Power supply system for supplying power to LED load of vehicle lamp

Abstract

The invention provides a power supply system for supplying power to a car lamp LED load. The power supply system comprises a gallium nitride DCDC circuit, an LED dynamic load and an LED peak current absorption circuit, the output end of the gallium nitride DCDC circuit is connected with the input end of the LED dynamic load; the input end of the LED peak current absorption circuit is connected with the output end of the gallium nitride DCDC circuit, and the output end of the LED peak current absorption circuit is connected with the input end of the LED dynamic load and the control end of the gallium nitride DCDC circuit. By providing the DCDC circuit taking gallium nitride as a switching tube, the circuit can work at a relatively high frequency, the efficiency is improved, the number of output filter capacitors and the capacitance value of the capacitors are reduced, the inrush current when an LED dynamic load is driven is directly reduced, and the effects of protecting LED lamp beads and prolonging the service life are achieved.

Description

Technical Field

[0001] This invention relates to the field of gallium nitride DC-DC circuit technology, and more specifically, to a power supply system for supplying power to automotive LED loads. Background Technology

[0002] Compared to traditional DC-DC circuits using Silicon MOSFETs as switches, Silicon MOSFETs suffer from significant losses and reduced efficiency at high-frequency switching (2.2MHz) due to their dynamic parameters. At low-frequency switching (400kHz), they require large inductors and capacitors for filtering and stabilization loops, making them unsuitable for driving dynamic loads, such as those used for ADB (Automatic Delay) functions. DC-DC circuits using Gallium Nitride (GaN) as switches effectively solve these problems. They offer lower losses at higher switching frequencies, require smaller output capacitors, and, combined with current peak absorption circuits, can effectively drive dynamic loads.

[0003] Patent application CN102695341A discloses an LED driver power supply adapted to an electronic transformer. It controls the current flowing through an inductor via a first control circuit, ensuring the electronic transformer meets the minimum load current requirement under any load condition. Therefore, it operates normally throughout the entire AC cycle and maintains a substantially constant output voltage for the power stage circuit. A current stabilization control circuit controls the current flowing through the LED load, ensuring stable LED illumination with high control precision and fast response. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of this invention. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the purpose of this invention is to provide a power supply system for supplying power to vehicle headlight LED loads.

[0005] The power supply system for supplying power to the LED load of a vehicle lamp according to the present invention includes: a gallium nitride DC-DC circuit, an LED dynamic load, and an LED peak current absorption circuit; The output terminal of the gallium nitride DC-DC circuit is connected to the input terminal of the LED dynamic load; The input terminal of the LED peak current absorption circuit is connected to the output terminal of the gallium nitride DC-DC circuit, and the output terminal of the LED peak current absorption circuit is connected to the input terminal of the LED dynamic load and the control terminal of the gallium nitride DC-DC circuit.

[0006] Preferably, the gallium nitride DC-DC circuit includes a gallium nitride MOSFET and a gate drive circuit or a gate drive integrated circuit; The signal output terminal of the gate drive circuit or gate drive integrated circuit is connected to the gate of the gallium nitride MOSFET. The source and drain of the gallium nitride MOSFET are connected to the power conversion path of the gallium nitride DC-DC circuit.

[0007] Preferably, the gate drive circuit includes a second control module and a push-pull circuit; The signal output terminal of the second control module is connected to the signal input terminal of the push-pull circuit; The power output terminal of the push-pull circuit is connected to the gate of the gallium nitride MOSFET.

[0008] Preferably, the signal output terminal of the gate drive circuit or gate drive integrated circuit is connected to the gate of the gallium nitride MOSFET via a wire to transmit a pulse width modulation signal.

[0009] Preferably, the LED peak current absorption circuit includes a detection resistor, which is connected in series in the main current loop between the output terminal of the gallium nitride DC-DC circuit and the input terminal of the LED dynamic load; The two ends of the detection resistor are respectively connected to the two voltage detection terminals of the gallium nitride DC-DC circuit via wires.

[0010] Preferably, the LED peak current absorption circuit further includes a power switching device and a resistor; The control terminal of the power switching device is connected to the control signal output terminal of the gallium nitride DC-DC circuit via a wire; the first conducting terminal of the power switching device is connected to one end of the resistor, and the other end of the resistor is grounded; the second conducting terminal of the power switching device is connected to the node between the output terminal of the gallium nitride DC-DC circuit and the detection resistor via a wire.

[0011] Preferably, the gallium nitride DC-DC circuit sends a control signal to the control terminal of the power switching device based on the comparison result between the voltage across the detection resistor and the internal reference voltage; The internal reference voltage includes a first reference voltage and a second reference voltage, wherein the value of the first reference voltage is 120% × ILED × Rsense, and the value of the second reference voltage is 110% × ILED × Rsense, where ILED is the steady-state operating current of the LED dynamic load, and Rsense is the resistance value of the sensing resistor.

[0012] Preferably, the gallium nitride DC-DC circuit includes an output filter capacitor, the positive terminal of which is connected to the positive terminal of the output of the gallium nitride DC-DC circuit, and its negative terminal is grounded. The switching frequency of the gallium nitride MOSFET in the gallium nitride DC-DC circuit is inversely related to the capacitance of the output filter capacitor.

[0013] Preferably, it further includes a first control module or an electronic control unit; The first input / output port of the first control module or electronic control unit is connected to the enable terminal and the status feedback terminal of the gallium nitride DC-DC circuit via wires; The second input / output port of the first control module or electronic control unit is connected to the control signal input terminal of the LED dynamic load via a wire.

[0014] Preferably, the input terminal of the gallium nitride DC-DC circuit is connected to the vehicle power supply, the LED dynamic load consists of multiple LED beads and a switch array that controls their on / off state, and the control terminal of the switch array is connected to an external control signal source.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) By providing a DCDC circuit with gallium nitride as the switching transistor, the circuit can operate at a higher frequency, which improves efficiency and reduces the number and capacitance of the output filter capacitors, directly reducing the inrush current when driving the LED dynamic load, thus protecting the LED beads and extending their service life. (2) Through the LED peak current absorption circuit, when the LED dynamic load is in operation, the current flowing through the LED will generate a momentary surge current that exceeds the current carrying capacity of the LED due to the existence of the load capacitance. The LED peak current absorption circuit can suppress the large current flowing through the LED, and also play the role of protecting the LED beads and extending their service life. (3) By using a DCDC circuit with gallium nitride as the switching transistor, vehicle lights can drive the dynamic load of LEDs without the need for an additional control module (ECU-less solution), thus achieving a lightweight design for vehicle lights. Attached Figure Description

[0016] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the power supply system structure; Figure 2 This is a schematic diagram of a gallium nitride DC-DC circuit. Figure 3 This is a schematic diagram of an LED dynamic load structure; Figure 4 This is a schematic diagram of the LED peak current absorption circuit. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0018] Example This invention provides a power supply system for supplying power to automotive LED loads, mainly comprising a DC-DC circuit using gallium nitride as the switching transistor and a load peak current absorption circuit. This system can effectively control the dynamic load of automotive lights.

[0019] The system includes the following circuit components: first control module 1, gallium nitride DC-DC module 2, and LED dynamic load 3.

[0020] Specifically: the first control module 1 is connected to the gallium nitride DC-DC module 2. The first control module 1 enables the gallium nitride DC-DC module 2 to turn on and off, and detects the output voltage or status of the gallium nitride DC-DC module 2; the first control module 1 is connected to the LED dynamic load 3, and provides control logic for the LED dynamic load; the gallium nitride DC-DC module 2 is connected to the LED dynamic load 3, and provides a constant current power supply for the LED dynamic load.

[0021] The first control module 1 is not mandatory. The first control module 1 can be an independent control module on the vehicle body side, or it can be a part of the module circuit of an ECU on the vehicle body side.

[0022] Gallium nitride DC-DC module 2, reference Figure 2 The core includes a gallium nitride MOSFET14 (GaN MOSFET) and a gallium nitride driver to drive the gallium nitride MOSFET. The gallium nitride driver includes a gate drive circuit 11 or a gate drive IC 11. The gate drive circuit 11 includes a second control module 12 and a push-pull circuit 13. The second control module 12 is connected to the push-pull circuit 13, and the push-pull circuit 13 is connected to the gallium nitride MOSFET14. The second control module 12 and the push-pull circuit 13 can be discrete circuits or a combination circuit formed by multiple independent chips to drive the gallium nitride MOSFET14. The second control module 12 and the push-pull circuit 13 can also be transistor circuits included in the gate drive IC 11. The gate drive IC 11 should be understood as a chip provided by a mature supplier, which integrates the drive circuit of the gallium nitride MOSFET14.

[0023] LED dynamic load 3, reference Figure 3The LED dynamic load 3 is the light-emitting unit of the vehicle lamp. Its input side is connected to the gallium nitride DC-DC module 21, the output capacitor 22 and the LED peak current absorption circuit 23. The gallium nitride DC-DC module 21, the output capacitor 22 and the LED peak current absorption circuit 23 together form a constant current output power supply. The ECU 26 is connected to the LED dynamic load 3 and provides the control function for lighting the LED. It can realize the dynamic effects of LED flowing and breathing. At the same time, the ECU 26 should be equivalent to the first control module 1 or a part of the circuit of the first control module 1.

[0024] This embodiment operates through the following steps: This invention provides a constant current output system consisting of a DC-DC circuit using a gallium nitride MOSFET as the switching transistor and a load peak current absorption circuit. As the core component for energy conversion, the MOSFET in this system is replaced with a GaN MOSFET, unlike the DC-DC circuits used in traditional automotive LED lighting. (Reference) Figure 2 The output stage of the gate drive circuit 11 or the gate drive IC 11 is connected to the GaN MOSFET 14. Since the GaN MOSFET is a low gate charge device, its gate charge is only 1 / 3 of that of the same specification Silicon MOSFET. The instantaneous drive current capability requirement of the gate drive circuit 11 or the gate drive IC 11 is lower than that of the Silicon MOSFET, and the drive loss will be significantly reduced.

[0025] Both the gate drive circuit 11 and the gate drive IC 11 can provide a PWM signal with a specific switching frequency. This PWM signal is generally around 2.2MHz, with a variable duty cycle and a maximum level that does not exceed the gate voltage of the gallium nitride MOSFET 14 (generally a maximum of 6.5V), and is used to drive the gallium nitride MOSFET 14 to work in the switching state.

[0026] Furthermore, GaN MOSFET 14 generally adopts a top-heat-dissipating package, while Silicon MOSFET of the same specifications is bottom-heat-dissipating. Top-heat-dissipating can be achieved by attaching a heat sink with high thermal conductivity thermal silicone, rather than just by heat dissipation through the PCB copper foil, thus achieving better heat dissipation under the same power load.

[0027] Furthermore, in a DC-DC circuit using GaN MOSFET 14 as the power switch, compared to silicon (Si) MOSFETs, gallium nitride (GaN) can easily operate at 1MHz to 10MHz (Si is mostly limited to <500kHz). Because GaN operates at a higher frequency, and the switching frequency and the size of the output filter capacitor are inversely related, the output filter capacitor 22 required to meet the same output ripple requirements is smaller. (Reference) Figure 3When the LED load of the lighting fixture has dynamic changing requirements, such as the ADB function of the high beam, the LMM circuit 25 controls the LED load to light up alternately. When the total conduction voltage of the load changes from high to low, the output filter capacitor 22, due to the characteristic that the voltage cannot change abruptly, will instantaneously discharge a large current to the LED dynamic load 24 (the LED dynamic load 24 is one specific form of the LED dynamic load 3), so that the voltage at the output filter capacitor 22 drops rapidly to a level comparable to the total conduction voltage of the load. The total capacitance of the output filter capacitor 22 is inversely related to the magnitude and duration of this discharge current. A smaller discharge current avoids the LED being impacted by a large current, which can effectively extend the life of the LED. The use of gallium nitride DC-DC circuit 21 can adapt to the needs of the LED dynamic load while reducing the number and capacitance of the output filter capacitor 22.

[0028] Further, refer to Figure 3 To further suppress the discharge current generated during dynamic load changes, the system employs an LED peak current absorption circuit 23. (Refer to...) Figure 4 The circuit comprises two parts: an LED peak current detection circuit and a peak current discharge circuit. The peak current detection circuit mainly consists of a detection resistor 32 to sense current changes. When the current flowing through the detection resistor 32 is too large and reaches the threshold set by the gallium nitride DC-DC circuit 31, the threshold is generally set to be greater than 1.2 times the normal operating current of the LED load. The gallium nitride DC-DC circuit 31 controls the current discharge path 33, which is a combination of a power MOSFET and a power resistor. When the output current spike is higher than the internally set threshold (120% × ILED), that is, when the voltage drop across the detection resistor 32 reaches 120% × ILED × R23, it will be detected by the gallium nitride DC-DC circuit 31. The gallium nitride DC-DC circuit 31 will turn on the power MOSFET in the current discharge path 33 to provide a low-impedance energy discharge path, where the power resistor is an energy-consuming device. When the output current spike is discharged below the internally set threshold (110% × ILED), that is, when the voltage drop across the sensing resistor 32 reaches 110% × ILED × R23, it will also be detected by the gallium nitride DC-DC circuit 31. The gallium nitride DC-DC circuit 31 will then turn off the power MOSFET in the current discharge path 33, and the current will flow to the LED load in the subsequent stage. Among them, gallium nitride DC-DC circuit 2, gallium nitride DC-DC circuit 21 and gallium nitride DC-DC circuit 31 are the same component.

[0029] Discharge output capacitor. After the current discharge path 33 is enabled by the gallium nitride DC-DC circuit 31, the discharge current generated by the output filter capacitor 22 will first flow through itself to the ground network, thereby suppressing the large current flowing through the LED and achieving the purpose of protecting the LED.

[0030] Furthermore, compared to traditional automotive lighting controller solutions that often employ a two-stage DC-DC architecture with a boost-then-buck converter and silicon (Si) MOSFETs as the switching transistors, the total capacitance of the output filter capacitors in this two-stage architecture can be very small. However, these chips use an SPI interface and must be used in conjunction with an MCU, encompassing both the DC-DC power supply section and the logic control section. (Reference) Figure 3 Compared to traditional automotive lighting controller solutions, the constant current output system, consisting of a DCDC circuit using gallium nitride MOSFETs as switches and a load peak current absorption circuit, can directly drive LED loads. Especially under dynamic LED loads, the logic control unit (ECU26) can be separated. Vehicle lighting can drive LED loads without requiring additional control modules (ECU-less solution).

[0031] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0032] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A power supply system for supplying power to an LED load in a vehicle headlight, characterized in that, include: Gallium nitride DC-DC circuit, LED dynamic load and LED peak current absorption circuit; The output terminal of the gallium nitride DC-DC circuit is connected to the input terminal of the LED dynamic load; The input terminal of the LED peak current absorption circuit is connected to the output terminal of the gallium nitride DC-DC circuit, and the output terminal of the LED peak current absorption circuit is connected to the input terminal of the LED dynamic load and the control terminal of the gallium nitride DC-DC circuit.

2. The power supply system for supplying power to the LED load of vehicle lights according to claim 1, characterized in that, The gallium nitride DC-DC circuit includes a gallium nitride MOSFET and a gate drive circuit or a gate drive integrated circuit. The signal output terminal of the gate drive circuit or gate drive integrated circuit is connected to the gate of the gallium nitride MOSFET. The source and drain of the gallium nitride MOSFET are connected to the power conversion path of the gallium nitride DC-DC circuit.

3. The power supply system for supplying power to the LED load of vehicle lights according to claim 2, characterized in that, The gate drive circuit includes a second control module and a push-pull circuit; The signal output terminal of the second control module is connected to the signal input terminal of the push-pull circuit; The power output terminal of the push-pull circuit is connected to the gate of the gallium nitride MOSFET.

4. The power supply system for supplying power to the LED load of vehicle lights according to claim 2, characterized in that, The signal output terminal of the gate drive circuit or gate drive integrated circuit is connected to the gate of the gallium nitride MOSFET via a wire to transmit a pulse width modulation signal.

5. The power supply system for supplying power to the LED load of a vehicle headlight according to claim 1, characterized in that, The LED peak current absorption circuit includes a detection resistor, which is connected in series in the main current loop between the output terminal of the gallium nitride DC-DC circuit and the input terminal of the LED dynamic load. The two ends of the detection resistor are respectively connected to the two voltage detection terminals of the gallium nitride DC-DC circuit via wires.

6. The power supply system for supplying power to the LED load of a vehicle lamp according to claim 5, characterized in that, The LED peak current absorption circuit also includes power switching devices and resistors; The control terminal of the power switching device is connected to the control signal output terminal of the gallium nitride DC-DC circuit via a wire; the first conducting terminal of the power switching device is connected to one end of the resistor, and the other end of the resistor is grounded; the second conducting terminal of the power switching device is connected to the node between the output terminal of the gallium nitride DC-DC circuit and the detection resistor via a wire.

7. The power supply system for supplying power to the LED load of a vehicle headlight according to claim 6, characterized in that, The gallium nitride DC-DC circuit sends a control signal to the control terminal of the power switching device based on the comparison result between the voltage across the detection resistor and the internal reference voltage. The internal reference voltage includes a first reference voltage and a second reference voltage, wherein the value of the first reference voltage is 120% × ILED × Rsense, and the value of the second reference voltage is 110% × ILED × Rsense, where ILED is the steady-state operating current of the LED dynamic load, and Rsense is the resistance value of the sensing resistor.

8. The power supply system for supplying power to the LED load of a vehicle lamp according to claim 1, characterized in that, The gallium nitride DC-DC circuit includes an output filter capacitor, the positive terminal of which is connected to the positive terminal of the output of the gallium nitride DC-DC circuit, and its negative terminal is grounded. The switching frequency of the gallium nitride MOSFET in the gallium nitride DC-DC circuit is inversely related to the capacitance of the output filter capacitor.

9. The power supply system for supplying power to the LED load of a vehicle lamp according to claim 1, characterized in that, It also includes a first control module or electronic control unit; The first input / output port of the first control module or electronic control unit is connected to the enable terminal and the status feedback terminal of the gallium nitride DC-DC circuit via wires; The second input / output port of the first control module or electronic control unit is connected to the control signal input terminal of the LED dynamic load via a wire.

10. The power supply system for supplying power to the LED load of a vehicle lamp according to claim 1, characterized in that, The input terminal of the gallium nitride DC-DC circuit is connected to the vehicle power supply. The LED dynamic load consists of multiple LED beads and a switch array that controls their on / off state. The control port of the switch array is connected to an external control signal source.

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