as main stream light sources in part because of energy savings through high efficiency light output, long life, and environmental incentives such as the reduction of mercury.

[0015] LEDs are semiconductor devices and are best driven by direct current. The brightness of the LED varies in direct proportion to the current flowing through the LED. Thus, increasing current supplied to an LED increases the brightness of the LED and decreasing current supplied to the LED dims the LED.

[0016] Dimming a light source saves energy when operating a light source and also allows a user to adjust the brightness of the light source to a desired level. Many facilities, such as homes and buildings, include light source dimming circuits (referred to herein as “dimmers”).

[0017] FIG. 1 depicts a lighting circuit 100 with a conventional dimmer 102 for dimming incandescent light source 104 in response to inputs to variable resistor 106. The dimmer 102, light source 104, and voltage source 108 are connected in series. Voltage source 108 supplies alternating current at line voltage V_line. The line voltage V_linecan vary depending upon geographic location. The line voltage V_lineis typically 120 Vac with a typical frequency of 60 Hz or 230 Vac with a typical frequency of 50 Hz. Instead of diverting energy from the light source 104 into a resistor, dimmer 102 switches the light source 104 off and on many times every second to reduce the total amount of energy provided to light source 104. A user can select the resistance of variable resistor 106 and, thus, adjust the charge time of capacitor 110. A second, fixed resistor 112 provides a minimum resistance when the variable resistor 106 is set to 0 ohms. When capacitor 110 charges to a voltage greater than a trigger voltage of diac 114, the diac 114 conducts and the gate of triac 116 charges. The resulting voltage at the gate of triac 116 and across bias resistor 118 causes the triac 116 to conduct. When the current I passes through zero, the triac 116 becomes nonconductive, i.e. turns ‘off’. When the triac 116 is nonconductive, the dimmer output voltage V_DIMis 0 V. When triac 116 conducts, the dimmer output voltage V_DIMequals the line voltage V_line. The charge time of capacitor 110 required to charge capacitor 110 to a voltage sufficient to trigger diac 114 depends upon the value of current I. The value of current I depends upon the resistance of variable resistor 106 and resistor 112. Thus, adjusting the resistance of variable resistor 106 adjusts the phase angle of dimmer output voltage V_DIM. Adjusting the phase angle of dimmer output voltage V_DIMis equivalent to adjusting the phase angle of dimmer output voltage V_DIM. Adjusting the phase angle of dimmer output voltage V_DIMadjusts the average power to light source 104, which adjusts the intensity of light source 104. The term “phase angle” is also commonly referred to as a “phase delay”. Thus, adjusting the phase angle of dimmer output voltage V_DIMcan also be referred to as adjusting the phase delay of dimmer output signal V_DIM. Dimmer 102 only modifies the leading edge of each half cycle of voltage V_line.

[0018] FIG. 2 depicts the dimmer output voltage V_DIMwaveform of dimmer 102. The dimmer output voltage V_DIMfluctuates during each period from a positive voltage to a negative voltage. (The positive and negative voltages are characterized with respect to a reference to a direct current (DC) voltage level, such as a neutral or common voltage reference.) The period of each voltage sine wave 202.0 through 202.N is the same as 1/frequency of V_line(FIG. 1), where N is an integer. The dimmer output voltage V_DIMis a phase modulated dimmer signal. The dimmer 102 chops the voltage sine waves 202.0 through 202.N to alter the duty cycle of each sine wave 202.0 through 202.N. The dimmer 102 chops the positive half of sine wave 202.0 at time t₁so that the positive portion of sine wave 202.0 is 0 V from time t₀through time t₁and has a positive voltage from time t₁to time t₂. The difference in time between time t₀at which a full cycle of sine wave 202 would have started but for the chopping and the time t₁at which dimmer output voltage V_DIMis chopped introduces a phase delay α into sine wave 202. For example, for sine wave 202.0, α_202.0=sine wave chop time t₁-full cycle start time t₀and α_202.N=t₄−t₃. The phase delay α is the same for the negative half of sine wave 202. Additionally, since the dimmer output voltage V_DIMis periodic, the phase delay can also be referred to as a phase angle. Each half cycle of sine wave 202 is 180 degrees, and the phase angle is 180 degrees minus the (phase delay/the half period) times 180 degrees. For example, the phase angle □_202.0equals 180·[1−(t₁−t₀)/(t₂−t₀)] for sine wave 202.0 The “Sine wave 202” represents all sine waves 202.0 through 202.N. The light source 104 is, thus, turned ‘off’ from times t₀through t₁and turned ‘on’ from times t₁through t₂. Dimmer 102 chops the negative half of sine wave 202.0 with the same timing as the positive half Equation [1] represents the duty cycle of dimmer 102:

[0019]

\begin{matrix} Duty Cycle = \frac{(t_{2} - t_{1})}{(t_{2} - t_{0})} . & [1] \end{matrix}

[0020] When the resistance of variable resistance 106 is increased, the duty cycle of dimmer 102 decreases. Between time t₂and time t₃, the resistance of variable resistance 106 is increased, and, thus, dimmer 102 chops the full cycle 202.N at later times in the first half cycle 204.N and the second half cycle 206.N of the full cycle of voltage sine wave 202.N with respect to voltage sine wave 202.0. Dimmer 102 chops the first half cycle 204.N with the same timing as the second half cycle 206.N. So, the duty cycles of each half cycle of voltage sine wave 202.N are the same. Thus, the full duty cycle of dimmer 102 for voltage sine wave 202.N is:

[0021]

\begin{matrix} Duty Cycle = \frac{(t_{5} - t_{4})}{(t_{5} - t_{3})} . & [2] \end{matrix}

[0022] Since times (t₅−t₄)<(t₂−t₁), less average power is delivered to light source 104 by the sine wave 202.N than sine wave 202.0 of dimmer voltage V_DIM, and the intensity of light source 104 decreases at time t₃relative to the intensity at time t₂.

[0023] The voltage and current fluctuations of conventional dimmer circuits, such as dimmer 102, can destroy LEDs. U.S. Pat. No. 7,102,902, filed Feb. 17, 2005, inventors Emery Brown and Lodhie Pervaiz, and entitled “Dimmer Circuit for LED”(referred to here as the “Brown Patent”) describes a circuit that supplies a specialized load to a conventional AC dimmer which, in turn, controls an LED device. The Brown Patent describes dimming the LED by adjusting the duty cycle of the voltage and current provided to the load and providing a minimum load to the dimmer to allow dimmer current to go to zero.

[0024] Exemplary modification of leading edges and trailing edges of dimmer signals is discussed in “Real-Time Illumination Stability Systems for Trailing-Edge (Reverse Phase Control) Dimmers” by Don Hausman, Lutron Electronics Co., Inc. of Coopersburg, Pa., U.S.A., Technical White Paper, December 2004, which is incorporated herein by reference.

[0025] Line voltage fluctuations adversely affect LEDs. Line voltage fluctuations can produce a disproportional change in drive current to the LED. Increases in drive current increase heat and, thus, reduce the useful life of the LED. Useful life can be defined, for example, when the light output of the LED declines by thirty percent or more.

Summary of the Invention

[0026] In one embodiment of the present invention, a lighting system ballast includes a light source driver stage configured to deliver power to one or more light emitting diodes with an adjustable drive current. The lighting system also includes a sensor having one or more input terminals to receive a phase modulated dimmer signal, wherein a phase delay of the phase modulated dimmer signal indicates a dimming level and the sensor is configured to detect the dimming level and to generate a dimmer output signal representing a dimming level indicated by the dimmer signal. The lighting system also includes a controller coupled to the light source driver stage and the sensor. The controller includes at least one input terminal to receive the dimmer output signal from the sensor and to generate a drive control signal to cause a drive current supplied to each light emitting diode to dim each light emitting diode in response to the dimmer signal. The drive current is approximately constant for each dimming level throughout a cycle of the phase modulated dimmer signal.

[0027] In another embodiment of the present invention, a method of supplying a drive current to one or more light emitting diodes includes receiving a phase modulated dimmer signal wherein a phase delay of the phase modulated dimmer signal indicates a dimming level. The method further includes generating a dimmer output signal representing a dimming level indicated by the dimmer signal and generating a drive control signal to cause the drive current to respond to the dimmer output signal. The method also includes providing the drive control signal to a switch to vary conductivity of the switch and cause the drive current supplied by the light source driver stage to each of the light emitting diodes to be approximately constant through a cycle of the phase modulated dimming signal.

[0028] In a further embodiment of the present invention, a lighting system includes a light source ballast system. The light source ballast system includes a power factor converter and drive system to receive an alternating current, phase modulated dimmer input voltage, to convert the input voltage into a power factor corrected direct current (DC) output voltage, and to generate a light emitting diode drive current. A phase delay of the dimmer input voltage indicates a dimming level. The system also includes a ballast controller, coupled to the power factor converter and drive system, to generate one or more control signals for the power factor converter and drive system to control power factor correction and to adjust the drive current in conformance with the dimming level represented by the dimmer signal. The drive current is approximately constant throughout a cycle of the phase modulated input voltage for each dimming level and the level of the constant drive current varies in response to variations in the indicated dimming level.

[0029] In another embodiment of the present invention, a method of responding to a dimmer signal and supplying a constant voltage and variable drive current to a light source includes receiving an alternating current, phase modulated dimmer input voltage. A phase delay of the dimmer input voltage indicates a dimming level; generating one or more control signals for a power factor converter and drive system to control power factor correction and to vary the drive current in conformance with the dimming level represented by the dimmer signal. The drive current is approximately constant throughout a cycle of the phase modulated input signal for each dimming level and the level of the constant drive current is varied in response to variations in the indicated dimming level.

Brief Description of the Drawings

[0030] The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element.

[0031] FIG. 1 (labeled prior art) depicts a lighting circuit with a conventional dimmer for dimming an incandescent light source.

[0032] FIG. 2 (labeled prior art) depicts a dimmer circuit output voltage waveform.

[0033] FIG. 3 depicts a lighting circuit with an electronic ballast for providing power to an LED light source.

[0034] FIG. 4A depicts a lighting circuit.

[0035] FIG. 4B depicts graphical relationships between a drive current and various dimming levels indicated by a dimmer signal.

[0036] FIG. 4C depicts a magnified view of the drive current of FIG. 4B.

[0037] FIG. 5A depicts a voltage sensor.

[0038] FIG. 5B depicts a specific embodiment of the voltage sensor in FIG. 5A.

[0039] FIG. 6 depicts a phase delay detector

[0040] FIG. 7 depicts another phase delay detector.

[0041] FIG. 8 depicts a phase delay detector.

[0042] FIGS. 9-11 depict graphical relationships between various control signals, sense signals, and drive currents.

[0043] FIG. 12 depicts an LED bank.

Detailed Description

[0044] A lighting source ballast utilizes switching and control technology to convert an alternating current (AC) phase modulated dimmer input voltage into an approximately constant drive current to illuminate one or more light emitting diodes (LED(s)). In at least one embodiment, the state of the drive current conforms to a phase delay of the input voltage to facilitate, for example, dimming. The phase delay of the input voltage indicates a particular dimming level. The drive current varies for different dimming levels. However, the light source ballast controls drive current so that the drive current is approximately constant for each dimming level throughout the cycle of an input sine wave of the AC dimmer input voltage. In at least one embodiment, the ballast emulates a resistive load and, thus, the ballast has an approximately unity power factor. The switching frequency of one or more switches can be modified to spread the spectrum of electromagnetic radiation generated by the ballast.

[0045] FIG. 3 depicts a lighting circuit 300 with an electronic LED ballast 302. The electronic ballast 300 converts an alternating current (AC), phase modulated input voltage V_ininto a drive current I_drivefor light source 304. The phase modulated input signal V_inis a phase modulated dimmer signal that can be generated using any device that generates a phase modulated, AC input voltage. In at least one embodiment, the input voltage V_inis the dimmer output voltage V_DIM(FIGS. 1 and 2). In at least one embodiment, the light source 304 includes one or more individual LEDs or one or more groups of intraconnected LEDs. The AC-DC power factor converter 306 converts the phase modulated AC input voltage V_ininto a voltage V_C1across hold-up capacitor 312. In at least one embodiment, voltage V_C1is an approximately constant value over time and, thus, approximates a DC voltage.

[0046] A line voltage sensor 308 samples the input voltage V_inover time. The line voltage sensor 308 samples the input voltage V_inat a frequency sufficient to detect the phase delay of input voltage V_in. By detecting the phase delay of input voltage V_in, the line voltage sensor 308 detects the dimming level indicated by input voltage V_in. The line voltage sensor 308 generates a dimmer output signal V_THthat represents the dimming level indicated by the phase delay of the input voltage V_in. It is possible, and straightforward, to dim the LED(s) 422 by turning the LEDs 422 off when the input voltage V_inis cutoff by a phase modulation dimmer. This cutting off unfortunately leads to a narrow dimming range and to flicker of the LED(s) 422 when dimmed. By keeping an approximately constant voltage V_C1fed to a constant current driver, these problems can be eliminated.

[0047] The drive stage 310 and ballast controller 314 convert the detected phase delay of the input voltage V_ininto a drive current I_drivefor driving light source 304 and dimming the light source 304. The drive current I_driveconforms to a phase delay of the input voltage V_inand has an approximately constant value for each dimming level indicated by the input voltage V_in. In other words, variations of the phase angle of input voltage V_inindicates different dimming levels. The drive current I_drivealso varies in response to variations in the phase angle of the input voltage V_inand has a respective, approximately constant value for each dimming level. Thus, since the dimming level indicated by the input voltage remains constant for at least one cycle of the input voltage V_in, the drive current remains approximately constant for each cycle of the input voltage V_inuntil the dimming level indicated by the input voltage V_inchanges.

[0048] By conforming to the dimming level, in at least one embodiment, the drive current I_driveis directly proportional to the input voltage V_in. In another embodiment, the drive current I_driveconforms to the duty cycle of the input voltage V_invia a mapping function as, for example, described in Melanson III.

[0049] The drive stage 310 can also be referred to as a DC-DC ballast controller because the drive stage 310 converts the approximately DC voltage from the power factor converter 306 into a DC voltage and drive current for constant voltage light source 304. The drive stage 310 provides a link voltage V_C1and drive current I_driveto voltage light source 304 so that the power supplied by drive stage 310 is responsive to the dimming level indicated by the input voltage V_in.

[0050] In at least one embodiment, the line voltage sensor 308 senses the dimming level indicated by the input voltage V_inby determining the duty cycle, phase angle, and/or phase delay of the input voltage V_inand generates a threshold voltage V_THthat conforms to the dimming level indicated by the input signal V_in. The duty cycle, phase angle, and/or phase delay represent the dimming level indicated by the input signal V_in.

[0051] The ballast controller 314 generates control signals to control power factor correction by the AC-DC power factor converter 306 and drive stage 310. In at least one embodiment, the ballast controller 314 generates control signals for the AC-DC power factor converter 306 in accordance with the exemplary systems and methods described in Melanson V and Melanson VI. In at least one embodiment, the ballast controller 314 generates a control signal to control the generation of drive current I_drivein accordance with the exemplary systems and methods described in Melanson IV.

[0052] As previously stated, the drive current I_driveconforms to a duty cycle of the input voltage V_inand has an approximately constant value for each dimming level indicated by the input voltage V_in. In at least one embodiment, the threshold voltage V_THis directly proportional to the dimming level indicated by input signal V_in. In at least one embodiment, the threshold signal V_THrepresents a mapping of the dimming level indicated by input voltage V_into predetermined values different than the dimming levels indicated by the input voltage V_in. In at least one embodiment, the mapping maps measured light levels to perception based light levels as described in conjunction with the exemplary systems and methods of Melanson I and Melanson II.

[0053] FIG. 4A depicts a lighting circuit 400, which is one embodiment of lighting circuit 300. Lighting circuit 400 includes an AC-DC power factor converter 402 to convert an AC, phase modulated, input voltage dimmer signal V_DIMinto an approximately constant light source drive current I_drive. The dimmer signal V_DIMcan be generated using any phase modulation dimmer circuit, such as the dimmer 102 (FIG. 1). The AC-DC switching power converter 402 includes a switch 404 that turns ‘on’ (conducts) and turns ‘off’ (nonconductive) in response to a control signal C_S1generated by ballast controller 406. When switch 404 is ‘on’, inductor 408 energizes with the current I_L1from the full-bridge diode rectifier 410. When switch 404 is ‘off’, the inductor 408 drives current I_L1through diode 412 to charge capacitor 409. The control signal C_S1varies the duty cycle of switch 404 so that the direct current (DC) voltage on storage capacitor 409 averages to a desired value of raw DC voltage V_C1. In at least one embodiment, link voltage V_C1has an average value in the range of 200 V to 400 V. Ballast controller 406 controls the duty cycle of switch 404 such that current I_L1is proportional to the input voltage V_x(t). In at least one embodiment, switch 404 is an N-channel field effect transistor (FET), and control signal C_S1is a gate voltage.

[0054] Ballast controller 406 controls the timing of switches 404 and 416 and, thus, controls the voltage V_C1and current I_drive. The voltage V_C1is controlled to remain approximately constant over time, and drive current I_driveis approximately constant for each dimming level indicated by the threshold voltage V_TH. The drive current I_driveis a drive current for LED(s) 422. The current I_driveis controlled so as to be responsive to dimmer signal V_DIMand to dim light source 418 in accordance with, for example, the dimming level indicated by dimmer signal V_DIM. In at least one embodiment, the current I_driveis controlled so that the intensity of the LEDs of light source 418 conforms to a mapping function as, for example, described in Melanson and Melanson II. In at least one embodiment, the light circuit includes an auxiliary power supply 420 to supply power to ballast controller 406. In at least one embodiment, switch 416 is also an N-channel FET, and control signal C_S2is a gate voltage. In another embodiment, switch 416 is a bipolar junction transistor with control signal C_S2providing current to the base of the transistor. In at least one embodiment, the switching frequencies of switch 404 and/or switch 416 are greater than an upper audio baseband frequency, e.g. greater than 25 kHz. Ballast controller 406 can generate control signal C_S2in any of a variety of ways. Melanson IV describes an exemplary system and method for generating control signal C_S2.

[0055] Lighting source 418 includes one or more LED(s) 422. The LED(s) 422 can be any type of LED including white, amber, other colors, or any combination of LED colors. Additionally, the LED(s) 422 can be configured into any type of physical arrangement, such as linearly, circular, spiral, or any other physical arrangement. In at least one embodiment, each of LED(s) 422 is serially connected. Capacitor 424 is connected in parallel with LED(s) 422 and provides filtering to protect the LED(s) 422 from AC signals. Inductor 426 stores energy from LED current I_driveto maintain an approximately constant current I_drive, for a given dimming level indicated by the threshold voltage V_TH, when switch 416 conducts. Diode 428 prevents reverse current flow when the polarity of inductor 426 reverses during switching of switch 416. A typical switching frequency for this approximately constant-current I_drivewould be 50 kHz-100 kHz. The frequency is chosen to optimize efficiency and minimize size of a switch 416. The ripple of the current I_drive(as shown in FIGS. 4B and 4C) at the switching frequency is selected to be about 10-20% at full intensity, again chosen for efficiency and size of switch 416. This remaining high-frequency ripple has minimal effect on the performance of the LEDs, and is herein referred to as “approximately constant current”. This is contrasted with pulse-width modulation at 120 Hz, which has detrimental effects on flicker and efficiency.

[0056] To reduce radio frequency interference, the timing of conductive transitions (i.e. “on” and “off” times) of switches 404 and 416 can be modified with respect to each other and also dithered to spread the spectrum of electromagnetic energy and, thus, minimize radio frequency interference. Dithering can be accomplished, for example, by modifying the “off” time of switch 404 with a random or pseudo random noise source. Inductor 430 and capacitor 432 provide filtering to smooth drive current I_L1so that the average drive current I_L1is sinusoid in phase with dimmer signal V_DIM. Thus, a power factor of unity or approximately unity is achieved.

[0057] The lighting system 400 includes a phase delay detector 434, an optional mapping system and filter 436, and a digital-to-analog converter (DAC) 438 to generate a threshold voltage V_TH. The threshold voltage V_THis a dimmer output signal indicating a dimming level conforming to a dimming level indicated by the dimmer signal V_DIM. In at least one embodiment, the phase delay detector 434 detects the phase delay, duty cycle, and/or the corresponding phase angle of the dimmer signal V_DIMand generates a phase delay signal □_D. In at least one embodiment, the lighting system 400 includes a mapping system and filter 436 that uses a mapping function to map the dimming level indicated by phase delay signal □_Dinto different dimming levels. In at least one embodiment, the mapping function converts the dimming levels indicated by dimmer signal V_DIM(and, thus, indicated by phase delay signal □_D) into a digital dimming signal D_V_—_digitalhaving values that map measured light levels to perception based light levels as described in conjunction with the exemplary systems and methods of Melanson I and Melanson II. DAC 438 converts the mapped dimmer signal D_V_—_digitalinto the threshold voltage V_TH. In at least one embodiment, the phase delay signal □_Dis a digital signal. DAC 438 converts the digital phase delay signal □_Dinto an analog threshold voltage V_TH. In at least one embodiment, the threshold voltage V_THis updated at least the same frequency as the frequency of dimmer signal V_DIM. This update is desirable, as the phase modulated dimmer signal V_DIMoperates only over a narrow range (<10:1), whereas it is desirable to dim over a wide range, say 100:1.

[0058] The threshold voltage V_THis compared by comparator 438 with voltage V_sense. Voltage V_senseis taken across sense resistor 440 and is proportional to drive current I_drive. In at least one embodiment, resistor 440 is 1 ohm. In another embodiment, the drive current I_driveis sensed by a magnetic current sensor in the proximity of current flowing through inductor 426. The comparator 438 provides an output voltage V_COMPas input data to ballast controller 406. The output voltage V_COMPis used by ballast controller 406 to control the conductivity of switch 416 and, thus, control drive current I_driveas, for example, described in Melanson IV. The conductivity of switch 416 is modulated by the control signal C_S2provided by ballast controller 406 such that the average drive current I_driveis responsive to dimmer signal V_DIM. The drive current I_driveserves as the drive current for light source 418. Adjusting the drive current I_drivemodifies the intensity of light source 418.

[0059] FIG. 4B depicts a graphical relationship 452 between an approximately constant LED drive current I_driveand a phase modulated dimmer signal V_DIMindicating a 50% dimming level and a graphical relationship 454 between an approximately constant LED drive current I_drivethat is varied to respond to a phase modulated dimmer signal V_DIMindicating a 25% dimming level. The dimmer signal V_DIM456 has phase delays α of T/4 representing a dimming level of 50%, where T is the period of a full cycle of dimmer signal V_DIM456. In at least one embodiment, T is 1/60 (16.7 msec) or 1/50 (20 msec). Lighting system 400 generates an LED drive current I_drive458 that is approximately constant during each cycle of dimmer signal V_DIM406. The dimmer signal V_DIM460 changes from the dimming level of 50% indicated by dimmer signal V_DIM456 to a dimming level of 25%. The phase delay of dimmer signal V_DIM460 is T/8. Lighting system 400 generates an LED drive current I_drive462 that is approximately constant during each cycle of dimmer signal V_DIM460. Thus, the LED drive current I_drivevaries with variations of the dimming level indicated by dimmer signal V_DIM, and LED drive current I_driveremains approximately constant for each dimming level indicated by dimmer signal V_DIM. The LED drive current I_drivechanges in response to other dimming levels indicated by dimmer signal V_DIMin the same manner as depicted in FIG. 4B.

[0060] FIG. 4C depicts a 1,000× magnified view 480 of LED drive currents I_drive458 and 462. The LED drive currents I_drive458 and 462 rise and fall in accordance with pulses of control signal CS₂. For each dimming level, the peak-to-peak values of the LED drive current I_driveis, for example, 100-200 mA, which is approximately constant for LED lighting applications. The average value of the LED drive current I_driverepresents a DC offset of the LED drive current I_drive. The DC offset of the LED drive current I_driverepresents the dimming level of the LEDs 418.

[0061] FIG. 5A depicts an exemplary voltage sensor 550, which is one embodiment of V_C1sensor 414. The voltage sensor 550 is an analog-to-digital converter (ADC) 552 that generates a digital value V_Srepresenting the voltage V_C1.

[0062] FIG. 5B represents an exemplary voltage sensor 500, which represents one embodiment of the ADC 552. Resistors 502 and 514 provide a voltage divider to compare a percentage X of voltage V_C1to a reference voltage V_REF. The reference voltage V_REFis chosen to be the same percentage X as the desired value of voltage V_C1. In one embodiment, the desired value of voltage V_C1is 250 V, and the reference voltage is 1 V. So the ratio of resistor 502 to resistor 514 is 250:1. In one embodiment, the value of resistor 502 is 2.5 Mohms, and the value of resistor 514 is 10 kohms. The comparator 504 provides an output voltage V_S. When voltage V_Sis high, voltage V_C1is high, so the switching frequency of switch 404 is decreased to decrease the voltage V_C1. When voltage V_Sis low, voltage V_C1is high, so the switching frequency of switch 404 is increased to increase the voltage V_C1.

[0063] FIG. 6 depicts a phase delay detector 600, which represents one embodiment of phase delay detector 434. The phase delay detector 600 includes an analog integrator 602 that integrates dimmer signal V_DIMduring each cycle (full or half cycle) of dimmer signal V_DIM. The analog integrator 602 generates a current I corresponding to the duty cycle of dimmer signal V_DIMfor each cycle of dimmer signal V_DIM. The current provided by the analog integrator 602 charges a capacitor 604 to a value representing the phase delay of dimmer signal V_DIM. The ADC 612 generates the phase delay signal □_Dfrom the voltage across capacitor 604. The analog integrator 602 can be reset after each cycle of dimmer signal V_DIMby discharging capacitors 606 and 604. Switch 608 includes a control terminal to receive reset signal S_R. Switch 610 includes a control terminal to receive sample signal S_S. The charge on capacitor 604 is sampled by capacitor 606 when control signal S_Scauses switch 610 to conduct. After sampling the charge on capacitor 604, reset signal S_Ropens switch 608 to discharge and, thus, reset capacitor 604. In at least one embodiment, switches 608 and 610 are n-channel field effect transistors, and sample signal S_Sand reset signal S_Rhave non-overlapping pulses. In at least one embodiment, each cycle of dimmer signal V_DIMcan be detected by every other zero crossing of dimmer signal V_DIM.

[0064] FIG. 7 depicts a phase delay detector 700 that converts the dimmer input signal V_DIMinto a digital dimmer signal value □_D. The digital data of dimmer signal value □_Drepresents the phase delay of dimmer signal V_DIM. The phase delay detector 700 determines the duty cycle of dimmer signal V_DIMby counting the number of cycles of clock signal f_clkthat occur until the chopping point of dimmer signal V_DIMis detected by the duty cycle time converter 700.

[0065] FIG. 8 depicts a phase delay detector 800 that represents one embodiment of phase delay detector 800. Comparator 802 compares dimmer signal V_DIMagainst a known reference. The reference is generally the cycle cross-over point voltage of dimmer output voltage V_DIM, such as a neutral potential of a household AC voltage. The counter 804 counts the number of cycles of clock signal f_clkthat occur until the comparator 802 indicates that the chopping point of dimmer signal V_DIMhas been reached. Since the frequency of dimmer signal V_DIMand the frequency of clock signal f_clkis known, the phase delay can be determined from the count of cycles of clock signal f_clkthat occur until the comparator 802 indicates that the chopping point of dimmer signal V_DIM. Likewise, the phase angle can also be determined by knowing the elapsed time from the beginning of a cycle of dimmer signal V_DIMuntil a chopping point of dimmer signal V_DIMis detected.

[0066] FIG. 9 depicts a graphical relationship 900 in time between the switch 404 control signal CS₁and drive current I_L1. When control signal CS₁causes switch 404 to conduct, drive current I_L1ramps up. When control signal CS₁causes switch 404 to turn “off”, drive current I_L1ramps down. Thus, in this embodiment, the drive current I_L1is controlled by pulse width modulation. The period of control signal CS₁is a matter of design choice and is preferably chosen to avoid audio baseband frequencies.

[0067] FIG. 10 depicts a graphical relationship 1000 between the comparator voltage V_COMP, control signal C_S2, and current I₂across sense resistor 440 (FIG. 4). When control signal C_S2is high, switch 416 conducts, and drive current I_driveincreases. When the comparator voltage V_COMPgoes high, ballast controller 406 keeps control signal C_S2high until the comparator voltage V_COMPgoes low again. In another embodiment, the control signal C_S2goes high when comparator voltage V_COMPgoes high, and ballast controller 406 keeps control signal C_S2high for twice as long as the amount of time that comparator voltage V_COMPis high. In this manner, the average drive current I_driveis responsive to the dimmer signal V_DIM, and, thus, the intensity of light source 418 is also responsive to dimmer signal V_DIM.

[0068] FIG. 11 depicts a graphical relationship 1100 between control signal C_S2and drive current I_drive. The drive current I_driveramps up when control signal C_S2is high (i.e. causes switch 416 to conduct) and ramps down when control signal C_S2is low (i.e. causes switch 416 to turn ‘off’). The average drive current I_drivetracks the dimmer signal V_DIMeither directly or via a mapping function. The intensity of light source 418 is approximately directly proportional to the driving drive current _drive.

[0069] FIG. 12 depicts an LED bank 1200, which represents a substitution of light source 418. The raw DC voltage V_c2 is applied across the series connected LEDs 1202 and the LEDs 1204. Ballast controller 406 supplies control signals C_S2Aand C_S2Bto turn respective switches 1208 and 1210 ‘on’ (conductive) and ‘off’ (nonconductive). In at least one embodiment, switches 1208 and 1210 are n-channel field effect transistors (FETs). In this embodiment, ballast controller 406 provides the gate voltages to switches 1208 and 1210. The average values of the drive currents I_Aand I_Bcontrol the respective intensity of LEDs 1202 and 1204. The diodes 1212 and 1214 permit current flow in only one direction. Inductors 1216 and 1218 and capacitors 1220 and 1222 regulate the voltage across the respective LEDs 1202 and LEDs 1204 and provide filtering. The voltage across resistors 1224 and 1226 is fed back to ballast controller 406 to allow ballast controller 406 to adjust the switching frequency of switches 1208 and 1210 and, thus, correlate drive currents I_Aand I_Bwith the selected dimming level. The type, number, and arrangement of LEDs in LED bank 1200 is a matter of design choice and depends, for example, on the range of desired intensity and color temperatures of LED bank 1200.

[0070] Thus, a lighting source ballast utilizes switching and control technology to convert an alternating current (AC) phase modulated dimmer input voltage into an approximately constant drive current to illuminate one or more light emitting diodes (LED(s)). In at least one embodiment, the state of the drive current conforms to a phase delay of the input voltage to facilitate, for example, dimming. The phase delay of the input voltage indicates a particular dimming level. The drive current varies for different dimming levels. However, the light source ballast controls drive current so that the drive current is approximately constant for each dimming level. In at least one embodiment, the ballast emulates a resistive load and, thus, the ballast has an approximately unity power factor. The switching frequency of one or more switches can be modified to spread the spectrum of electromagnetic radiation generated by the ballast. The light sources can be configured in any of a variety of configurations, such as multiple LED banks. In at least one embodiment, the ballast emulates a resistive load and, thus, the ballast has an approximately unity power factor. Additionally, the switches can be timed to spread the spectrum of electromagnetic radiation generated by the ballast.

[0071] Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

What is claimed is:

1. A lighting system ballast comprising:

a light source driver stage configured to deliver power to one or more light emitting diodes with an adjustable drive current;

a sensor having one or more input terminals to receive a phase modulated dimmer signal, wherein a phase delay of the phase modulated dimmer signal indicates a dimming level and the sensor is configured to detect the dimming level and to generate a dimmer output signal representing a dimming level indicated by the dimmer signal; and

a controller coupled to the light source driver stage and the sensor, wherein the controller includes at least one input terminal to receive the dimmer output signal from the sensor and to generate a drive control signal to cause a drive current supplied to each light emitting diode to dim each light emitting diode in response to the dimmer signal, wherein the drive current is approximately constant for each dimming level throughout a cycle of the phase modulated dimmer signal.

2. The lighting system ballast of claim 1 wherein the phase modulated dimmer signal comprises a line input voltage to supply power to the light source driver stage.

3. The lighting system ballast of claim 1 further comprising:

a switch having a control terminal coupled to the controller to receive the drive control signal and having a terminal coupled to each light emitting diode to control the drive current delivered to each light emitting diode.

4. The lighting system ballast of claim 1 further comprising a converter to convert the dimming output signal into a digital dimmer output signal.

5. The lighting system ballast of claim 1 wherein the controller is further configured to spread a spectrum of the drive control signal.

6. The lighting system ballast of claim 1 further comprising a mapping system to map the dimming level to the drive control signal using a predetermined lighting output function.

7. The lighting system ballast of claim 6 wherein the lighting output function maps dimming levels indicated by input voltage to predetermined values different than the dimming levels indicated by the input voltage.

8. The lighting system ballast of claim 1 wherein the lighting ballast system further comprises a comparator to generate a comparison signal representing an outcome of a comparison between a signal proportional to the drive current and the threshold signal, and wherein the controller is further configured to adjust the drive control signal in response to the comparison signal so that the energy supplied by the light source driver stage is responsive to the dimmer signal.

9. The lighting system ballast of claim 1 wherein the sensor comprises a phase angle detector to detect the phase delay of the dimmer signal to determine the dimming level.

10. The lighting system ballast of claim 1 further comprising a power factor converter coupled to the light source driver stage and the controller, wherein the controller is further configured to generate a power factor control signal to control power factor correction of the power factor converter and the power factor converter is configured to provide power factor corrected energy to the light source driver stage.

11. A method of supplying a drive current to one or more light emitting diodes, the method comprising:

receiving a phase modulated dimmer signal wherein a phase delay of the phase modulated dimmer signal indicates a dimming level;

generating a dimmer output signal representing a dimming level indicated by the dimmer signal;

generating a drive control signal to cause the drive current to respond to the dimmer output signal; and

providing the drive control signal to a switch to vary conductivity of the switch and cause the drive current supplied by the light source driver stage to each of the light emitting diodes to be approximately constant through a cycle of the phase modulated dimming signal.

12. The method of claim 11 further comprising converting the dimming signal into a digital dimmer signal.

13. The method of claim 11 further comprising spreading a spectrum of the drive control signal.

14. The method of claim 11 further comprising mapping the dimming level to the drive control signal using a predetermined lighting output function.

15. The method of claim 14 wherein the lighting output function maps dimming levels indicated by input voltage to predetermined values different than the dimming levels indicated by the input voltage.

16. The method of claim 11 further comprising:

detecting a phase angle of the dimmer signal; and

determining a dimming level of the dimmer signal from the phase angle.

17. The method of claim 16 further comprising:

generating a threshold signal representing the duty cycle of the dimmer signal;

receiving a feedback signal proportional to a drive current level;

generating a comparison signal representing an outcome of a comparison between the feedback signal and the threshold signal; and

adjusting the drive control signal in response to the comparison signal so that the energy delivered by the light source driver stage is responsive to the dimmer signal.

18. The method of claim 11 further comprising generating a power factor control signal to control power factor correction of a power factor converter, wherein the power factor converter is configured to provide power factor corrected energy to the light source driver stage.

19. A lighting system comprising:

a light source ballast system, wherein the light source ballast system comprises:

a power factor converter and drive system to receive an alternating current, phase modulated dimmer input voltage, to convert the input voltage into a power factor corrected direct current (DC) output voltage, and to generate a light emitting diode drive current, wherein a phase delay of the dimmer input voltage indicates a dimming level; and

a ballast controller, coupled to the power factor converter and drive system, to generate one or more control signals for the power factor converter and drive system to control power factor correction and to adjust the drive current in conformance with the dimming level represented by the dimmer signal, wherein the drive current is approximately constant throughout a cycle of the phase modulated input voltage for each dimming level and the level of the constant drive current varies in response to variations in the indicated dimming level.

20. The lighting system of claim 19 further comprising:

a dimming level detector and converter coupled to the ballast controller to receive the phase modulated dimmer input voltage and to detect a dimming level indicated by the input voltage signal; and

a dimmer mapping system to map the dimming levels indicated by the input voltage to predetermined values different than the dimming levels indicated by the input voltage.

21. A method of responding to a dimmer signal and supplying a constant voltage and variable drive current to a light source, the method comprising:

receiving an alternating current, phase modulated dimmer input voltage, wherein a phase delay of the dimmer input voltage indicates a dimming level;

generating one or more control signals for a power factor converter and drive system to control power factor correction and to vary the drive current in conformance with the dimming level represented by the dimmer signal, wherein the drive current is approximately constant throughout a cycle of the phase modulated input signal for each dimming level and the level of the constant drive current is varied in response to variations in the indicated dimming level.

22. The method of claim 21 further comprising:

detecting a dimming level indicated by the input voltage signal; and

a dimmer mapping system to map the dimming levels indicated by input voltage to predetermined values different than the dimming levels indicated by the input voltage.

Patent Citations (164)

Patent	Date	Inventor	Cited By
US3790878(A)	1974-02-01	Brokaw	Applicant
US3881167(A)	1975-04-01	Pelton et al.	Applicant
US4075701(A)	1978-02-01	Hofmann	Applicant
US4334250(A)	1982-06-01	Theus	Applicant
US4414493(A)	1983-11-01	Henrich	Applicant
US4476706(A)	1984-10-01	Hadden et al.	Applicant
US4677366(A)	1987-06-01	Wilkinson et al.	Applicant
US4683529(A)	1987-07-01	Bucher	Applicant
US4700188(A)	1987-10-01	James	Applicant
US4737658(A)	1988-04-01	Kronmuller et al.	Applicant
US4797633(A)	1989-01-01	Humphrey	Applicant
US4940929(A)	1990-07-01	Williams	Applicant
US4973919(A)	1990-11-01	Allfather	Applicant
US4979087(A)	1990-12-01	Sellwood et al.	Applicant
US4992919(A)	1991-02-01	Lee et al.	Applicant
US4994952(A)	1991-02-01	Silva et al.	Applicant
US5206540(A)	1993-04-01	da Sa e Silva et al.	Applicant
US5278490(A)	1994-01-01	Smedley	Applicant
US5323157(A)	1994-06-01	Ledzius et al.	Applicant
US5359180(A)	1994-10-01	Park et al.	Applicant
US5383109(A)	1995-01-01	Maksimovic et al.	Applicant
US5477481(A)	1995-12-01	Kerth	Applicant
US5481178(A)	1996-01-01	Wilcox et al.	Applicant
US5565761(A)	1996-10-01	Hwang	Applicant
US5638265(A)	1997-06-01	Gabor	Applicant
US5691890(A)	1997-11-01	Hyde	Applicant
US5747977(A)	1998-05-01	Hwang	Applicant
US5781040(A)	1998-07-01	Myers	Applicant
US5783909(A)	1998-07-01	Hochstein	Applicant
US5900683(A)	1999-05-01	Rinehart et al.	Applicant
US5929400(A)	1999-07-01	Colby et al.	Applicant
US5946202(A)	1999-08-01	Balogh	Applicant
US5952849(A)	1999-09-01	Haigh et al.	Applicant
US5963086(A)	1999-10-01	Hall	Applicant
US5966297(A)	1999-10-01	Minegishi	Applicant
US5994885(A)	1999-11-01	Wilcox et al.	Applicant
US6016038(A)	2000-01-01	Mueller et al.	Applicant
US6043633(A)	2000-03-01	Lev et al.	Applicant
US6072969(A)	2000-06-01	Yokomori et al.	Applicant
US6083276(A)	2000-07-01	Davidson et al.	Applicant
US6084450(A)	2000-07-01	Smith et al.	Applicant
US6150774(A)	2000-11-01	Mueller et al.	Applicant
US6211626(B1)	2001-04-01	Lys et al.	Applicant
US6211627(B1)	2001-04-01	Callahan	Applicant
US6229271(B1)	2001-05-01	Liu	Applicant
US6246183(B1)	2001-06-01	Buonavita	Applicant
US6259614(B1)	2001-07-01	Ribarich et al.	Applicant
US6300723(B1)	2001-10-01	Wang et al.	Applicant
US6304066(B1)	2001-10-01	Wilcox et al.	Applicant
US6304473(B1)	2001-10-01	Telefus et al.	Applicant
US6344811(B1)	2002-02-01	Melanson	Applicant
US6385063(B1)	2002-05-01	Sadek et al.	Applicant
US6407691(B1)	2002-06-01	Yu	Applicant
US6441558(B1)	2002-08-01	Muthu et al.	Applicant
US6445600(B2)	2002-09-01	Ben-Yaakov	Applicant
US6452521(B1)	2002-09-01	Wang	Applicant
US6495964(B1)	2002-12-01	Muthu et al.	Applicant
US6509913(B2)	2003-01-01	Martin, Jr. et al.	Applicant
US6580258(B2)	2003-06-01	Wilcox et al.	Applicant
US6583550(B2)	2003-06-01	Iwasa et al.	Applicant
US6636003(B2)	2003-10-01	Rahm et al.	Applicant
US6713974(B2)	2004-03-01	Patchornik et al.	Applicant
US6727832(B1)	2004-04-01	Melanson	Applicant
US6741123(B1)	2004-05-01	Anderson et al.	Applicant
US6753661(B2)	2004-06-01	Muthu et al.	Applicant
US6768655(B1)	2004-07-01	Yang et al.	Applicant
US6781351(B2)	2004-08-01	Mednik et al.	Applicant
US6788011(B2)	2004-09-01	Mueller et al.	Applicant
US6806659(B1)	2004-10-01	Mueller et al.	Applicant
US6839247(B1)	2005-01-01	Yang	Applicant
US6860628(B2)	2005-03-01	Robertson et al.	Applicant
US6870325(B2)	2005-03-01	Bushell et al.	Applicant
US6873065(B2)	2005-03-01	Haigh et al.	Applicant
US6882552(B2)	2005-04-01	Telefus et al.	Applicant
US6888322(B2)	2005-05-01	Dowling et al.	Applicant
US6894471(B2)	2005-05-01	Corva et al.	Applicant
US6933706(B2)	2005-08-01	Shih	Applicant
US6940733(B2)	2005-09-01	Schie et al.	Applicant
US6944034(B1)	2005-09-01	Shytenberg et al.	Applicant
US6956750(B1)	2005-10-01	Eason et al.	Applicant
US6958920(B2)	2005-10-01	Mednik et al.	Applicant
US6967448(B2)	2005-11-01	Morgan et al.	Applicant
US6970503(B1)	2005-11-01	Kalb	Applicant
US6975079(B2)	2005-12-01	Lys et al.	Applicant
US7003023(B2)	2006-02-01	Krone et al.	Applicant
US7050509(B2)	2006-05-01	Krone et al.	Applicant
US7064498(B2)	2006-06-01	Dowling et al.	Applicant
US7064531(B1)	2006-06-01	Zinn	Applicant
US7075329(B2)	2006-07-01	Chen et al.	Applicant
US7078963(B1)	2006-07-01	Andersen et al.	Applicant
US7088059(B2)	2006-08-01	McKinney et al.	Applicant
US7102902(B1)	2006-09-01	Brown et al.	Applicant
US7106603(B1)	2006-09-01	Lin et al.	Applicant
US7109791(B1)	2006-09-01	Epperson et al.	Applicant
US7135824(B2)	2006-11-01	Lys et al.	Applicant
US7145295(B1)	2006-12-01	Lee et al.	Applicant
US7158633(B1)	2007-01-01	Hein	Applicant
US7161816(B2)	2007-01-01	Shytenberg et al.	Applicant
US7183957(B1)	2007-02-01	Melanson	Applicant
US7221130(B2)	2007-05-01	Ribeiro et al.	Applicant
US7233135(B2)	2007-06-01	Noma et al.	Applicant
US7255457(B2)	2007-08-01	Ducharm et al.	Applicant
US7266001(B1)	2007-09-01	Notohamiprodjo et al.	Applicant
US7288902(B1)	2007-10-01	Melanson	Applicant
US7292013(B1)	2007-11-01	Chen et al.	Applicant
US7310244(B2)	2007-12-01	Yang et al.	Applicant
US7538499(B2)	2009-05-01	Ashdown	Applicant
US7545130(B2)	2009-06-01	Latham	Applicant
US7554473(B2)	2009-06-01	Melanson	Applicant
US7569996(B2)	2009-08-01	Holmes et al.	Applicant
US7656103(B2)	2010-02-01	Shteynberg et al.	Applicant
US2002/0145041(A1)	2002-10-01	Muthu et al.	Applicant
US2002/0150151(A1)	2002-10-01	Krone et al.	Applicant
US2002/0166073(A1)	2002-11-01	Nguyen et al.	Applicant
US2003/0095013(A1)	2003-05-01	Melanson et al.	Applicant
US2003/0223255(A1)	2003-12-01	Ben-Yaakov	Applicant
US2004/0046683(A1)	2004-03-01	Mitamura et al.	Applicant
US2004/0085030(A1)	2004-05-01	Laflamme et al.	Applicant
US2004/0085117(A1)	2004-05-01	Melbert et al.	Applicant
US2004/0169477(A1)	2004-09-01	Yancie et al.	Applicant
US2004/0227571(A1)	2004-11-01	Kuribayashi	Applicant
US2004/0228116(A1)	2004-11-01	Miller et al.	Applicant
US2004/0232971(A1)	2004-11-01	Kawasake et al.	Applicant
US2004/0239262(A1)	2004-12-01	Ido et al.	Applicant
US2005/0057237(A1)	2005-03-01	Clavel	Applicant
US2005/0156770(A1)	2005-07-01	Melanson	Applicant
US2005/0184895(A1)	2005-08-01	Petersen et al.	Applicant
US2005/0207190(A1)	2005-09-01	Gritter	Applicant
US2005/0218838(A1)	2005-10-01	Lys	Applicant
US2005/0253533(A1)	2005-11-01	Lys et al.	Applicant
US2005/0270813(A1)	2005-12-01	Zhang et al.	Applicant
US2005/0275354(A1)	2005-12-01	Hausman, Jr. et al.	Applicant
US2005/0275386(A1)	2005-12-01	Jepsen et al.	Applicant
US2006/0022916(A1)	2006-02-01	Aiello	Applicant
US2006/0023002(A1)	2006-02-01	Hara et al.	Applicant
US2006/0125420(A1)	2006-06-01	Boone et al.	Applicant
US2006/0226795(A1)	2006-10-01	Walter et al.	Applicant
US2006/0261754(A1)	2006-11-01	Lee	Applicant
US2007/0029946(A1)	2007-02-01	Yu et al.	Applicant
US2007/0040512(A1)	2007-02-01	Jungwirth et al.	Applicant
US2007/0053182(A1)	2007-03-01	Robertson	Applicant
US2007/0103949(A1)	2007-05-01	Tsuruya	Applicant
US2007/0182699(A1)	2007-08-01	Ha et al.	Applicant
US2008/0174372(A1)	2008-07-01	Tucker et al.	Applicant
US2008/0192509(A1)	2008-08-01	Dhuyvetter et al.	Applicant
US2008/0224635(A1)	2008-09-01	Hayes	Applicant
US2008/0259655(A1)	2008-10-01	Wei et al.	Applicant
US2008/0278132(A1)	2008-11-01	Kesterson et al.	Applicant
US2009/0147544(A1)	2009-06-01	Melanson	Applicant
US2009/0218960(A1)	2009-09-01	Lyons et al.	Applicant
EP585789(A1)	1994-03-01		Applicant
EP910168(A1)	1999-04-01		Applicant
EP1014563	2000-06-01		Applicant
EP1164819(A)	2001-12-01		Applicant
EP1213823(A2)	2002-06-01		Applicant
EP1528785(A)	2005-05-01		Applicant
WO1/97384(A)	2001-12-01		Applicant
WO227944	2002-04-01		Applicant
WO2/091805(A2)	2002-11-01		Applicant
WO2006/022107(A2)	2006-03-01		Applicant
WO2006/067521(A)	2006-06-01		Applicant
WO2006135584	2006-12-01		Applicant
WO2007/026170(A)	2007-03-01		Applicant
WO2007/079362(A)	2007-07-01		Applicant

Non-Patent Literature (166)

Linear Technology, “Single Switch PWM Controller with Auxiliary Boost Converter,” LT1950 Datasheet, Linear Technology, Inc. Milpitas, CA, 2003.Applicant
Yu, Zhenyu, 3.3V DSP for Digital Motor Control, Texas Instruments, Application Report SPRA550 dated Jun. 1999.Applicant
International Rectifier, Data Sheet No. PD60143-O, Current Sensing Single Channel Driver, El Segundo, CA, dated Sep. 8, 2004.Applicant
Balogh, Laszlo, “Design and Application Guide for High Speed MOSFET Gate Drive Circuits” [Online] 2001, Texas Instruments, Inc., SEM-1400, Unitrode Power Supply Design Seminar, Topic II, TI literature No. SLUP133, XP002552367, Retrieved from the Internet: URL:htt/://focus.ti.com/lit/ml/slup169/slup169.pdf the whole document.Applicant
ST Datasheet L6562, Transition-Mode PFC Controller, 2005, STMicroelectronics, Geneva, Switzerland.Applicant
Maksimovic, Regan Zane and Robert Erickson, Impact of Digital Control in Power Electronics, Proceedings of 2004 International Symposium on Power Semiconductor Devices & Ics, Kitakyushu, , Apr. 5, 2010, Colorado Power Electronics Center, ECE Department, University of Colorado, Boulder, CO.Applicant
Freescale Semiconductor, Inc., Dimmable Light Ballast with Power Factor Correction, Design Reference Manual, DRM067, Rev. 1, Dec. 2005.Applicant
J. Zhou et al., Novel Sampling Algorithm for DSP Controlled 2 kW PFC Converter, IEEE Transactions on Power Electronics, vol. 16, No. 2, Mar. 2001.Applicant
A. Prodic, Compensator Design and Stability Assessment for Fast Voltage Loops of Power Factor Correction Rectifiers, IEEE Transactions on Power Electronics, vol. 22, No. 5, Sep. 2007.Applicant
M. Brkovic et al., “Automatic Current Shaper with Fast Output Regulation and Soft-Switching,” S.15.C Power Converters, Telecommunications Energy Conference, 1993.Applicant
Dallas Semiconductor, Maxim, “Charge-Pump and Step-Up DC-DC Converter Solutions for Powering White LEDs in Series or Parallel Connections,” Apr. 23, 2002.Applicant
Freescale Semiconductor, AN3052, Implementing PFC Average Current Mode Control Using the MC9S12E128, Nov. 2005.Applicant
D. Maksimovic et al., “Switching Converters with Wide DC Conversion Range,” Institute of Electrical and Electronic Engineer's (IEEE) Transactions on Power Electronics, Jan. 1991.Applicant
V. Nguyen et al., “Tracking Control of Buck Converter Using Sliding-Mode with Adaptive Hysteresis,” Power Electronics Specialists Conference, 1995. PESC apos; 95 Record., 26th Annual IEEE vol. 2, Issue , Jun. 18-22, 1995 pp. 1086-1093.Applicant
S. Zhou et al., “A High Efficiency, Soft Switching DC-DC Converter with Adaptive Current-Ripple Control for Portable Applications,” IEEE Transactions on Circuits and Systems—II: Express Briefs, vol. 53, No. 4, Apr. 2006.Applicant
K. Leung et al., “Use of State Trajectory Prediction in Hysteresis Control for Achieving Fast Transient Response of the Buck Converter,” Circuits and Systems, 2003. ISCAS apos;03. Proceedings of the 2003 International Symposium, vol. 3, Issue , May 25-28, 2003 pp. III-439-III-442 vol. 3.Applicant
K. Leung et al., “Dynamic Hysteresis Band Control of the Buck Converter with Fast Transient Response,” IEEE Transactions on Circuits and Systems—II: Express Briefs, vol. 52, No. 7, Jul. 2005.Applicant
Y. Ohno, Spectral Design Considerations for White LED Color Rendering, Final Manuscript, Optical Engineering, vol. 44, 111302 (2005).Applicant
S. Skogstad et al., A Proposed Stability Characterization and Verification Method for High-Order Single-Bit Delta-Sigma Modulators, Norchip Conference, Nov. 2006 http://folk.uio.no/savskogs/pub/A—Proposed—Stability—Characterization.pdf.Applicant
J. Turchi, Four Key Steps to Design a Continuous Conduction Mode PFC Stage Using the NCP1653, ON Semiconductor, Publication Order No. AND184/D, Nov. 2004.Applicant
Megaman, D or S Dimming ESL, Product News, Mar. 15, 2007.Applicant
J. Qian et al., New Charge Pump Power-Factor-Correction Electronic Ballast with a Wide Range of Line Input Voltage, IEEE Transactions on Power Electronics, vol. 14, No. 1, Jan. 1999.Applicant
P. Green, A Ballast that can be Dimmed from a Domestic (Phase-Cut) Dimmer, IRPLCFL3 rev. b, International Rectifier, http://www.irf.com/technical-info/refdesigns/cfl-3.pdf, printed Mar. 24, 2007.Applicant
J. Qian et al., Charge Pump Power-Factor-Correction Technologies Part II: Ballast Applications, IEEE Transactions on Power Electronics, vol. 15, No. 1, Jan. 2000.Applicant
Chromacity Shifts in High-Power White LED Systems due to Different Dimming Methods, Solid-State Lighting, http://www.lrc.rpi.edu/programs/solidstate/completedProjects.asp?ID=76, printed May 3, 2007.Applicant
S. Chan et al., Design and Implementation of Dimmable Electronic Ballast Based on Integrated Inductor, IEEE Transactions on Power Electronics, vol. 22, No. 1, Jan. 2007.Applicant
M. Madigan et al., Integrated High-Quality Rectifier-Regulators, IEEE Transactions on Industrial Electronics, vol. 46, No. 4, Aug. 1999.Applicant
T. Wu et al., Single-Stage Electronic Ballast with Dimming Feature and Unity Power Factor, IEEE Transactions on Power Electronics, vol. 13, No. 3, May 1998.Applicant
F. Tao et al., “Single-Stage Power-Factor-Correction Electronic Ballast with a Wide Continuous Dimming Control for Fluorescent Lamps,” IEEE Power Electronics Specialists Conference, vol. 2, 2001.Applicant
Azoteq, IQS17 Family, IQ Switch®—ProxSense™ Series, Touch Sensor, Load Control and User Interface, IQS17 Datasheet V2.00.doc, Jan. 2007.Applicant
C. Dilouie, Introducing the LED Driver, EC&M, Sep. 2004.Applicant
S. Lee et al., TRIAC Dimmable Ballast with Power Equalization, IEEE Transactions on Power Electronics, vol. 20, No. 6, Nov. 2005.Applicant
L. Gonthier et al., EN55015 Compliant 500W Dimmer with Low-Losses Symmetrical Switches, 2005 European Conference on Power Electronics and Applications, Sep. 2005.Applicant
Why Different Dimming Ranges? The Difference Between Measured and Perceived Light, http://www.lutron.com/ballast/pdf/LutronBallastpg3.pdf.Applicant
D. Hausman, Real-Time Illumination Stability Systems for Trailing-Edge (Reverse Phase Control) Dimmers, Technical White Paper, Lutron, version 1.0, Dec. 2004, http://www.lutron.com/technical—info/pdf/RTISS-TE.pdf.Applicant
Light Dimmer Circuits, www.epanorama.net/documents/lights/lightdimmer.html, printed Mar. 26, 2007.Applicant
Light Emitting Diode, http://en.wikipedia.org/wiki/Light-emitting—diode, printed Mar. 27, 2007.Applicant
Color Temperature, www.sizes.com/units/color—temperature.htm, printed Mar. 27, 2007.Applicant
S. Lee et al., A Novel Electrode Power Profiler for Dimmable Ballasts Using DC Link Voltage and Switching Frequency Controls, IEEE Transactions on Power Electronics, vol. 19, No. 3, May 2004.Applicant
Y. Ji et al., Compatibility Testing of Fluorescent Lamp and Ballast Systems, IEEE Transactions on Industry Applications, vol. 35, No. 6, Nov./Dec. 1999.Applicant
National Lighting Product Information Program, Specifier Reports, “Dimming Electronic Ballasts,” vol. 7, No. 3, Oct. 1999.Applicant
Supertex Inc., Buck-based LED Drivers Using the HV9910B, Application Note AN-H48, Dec. 28, 2007.Applicant
D. Rand et al., Issues, Models and Solutions for Triac Modulated Phase Dimming of LED Lamps, Power Electronics Specialists Conference, 2007.Applicant
Supertex Inc., HV9931 Unity Power Factor LED Lamp Driver, Application Note AN-H52, Mar. 7, 2007.Applicant
Supertex Inc., 56W Off-line LED Driver, 120VAC with PFC, 160V, 350mA Load, Dimmer Switch Compatible, DN-H05, Feb. 2007.Applicant
ST Microelectronics, Power Factor Corrector L6561, Jun. 2004.Applicant
Fairchild Semiconductor, Application Note 42047 Power Factor Correction (PFC) Basics, Rev. 0.9.0 Aug. 19, 2004.Applicant
M. Radecker et al., Application of Single-Transistor Smart-Power IC for Fluorescent Lamp Ballast, Thirty-Fourth Annual Industry Applications Conference IEEE, vol. 1, Oct. 3, 1999-Oct. 7, 1999.Applicant
M. Rico-Secades et al., Low Cost Electronic Ballast for a 36-W Fluorescent Lamp Based on a Current-Mode-Controlled Boost Inverter for a 120-V DC Bus Power Distribution, IEEE Transactions on Power Electronics, vol. 21, No. 4, Jul. 2006.Applicant
Fairchild Semiconductor, FAN4800, Low Start-up Current PFC/PWM Controller Combos, Nov. 2006.Applicant
Fairchild Semiconductor, FAN4810, Power Factor Correction Controller, Sep. 24, 2003.Applicant
Fairchild Semiconductor, FAN4822, ZVS Average Current PFC Controller, Aug. 10, 2001.Applicant
Fairchild Semiconductor, FAN7527B, Power Factor Correction Controller, 2003.Applicant
Fairchild Semiconductor, ML4821, Power Factor Controller, Jun. 19, 2001.Applicant
Freescale Semiconductor, AN1965, Design of Indirect Power Factor Correction Using 56F800/E, Jul. 2005.Applicant
International Search Report for PCT/US2008/051072, mailed Jun. 4, 2008.Applicant
Infineon, CCM-PFC Standalone Power Factor Correction (PFC) Controller in Continuous Conduction Mode (CCM), Version 2.1, Feb. 6, 2007.Applicant
International Rectifier, IRAC1150-300W Demo Board, User's Guide, Rev 3.0, Aug. 2, 2005.Applicant
International Rectifier, Application Note AN-1077,PFC Converter Design with IR1150 One Cycle Control IC, rev. 2.3, Jun. 2005.Applicant
International Rectifier, Data Sheet PD60230 revC, Feb. 5, 2007.Applicant
Lu et al., International Rectifier, Bridgeless PFC Implementation Using One Cycle Control Technique, 2005.Applicant
Linear Technology, LT1248, Power Factor Controller, Apr. 20, 2007.Applicant
ON Semiconductor, AND8123/D, Power Factor Correction Stages Operating in Critical Conduction Mode, Sep. 2003.Applicant
ON Semiconductor, MC33260, GreenLine Compact Power Factor Controller: Innovative Circuit for Cost Effective Solutions, Sep. 2005.Applicant
ON Semiconductor, NCP1605, Enhanced, High Voltage and Efficient Standby Mode, Power Factor Controller, Feb. 2007.Applicant
ON Semconductor, NCP1606, Cost Effective Power Factor Controller, Mar. 2007.Applicant
ON Semiconductor, NCP1654, Product Review, Power Factor Controller for Compact and Robust, Continuous Conduction Mode Pre-Converters, Mar. 2007.Applicant
Philips, Application Note, 90W Resonant SMPS with TEA1610 SwingChip, AN99011, 1999.Applicant
NXP, TEA1750, GreenChip III SMPS control IC Product Data Sheet, Apr. 6, 2007.Applicant
Renesas, HA16174P/FP, Power Factor Correction Controller IC, Jan. 6, 2006.Applicant
Renesas Technology Releases Industry's First Critical-Conduction-Mode Power Factor Correction Control IC Implementing Interleaved Operation, Dec. 18, 2006.Applicant
Renesas, Application Note R2A20111 EVB, PFC Control IC R2A20111 Evaluation Board, Feb. 2007.Applicant
STMicroelectronics, L6563, Advanced Transition-Mode PFC Controller, Mar. 2007.Applicant
Texas Instruments, Application Note SLUA321, Startup Current Transient of the Leading Edge Triggered PFC Controllers, Jul. 2004.Applicant
Texas Instruments, Application Report, SLUA309A, Avoiding Audible Noise at Light Loads when using Leading Edge Triggered PFC Converters, Sep. 2004.Applicant
Texas Instruments, Application Report SLUA369B, 350-W, Two-Phase Interleaved PFC Pre-Regulator Design Review, Mar. 2007.Applicant
Unitrode, High Power-Factor Preregulator, Oct. 1994.Applicant
Texas Instruments, Transition Mode PFC Controller, SLUS515D, Jul. 2005.Applicant
Unitrode Products From Texas Instruments, Programmable Output Power Factor Preregulator, Dec. 2004.Applicant
Unitrode Products From Texas Instruments, High Performance Power Factor Preregulator, Oct. 2005.Applicant
Texas Instruments, UCC3817 BiCMOS Power Factor Preregulator Evaluation Board User's Guide, Nov. 2002.Applicant
Unitrode, L. Balogh, Design Note UC3854A/B and UC3855A/B Provide Power Limiting with Sinusoidal Input Current for PFC Front Ends, SLUA196A, Nov. 2001.Applicant
A. Silva De Morais et al., A High Power Factor Ballast Using a Single Switch with Both Power Stages Integrated, IEEE Transactions on Power Electronics, vol. 21, No. 2, Mar. 2006.Applicant
M. Ponce et al., High-Efficient Integrated Electronic Ballast for Compact Fluorescent Lamps, IEEE Transactions on Power Electronics, vol. 21, No. 2, Mar. 2006.Applicant
A. R. Seidel et al., A Practical Comparison Among High-Power-Factor Electronic Ballasts with Similar Ideas, IEEE Transactions on Industry Applications, vol. 41, No. 6, Nov.-Dec. 2005.Applicant
F. T. Wakabayashi et al., An Improved Design Procedure for LCC Resonant Filter of Dimmable Electronic Ballasts for Fluorescent Lamps, Based on Lamp Model, IEEE Transactions on Power Electronics, vol. 20, No. 2, Sep. 2005.Applicant
J. A. Vilela Jr. et al., An Electronic Ballast with High Power Factor and Low Voltage Stress, IEEE Transactions on Industry Applications, vol. 41, No. 4, Jul./Aug. 2005.Applicant
S. T.S. Lee et al., Use of Saturable Inductor to Improve the Dimming Characteristics of Frequency-Controlled Dimmable Electronic Ballasts, IEEE Transactions on Power Electronics, vol. 19, No. 6, Nov. 2004.Applicant
M. K. Kazimierczuk et al., Electronic Ballast for Fluorescent Lamps, IEEETransactions on Power Electronics, vol. 8, No. 4, Oct. 1993.Applicant
S. Ben-Yaakov et al., Statics and Dynamics of Fluorescent Lamps Operating at High Frequency: Modeling and Simulation, IEEE Transactions on Industry Applications, vol. 38, No. 6, Nov.-Dec. 2002.Applicant
H. L. Cheng et al., A Novel Single-Stage High-Power-Factor Electronic Ballast with Symmetrical Topology, IEEE Transactions on Power Electronics, vol. 50, No. 4, Aug. 2003.Applicant
J.W.F. Dorleijn et al., Standardisation of the Static Resistances of Fluorescent Lamp Cathodes and New Data for Preheating, Industry Applications Conference, vol. 1, Oct. 13, 2002-Oct. 18, 2002.Applicant
Q. Li et al., An Analysis of the ZVS Two-Inductor Boost Converter under Variable Frequency Operation, IEEE Transactions on Power Electronics, vol. 22, No. 1, Jan. 2007.Applicant
H. Peng et al., Modeling of Quantization Effects in Digitally Controlled DC-DC Converters, IEEE Transactions on Power Electronics, vol. 22, No. 1, Jan. 2007.Applicant
G. Yao et al., Soft Switching Circuit for Interleaved Boost Converters, IEEE Transactions on Power Electronics, vol. 22, No. 1, Jan. 2007.Applicant
C. M. De Oliviera Stein et al., A ZCT Auxiliary Communication Circuit for Interleaved Boost Converters Operating in Critical Conduction Mode, IEEE Transactions on Power Electronics, vol. 17, No. 6, Nov. 2002.Applicant
W. Zhang et al., A New Duty Cycle Control Strategy for Power Factor Correction and FPGA Implementation, IEEE Transactions on Power Electronics, vol. 21, No. 6, Nov. 2006.Applicant
H. Wu et al., Single Phase Three-Level Power Factor Correction Circuit with Passive Lossless Snubber, IEEE Transactions on Power Electronics, vol. 17, No. 2, Mar. 2006.Applicant
O. Garcia et al., High Efficiency PFC Converter to Meet EN61000-3-2 and A14, Proceedings of the 2002 IEEE International Symposium on Industrial Electronics, vol. 3, 2002.Applicant
P. Lee et al., Steady-State Analysis of an Interleaved Boost Converter with Coupled Inductors, IEEE Transactions on Industrial Electronics, vol. 47, No. 4, Aug. 2000.Applicant
D.K.W. Cheng et al., A New Improved Boost Converter with Ripple Free Input Current Using Coupled Inductors, Power Electronics and Variable Speed Drives, Sep. 21-23, 1998.Applicant
B.A. Miwa et al., High Efficiency Power Factor Correction Using Interleaved Techniques, Applied Power Electronics Conference and Exposition, Seventh Annual Conference Proceedings, Feb. 23-27, 1992.Applicant
Z. Lai et al., A Family of Power-Factor-Correction Controllers, Twelfth Annual Applied Power Electronics Conference and Exposition, vol. 1, Feb. 23, 1997-Feb. 27, 1997.Applicant
L. Balogh et al., Power-Factor Correction with Interleaved Boost Converters in Continuous-Inductor-Current Mode, Eighth Annual Applied Power Electronics Conference and Exposition, 1993. APEC '93. Conference Proceedings, Mar. 7, 1993-Mar. 11, 1993.Applicant
Fairchild Semiconductor, Application Note 42030, Theory and Application of the ML4821 Average Current Mode PFC Controller, Oct. 25, 2000.Applicant
Unitrode Products From Texas Instruments, BiCMOS Power Factor Preregulator, Feb. 2006.Applicant
D. Hausman, Lutron, RTISS-TE Operation, Real-Time Illumination Stability Systems for Trailing-Edge (Reverse Phase Control) Dimmers, v. 1.0 Dec. 2004.Applicant
International Rectifier, Data Sheet No. PD60230 revC, IR1150(S)(PbF), uPFC One Cycle Control PFC IC Feb. 5, 2007.Applicant
Texas Instruments, Application Report SLUA308, UCC3817 Current Sense Transformer Evaluation, Feb. 2004.Applicant
Texas Instruments, Application Report SPRA902A, Average Current Mode Controlled Power Factor Correctiom Converter using TMS320LF2407A, Jul. 2005.Applicant
Unitrode, Design Note DN-39E, Optimizing Performance in UC3854 Power Factor Correction Applications, Nov. 1994.Applicant
Fairchild Semiconductor, Application Note 42030, Theory and Application of the ML4821 Average Currrent Mode PFC Controller, Aug. 1997.Applicant
Fairchild Semiconductor, Application Note AN4121, Design of Power Factor Correction Circuit Using FAN7527B, Rev.1.0.1, May 30, 2002.Applicant
Fairchild Semiconductor, Application Note 6004, 500W Power-Factor-Corrected (PFC) Converter Design with FAN4810, Rev. 1.0.1, Oct. 31, 2003.Applicant
Fairchild Semiconductor, FAN4822, ZVA Average Current PFC Controller, Rev. 1.0.1 Aug. 10, 2001.Applicant
Fairchild Semiconductor, ML4821, Power Factor Controller, Rev. 1.0.2, Jun. 19, 2001.Applicant
Fairchild Semiconductor, ML4812, Power Factor Controller, Rev. 1.0.4, May 31, 2001.Applicant
Linear Technology, 100 Watt LED Driver, undated.Applicant
Fairchild Semiconductor, FAN7544, Simple Ballast Controller, Rev. 1.0.0.Applicant
Fairchild Semiconductor, FAN7532, Ballast Controller, Rev. 1.0.2.Applicant
Fairchild Semiconductor, FAN7711, Ballast Control IC, Rev. 1.0.2.Applicant
Fairchild Semiconductor, KA7541, Simple Ballast Controller, Rev. 1.0.3.Applicant
ST Microelectronics, L6574, CFL/TL Ballast Driver Preheat and Dimming, Sep. 2003.Applicant
ST Microelectronics, AN993, Application Note, Electronic Ballast with PFC Using L6574 and L6561, May 2004.Applicant
International Search Report and Written Opinion for PCT/US2008/062384 dated Jan. 14, 2008.Applicant
S. Dunlap et al., Design of Delta-Sigma Modulated Switching Power Supply, Circuits & Systems, Proceedings of the 1998 IEEE International Symposium, 1998.Applicant
Power Integrations, Inc., “TOP200-4/14 TOPSwitch Family Three-terminal Off-line PWM Switch”, XP-002524650, Jul. 1996, Sunnyvale, California.Applicant
Texas Instruments, SLOS318F, “High-Speed, Low Noise, Fully-Differential I/O Amplifiers,” THS4130 and THS4131, US, Jan. 2006.Applicant
International Search Report and Written Opinion, PCT US20080062387, dated Feb. 5, 2008.Applicant
International Search Report and Written Opinion, PCT US200900032358, dated Jan. 29, 2009.Applicant
Hirota, Atsushi et al, “Analysis of Single Switch Delta-Sigma Modulated Pulse Space Modulation PFC Converter Effectively Using Switching Power Device,” IEEE, US, 2002.Applicant
Prodic, Aleksandar, “Digital Controller for High-Frequency Rectifiers with Power Factor Correction Suitable for On-Chip Implementation,” IEEE, US, 2007.Applicant
International Search Report and Written Opinion, PCT US20080062378, dated Feb. 5, 2008.Applicant
International Search Report and Written Opinion, PCT US20090032351, dated Jan. 29, 2009.Applicant
Erickson, Robert W. et al, “Fundamentals of Power Electronics,” Second Edition, Chapter 6, Boulder, CO, 2001.Applicant
Allegro Microsystems, A1442, “Low Voltage Full Bridge Brushless DC Motor Driver with Hall Commutation and Soft-Switching, and Reverse Battery, Short Circuit, and Thermal Shutdown Protection,” Worcester MA, 2009.Applicant
Texas Instruments, SLUS828B, “8-Pin Continuous Conduction Mode (CCM) PFC Controller”, UCC28019A, US, revised Apr. 2009.Applicant
Analog Devices, “120 kHz Bandwidth, Low Distortion, Isolation Amplifier”, AD215, Norwood, MA, 1996.Applicant
Burr-Brown, ISO120 and ISO121, “Precision Los Cost Isolation Amplifier,” Tucson AZ, Mar. 1992.Applicant
Burr-Brown, ISO130, “High IMR, Low Cost Isolation Amplifier,” SBOS220, US, Oct. 2001.Applicant
International Search Report and Written Report PCT US20080062428 dated Feb. 5, 2008.Applicant
Prodic, A. et al, “Dead Zone Digital Controller for Improved Dynamic Response of Power Factor Preregulators,” IEEE, 2003.Applicant
PCT US2009/051746, International Search Report and Written Opinion dated Sep. 1, 2009.Applicant
PCT US09/51757, International Search Report and Written Opinion dated Aug. 28, 2009.Applicant
“HV9931 Unity Power Factor LED Lamp Driver, Initial Release” 2005, Supertex Inc., Sunnyvale, CA USA.Applicant
AN-H52 Application Note: “HV9931 Unity Power Factor LED Lamp Driver” Mar. 7, 2007, Supertex Inc., Sunnyvale, CA, USA.Applicant
Dustin Rand et al: “Issues, Models and Solutions for Triac Modulated Phase Dimming of LED Lamps” Power Electronics Specialists Conference, 2007. PESC 2007, IEEE, IEEE, P1, Jun. 1, 2007, pp. 1398-1404.Applicant
Spiazzi G et al: “Analysis of a High-Power-Factor Electronic Ballast for High Brightness Light Emitting Diodes” Power Electronics Specialists, 2005 IEEE 36th Conference on Jun. 12, 2005, Piscatawa, NJ USA, IEEE, Jun. 12, 2005, pp. 1494-1499.Applicant
International Search Report PCT/US2008/062381 dated Feb. 5, 2008.Applicant
International Search Report PCT/US2008/056739 dated Dec. 3, 2008.Applicant
Written Opinion of the International Searching Authority PCT/US2008/062381 dated Feb. 5, 2008.Applicant
Ben-Yaakov et al, “The Dynamics of a PWM Boost Converter with Resistive Input” IEEE Transactions on Industrial Electronics, IEEE Service Center, Piscataway, NJ, USA, vol. 46, No. 3, Jun. 1, 1999.Applicant
International Search Report PCT/US2008/062398 dated Feb. 5, 2008.Applicant
Partial International Search PCT/US2008/062387 dated Feb. 5, 2008.Applicant
Noon, Jim “UC3855A/B High Performance Power Factor Preregulator”, Texas Instruments, SLUA146A, May 1996, Revised Apr. 2004.Applicant
“High Performance Power Factor Preregulator”, Unitrode Products from Texas Instruments, SLUS382B, Jun. 1998, Revised Oct. 2005.Applicant
International Search Report PCT/GB2006/003259 dated Jan. 12, 2007.Applicant
Written Opinion of the International Searching Authority PCT/US2008/056739.Applicant
International Search Report PCT/US2008/056606 dated Dec. 3, 2008.Applicant
Written Opinion of the International Searching Authority PCT/US2008/056606 dated Dec. 3, 2008.Applicant
International Search Report PCT/US2008/056608 dated Dec. 3, 2008.Applicant
Written Opinion of the International Searching Authority PCT/US2008/056608 dated Dec. 3, 2008.Applicant
International Search Report PCT/GB2005/050228 dated Mar. 14, 2006.Applicant
International Search PCT/US2008/062387 dated Jan. 10, 2008.Applicant
Data Sheet LT3496 Triple Output LED Driver, 2007, Linear Technology Corporation, Milpitas, CA.Applicant
News Release, Triple Output LED, LT3496.Applicant