Car lamp LED constant current driving circuit

Abstract

The utility model discloses a car light LED constant current drive circuit, including: reference source generating circuit, constant current source operational circuit and current drive circuit, wherein the reference source generating circuit generates reference voltage through the cooperation of voltage reference source chip and divider resistor, constant current source operational circuit includes operational amplifier, current drive circuit is connected with the operational amplifier. The non-inverting input end of the operational amplifier is connected with reference voltage, the inverting input end of the operational amplifier is connected with a feedback voltage port of the current driving circuit, the gate pole of the NMOS tube is connected with the output end of the operational amplifier, the gate pole voltage of the NMOS tube is adjusted in a current feedback mode, and high-precision constant-current output is achieved. The car lamp LED constant-current driving circuit is high in constant-current precision, good in stability, simple in circuit, higher in integration level and smaller in occupied PCB area, the influence of parameter change and temperature of the NMOS tube is small, and the output current can be conveniently adjusted by changing the reference voltage.

Description

Technical Field

[0001] This utility model relates to a circuit structure, and in particular provides a constant current driving circuit for vehicle LED lights. Background Technology

[0002] In automotive lighting electronic control systems, LED light sources require a constant current supply to produce stable luminous intensity. However, traditional constant current source circuits are mostly discrete component circuits, employing transistor designs. They stabilize the current by adjusting the base voltage through resistors and the power supply voltage, ensuring the transistor operates within a suitable range to provide a stable current. For high-current LED drivers, this approach requires multiple high-current transistors connected in parallel to achieve constant current, resulting in a large circuit footprint and significant susceptibility of constant current accuracy to transistor parameter variations and temperature fluctuations.

[0003] Therefore, providing a simple, highly accurate, and stable constant current drive circuit for automotive LED lights has become an urgent problem to be solved. Utility Model Content

[0004] Therefore, the purpose of this utility model is to provide a constant current driving circuit for automotive LED lights to solve the problems existing in traditional constant current source circuits.

[0005] The technical solution provided by this utility model is: a constant current driving circuit for automotive LED lights, comprising: a reference source generating circuit, a constant current source operating circuit, and a current driving circuit. The reference source generating circuit includes a voltage reference chip V1, a current-limiting resistor VR1, a filter capacitor VC1, a voltage divider resistor VR2, a voltage divider resistor VRx, and a bypass capacitor VC2. The cathode of the reference chip V1 is connected to the power supply VCC through the current-limiting resistor VR1. The reference output pin of the reference chip V1 is connected to the cathode of the reference chip V1. The anode of the reference chip V1 is grounded to GND. The two ends of the filter capacitor VC1 are connected to the power supply VCC and grounded to GND, respectively. One end of the voltage divider resistor VR2 is connected to the cathode of the reference chip V1, and the other end of the voltage divider resistor VR2 is grounded to GND through the bypass capacitor VC2. The voltage divider resistor VRx is connected in parallel across the bypass capacitor VC2. The constant current source operating circuit includes... Operational amplifier U1A is included, with its non-inverting input connected to the voltage divider resistors VR2 and VRx. The current drive circuit includes a current-limiting resistor R1, a vehicle headlight LED, an ESD capacitor CP3, an NMOS transistor Q1, a sampling resistor RS1, and a bypass capacitor CP2. The anode of the vehicle headlight LED is connected to the power supply VCC, and the cathode is connected to the drain of the NMOS transistor Q1. The ESD capacitor CP3 is connected in parallel with the vehicle headlight LED. The gate of the NMOS transistor Q1 is connected to the output of operational amplifier U1A through the current-limiting resistor R1. The source of the NMOS transistor Q1 is grounded to GND through the sampling resistor RS1. The bypass capacitor CP2 is connected in parallel with the sampling resistor RS1, and the source of the NMOS transistor Q1 is connected to the inverting input of operational amplifier U1A.

[0006] Preferably, the constant current source operational circuit further includes a bypass capacitor CP1, one end of which is connected to the power supply VCC and the other end is grounded. The power supply VCC is connected to the power supply pin of the operational amplifier U1A.

[0007] In a further preferred embodiment, the anode of the LED light-emitting diode of the vehicle headlight is connected to the power supply VCC through a current-limiting resistor R2.

[0008] The constant current driving circuit for automotive LEDs provided by this utility model consists of an operational amplifier, an enhancement-mode N-channel MOSFET, a voltage reference source, and several resistors and capacitors. The NMOS transistor operates in the variable resistance region. The non-inverting input of the operational amplifier is connected to the reference voltage, and the inverting input acquires the LED current through a sampling resistor RS1. The gate of the NMOS transistor is connected to the output of the operational amplifier. By adjusting the gate voltage of the NMOS transistor through current feedback, high-precision constant current output can be achieved. Compared with traditional constant current source circuits, the constant current driving circuit provided in this application can improve the constant current accuracy by several times or even an order of magnitude, which not only meets the requirements of automotive lighting applications with extremely high current accuracy requirements but also improves the luminous efficiency of LEDs and extends their lifespan.

[0009] The constant current driving circuit for automotive LED lights provided by this utility model has high constant current accuracy, good stability, simple circuit, higher integration, smaller PCB area, less influence from NMOS transistor parameter changes and temperature, and the output current can be easily adjusted by changing the reference voltage. Attached Figure Description

[0010] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0011] Figure 1 Circuit diagram of the constant current drive circuit for vehicle LED lights provided by this utility model;

[0012] Figure 2 The circuit diagram for the reference source generation circuit;

[0013] Figure 3 The equivalent circuit diagram of the reference source generation circuit;

[0014] Figure 4 The circuit diagram is for a constant current source operational circuit.

[0015] Figure 5 This is a circuit diagram of a current-driven circuit. Detailed Implementation

[0016] The present invention will be further explained below with reference to specific implementation schemes, but it is not limited to the present invention.

[0017] like Figure 1 , Figure 2 , Figure 4 , Figure 5As shown, this utility model provides a constant current driving circuit for automotive LED lights, including: a reference source generating circuit, a constant current source operating circuit, and a current driving circuit. The reference source generating circuit includes a voltage reference chip V1, a current-limiting resistor VR1, a filter capacitor VC1, a voltage divider resistor VR2, a voltage divider resistor VRx, and a bypass capacitor VC2. The cathode of the reference chip V1 is connected to the power supply VCC through the current-limiting resistor VR1. The reference output pin of the reference chip V1 is connected to the cathode of the reference chip V1, and the anode of the reference chip V1 is grounded to GND. The two ends of the filter capacitor VC1 are connected to the power supply VCC and ground GND respectively, thus forming a conducting loop. One end of the voltage divider resistor VR2 is connected to the cathode of the reference chip V1, and the other end of the voltage divider resistor VR2 is grounded to GND through the bypass capacitor VC2. The voltage divider resistor VRx is connected in parallel across the bypass capacitor VC2. The reference output pin of the reference chip V1, after voltage division by the voltage divider resistors VR2 and VRx, can be driven by the bypass capacitor VC2. The required reference voltage VREF is generated on the 2nd. The constant current source operational circuit includes an operational amplifier U1A. The non-inverting input terminal of the operational amplifier U1A is connected to the connection terminal of the voltage divider resistors VR2 and VRx, that is, it is connected to the reference voltage output by the reference source generation circuit. The current driving circuit includes a current limiting resistor R1, a vehicle headlight LED, an ESD anti-static capacitor CP3, an NMOS transistor Q1, a sampling resistor RS1, and a bypass capacitor CP2. The anode of the vehicle headlight LED is connected to the power supply VCC. The cathode of the vehicle headlight LED is connected to the drain of the NMOS transistor Q1. The ESD anti-static capacitor CP3 is connected in parallel with the vehicle headlight LED. The gate of the NMOS transistor Q1 is connected to the output terminal of the operational amplifier U1A through the current limiting resistor R1. The source of the NMOS transistor Q1 is grounded to GND through the sampling resistor RS1. The bypass capacitor CP2 is connected in parallel with the sampling resistor RS1. The source of the NMOS transistor Q1 is connected to the inverting input terminal of the operational amplifier U1A.

[0018] The working principle of the LED constant current drive circuit for this car headlight is as follows:

[0019] The reference source generating circuit is used to generate the required reference voltage VREF, and the equivalent circuit of this circuit is as follows: Figure 3In the equivalent circuit, the inverting input VN1 of operational amplifier U2B is fixed by an internally generated voltage bias (2.5V). When the non-inverting input VP1 of U2B is higher than 2.5V, the base of transistor Q2 generates a high level, and the collector and emitter of transistor Q2 are linearly connected. At this time, the current flowing through resistor VR1 increases, resulting in a larger voltage drop across VR1, and thus a decrease in the voltage at the non-inverting input VP1 of U2B. When the non-inverting input VP1 of U2B is less than 2.5V, the operational amplifier output of U2B is low, transistor Q2 is cut off, the current flowing through VR1 decreases, resulting in a smaller voltage drop across VR1, and thus an increase in the voltage at VP1. A stable 2.5V voltage source is generated at the measurement point TP1. TP1 serves as a precise 2.5V constant voltage reference source. After voltage division by VR2 and VRx, the reference voltage VREF can be obtained by adjusting the ratio of these two resistors.

[0020] The operational amplifier U1A in the constant current source operational circuit has virtual short and virtual open characteristics, meaning that the potentials of its non-inverting input terminal VP and inverting input terminal VN are approximately equal, its input impedance is infinite, and its input current is approximately zero. After the op-amp starts operating, it will always maintain VP = VN. When the voltage at the inverting input terminal of operational amplifier U1A is higher than the voltage at the non-inverting input terminal, the op-amp output voltage decreases, thus reducing the feedback voltage; similarly, when the voltage at the inverting input terminal of operational amplifier U1A is lower than the voltage at the non-inverting input terminal, the op-amp output voltage increases, thus increasing the feedback voltage. The output terminal of operational amplifier U1A is connected to the drive port of the current drive circuit, and the inverting input terminal of operational amplifier U1A is used to connect to the voltage feedback port of the current drive circuit.

[0021] The current-driven circuit feeds back a voltage to the inverting input of operational amplifier U1A. This feedback voltage is always equal to the reference voltage VREF, i.e., VREF = feedback voltage. Since VREF is fixed, according to the formula "feedback voltage = RS1 * Ix", and because the value of RS1 is also fixed, Ix will ultimately remain constant, achieving constant current output. Therefore, in practical applications, precise constant current output of Ix can be achieved simply by adjusting the ratio of the voltage divider resistors VR2 and VRx.

[0022] Figure 4 , Figure 5 In this circuit, the voltage at the driver terminal is adjusted in real time based on the voltage across the sampling resistor RS1 to ensure that the current flowing through RS1 is Ix = VREF / RS1. The filter capacitor CP2 connected in parallel across the sampling resistor RS1 can filter out some spikes and glitches on RS1, thereby providing a stable negative feedback signal.

[0023] As an improvement to the technical solution, the constant current source operational circuit also includes a bypass capacitor CP1. One end of the bypass capacitor CP1 is connected to the power supply VCC, and the other end is grounded. The power supply VCC is connected to the power supply pin of the operational amplifier U1A.

[0024] The NMOS transistor Q1 operates in the variable resistance region. To reduce the power dissipation of the NMOS transistor during unsaturated conduction, thereby reducing its heat generation, as an improvement to the technical solution, the anode of the LED light-emitting diode in the vehicle headlight is connected to the power supply VCC through a current-limiting resistor R2. By introducing resistor R2, the power dissipation of the NMOS transistor Q1 can be dispersed, increasing the circuit's load current and enabling it to drive higher-power LED chips. P = U 2 / R, when Q1's V DS When the voltage decreases, the power dissipation P decreases exponentially, thereby reducing the heat generation of the NMOS.

[0025] In practical applications, multi-channel operational amplifiers can be selected to achieve multi-channel constant current output. Utilizing multiple op-amps and independent feedback loops, independent constant current control of multiple channels is achieved, with each channel isolated from the others and free from interference. Multiple channels can drive more LED light sources and simultaneously provide precise constant current control for multiple LED loads.

[0026] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A constant current driving circuit for automotive LED lights, characterized in that, include: The system comprises a reference source generation circuit, a constant current source operation circuit, and a current drive circuit. The reference source generation circuit includes a voltage reference chip V1, a current-limiting resistor VR1, a filter capacitor VC1, a voltage divider resistor VR2, a voltage divider resistor VRx, and a bypass capacitor VC2. The cathode of the reference chip V1 is connected to the power supply VCC via the current-limiting resistor VR1. The reference output pin of the reference chip V1 is connected to the cathode of the reference chip V1. The anode of the reference chip V1 is grounded to GND. The two ends of the filter capacitor VC1 are connected to the power supply VCC and grounded to GND, respectively. One end of the voltage divider resistor VR2 is connected to the cathode of the reference chip V1, and the other end of the voltage divider resistor VR2 is grounded to GND via the bypass capacitor VC2. The voltage divider resistor VRx is connected in parallel across the bypass capacitor VC2. The constant current source operation circuit includes an operational amplifier U1A. The non-inverting input terminal of the amplifier U1A is connected to the connection terminals of the voltage divider resistors VR2 and VRx. The current driving circuit includes a current-limiting resistor R1, a vehicle headlight LED, an ESD capacitor CP3, an NMOS transistor Q1, a sampling resistor RS1, and a bypass capacitor CP2. The anode of the vehicle headlight LED is connected to the power supply VCC, and the cathode of the vehicle headlight LED is connected to the drain of the NMOS transistor Q1. The ESD capacitor CP3 is connected in parallel with the vehicle headlight LED. The gate of the NMOS transistor Q1 is connected to the output terminal of the operational amplifier U1A through the current-limiting resistor R1. The source of the NMOS transistor Q1 is grounded to GND through the sampling resistor RS1. The bypass capacitor CP2 is connected in parallel with the sampling resistor RS1. The source of the NMOS transistor Q1 is connected to the inverting input terminal of the operational amplifier U1A.

2. The constant current driving circuit for automotive LED lights according to claim 1, characterized in that: The constant current source operational circuit also includes a bypass capacitor CP1. One end of the bypass capacitor CP1 is connected to the power supply VCC, and the other end is grounded. The power supply VCC is connected to the power supply pin of the operational amplifier U1A.

3. The constant current driving circuit for automotive LED lights according to claim 1, characterized in that: The anode of the LED light-emitting diode in the vehicle headlight is connected to the power supply VCC through a current-limiting resistor R2.

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