TWI729540B - Led driver and illumination system related to the same - Google Patents

Abstract

Herein disclosed is a driver for driving a light-emitting device. The driver includes a rectifier, a power factor corrector, and a current driver. The rectifier has at least one rectifying diode connected to an alternating-current input power source to generate a direct-current power source across a DC power line and a ground power line. The power factor corrector corrects the power factor of the current driver, and includes several diodes reversely connected in series between the DC and ground power lines. The current driver has at least one constant current source connected in series with the light emitting device between the DC and ground power lines. The constant current source is capable of providing a constant current to drive the light emitting device. The rectifying diode, the diodes, and the constant current source are commonly formed on one single semiconductor chip.

Description

Drivers of light-emitting diodes and related lighting systems

The present invention relates to a driver for driving a light emitting diode and a related lighting system, especially a driver and lighting system with a good power factor and a simple structure.

In recent years, due to good electro-optical conversion efficiency and small product volume, light emitting diodes have gradually replaced cathode lamps or tungsten filaments as the light source of backlights or lighting systems. However, because of the voltage and current characteristics of the light-emitting diode (about 3 volts, DC drive), the AC input power of general commercial power cannot directly drive the light-emitting diode, but a power converter is needed to convert the AC input power into a proper DC power supply.

Lighting electricity often occupies a very large part of the mains power supply. Therefore, for the power converter used in lighting, in addition to the very low conversion loss required by regulations, it must also provide a good power factor, which is between 0 and 1. The closer the power factor of an electronic device is to 1, the closer the electronic device is to the resistive load.

FIG. 1 shows a conventional lighting system 10, which includes a bridge rectifier 12, a power factor corrector 14, an LED driving circuit 16, and an LED 18. The power factor corrector 14 may be a booster circuit, and the LED driving circuit 16 may be a buck converter. However, a switching power converter such as a boost circuit or a step-down circuit not only requires a very large and expensive inductance element, but also requires a lot of electronic components for the entire system architecture. Therefore, the production cost of a lighting system using a switching power converter will be relatively uncompetitive in the market.

The embodiment discloses a driver for driving a light-emitting element, including a rectifier circuit, a power factor corrector, and a current driving circuit. The rectifier circuit includes at least one rectifier diode, which is electrically connected to an AC input power source to generate a DC power source, which straddles the DC power line and a ground line. The power factor corrector is used to correct the power factor of the driver, and includes a plurality of first diodes connected in reverse series between the DC power line and the ground line. The current drive circuit includes at least a certain current source. The constant current source and the light-emitting element are connected in series between the DC power line and the ground line. The constant current source can provide a certain current to drive the light-emitting element. The rectifier diode, the first diode, and the constant current source are jointly formed on a single semiconductor chip.

The embodiment discloses a lighting system including a single semiconductor chip, a first capacitor, a second capacitor, and a light emitting diode. A single semiconductor chip is packaged in an integrated circuit. The integrated circuit has a first drive pin and a second drive pin, two AC input pins, a high voltage pin, a low voltage pin, first and second power factor correction pins. The first capacitor is electrically connected between the high voltage pin and the first power factor correction pin, and the second capacitor is electrically connected between the low voltage pin and the second power factor correction pin. The light emitting diode is electrically connected between one of the high voltage pin and the low power pin and the first driving pin. The AC input pin is used for electrically connecting to an AC input power source.

In this specification, there are some identical symbols, which indicate components with the same or similar structure, function, and principle, and those with general knowledge in the industry can infer it based on the teaching of this specification. For the sake of simplicity in the description, the elements with the same symbols will not be repeated.

In an embodiment of the present invention, the entire LED lighting system has a simple circuit design, and the main components are only an integrated circuit packaged with a single semiconductor chip, two capacitors, and an LED as a light source. The LED lighting system in the embodiment may not need to connect additional inductance elements. Therefore, the circuit cost of the LED lighting system will be quite low. In addition, the LED lighting system in the embodiment also provides a fairly good power factor, which can meet the requirements of most specifications.

FIG. 2 shows an LED driver 60 according to an embodiment of the present invention, which can be used to drive the LED 18. The LED 18 may be a high-voltage LED, which is composed of many micro LEDs (micro LEDs) connected in series. For example, in one embodiment, the forward voltage of each micro LED is about 3.4 volts, and the LED 18 is formed by connecting more than 10 micro LEDs in series, and its equivalent forward voltage is about 50V.

The LED driver 60 roughly has three stages. The first stage connected to the AC input power V _AC-IN is a bridge rectifier 62. The second stage is a valley-fill circuit 64, as a power factor corrector, which can improve the power factor of the entire LED driver 60. The third stage has two high electron mobility transistors (HEMT) T1 and T2 as the current driving circuit 66 to provide a certain current to drive the LED 18.

The bridge rectifier 62 includes four rectifying diodes DB1-DB4. The bridge rectifier 62 rectifies the AC input power V _AC-IN to generate the DC power V _DC-IN across the DC power line VDD and the ground line GND. For example, the AC input power source V _AC-IN may be 110VAC or 220VAC provided by general commercial power.

The valley filling circuit 64 is electrically connected between the DC power line VDD and the ground line GND, and includes three diodes DVF1-DVF3 and capacitors C1 and C2. The diodes DVF1-DVF3 are reversely connected in series between the DC power line VDD and the ground line GND. In this embodiment, the capacitance values of the capacitors C1 and C2 are approximately equal, but the invention is not limited to this. It can be inferred from the circuit theory that the capacitor voltages V _C1 and V _{C2 of the capacitors C1 and C2} can be charged to approximately half of the peak voltage V _{PEAK of the DC power supply V DC-IN} (0.5*V _PEAK ). When the absolute value of the voltage of the AC input power V _{AC-IN is lower than 0.5*V PEAK} , the capacitors C1 and C2 can discharge the DC power line VDD and the ground line GND. As long as the capacitors C1 and C2 are large enough, the valley filling circuit 64 can make the minimum voltage of _{the DC power supply V DC-IN approximately equal to 0.5V PEAK} , and provide enough voltage to make the LED 18 continue to emit light.

Both HEMT T1 and T2 are depletion mode transistors, which means that their threshold voltage (V _TH ) is both negative. The gate and source of each HEMT T1 and T2 are short-circuited to each other. Take HEMT T1 as an example, when its drain-to-source voltage (V _DS ) is large enough, the drain-to-source current (I _DS ), that is, flows from the drain to the source The current of, will be approximately a constant, almost independent of _{V DS.} Therefore, no matter the HEMT T1 or T2, it can be roughly regarded as a certain current source, providing a stable certain current to drive the LED 18, so that the luminous intensity of the LED 18 can be maintained at a certain level, and there will be no flicker problem. In Figure 2, the HEMT T1 drives the LED 18, which together serve as a load and are connected in series between the DC power line VDD and the ground line GND. In Figure 2, the HEMT T2 and the LED 18 are connected by a dotted line 67, which indicates that the HEMT T2 can selectively drive the LED 18 together with the HEMT T1, which will be described in detail later.

3. FIG display input AC power supply V _AC-IN voltage waveform 72, does not fill the DC power supply V is valley circuit 64 _DC-IN of the voltage waveform 74, and the DC power supply V when there is valley-fill circuit 64 _DC-IN voltage Waveform 76. For example, the AC input power V _AC-IN is 220VAC, which is a sine wave, as shown in Figure 3. The voltage waveform 74 is represented as a virtual result when there is no valley filling circuit 64. If there is no valley filling circuit 64, the bridge rectifier 62 will provide simple full-wave rectification, so the negative part of the voltage waveform 72 will be converted to positive, as shown by the voltage waveform 74. The valley filling circuit 64 will fill in the valleys in the voltage waveform 74 or make the valleys in the voltage waveform 74 no longer so deep, as shown by the voltage waveform 76. For the convenience of description, the following description will sometimes use the virtual result of the voltage waveform 74 to explain the time point of the event. For example, when the voltage waveform 74 reaches the peak, it represents when the voltage waveform 72 (AC input power V _AC-IN ) reaches the peak or valley.

In the period TP1, when the voltage waveform 74 is greater than 0.5V _PEAK , the voltage waveform 74 will rise to V _PEAK over time. The power generated by the LED 18 will directly come from the AC input power source V _AC-IN , so the voltage waveform 76 is equal to the voltage waveform 74. At this time, once the voltage of the DC power supply V _DC-IN is greater than the sum of the capacitor voltages V _C1 and V _C2 , the capacitors C1 and C2 will be charged by the AC input power supply V _AC-IN . When the voltage waveform 74 reaches the peak value V _PEAK , the capacitor voltages V _C1 and V _C2 will both be approximately 0.5V _PEAK .

The period TP2 starts after the voltage waveform 74 reaches the peak value V _PEAK . In the period TP2, the voltage waveform 74 starts to decrease with time. The power generated by the LED 18 will directly come from the AC input power source V _AC-IN , so the voltage waveform 76 is equal to the voltage waveform 74. Because the capacitors C1 and C2 are not charged or discharged, the capacitor voltages V _C1 and V _C2 will both be maintained at 0.5V _PEAK .

The period TP3 starts after the voltage waveform 74 is lower than 0.5V _PEAK , which is approximately the time when the valley of the voltage waveform 74 appears. During the period TP3, the capacitor C1 will be discharged through the diode DVF3 to supply power to the HEMT T1 and the LED 18. Similarly, the capacitor C2 is discharged through the diode DVF1, and the same power is supplied to the HEMT T1 and the LED 18. The capacitor voltages V _C1 and V _C2 will decrease over time, and the rate of decrease depends on the capacitance values of the capacitors C1 and C2. The period TP3 ends when the voltage waveform 74 rebounds from the valley and is higher than the capacitor voltage V _C1 or V _C2 . After that, another time period TP1 continues. As shown in the voltage waveform 76 in Figure 3, as long as the capacitors C1 and C2 are large enough, the DC power supply V _DC-IN may provide enough voltage to make the LED 18 continue to emit light.

As long as the capacitors C1 and C2 are large enough, the power factor achieved by the valley filling circuit 64 can meet the power factor requirements of most countries.

In one embodiment, the rectifier diodes DB1-DB4, diodes DVF1-DVF3, and HEMT T1 and T2 in Figure 2 are all formed on a single semiconductor chip. FIG. 4A shows the pattern of a metal layer 104 on a semiconductor chip 80 and indicates the relative positions of the diode and the HEMT on the semiconductor chip 80 in FIG. 2. The semiconductor chip 80 may be a monolithic microwave integrated circuit (MMIC) using gallium nitride as the conduction channel material (GaN-based). In Figure 4A, the element structure of each diode is approximately similar, and the element structures of HEMT T1 and T2 are also similar. Figure 5 shows a cross-sectional view of the HEMT T1 in Figure 4A along the line ST-ST; Figure 6 shows a cross-sectional view of the diode DVF3 in Figure 4A along the line SD-SD. The device structure of other diodes and HEMT in the figure can be inferred by analogy.

In the example of FIG. 5, the buffer layer 94 on the silicon substrate 92 may be C-doped intrinsic GaN. The channel layer 96 may be intrinsic GaN, and a high-band gap layer 98 is formed thereon, and its material may be intrinsic AlGaN. The cap layer 100 may be intrinsic GaN. The cap layer 100, the high-price band gap layer 98 and the channel layer 96 are patterned to become a mesa 95. A two-dimensional electron gas (2D-electron gas) can be formed in a quantum well in the channel layer 96 adjacent to the high-valence band gap layer 98 as a conductive channel. The material of the patterned metal layer 102 may be titanium, aluminum, or a laminate of these two materials. In Figure 5, the metal layer 102 forms two metal strips 102a and 102b above the platform area 95, and forms two ohmic contacts with the platform area 95, so that the metal strips 102a and 102b are respectively As the source and drain of HEMT T1. The material of the metal layer 104 may be titanium, gold, or a laminate of these two materials. For example, from bottom to top, the metal layer 104 has a nickel layer (Ni), a copper layer (Cu), and a platinum layer (Pt). The platinum layer can increase the adhesion between the protective layer 105 to be formed later. Adhesion (adhesion), to prevent the problem of peeling during the pad manufacturing process. In other embodiments, the metal layer 104 may also be a stack of a nickel layer (Ni), a gold layer (Au), and a platinum layer (Pt), or a nickel layer (Ni), a gold layer (Au), and a titanium layer (Ti ) Of the stack. In Figure 5, the patterned metal layer 104 forms metal sheets 104a, 104b, and 104c. The metal piece 104b contacts the upper center of the platform area 95 to form a schottky contact, which serves as the gate of the HEMT T1. 104a and 104c in Figure 5 are in contact with 102a and 102b, respectively, to provide electrical connections between the source and drain of the HEMT T1 and other electronic components. Please refer to FIG. 5 and FIG. 4A at the same time. It can be found that the gate (metal piece 104b) of the HEMT T1 is short-circuited to the metal piece 104a through the metal layer 104 and also short-circuited to the source of the HEMT T1. The right part of Figure 5 shows the equivalent circuit diagram of HEMT T1. There is a protective layer 105 above the metal layer 104, the material of which can be silicon oxinitride (SiON). The protective layer 105 is patterned to form bonding pads required for packaging. For example, in Figure 5, the part of the left half of the protective layer 105 that is not covered can be soldered to the bonding wire of the low voltage pin VSS (explained later); while the right half of the protective layer 105 is not covered The live part can be soldered to the solder wire of the drive pin D1 (explained later).

For the sake of brevity, the same or similar parts of Fig. 6 and Fig. 5 will not be repeated. In FIG. 6, the metal layer 102 forms two metal sheets 102c and 102d above the terrace area 95, and the patterned metal layer 104 forms the metal sheets 104d, 104e, and 104f. Similar to Fig. 5, the metal sheet 104e can be used as a gate of a HEMT. Although the metal sheet 102d can be used as a source of a HEMT, the metal sheet 102d is not in contact with the metal layer 104. In another embodiment, the metal sheet 102d may not be needed. The metal piece 104f contacts a part of the upper surface of the platform region 95 and a side wall to form another Schottky contact, which can be used as a Schottky diode, and its cathode is equivalently short-circuited to the source of the HEMT in FIG. 6. Please refer to Figure 6 and Figure 4A at the same time. The metal piece 104e passes through the metal layer 104 and is short-circuited to the metal piece 104f, which is the anode of the Schottky diode. The right part of Figure 6 shows the equivalent circuit connection diagram of the left half. The circuit behavior is equivalent to a diode. The right part of Figure 6 also shows a special diode symbol 120 to represent the equivalent circuit in Figure 6. The diode symbol 120 is also used in Figure 2 to indicate the rectifier diodes DB1-DB4 and diodes DVF1-DVF3, each of which is a composite of a HEMT and a Schottky diode. Polar body.

Figure 4B shows an integrated circuit 130 after the semiconductor chip 80 is packaged. It has only 8 pins, namely: high voltage pin VCC, power factor correction pins PF1 and PF2, low voltage pin VSS , AC input pins AC+ and AC-, drive pins D1 and D2. Please refer to Figure 4A, which also shows that each pin is electrically short-circuited to the metal sheet formed by patterning the metal layer 104 through a bonding wire, and these metal sheets also provide a semiconductor chip 80 The corresponding input or output terminals of the electronic components are connected to each other. For example, the driving pin D1 is electrically connected to the drain of the HEMT T1, and the power factor correction pin PF1 is electrically connected to the cathode of the diode DVF3.

Figure 7 shows a lighting system 200 implemented in accordance with the present invention. The integrated circuit 130 is fixed on the printed circuit board 202. Through the metal wire on the printed circuit 202, the capacitor C1 is electrically connected between the high voltage pin VCC and the power factor correction pin PF1, and the capacitor C2 is electrically connected between the low voltage pin VSS and the power factor correction pin PF2. LED 18 is electrically connected between the high voltage pin VCC and the drive pin D1, and the AC input pins AC+ and AC- are electrically connected to the AC input power V _AC-IN . From the previous explanation, we can understand that the lighting system 200 in Figure 7 is very simple, using only 4 electronic components (two capacitors C1 and C2, integrated circuit 130 and LED 18) to achieve the LED driver 60. Without expensive and bulky inductance components, the cost of the lighting system 200 can be very low, and the volume of the entire product can also be small and streamlined.

In FIG. 7, the driving pin D2 of the integrated circuit 130 (electrically connected to the drain of the HEMT T2) can determine whether to be electrically connected to the LED 18 according to the AC voltage of the _{AC input power V AC-IN.} In other words, the integrated circuit 130 can selectively use a single HEMT (T1) or use two HEMTs (T1 and T2) in parallel to drive the LED 18 to emit light. For example, it is assumed that the HEMT T1 and T2 in the integrated circuit 130 can provide approximately the same constant current of 1 u. When the lighting system 200 of Figure 7 is applied to the AC input power V _AC-IN of 110VAC, an LED with a forward voltage of 50V can be selected as the LED 18, and the driving pins D1 and D2 are connected to the LED 18 together. , The power consumed by the LED 18 at this time is about 2u*50 (=100u). When the lighting system 200 in Figure 7 is applied to the AC input power V _AC-IN of 220VAC, an LED with a forward voltage of 100V can be selected as the LED 18, and only connect the driving pins D1 to the LED 18, and keep the driving connection Pin D2 is floating and connected, and the power consumed by the LED 18 at this time is about 1u*100 (=100u). In this way, although _{the AC voltage of the AC input power supply V AC-IN} is different, as long as the LEDs with different forward voltages are selected, the power consumed by the LED 18 can be about the same (both 100u), and the brightness of the lighting produced by the lighting system 200 is about It will be the same. In other words, the integrated circuit 130 is not only suitable for 220VAC AC input power, but also for 110VAC AC input power. This is very convenient for the manufacturer of the lighting system 200, and can save the cost of parts inventory management of the lighting system 200.

In Figure 2, the current drive circuit 66 is connected between the LED 18 and the ground line GND, but the present invention is not limited to this. FIG. 8 shows another LED driver 300 implemented in accordance with the present invention to drive the LED 18. In FIG. 8, the current driving circuit 302 has HEMT T3 and T4. The drains of the HEMT T3 and T4 are electrically connected to the DC power line VDD, and the LED 18 is electrically connected between the ground line GND and the current driving circuit 302. FIG. 9A shows the pattern of the metal layer 140 on a semiconductor chip 310, and indicates the relative position of the diode and the HEMT in FIG. 8. FIG. 5 may also represent a cross-sectional view of the chip of the HEMT T3 along the line ST-ST in FIG. 9A; FIG. 6 may also represent a cross-sectional view of the chip of the diode DVF3 in FIG. 9A along the line SD-SD. Figure 9B shows an integrated circuit 320 after packaging the semiconductor chip 310. It has only 8 pins, namely: high voltage pin VCC, power factor correction pins PF1 and PF2, low voltage pin VSS , AC input pins AC+ and AC-, drive pins S1 and S2. Fig. 10 shows another lighting system 330 implemented in accordance with the present invention, which implements the LED driver 300 in Fig. 8. Figures 8, 9A, 9B, and 10, you can refer to the previous figures 2, 4A, 4B, and 7 and related explanations to understand the principle, operation, and advantages. For the sake of brevity, we will not repeat them.

As shown in the embodiment in FIG. 11, an additional voltage stabilizing capacitor 19 can be connected in parallel with the LED 18. The voltage stabilizing capacitor 19 can reduce _{the variation of the cross voltage V LED} of the LED 18, and even increase the duty cycle of the LED 18 within one cycle of the _{AC input power V AC-IN, reducing the possibility of LED 18 flickering} Sex.

The pattern in Figure 4A is merely an example, and the present invention is not limited to this. Figure 12 shows the pattern of a metal layer 104 on another semiconductor wafer. Figure 12 is roughly similar to Figure 4A. For the sake of brevity, the same or similar parts will not be repeated. In Figure 4A, a gate located in the middle of each diode has only an upper arm ARM1 patterned through a metal layer 104 connected to its anode (such as the metal sheet 104f in Figure 6); A gate in the middle of each HEMT is also connected to its source through an upper arm ARM2 patterned on a metal layer 104 (for example, the metal sheet 104a in Figure 5); However, in Figure 12, as illustrated in the gate region GG, the gate in the middle of each diode is connected to its anode through the upper and lower arms ART and ARB after patterning of the metal layer 104; and is located in each HEMT A gate in the middle position is also connected to its source through the upper and lower arms of the patterned metal layer 104. Compared with the design in Figure 4A, the diode in Figure 12 has a higher breakdown voltage tolerance.

The cross-sectional views in Fig. 5 and Fig. 6 are not intended to limit the scope of rights of the present invention. For example, as shown in FIG. 13, the diode DVF3 in FIG. 4A along the line SD-SD is a cross-sectional view of a chip according to another embodiment. Figures 13 and 6 are for the sake of brevity, and the parts that are the same or similar to each other will not be repeated. Different from FIG. 6, an insulating layer 103 is sandwiched between the metal sheet 104e and the cap layer 100 in FIG. 13, the material of which is, for example, silicon oxide. The existence of the insulating layer 103 can also enhance the breakdown voltage tolerance of the diode.

Figure 14 shows the flow chart used to make the diode in Figure 13. Step 140 first forms a platform area. For example, the channel layer 96, the high-valence band gap layer 98, and the cap layer 100 are formed on the buffer layer 94, and then the three layers are patterned by inductively coupled plasma etching to complete the terrace area 95. Step 142 forms an ohmic contact. For example, titanium/aluminum/titanium/gold are respectively deposited as the metal layer 102, and then the metal layer 102 is patterned to form metal sheets 102a, 102b, and so on. In step 144, the insulating layer 103 is formed. For example, a silicon dioxide layer is deposited first and then patterned, and the remaining silicon dioxide layer becomes the insulating layer 103. Step 146 forms Schottky contacts and patterning. For example, in step 146, nickel/gold/platinum is deposited sequentially as the metal layer 104, and then the metal layer 104 is patterned to form metal sheets 104a, 104b, 104c, and so on. The metal layer 104 and the metal layer 102 are in ohmic contact, but the metal layer 104 and the terrace area 95 are in Schottky contact. In step 148, the protective layer 105 is formed and patterned to form openings for the solder pads. Of course, the flowchart in Figure 14 is also applicable to the production of the HEMT in Figure 12. With appropriate adjustments, the flowchart in Figure 14 can also be used to fabricate diodes and HEMTs as in Figure 4A, for example, step 144 can be omitted, or other manufacturing processes can be added.

Although the HEMT T1 and T2 in Figures 2 and 5 can be regarded as constant current sources, they may not be a completely ideal current source. The drain current (I _DS ) of the HEMT T1 and T2 may still be slightly related to the drain voltage (V _{DS) in the saturation region.} Figure 15 shows the relationship between _{I DS and} V _DS in a MOSFET and HEMT. Curves 150 and 152 are respectively for a MOSFET and a HEMT based on silicon. It can be found from the curve 150 that in the MOSFET, _IDS and _{VDS are} approximately positively correlated, that is, the larger the _{V DS, the larger the IDS} . But HEMT is different. It can be found from the curve 152 that in HEMT, when V _DS exceeds a certain value, _{the relationship between IDS} and IDS changes from a positive correlation to a negative correlation. And this specific value can be set through the parameters on the manufacturing process. This feature of HEMT has a special benefit. When V _DS suddenly rises due to the unstable mains voltage, I _DS will drop instead, which may reduce the electric power consumed by HEMT, so as to prevent HEMT from being burnt.

In the previous several embodiments, the LED driver has a valley filling circuit, but the invention is not limited to this. Figure 16 shows another LED driver 500 for driving an LED 518, which includes several LEDs 520 ₁ , 520 ₂ , and 520 ₃ connected in series. There is no valley filling circuit in the LED driver 500. The bridge rectifier 502 and the current driving circuit 504 in the LED driver 500 can be integrated on a semiconductor chip and packaged as an integrated circuit. FIG. 17 shows the pattern of a metal layer 104 on a semiconductor chip 550, and indicates the relative positions of the diode and the HEMT on the semiconductor chip 550 in FIG. 16. The semiconductor chip 550 integrates the bridge rectifier 502 and the current driving circuit 504 in the LED driver 500. Figure 18 shows an integrated circuit 552 after the semiconductor chip 550 has been packaged. FIG. 19 shows a lighting system 560 using the integrated circuit 552 in FIG. 18 to implement the LED driver 500. Figures 16 to 19 can be understood through the previous teaching, so the details will not be repeated here. From Figure 19, it can be found that the entire lighting system 560 uses a very small number of electronic components (a capacitor CF, integrated circuit 552 and LED 518). The cost of the lighting system 560 will be reduced, and the overall product volume will be more streamlined.

Figures 16 and 19 are not intended to limit the application of the integrated circuit 552. FIG. 20 illustrates an LED driver 600, which can be used to illustrate another application of the integrated circuit 552. In Figure 20, the bridge rectifier 502 is integrated into the integrated circuit 552 like the current drive circuit 504. The HMET T1 and T2 in the current drive circuit 504 can be selectively used to drive the LED 518, which includes several LEDs 520. ₁ , 520 ₂ , 520 ₃ . The LED driver 600 has segmented circuits IC1 and IC2, which can be short-circuited or open-circuited according to the level of the _{DC power supply V DC-IN.} For example, when the DC power supply V _DC-IN is slightly higher than the forward voltage of the LED 520 ₃ , the segment circuits IC1 and IC2 are short circuits, so the LED 520 ₃ emits light, but the LEDs 520 ₁ and 520 ₂ do not emit light; When the DC power supply V _DC-IN increases to exceed the _{sum of the forward voltages of the LEDs 520 2} and 520 ₃ , the segment circuit IC1 is a short circuit and the segment circuit IC2 is an open circuit, so the LEDs 520 ₂ and 520 ₃ emit light, and the LED 520 ₁ does not emit light; when the DC power supply V _DC-IN increases to exceed the _{sum of the forward voltages of LEDs 520 1} , 520 ₂ and 520 ₃ , the segment circuit IC1 also becomes an open circuit, so LEDs 520 ₁ , 520 ₂ and 520 ₃ all glow. As a result, the electro-optical conversion efficiency of the LED driver 600 is better, and the power factor and the total harmonic distortion rate can be well controlled.

An integrated circuit implemented according to the present invention is not limited to only integrating a bridge rectifier and a current driving circuit. The aforementioned integrated circuits 130 and 552 are merely examples. For example, in addition to a bridge rectifier and a current drive circuit, an integrated circuit implemented according to the present invention also integrates some diodes, which can be used in the segment circuits IC1 and IC2 in FIG. 20.

The integrated circuit implemented by the present invention is not limited to the HEMT that only includes the depletion mode. In some embodiments, the integrated circuit includes an enhancement-mode HEMT whose on-current can be controlled by providing an appropriate gate voltage, thereby changing the intensity of the light source from the connected LED. For example, in Figure 20, while the segmented circuits IC1 and IC2 are used to adjust the activated LEDs _{520 1} , 520 ₂ , and 520 ₃ , the gate voltage of the enhanced mode HEMT can be adjusted to change the HEMT input to the LEDs _{520 1} , 520 ₂ , and 520 ₃ The current in turn changes the intensity of light emitted by the _{LEDs 520 1} , 520 ₂ , and 520 _3.

Although the previously disclosed LED drivers or lighting systems are each used to drive a single LED 518, the present invention is not limited to this. In some embodiments, there may be two or more LEDs that are driven separately with different currents. FIG. 21 illustrates an LED driver 700 in which the HEMT T1 and T2 in the current driving circuit 504 drive the LEDs 18R and 18B, respectively. For example, the driving current provided by HEMT T1 is less than the driving current provided by HEMT T2, while LED 18R is roughly a red LED, and LED 18B is roughly a blue LED.

The diodes in Fig. 6 and Fig. 13 are respectively formed on a single platform region 95, but the present invention is not limited to this. Figure 22 shows a cross-sectional view of a diode chip in another embodiment. The parts in Fig. 22 that are the same as or similar to those in Fig. 6 and Fig. 13 are omitted for the sake of brevity. In Figure 22, there are two platform areas 95 and 95a. The metal sheet 102e forms an ohmic contact on the mesa region 95a; and the metal sheet 102d forms another ohmic contact on the mesa region 95. The metal sheets 102d and 102e pass through the metal sheet 104g, and are electrically connected to each other in a short circuit. The metal piece 104f serves as an anode of the diode, and the metal piece 104d serves as a cathode of the diode. The structure in Figure 22 can enhance the breakdown voltage tolerance of the diode.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention should fall within the scope of the present invention.

10: Lighting system 12: Bridge rectifier 14: Power factor corrector 16: LED drive circuit 18, 18B, 18R: LED 19: Stabilizing capacitor 60: LED driver 62: Bridge rectifier 64: Valley filling circuit 66: Current drive Circuit 67: dashed lines 72, 74, 76: voltage waveform 80: semiconductor wafer 92: silicon substrate 94: buffer layer 95, 95a: platform area 96: channel layer 98: high-price band gap layer 100: cap layer 102: metal layer 102a, 102b, 102c, 102d, 102e: metal sheet 103: insulating layer 104: metal layer 104a, 104b, 104c, 104d, 104e, 104f, 104g: metal sheet 105: protective layer 120: diode symbol 130: integrated circuit 140 , 142, 144, 146, 148: steps 150, 152: curve 200: lighting system 300: LED driver 302: current driving circuit 330: lighting system 500: LED driver 502: bridge rectifier 504: current driving circuit 518, 520 ₁ , 520 ₂ , 520 ₃ : LED 550: semiconductor chip 552: integrated circuit 560: lighting system 600: LED driver 700: LED driver AC+, AC-: AC input pins ARM1, ARM2: upper arm ART, ARB: upper and lower arms C1, C2, CF: Capacitor DB1-DB4: Rectifier diode DVF1-DVF3: Diode D1, D2: Drive pin GND: Ground wire GG: Gate area IC1, IC2: Segment circuit PF1, PF2: Power factor Correction pins S1, S2: drive pins T1, T2, T3, T4: HEMT (High Electron Mobility Field Effect Transistor) TP1, TP2, TP3: time period V _AC-IN : AC input power VCC: high voltage pin V _DC-IN : DC power supply VDD: DC power supply line V _PEAK : Peak voltage VSS: Low voltage pin

The first picture shows the conventional lighting system. Figure 2 shows an LED driver according to an embodiment of the invention. Figure 3 shows three voltage waveforms. Figure 4A shows the pattern of a metal layer on a semiconductor wafer. FIG. 4B shows a schematic diagram of an integrated circuit after packaging the semiconductor chip of FIG. 4A. Figure 5 shows a cross-sectional view of the HEMT T1 in Figure 4A along the line ST-ST. Fig. 6 shows a cross-sectional view of the diode DVF3 in Fig. 4A along the line SD-SD. Figure 7 shows a lighting system according to an embodiment of the invention. Figure 8 shows an LED driver according to another embodiment of the present invention. Figure 9A shows the pattern of a metal layer on another semiconductor wafer. FIG. 9B shows a schematic diagram of an integrated circuit after packaging the semiconductor chip of FIG. 9A. Figure 10 shows a lighting system according to another embodiment of the invention. Figure 11 shows the circuit diagram of the LED and an additional voltage stabilizing capacitor connected in parallel. Figure 12 shows the pattern of a metal layer on another semiconductor wafer. FIG. 13 shows a cross-sectional view of a chip according to another embodiment of the diode DVF3 in FIG. 4A along the line SD-SD. Figure 14 shows a flow chart that can be used to make the diode in Figure 13. FIG. 15 shows the relationship between _{I DS and} V _DS in a MOSFET and HEMT according to an embodiment of the present invention. Figure 16 shows an LED driver according to another embodiment of the present invention. Figure 17 shows a pattern of a metal layer on a semiconductor wafer according to an embodiment of the invention. Figure 18 shows an integrated circuit after the semiconductor chip of Figure 17 is packaged. Figure 19 shows a lighting system implemented using the integrated circuit in Figure 18. Figure 20 shows the circuit design of an LED driver according to an embodiment of the invention. Figure 21 shows an LED driver according to another embodiment of the present invention, which has a plurality of LEDs. Figure 22 shows a cross-sectional view of a diode chip according to an embodiment of the present invention.

18: LED

60: LED driver

62: Bridge rectifier

64: Valley Filling Circuit

66: Current drive circuit

67: dotted line

C1, C2: Capacitance

DB1-DB4: rectifier diode

DVF1-DVF3: Diode

GND: Ground wire

T1, T2: HEMT (High Electron Mobility Field Effect Transistor)

V _AC-IN : AC input power

V _DC-IN : DC power supply

VDD: DC power line

Claims (10)

A semiconductor chip for a driving circuit, comprising: a single buffer layer; a first diode; a first high electron mobility field effect transistor, which is formed in the single buffer together with the first diode And a metal layer, including a first electrode covering the first diode and a second electrode covering the first high electron mobility field effect transistor. For example, the semiconductor chip of item 1 of the scope of patent application further includes a second diode electrically connected to the first diode, and a second high electron mobility field effect transistor and the first diode electrically connected. Sexual connection. For example, the semiconductor chip of the second item of the scope of patent application, wherein the second diode and the second high electron mobility field effect transistor are jointly formed on the single buffer layer. For example, the first semiconductor chip in the scope of the patent application, wherein the first diode includes a schottky barrier diode electrically connected to a second high electron mobility field effect transistor. For example, the semiconductor chip of item 1 in the scope of patent application further includes a power factor corrector electrically connected to the first diode. For example, the semiconductor chip of item 5 of the scope of patent application, wherein the power factor corrector further includes a third diode and a fourth diode connected in series with each other. For example, the semiconductor chip of item 6 of the scope of patent application, wherein the anode of the third diode is directly connected to the cathode of the fourth diode. For example, the semiconductor wafer of item 6 of the scope of patent application, wherein the cathode of the third diode and the anode of the fourth diode are not directly connected. For example, the semiconductor chip of item 6 of the scope of patent application further includes a capacitor connected in parallel with the third diode and the fourth diode. For example, the semiconductor wafer of item 1 in the scope of patent application, wherein the metal layer covers the buffer layer.

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