LED lighting fixtures

[0001] This application claims the benefit of U.S. provisional application Ser. No. 60/721,018, filed Sep. 27, 2005, the entire subject matter of which is hereby incorporated by reference.

[0002] The present invention generally relates to lighting fixtures of any type. The present invention specifically relates to mechanically enclosing light emitting diode (“LED”) modules within lighting fixtures.

[0003] FIGS. 1-4 illustrate general views of known lighting fixtures 20-23. Typically, incandescent lamps are used in lighting fixtures 20-23 with a power generally in a range of twenty (20) watts to fifty (50) watts. The present invention is based on a discovery that mechanically enclosing LED modules within lighting fixtures 20-23 can provide numerous benefits over the present day use of incandescent lamps in lighting fixtures 20-23. For example, a general lifetime for a LED module of 50,000 hours is significantly greater than a maximum lifetime achievable by an incandescent lamp. Further, LED modules can be designed to use between five (5) watts and fifteen (15) watts of power, which is considerably less than the power range of incandescent lamps. Additionally, a lower operation temperature is achievable with LED modules.

[0004] Based on this discovery, the present invention is a lighting apparatus comprising a LED module mechanically enclosed within a lighting fixture (e.g., lighting fixtures 20-23 shown in FIGS. 1-4).

[0005] In a first form of the present invention, the LED module includes one or more LEDs and a LED driver (a.k.a., a LED ballast) in electrical communication with the LED(s) to operably provide a LED drive signal to the LED(s). The LED module further includes a thermal sensor operable to facilitate a control by the LED driver of a magnitude of the LED drive signal based on an operating temperature of the LED(s) as sensed by the thermal sensor.

[0006] In a second form of the present invention, the LED module includes one or more LEDs mounted on a thermal management system in thermal communication with the lighting fixture to facilitate heat transfer from the LED(s) to the lighting fixture.

[0007] In a third form of the present invention, the LED module includes an LED emitting a radiation beam having an illumination profile and a beam shaper in optical communication with the LED to modify the illumination profile of the emitted radiation beam. The beam shaper includes one or more optical components optically aligned with the LED(s) to thereby modify the illumination profile of the radiation beam emitted by the LED(s). The beam shaper further includes one or more heat shrink tubes fitted around the optical component(s) to securely maintain the optical alignment of the optical component(s) with the LED(s).

[0018] A LED module 30 as shown in FIG. 5 employs LED(s) 40, a LED driver/ballast 50, a thermal management system 60 and a beam shaper 70. LED(s) 40 (e.g., Luxeon LEDs) can be embodied as a single LED of any color, or as a series coupling of LEDs of any color combination, a parallel coupling of LEDs of any color combination or any coupling combination thereof.

[0019] LED driver/ballast 50 is structurally configured to electrically communicate a N number of LED drive signals I_DS to LED(s) 40 in dependence upon the structural configuration of LED(s) 40 as would be appreciated by those having ordinary skill in the art. In practice, each structural configuration of a LED driver/ballast 50 of the present invention is dependent upon its commercial implementation. Thus, the present invention does not impose any limitations or any restrictions to each structural configuration of LED driver/ballast 50 of the present invention. In one embodiment, LED driver/ballast 50 includes a converter 51 as shown in FIG. 5 for converting an incoming AC signal into the N number of LED drive signals I_DS. To control an illumination intensity of LED(s) 40, LED driver/ballast can further include a dimmer 52, a thermal sensor 53 and/or an optical sensor 54 as shown in FIG. 5.

[0020] Dimmer 52 facilitates a control by converter 51 of a magnitude of the LED drive signal(s) I_DS based on dimming control signal(s) as would be appreciated by those having ordinary skill in the art. Thermal sensor 53 facilitates a control by converter 51 of a magnitude of the LED drive signal(s) I_DS based on an operating temperature of LED(s) 40 as sensed by thermal sensor 53.

[0021] Optical sensor 54 facilitates a control by converter 51 of a magnitude of the LED drive signal(s) I_DS based on an illumination level of an ambient light exterior to the lighting fixture as sensed by optical sensor 54 (e.g., controlling a powering ON and OFF of LEDs (40) based on whether the optical sensor 54 senses daytime light or nighttime light ambient to the exterior of the lighting fixture).

[0022] FIG. 6 illustrates an embodiment 151 of converter 51 (FIG. 5). Referring to FIG. 6, converter 51 is operated based on a buck converter U1 in the form of a L4976, 1A step down switching regulator having a voltage doubling input. Buck converter U1 has a pin 2 GND connected to a ground node N4, a pin 3 REF connected to a node N5, a pin 4 OSC connected to a node N6, a pair of pins 5 and 6 OUT connected to a node N9, a pin 11 VCC connected to a node N3, a pin 12 BOOT connected to a capacitor C8, a pin 13 COMP connected to a capacitor C7 and a pin 14 FB connected to a node N7.

[0023] Converter 151 further includes a fuse F1 connected to one input terminal and a node N1. A capacitor C1 (e.g., 1 μF) connected to node N1 and a node N2. A diode D1 (e.g., 60V 3A) connected to node N1 and node N3. A diode D2 (e.g., 60V 3A) connected to node N1 and node N4. A capacitor C2 (e.g., 1000 μF) connected to node N3 and node N2. A capacitor C3 (e.g., 1000 μF) connected to node N2 and node N4. A capacitor C4 (e.g., 100 ηF) connected to node N3 and node N4.

[0024] A capacitor C5 (e.g., 1 ηF) and a resistor R1 (e.g., 39 kΩ) connected in parallel to node N3 and node N6. A capacitor C6 (e.g., 100 ηF) connected to node N4 and node N5. Capacitor C7 (e.g., 47 ηF) further connected to node N4. A resistor R2 (e.g., 10.5 kΩ) connected to node N5 and node N7. A resistor R3 (e.g., 18 kΩ) connected to node N7 and a node N8. A resistor R4 (e.g., 2Ω), a resistor R5 (e.g., 2Ω), a resistor R6 (e.g., 2Ω) and a resistor R7 (e.g., 2Ω) connected in parallel to node N4 and node N8.

[0025] Capacitor C8 (e.g., 100 ηF) is further connected to node N9. A diode D3 (e.g., 60V 3A) connected to node N9 and node N4. An inductor L1 (e.g., 220 μH) connected to node N9 and a node N10. A capacitor C9 (e.g., 1 μF) connected to node N10 and node N4.

[0026] In one alternate embodiment, diode D3 is omitted and LED(s) 40 are connected to node N9 and N3 to thereby facilitate buck converter U1 operation as a step down switch regulator.

[0027] In another alternative embodiment, capacitors C2 and C3 are omitted and converter 151 is transformed into buck/boost configuration as would be appreciated by those having ordinary skill in the art.

[0028] FIG. 7 illustrates an embodiment 251 of converter 151 (FIG. 6) additionally employing a resistor R9 (e.g. 14 kΩ) and a thermistor TM1 (e.g., PTC) connected in series to node N7 and node N8, changing the value of resistor R2 (e.g., 1200Ω) and resistor R3 (e.g. 2.43 kΩ). Thermistor TM1 is strategically located relative to LED(s) 40 to sense, directly or indirectly, an operating temperature of LED(s) 40 as will be further explained herein in connection with FIGS. 9-12. Further, thermistor TM1 provides feedback to buck converter U1 indicative of the operating temperature of LED(s) 40 as sensed by thermistor TM1.

[0029] FIG. 8 illustrates an embodiment 351 of converter 151 (FIG. 6) additionally employing a resistor R10 connected to node N4 and a node N1. A thermistor TM2 is connected to node N5 and node N1. A PNP transistor Q1 having an emitter connected to node N5, a base connected to node N11, and a collector connected to a resistor R11, which is further connected to node N7. Thermistor TM2 is strategically located relative to LED(s) 40 to sense, directly or indirectly, an operating temperature of LED(s) 40 as will be further explained herein in connection with FIGS. 9-12. Further, thermistor TM2 provides feedback to buck converter U1 indicative of the operating temperature of LED(s) 40 as sensed by thermistor TM2 and transistor Q1 enhances this feedback as would be appreciated by those having ordinary skill in the art.

[0030] Referring again to FIG. 5, thermal management system 60 is structurally configured to serve as a mount for LED(s) 40 and LED driver/ballast 50 that transfers heat away from LED(s) 40 and LED driver/ballast 50 in a direction toward an interior of the lighting fixture. In practice, each structural configuration of a thermal management system 60 of the present invention is dependent upon its commercial implementation. Thus, the present invention does not impose any limitations or any restrictions to each structural configuration of a thermal management system 60 of the present invention. In one embodiment, thermal management system 60 employs a metal-core printed circuit board (“MCPCB”) 61 integrated with a heat sink 62 as shown in FIG. 5. MCPCB 61 may have a vertical connector, forward or reverse or a horizontal connector in any direction for powering the LED(s) 40 and/or LED driver/ballast 50 mounted thereon.

[0031] FIGS. 9 and 10 illustrate one embodiment 160 of thermal management system 60 (FIG. 5). Specifically, thermal management system 160 employs a MCPCB 161 having LED(s) 40, LED driver/ballast 50 and a reverse vertical connector 165 mounted on a top side thereof. If employed in LED driver/ballast 50, a thermal sensor in the form of thermistor TM1 (FIG. 7) or thermistor TM2 (FIG. 8) can be placed as close as possible to LED(s) 40 to directly sense the operating temperature of LED(s) 40 or anywhere else on MCPCB 161 to indirectly sense the operating temperature of LED(s) 40 as heat from LED(s) 40 is conducted by MCPCB 161 to the thermal sensor.

[0032] MCPCB 161 is aligned and integrated with a heat sink 162 having an inverted cup-shape with a cavity 163. A through-hole 164 bored through MCPCB 161 and heat sink 162 is below reverse vertical connector 165 facilitates a power connection to reverse vertical connector 165 from the bottom side of MCPCB 161 via heat sink 162. Reverse vertical connector 164 can be securely anchored to the top side of MCPCB 161 to reduce any stress on reverse vertical connector 164 when being connected to a power source (not shown). An asphalt potting or equivalent can be inserted within cavity 163 subsequent to the power connection of reverse vertical connector 164 to facilitate a reduction in the temperature of the LED module, spread the heat more equally in the LED module and to provide strain relief to the power wire connection.

[0033] In an alternate embodiment, a forward vertical connector or a horizontal connector can be substituted for reverse vertical connector 165. In such a case, the substituted connector will be offset from through-hole 164 to facilitate a running of the wires within through-hole 164 or in a gap between the lighting fixture and heat sink 162.

[0034] FIGS. 11 and 12 illustrate an embodiment 260 of thermal management system 60 (FIG. 5). Thermal management system 260 includes a FR4 printed circuit board (“PCB) 166 disposed within cavity 163 of heat sink 162 whereby a power connection is made to reverse vertical connector 165 from FR4 PCB 166. In this embodiment, an entirety of LED driver/ballast 50 can be mounted on FR4 PCB 166 as shown or LED driver/ballast 50 can be distributed between MCPCB 161 and FR4 PCB 166. For example, if employed in LED driver/ballast 50, a thermal sensor in the form of thermistor TM1 (FIG. 7) or thermistor TM2 (FIG. 8) can be mounted on MCPCB 161 and placed as close as possible to LED(s) 40 to thereby directly sense the operating temperature of LED(s) 40 or mounted on FR4 PCB 166 to indirectly sense the operating temperature of LED(s) 40 via the potting material in heat sink cavity 163.

[0035] FIG. 13 illustrates an exemplary mechanical enclosure of a LED module 130 with lighting fixture 20 (FIG. 1) based on the inventive principles of the present invention previously discussed herein. LED module 130 can be mounted within lighting fixture 20 by any means as would be appreciated by those having ordinary skill in the art. Additionally, an exterior of LED module 130, particularly the heat sink, should be as close as possible to an interior of lighting fixture 20 to facilitate a low thermal resistive path for heat transfer from LED module 130 to the exterior of lighting fixture 20. Additionally, to supplement the low thermal resistive path within the minimal gap between the exterior of LED module 130 and the interior of lighting fixture 20, a material 180 having a low thermal resistance than air (e.g., thermal grease, thermal pads, and potting material) can be inserted within the minimal gap as shown.

[0036] Referring again to FIG. 5, beam shaper 70 is structurally configured to modify the illumination profile of a radiation beam emitted from LED(s) 40, such as, for example, increase the size of the profile, decrease the size of the profile, and focus the profile in a particular direction or direction(s). This is particularly important for lighting fixtures having a physical structure that may produce shadows in the illumination profile of LED(s) 40, such as, for example, lighting fixture 20-23 shown in FIGS. 1-4, respectively.

[0037] In practice, each structural configuration of a beam shaper 70 of the present invention is dependent upon its commercial implementation. Thus, the present invention does not impose any limitations or any restrictions to each structural configuration of a beam shaper 70 of the present invention. In one embodiment, beam shaper 70 employs an optical diffuser 71 and/or a transparent plate 72 for each LED 40 or a grouping of LED(s) 40 where each optical diffuser 71/transparent plate 72 is a stand-alone optical component or is integrated with another optical component (e.g., a lens). Additionally, one or more pieces of heat shrink tubing 73 can be used as a basis for maintaining an optical alignment of optical diffuser 71 and/or transparent plate 72 to a LED 40 or a grouping of LED(s) 40. Heat shrink tubing 73 further provides protection against the environment by sealing all the gaps between the other components of beam shaper 70.

[0038] FIG. 14 illustrates an embodiment 170 of beam shaper 70. Beam shaper 170 employs a lens collimator 175 optically aligned with a LED 40, both of which are mounted in a lens holder 174. An optical diffuser 171 is positioned above the upper opening of lens collimator 175, and a transparent plate 172 of the lighting fixture, glass and/or plastic, is positioned above diffuser 171. A piece of heat shrink tubing 173 is used to couple and align all of the illustrated components. Specifically, heat shrink tubing 173 is initially loosely fitted around the other optical components of beam shaper 170 as shown in FIG. 15 whereby an application of appropriate degree of heat as would be appreciated by those having ordinary skill in the art will cause heat shrink tubing 173 to shrink to thereby tightly fit around the other optical components of beam shaper 170 to maintain the optical alignment of the other optical components of beam shaper 170 to LED 40 as well as protect these components from the environment. To enhance the tight fit of heat shrink tubing 173 around the other optical components, plate 172 can include a cylindrical extension 176 as represented by a dotted outline.

[0039] Referring to FIGS. 5-14, the inventive principles of the present invention were shown and described in connection with fitting lighting fixtures 20-23 (FIGS. 1-4) with LED modules to facilitate an understanding of the various inventive principles of the present invention. From these illustrations and descriptions, those having ordinary skill in the art will appreciate how to apply the various inventive principles of the present invention to of lighting fixtures other than lighting fixtures 20-23

[0040] While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.