Smart integrated semiconductor light emitting system including light emitting diodes and application specific integrated circuits (ASIC)

[0001] This invention relates generally to light emitting diodes (LED) and more particularly to systems incorporating light emitting diodes (LEDs).

[0002] Light emitting diodes (LEDs) are used in a wide range of electronic devices such as displays, communication devices, and lamps. Advances in LED technology have improved the efficiency and service life of light emitting diodes (LEDs), and have made them smaller and lighter. However, most advances have been directed to the structure and function of the light emitting diodes (LEDs), rather than the associated LED systems. Light emitting diodes (LEDs) are typically part of a LED system that includes driver circuitry and associated electronic devices such as resistors, capacitors, diodes and circuit boards.

[0003] FIG. 1 illustrates a prior art LED circuit 10. The prior art LED system 10 includes a LED driver IC 12, and two light emitting diode (LED) chips 14 in electrical communication with the LED driver IC chip 12. The LED driver IC 12 is configured to provide driver and functionality circuits for the light emitting diode (LED) chips 14. The LED driver IC 12 includes a VIN pin, a SEN pin, a DIM pin, a SW pin and a GND pin. The LED system 10 also includes various electronic components including resistors, capacitors, a Schottky diode, and an inductor configured substantially as shown. The LED system 10 requires a relatively complex manufacturing process to mount and interconnect all of the electronic elements. In addition, relatively large amounts of current and power are required to drive the electronic elements, which generates a large amount of heat.

[0004] In view of the foregoing, improved LED systems are needed in the art, which are more efficient than prior art LED systems. However, the foregoing examples of the related art and limitations related therewith, are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

[0029] Referring to FIG. 2, a LED system 30 includes a substrate 32, a light emitting diode (LED) 34 mounted to the substrate 32, and an application specific integrated circuit (ASIC) die 36 mounted to the substrate 32 in electrical communication with light emitting diode (LED) 34. The substrate 32 functions as a mounting substrate, and also provides functionality for operating the light emitting diode (LED) 34 and the application specific integrated circuit (ASIC) die 36 as an integrated assembly. The light emitting diode (LED) 34 can comprise a conventional LED fabricated using known processes. Suitable light emitting diodes (LEDs) are commercially available from SEMILEDS, INC. located in Boise Id., and Miao-Li County, Taiwan, R.O.C. The application specific integrated circuit (ASIC) die 36 can comprise a semiconductor die having application specific integrated circuits 38 formed therein.

[0030] As shown in FIG. 2, the substrate 32 includes a front side (circuit side) having conductors 40 formed thereon, which electrically connect the application specific integrated circuit (ASIC) die 36 to the light emitting diode (LED) 34. As will be further explained, the application specific integrated circuit (ASIC) die 36 and the light emitting diode (LED) 34 can be mounted to the substrate using a suitable technique such as flip chip or C4 bonding. The substrate 32 can comprise silicon, or another semiconductor material such as gallium arsenide, and the conductors 40 can be fabricated using well known semiconductor fabrication processes. Alternately, the substrate 32 can comprise a ceramic material, a printed circuit board (PCB) material, a metal core printed circuit board (PCB), an FR-4 printed circuit board (PCB), a metal lead frame, an organic lead frame, a silicone submount substrate, or any packaging substrate used in the art.

[0031] The substrate 32 can have any polygonal shape (e.g., square, rectangular) and any suitable size. In addition, the substrate 32 can be die-sized, such that the LED system 30 has a chip scale size similar to that of a chip scale package (CSP) or a system on a chip (COS). Alternately, the substrate 32 can be wafer sized such that a wafer scale system is provided.

[0032] Referring to FIG. 3, an alternate embodiment LED system 30A is substantially similar to the LED system 30 (FIG. 2), but includes a substrate 32A configured to provide additional electrical functionality. In particular, the substrate 32A comprises a semiconductor material having a segment 42 formed with application specific integrated circuits (ASICs) 44 configured to perform additional electrical functions. The application specific integrated circuits (ASICs) 44 can include semiconductor components, circuits, and base materials integrated into the substrate 32A. For example, the application specific integrated circuits (ASICs) 44 can include resistors, diodes (p-n), capacitors, gates, metal-oxide field effect transistors (MOSFET), and flip flops. The application specific integrated circuits (ASICs) 44 can be combined with the integrated circuits in the application specific integrated circuit (ASIC) die 36 to provide smart on-board control of the light emitting diode (LED) 34.

[0033] The semiconductor substrate 32A can comprise a portion of a semiconductor wafer having the application specific integrated circuits (ASICs) 44 formed therein using conventional semiconductor fabrication techniques such as implanting, photopatterning. The light emitting diode (LED) 34 can be mounted to a blank portion of the substrate 32A spaced from the application specific integrated circuits (ASICs) 44, and electrically connected to the application specific integrated circuits (ASICs) 44 using suitable connecting elements and interconnects.

[0034] As shown in FIG. 4, the substrate 32 or 32A includes a back side 48 having an array of contacts 46 in electrical communication with the application specific integrated circuit (ASIC) die 36 (FIG. 2), and with the application specific integrated circuits (ASICs) 44 (FIG. 3). The contacts 46 function as the terminal contacts for connecting the LED system 30 (FIG. 2) or 30A (FIG. 3) to the outside world. The contacts 46 can comprise bumps or pads made of a bondable material such as solder, metal or a conductive polymer, configured for bonding to corresponding electrodes on a module substrate, circuit board or other support substrate. In addition, the contacts 46 can be arranged in a suitable dense area array, such as a ball grid array (BGA) or fine ball grid array (FBGA). Further, the contacts 46 can be electrically connected to the application specific integrated circuit (ASIC) die 36 (FIG. 2) and to the application specific integrated circuits (ASICs) 44 (FIG. 3) using suitable elements, such as interconnects, conductive traces, redistribution conductors and conductive vias formed on the substrate 32 or 32A.

[0035] The contacts 46 can be configured to integrate and expand the electrical functions of the application specific integrated circuit (ASIC) die 36 (FIG. 2), the application specific integrated circuits (ASICs) 44 (FIG. 3), and the light emitting diode (LED) 34 (FIG. 2), and to provide smart control for the LED system 30 (FIG. 2) or 30A (FIG. 3). For example, the contacts 44 can be configured as: a.) multi purpose input-output ports; b.) power inputs (AC or DC) for driving the LED system 30 or 30A; c.) dimming control ports; d.) current setting ports; e.) feedback sensor ports; f.) communication ports; and g.) common ground ports.

[0036] Referring to FIGS. 5, 5A and 5B, an exemplary mounting arrangement for mounting the light emitting diode (LED) 34 and the application specific integrated circuit (ASIC) die 36 to the substrate 32 in LED system 30 are illustrated. In FIG. 5A, the LED chip 34 has a p-, n-same side configuration and is mounted in a chip-on-board (COB) configuration using interconnects 50, and a flip chip bonding method such as C4 (controlled collapse chip connection). Similarly, the application specific integrated circuit (ASIC) die 36 includes interconnects 52 and is flip chip mounted to the substrate 32 in a chip on board configuration. In FIG. 5B, the LED chip 34 has a p-, n-different side configuration and is mounted to the substrate 32 using a die attach bonding layer 54 (e.g., solder, silver epoxy), and a wire bonded wire 56 bonded to contacts on the LED chip 34 and the substrate 32.

[0037] Referring to FIGS. 6, 6A and 6B, an exemplary mounting arrangement for mounting the light emitting diode (LED) 34 and the application specific integrated circuit (ASIC) die 36 to the substrate 32A in LED system 30A are illustrated. In FIG. 6A, the LED chip 34 has a p-, n-same side configuration and is mounted in a chip-on-board (COB) configuration using interconnects 50, and a flip chip bonding method such as C4 (controlled collapse chip connection). The application specific integrated circuit (ASIC) die 36 can be flip chip mounted to the application specific integrated circuits 44 on the substrate 32A in a chip on board configuration substantially as previously described. In FIG. 6B, the LED chip 34 has a p-, n-different side configuration and is mounted to the substrate 32A using a die attach bonding layer 54 (e.g., solder, silver epoxy), and a wire bonded wire 56 bonded to contacts on the LED chip 34 and the substrate 32A.

[0038] Referring to FIGS. 7 and 7A, an exemplary electrical configuration for the application specific integrated circuit (ASIC) die 36 and the light emitting diode (LED) 34 for the LED system 30 or 30A are illustrated. As shown in FIG. 7A, the light emitting diode (LED) 34 can be electrically connected via the conductors 40 to ground pins on the application specific integrated circuit (ASIC) die 36. Alternately, the light emitting diode (LED) 34 can be connected to a dedicated ground pin on the substrate 32 or 32A.

[0039] Referring to FIGS. 8 and 8A, the LED system 30 or 30A can also include multiple light emitting diodes (LEDs) 34A-34D mounted directly to the substrate 32 or 32A. The light emitting diodes (LEDs) 34A-34D can all be configured to produce the same wavelengths and colors of light (e.g., red, green, blue, white, UV, laser, IR), or can be configured to produce different combinations thereof. For example, a first light emitting diode (LED) 34A can produce white light, a second light emitting diode (LED) 34B can produce green light, a third light emitting diode (LED) 34C can produce blue light, and a fourth light emitting diode (LED) 34D can produce red light. In addition, the application specific integrated circuit (ASIC) die 36, and the application specific integrated circuits 44 (FIG. 3) can be adapted to provide smart color control for the light emitting diodes (LEDs) 34A-34D. As shown in FIG. 8A, the light emitting diodes (LEDs) 34A-34D can be electrically connected in series and grounded to ground pins on the application specific integrated circuit (ASIC) die 36. Alternately, the light emitting diodes (LEDs) 34A-34D can be connected to a dedicated ground pin on the substrate 32 or 32A.

[0040] Referring to FIGS. 9 and 9A, the LED system 30 or 30A can also include multiple light emitting diodes (LEDs) 34A-34D electrically connected in parallel. As another alternative, the light emitting diodes (LEDs) 34A-34D can be electrically connected in multiple parallel strings with each string containing a plurality of light emitting diodes (LEDs) 34 connected in series.

[0041] Referring to FIGS. 10, 10A and 10B, electrical characteristics of the LED system 30 or 30A are illustrated. FIG. 10 illustrates an input/output configuration 44 for the application specific integrated circuit (ASIC) die 36. In general, the input/output configuration and the application specific integrated circuits of the application specific integrated circuit (ASIC) die 36 are configured to integrate the light emitting diode 34 and the application specific integrated circuit (ASIC) die 36 into an integrated assembly. FIG. 10A illustrates an output configuration for the application specific integrated circuit (ASIC) die 36 with a string of light emitting diodes (LED) 34 electrically connected in series to ground. FIG. 10B illustrates an output configuration for the application specific integrated circuit (ASIC) die 36 with a single light emitting diode (LED) 34 electrically connected to ground.

[0042] Table 1 describes the input port configuration for the application specific integrated circuit (ASIC) die 36.

[0043]

TABLE 1
INPUT PORT CONFIGURATION
PORT	PORT DESCRIPTION
Vin	Power Source input for LED Systems. Power input is enable for:
	a)	DC Voltage
		Range 1.5 VDC-60 VDAC
	a)	AC Voltage
		Range 90 VAC-264 VAC/50 Hz-60 Hz
DIM	This is dimming input control port. Dimming is allowed from
	0% to 100% brightness. Allow dimming type:
	a)	OVDC to 10 VDC Type Method
	b)	Pulse Width Modulation
	c)	Convention Triac Dimmer
SEN	This port has 2 functions
SPI EN	1)	Constant Current Output to LED setting.
	2)	Enable Serial Write to Flash/ROM for White Balance
		Setting
SW	This port is to use for Soft Turn ON/OFF purpose
A/D	This port has 2 functions:
SPI	1)	Multi-purpose A/D
		When SPI En is disable, A/D port function will be enable
	2)	SPI
		When SPI EN Port is Enable, LED Brightness Tuning/
		White Balance Parameter can be burn into Flash/ROM
GDN	Common

[0044] Some features of LED system 30 or 30A include:

• • [0045] Adjustable LED (load) current
  • [0046] LED Output port current can be scaled to multiple ratio for the purpose of:
    • [0047] White Balancing (for White or RGB applications) or White Color Coordinate Tuning
    • [0048] Brightness Calibration
  • [0049] Soft Turn On-Off
  • [0050] Dimmable
    • [0051] Dimming—PWM
    • [0052] Dimming—0-10V
    • [0053] Dimming—TRAC
  • [0054] Failsafe System
    • [0055] Build in Safety Protection
    • [0056] Over Temperature when Tj>150° C.
    • [0057] Over Voltage/Overload
    • [0058] Under voltage lockout
    • [0059] Reverse polarity protection

[0060] Referring to FIGS. 11A-11C, different packaging configurations for the LED system 30 or 30A are illustrated. In FIG. 11A, an LED package 58A includes the substrate 32 or 32A, the application specific integrated circuit (ASIC) die 36, and the light emitting diode (LED) 34, substantially as previously described. In addition, the light emitting diode (LED) 34 can include a phosphor layer 60 for producing white light. The LED package 58A also includes a polymer lens 66 on the substrate 32 or 32A, which encapsulates the LED system 30 or 30A. The polymer lens 66 can comprise a suitable polymer such as epoxy formed by molding or other suitable process.

[0061] In FIG. 11B, an LED package 58B includes the substrate 32 or 32A, the application specific integrated circuit (ASIC) die 36, and the light emitting diode (LED) 34, substantially as previously described. The LED package 58A also includes a polymer lens 66 on the substrate 32 or 32A which encapsulates the LED system 30 or 30A. In this embodiment, the polymer lens 66 also includes a phosphor layer 62 for producing white light.

[0062] In FIG. 11C, an LED package 58C includes the substrate 32 or 32A, the application specific integrated circuit (ASIC) die 36, and the light emitting diode (LED) 34, substantially as previously described. In this embodiment, the substrate 32 or 32A also includes a reflective recess 64 wherein the application specific integrated circuit (ASIC) die 36, and the light emitting diode (LED) 34 are mounted.

[0063] Referring to FIG. 12 an electrical schematic of an LED integrated circuit 68 formed by the LED system 30 or 30A is illustrated. The LED integrated circuit 68 includes the contacts 46 on the substrate 32 or 32A. The LED integrated circuit 68 can also include the application specific integrated circuits 44 on the substrate 32A. The LED integrated circuit 68 also includes the application specific integrated circuits 38 in the application specific integrated circuit (ASIC) die 36. The LED integrated circuit 68 also includes the light emitting diode 34. Because the LED integrated circuit 68 has integrated elements power consumption and heat generation are less than with the prior art LED circuit 10 (FIG. 1). In addition, the LED system 30 or 30A can be made smaller such that a chip scale system can be provided.

[0064] Thus the disclosure describes improved LED systems. While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.