Multi-path LED lamp driving circuit for automobile lamp, automobile lamp assembly and automobile

Abstract

The invention provides a multi-path LED lamp driving circuit for an automobile lamp, an automobile lamp assembly and an automobile. The multi-path LED lamp driving circuit comprises a constant-current current source; the mirror current source circuit comprises a plurality of mirror triodes and bias control triodes, and the number of the mirror triodes is the same as that of the LED lamps; the base electrodes of the plurality of mirror image triodes are all connected to a common-base bias node, the emitting electrodes of the plurality of mirror image triodes are all connected to the constant current source, and the collector electrode of each mirror image triode is connected with the voltage input end of one LED lamp; and the emitting electrode of the bias control triode is connected with the common-base bias node, and the base electrode and the collector electrode of the bias control triode are respectively connected with the voltage input end of one LED lamp. According to the scheme, the current consistency of each LED lamp is ensured, the circuit structure is simple, the complexity of circuit design and PCB layout is reduced, and the layout space is saved.

Description

Technical Field

[0001] This application relates to the field of automotive lighting control technology, specifically to a multi-channel LED lamp driver circuit for automotive lights, an automotive lighting assembly, and an automobile. Background Technology

[0002] LEDs are widely used as automotive lighting sources, and the performance of their driving circuits directly determines the stability and uniformity of the lighting effect and the reliability of the entire vehicle. Currently, the mainstream solution for constant current driving of multiple LEDs is to use a multi-channel chip constant current solution. However, when driving multiple LEDs, to achieve high-precision consistency of current across each channel, a parallel current-sharing resistor solution or a multi-channel constant current chip solution is typically used. While the parallel current-sharing resistor solution is simple, it suffers from poor accuracy and low efficiency. Although using a multi-channel constant current chip offers higher accuracy and efficiency, it leads to a significant increase in circuit size, complexity, and cost, resulting in a large PCB footprint, making it difficult to widely apply in cost-sensitive and space-constrained automotive lighting modules.

[0003] Therefore, the current field of multi-channel LED lighting drivers for automotive lights urgently needs a multi-channel driving solution that can balance high-precision current sharing, high efficiency, high reliability, low cost, low complexity, and small footprint. Summary of the Invention

[0004] The technical problem to be solved by this application is that the existing multi-channel LED lamp driving schemes for vehicle lamps have problems such as poor accuracy, low efficiency, or complex circuits, high cost, and large space requirements. Therefore, this application provides a multi-channel LED lamp driving circuit, a vehicle lamp assembly, and a vehicle.

[0005] In a first aspect, the technical solution of this application provides a multi-channel LED lamp driver circuit for vehicle lights, including: Constant current source; The current mirror circuit includes multiple mirror transistors and a bias control transistor. The number of mirror transistors is the same as the number of LEDs. The bases of the multiple mirror transistors are all connected to a common-base bias node, and the emitters of the multiple mirror transistors are all connected to the constant current source. The collector of each mirror transistor is connected to the voltage input terminal of one LED. The emitter of the bias control transistor is connected to the common-base bias node, and its base and collector are respectively connected to the voltage input terminal of one LED.

[0006] Preferably, the multi-channel LED lamp driver circuit for vehicle lights further includes: An emitter resistor unit is connected in series between the constant current source and the emitter of each of the mirror transistors.

[0007] Preferably, in the multi-channel LED lamp driving circuit for vehicle lights, the emitter resistor unit comprises two resistors with the same resistance value connected in parallel.

[0008] Preferably, the multi-channel LED lamp driver circuit for vehicle lights further includes: The first current-limiting resistor unit is disposed between the base of each of the mirror transistors and the common-base bias node.

[0009] Preferably, the multi-channel LED lamp driver circuit for vehicle lights further includes: The second current-limiting resistor unit is disposed between the base of each bias control transistor and the voltage input terminal of the corresponding LED.

[0010] Preferably, in the multi-channel LED lamp driving circuit for vehicle lights, both the mirror transistor and the bias control transistor are PNP bipolar transistors; preferably, a capacitor is connected in parallel between the base and emitter, and between the collector and emitter of each mirror transistor.

[0011] Preferably, in the multi-channel LED lamp driving circuit for vehicle lights, the mirror transistor is a medium-power, low-saturation-dropout bipolar transistor; and the bias control transistor is a small-signal bipolar transistor with high collector-emitter breakdown voltage.

[0012] Preferably, the multi-channel LED lamp driving circuit for vehicle lights includes two channels of LED lamps, and each channel of LED lamps includes multiple LED light sources connected in series.

[0013] Secondly, the present application provides a vehicle lamp assembly, including a multi-channel LED lamp driving circuit for vehicle lamps as described in any of the first aspects and a vehicle lamp; the LED light source in the vehicle lamp is divided into multiple LED lamps connected in series, and each LED lamp is connected to the base of a mirror transistor in the multi-channel LED lamp driving circuit.

[0014] Thirdly, the present application provides an automobile, including the headlight assembly described in the second aspect.

[0015] The technical solution provided in this application has the following technical effects compared with the prior art: This application provides a multi-channel LED driver circuit, a vehicle lighting assembly, and a car. It utilizes a mirror current source circuit to divide a constant current source into multiple channels. A bias control transistor is positioned between the mirror transistor and the LED, ensuring that different LED channels have the same bias, thus guaranteeing current consistency across all LED channels. The circuit employs discrete components to construct the current sharing circuit, eliminating the need for expensive multi-channel constant current driver chips and reducing overall material costs by approximately 40%, making it particularly suitable for cost-sensitive large-scale automotive lighting applications. Furthermore, the multi-channel LED driver circuit provided in this application has a simple structure, eliminating the need for complex sampling, operational amplification, or PWM feedback control loops, reducing the complexity of circuit design and PCB layout, and saving layout space. Attached Figure Description

[0016] Figure 1 This is a schematic block diagram of a multi-channel LED lamp driver circuit for vehicle lights according to one embodiment of this application; Figure 2 This is a circuit diagram of a two-channel LED driver circuit according to one embodiment of this application; Figure 3 This is a circuit diagram of a two-channel LED driver circuit according to another embodiment of this application. Detailed Implementation

[0017] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0018] It is readily understood that, based on the technical solution of this application, various structural and implementation methods can be interchanged by those skilled in the art without altering the essential spirit of this application. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this application and should not be considered as the entirety of this application or as limitations or restrictions on the technical solution of the application.

[0019] This application provides a multi-channel LED lamp driver circuit for vehicle lights. Its core lies in utilizing the basic principle of transistor current mirroring to achieve automatic replication and precise allocation of constant current sources by constructing a symmetrical transistor network with shared bias.

[0020] like Figure 1As shown, this embodiment provides a multi-channel LED driver circuit for vehicle lights, including a constant current source 100 and a mirror current source circuit 200. The constant current source can output a preset current. The mirror current source circuit 200 includes multiple mirror transistors and a bias control transistor, the number of which is the same as the number of LED channels. The bases of the multiple mirror transistors are all connected to a common-base bias node, and the emitters of the multiple mirror transistors are all connected to the constant current source. The collector of each mirror transistor is connected to the voltage input terminal of one LED channel, and the other end of each LED channel is grounded. The emitter of the bias control transistor is connected to the common-base bias node, and its base and collector are respectively connected to the voltage input terminal of one LED channel.

[0021] The theoretical basis of the above-mentioned scheme in this application is based on the current transfer characteristics of mirror transistors and bias-controlled transistors. When multiple mirror transistors are electrically matched and subjected to the same base-emitter bias voltage, their collector currents will exhibit a definite and consistent proportional relationship according to their carrier transport equation. This scheme creates a common-base, common-emitter symmetrical bias structure, so that the collector terminals of all mirror transistors operate under the same bias state, thereby enabling their output current to spontaneously and accurately track and equal the same reference current. Since the collector of each mirror transistor is connected to one LED, high-precision current sharing of multiple LEDs is achieved.

[0022] In the above embodiment, the constant current source 100 is divided into multiple paths using a mirror current source circuit 200. A bias control transistor is placed between the mirror transistor and the LED, ensuring that different LED paths have the same bias, thereby ensuring current consistency across all LED paths. This circuit uses discrete components to construct the current sharing circuit, eliminating the need for expensive multi-channel constant current driver chips and reducing overall material costs by approximately 40%, making it particularly suitable for cost-sensitive large-scale automotive lighting applications. Furthermore, the multi-channel LED driver circuit provided by this solution has a simple structure, eliminating the need for complex sampling, operational amplification, or PWM feedback control loops, reducing the complexity of circuit design and PCB layout, and saving layout space.

[0023] Figure 2 and Figure 3The circuit shown is an example using two LEDs. Transistors Q1 and Q2 are mirror transistors, and transistor Q3 is a bias control transistor. One LED string consists of LEDs 1-5 connected in series, and the other consists of LEDs 6-10 connected in series. As shown, the multi-LED driver circuit also includes an emitter resistor unit connected in series between the constant current source and the emitter of each mirror transistor. Preferably, the emitter resistor unit comprises two resistors of the same value connected in parallel. As shown in the figure, R1 and R2, R3 and R4 are all 10K ohms resistors. R1 and R2 in parallel form one emitter resistor unit, and R3 and R4 in parallel form another emitter resistor unit. Using two resistors in parallel to form an emitter resistor unit improves the circuit's power handling and heat dissipation capabilities. According to Joule's law, the power dissipated by the resistor is P = I² × R. The current flowing through the emitter resistor unit is the driving current of the LED, which is typically several hundred milliamps. If only one resistor is used, that resistor would have to bear all the heat generated. This solution uses two resistors of equal resistance in parallel, so the current flowing through each resistor is half the drive current. Therefore, the power consumed by each resistor is approximately half the total power, and heat generation is reduced. Furthermore, because resistors R1-R4 are introduced at the emitter of the transistor mirror, they act as negative feedback, effectively suppressing transistor parameter drift caused by temperature changes. This allows the multi-channel LED driver circuit in this solution to maintain stable current sharing performance under various automotive-grade temperature conditions.

[0024] Preferably, such as Figure 2 and Figure 3As shown, the multi-channel LED driver circuit also includes a first current-limiting resistor unit, disposed between the base of each of the mirror transistors and the common-base bias node. The first current-limiting resistor unit includes resistors R5 and R6 as shown in the figure. Resistor R5 is disposed between the base of transistor Q2 and the common-base bias node, and resistor R6 is disposed between the base of transistor Q1 and the common-base bias node. Further, the multi-channel LED driver circuit also includes a second current-limiting resistor unit, disposed between the base of each of the bias control transistors and the voltage input terminal of the corresponding LED. Resistor R7 as shown in the figure is disposed between the base of transistor Q3 and the voltage input terminal of the corresponding LED. In this scheme, resistors R5, R6, and R7 limit the current, set the operating point, and together with transistor Q3, form a voltage detection and switching control circuit. That is, by introducing transistor Q3 and the combined circuit with resistors R5, R6, and R7, a fault protection mechanism of "all LEDs turning off when one goes out" is achieved. When any LED light experiences an open-circuit fault, the multi-LED light driver circuit of this application can automatically cut off the power supply to all LED lights, avoiding potential safety hazards or misjudgments that may occur if one LED light fails while another LED light continues to work normally, thus improving the functional safety level of the entire vehicle.

[0025] In the above scheme, the LED light has two operating states: State 1: During normal operation All LEDs in each path functioned normally; LEDs 1-5 and 6-10 were all intact. The mirror transistors were turned on, and the constant current source drove current through transistors Q1 and Q2, causing them to operate in the amplification region. At this time, the collector voltage V_C1 of transistor Q1 was clamped to a relatively low potential, i.e., a low level. The collector voltage of transistor Q1 was directly applied to the base of transistor Q3. Because the collector voltage of transistor Q1 was low enough, the base-emitter voltage of transistor Q3 met the conduction condition, thus transistor Q3 turned on. After transistor Q3 turned on, its collector current flowed through resistors R5, R6, and R7, establishing a stable bias voltage at their common node, the common-base bias node. This voltage continuously provided base current for transistors Q1 and Q2, maintaining the stable operation of the entire mirror current source. Ultimately, both LEDs illuminated normally with equal current.

[0026] State 2: When a fault occurs Suppose that the power supply to one of the LEDs in an LED string (LED1-LED5) is open-circuited.

[0027] When transistor Q1 is turned off, the current path in that branch is cut off, and the collector current of transistor Q1 instantly becomes zero. As the constant current source attempts to maintain the current, the collector potential V_C1 of transistor Q1 is rapidly pulled high until it approaches the power supply voltage VCC. At this point, V_C1 changes from "low level" to "high level," and this high level is directly applied to the base of transistor Q3. Since the emitter voltage of transistor Q3 is VCC or close to VCC, its base-emitter voltage becomes extremely small or even reverse-biased, causing transistor Q3 to immediately turn off. After transistor Q3 turns off, it is equivalent to turning off a switch, completely cutting off the current flowing to resistors R5, R6, and R7. The common base node of transistors Q1 and Q2 loses the base current source necessary to maintain conduction. The residual charge at the common-base bias node is rapidly released to ground through paths such as the base-emitter resistors of transistors Q1 and Q2, and the voltage at that point is pulled down to ground potential. Because the common-base bias node voltage becomes 0, transistors Q1 and Q2 are simultaneously cut off due to the loss of bias. As a result, not only does the faulty LED go out, but the other LED also goes out because transistor Q2 is cut off, thus achieving "one goes out and all go out".

[0028] The solution described in this application enables a multi-LED driver circuit to ensure that if any LED fails, all other LEDs remain off. This characteristic allows the driver circuit to perform fault detection and assessment without requiring any changes to the hardware circuitry, thus avoiding any increase in design costs. This result is particularly applicable to turn signal driver circuits.

[0029] Preferably, in the above scheme, both the mirror transistor and the bias control transistor are PNP bipolar transistors. Using PNP transistors maximizes the use of the current source and reduces the output voltage of the current source. Further, the mirror transistor is a medium-power, low-saturation-dropout bipolar transistor; the bias control transistor is a small-signal bipolar transistor with high collector-emitter breakdown voltage. Specifically, transistors Q1 and Q2 use BCP53 transistors, and transistor Q3 uses a 2N5401 transistor. In this scheme, a high-power transistor is used for mirror adjustment to solve the problem of excessively high output voltage and excessively high boost ratio in the driving circuit when all LED power supplies are connected in series. The circuit shown in the diagram achieves two main improvements. First, it splits the previously series-connected LED power supply into two series-connected parts, reducing the input-output boost ratio of the driver circuit, improving the driver's conversion efficiency, reducing the energy consumption of the lamps, and enhancing the vehicle's overall range. Second, it divides one constant current source into two, increasing the load current and significantly improving the efficiency of the driver circuit. Actual testing shows that, using this solution, within an input voltage range of 12V ± 10% and an ambient temperature range of -40℃ to 85℃, the current deviation between the two LED sources can be stably controlled within ±3%, effectively solving the problem of uneven brightness across multiple LED sources.

[0030] Furthermore, such as Figure 3 As shown, the multi-channel LED light driver circuit and the vehicle light can also be configured with a capacitor bank for each mirror transistor. Among them, capacitors C1 and C3 are connected in parallel between the emitter and collector of Q1 and Q2 to suppress high-frequency oscillation, and capacitors C2 and C4 are connected in parallel between the base and emitter of Q1 and Q2 to filter out high-frequency interference / noise from the base.

[0031] To verify the effectiveness of the proposed solution, OrCAD software was used. Figure 3The circuit shown was simulated and analyzed under the following conditions: Mode: DRL / Input: 270mA / 25℃ / String1&2: Normal VF Bin (2.9V). The constant current source input current I1 was set to 270mA, and the LED's VF value was 2.9V at 25 degrees Celsius. The simulation results showed that one transistor output current was 136.2mA, and the other transistor output current was 133.8mA. The error calculation was: Δ = (136.2-135) / 135*100% = 0.89%, which is very small and meets the high-precision requirements. In practical applications, with the LED current at 150mA and the output current of the constant current source set to 300mA, the actual test showed that the current difference between the two LED paths was less than 1%, consistent with the simulation results. The current of the first LED path was 147mA, and the current of the other LED path was 153mA. The Vce voltage drop of transistors Q1 and Q2 was less than 1V. In practical applications, 24 white LEDs and 24 yellow LEDs were used, with each LED having a power of 0.5W. Before using the shunt circuit of this application, two boost / buck constant current drive circuits were required, with 12 LEDs connected in series in each circuit for driving. With an input voltage of 13.5V, the output voltage of the constant current circuit should be at least 12 * 3.5V = 42V, and the boost ratio is 42V / 13.5V, approximately 3:1. Using the driving circuit of this application, the 24 LED light sources are divided into two strings. Connecting this current mirror circuit to a single boost / buck constant current driving circuit meets the requirements. Simultaneously, the load current of the constant current driving circuit doubles, and the efficiency is improved by approximately 5%, reaching 84% (the SEPIC circuit has an output current of 150mA, a boost ratio of 3:1, and an output voltage of 42V, resulting in a conversion efficiency of approximately 79%). The above experiments demonstrate that the solution of this application successfully achieves an excellent balance between low cost, high reliability, small size, and high precision, providing a multi-channel LED driving circuit particularly suitable for automotive-grade applications.

[0032] This application embodiment also provides a vehicle lamp assembly, including the multi-channel LED lamp driving circuit for vehicle lamps described in the above embodiments and the vehicle lamp; the LED light source in the vehicle lamp is divided into multiple LED lamps connected in series, and each LED lamp is connected to the base of a mirror transistor in the multi-channel LED lamp driving circuit.

[0033] This application also provides an automobile, including the headlight assembly described in the above embodiments.

[0034] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0035] The above are merely the principles and preferred embodiments of this application. It should be noted that, for those skilled in the art, several other modifications can be made based on the principles of this application, and these modifications should also be considered within the scope of protection of this application.

Claims

1. A multi-channel LED lamp driver circuit for vehicle lights, characterized in that, include: Constant current source; A current mirror circuit includes multiple mirror transistors and a bias control transistor, wherein the number of mirror transistors is the same as the number of LEDs. The bases of the multiple mirror transistors are all connected to a common-base bias node, the emitters of the multiple mirror transistors are all connected to the constant current source, and the collector of each mirror transistor is connected to the voltage input terminal of an LED; the bias control transistor has its emitter connected to the common-base bias node, and its base and collector are respectively connected to the voltage input terminal of an LED.

2. The multi-channel LED lamp driver circuit for vehicle lights according to claim 1, characterized in that, Also includes: An emitter resistor unit is connected in series between the constant current source and the emitter of each of the mirror transistors.

3. The multi-channel LED lamp driver circuit for vehicle lights according to claim 2, characterized in that: The emitter resistor unit comprises two resistors with the same resistance value connected in parallel.

4. The multi-channel LED lamp driver circuit for vehicle lights according to claim 1, characterized in that, Also includes: The first current-limiting resistor unit is disposed between the base of each of the mirror transistors and the common-base bias node.

5. The multi-channel LED lamp driver circuit for vehicle lights according to claim 1, characterized in that, Also includes: The second current-limiting resistor unit is disposed between the base of each bias control transistor and the voltage input terminal of the corresponding LED.

6. The multi-channel LED lamp driver circuit for vehicle lights according to claim 1, characterized in that: Both the mirror transistor and the bias control transistor are PNP bipolar transistors; Preferably, a capacitor is connected in parallel between the base and emitter, and between the collector and emitter, of each mirror transistor.

7. The multi-channel LED lamp driver circuit for vehicle lights according to claim 6, characterized in that: The mirror transistor is a medium-power, low-saturation-dropout bipolar transistor; the bias control transistor is a small-signal bipolar transistor with high collector-emitter breakdown voltage.

8. The multi-channel LED lamp driver circuit for vehicle lights according to any one of claims 1-7, characterized in that: The LED lights include two paths, and each path contains multiple LED light sources connected in series.

9. A vehicle lighting assembly, characterized in that, The invention includes the multi-channel LED lamp driving circuit for vehicle lamps as described in any one of claims 1-8, and the vehicle lamp itself; wherein the LED light source in the vehicle lamp is divided into multiple LED lamps connected in series, and each LED lamp is connected to the base of a mirror transistor in the multi-channel LED lamp driving circuit.

10. A car, characterized in that, Includes the headlight assembly as described in claim 9.

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