Constant-current driving circuit and constant-current driving board for automobile lamp

Abstract

The utility model provides a constant-current driving circuit and a constant-current driving board for an automobile lamp. The constant-current driving circuit comprises a power supply, a BUCK topology module, a constant-current module and a load, the power supply is used for outputting power signals. The BUCK topology module is connected between the power supply and the constant current module, and the BUCK topology module is used for converting a power supply signal into a low-voltage signal; the constant current module comprises a main control chip and a current sampling unit, the main control chip is used for converting the low voltage signal into a first current signal, and the current sampling unit is used for converting the first current signal into a first voltage signal and feeding back the first voltage signal to the main control chip; wherein a switching device is arranged in the main control chip; when the load changes, the main control chip keeps the first current signal unchanged by adjusting the switching device. According to the utility model, the technical problem that the design cost is increased due to the fact that the scheme design of the traditional DDC-BUCK type LED drive circuit is often changed on different drive boards along with items and repeated work exists in processing experiment problems such as EMC and the like is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of automobile lighting, in particular to a constant current drive circuit for automobile lights and a constant current drive board for automobile lights. Background Art

[0002] As a new light source, LEDs offer energy-saving, environmentally friendly, and highly efficient features. The technology has matured and is now widely used in various fields. LEDs are widely used as lighting sources, and with them, a variety of LED driver circuits have emerged. With the rapid development of the automotive lighting industry and the diverse design of headlights, the space available for LED drivers is shrinking, and the requirements for driver integration are becoming increasingly demanding. Therefore, DCDC-BUCK drivers have become a necessary technology.

[0003] However, in actual use, there is such a problem: when designing traditional DCDC-BUCK type LED drivers, the circuit scheme design often changes with the project on different driver boards, and there is duplication of work in dealing with experimental problems such as EMC, which increases design costs. Utility Model Content

[0004] The utility model solves the technical problem that the traditional DCDC-BUCK type LED driving circuit solution design often involves repeated work on different driving boards as the project changes, and processing of experimental problems such as EMC, resulting in increased design costs.

[0005] To solve the above problems, the present invention provides a constant current drive circuit for automobile lights, comprising: a power supply, a BUCK topology module, a constant current module and a load; the power supply is used to output a power signal; the BUCK topology module is connected between the power supply and the constant current module, and the BUCK topology module is used to convert the power signal into a low-voltage signal; the constant current module includes a main control chip and a current sampling unit, the main control chip is used to convert the low-voltage signal into a first current signal, and the current sampling unit is used to convert the first current signal into a first voltage signal and feed it back to the main control chip; wherein a switching device is provided in the main control chip; when the load changes, the main control chip adjusts the switching device to keep the first current signal unchanged.

[0006] Compared with existing technologies, this technical solution achieves the following technical effects: After the power supply flows through the BUCK topology module, it outputs a stable low-voltage signal that enters the main control chip. After the low-voltage signal is converted by the main control chip, it outputs a stable current to power the load. After sampling, the high-side and low-side current sampling units flow through resistors to convert the current signal into a voltage signal that is fed back to the main control chip. When the load changes, the main control chip continuously adjusts the switching frequency and duty cycle of the switching device to maintain the first current signal unchanged, thereby maintaining the stability of the output current. Compared with traditional board-level integrated DCDC-BUCK LED drivers for adaptive projects, the constant current drive circuit of this utility model has further improved integration and standardization, making performance testing more stable and reliable, and improving the first-time test pass rate. At the same time, the modular design partially decouples the project from the design and production, enabling mass production and large-scale procurement to reduce procurement costs. The constant current module is used to provide a constant current for subsequent loads. The main control chip uses a step-down constant current chip. The current sampling unit includes a high-side current sampling unit and a low-side current sampling unit.

[0007] In one example of the present invention, the main control chip includes a first pin and an eighth pin, the first pin is connected to the load, and the eighth pin is connected to the power supply, and the constant current drive circuit also includes: a first resistor, the first resistor is connected between the first pin and the eighth pin; a second resistor, the second resistor is connected between the first pin and the eighth pin; a first inductor, one end of the first inductor is connected to the first pin, and the other end is connected to the eighth pin.

[0008] In one embodiment of the present invention, the constant current driving circuit further includes: a diode, the diode is connected between the first inductor and the main control chip, and the anode of the diode is connected to the first inductor, and the cathode of the diode is connected to the eighth pin.

[0009] Compared to existing technologies, this technical solution achieves the following technical benefits: During normal operation, when a normal input voltage is applied to VIN, the internal switch device of the main control chip turns on; current begins to flow through the first resistor, the second resistor, the first inductor, and the load LED. The current increases linearly, with the rate of increase determined by the input voltage VIN and the first inductor. This rising current generates a voltage ramp across the resistors. The internal circuitry of the main control chip senses the voltage between the first and second resistors and applies a proportional voltage to the input of an internal comparator. When this voltage reaches an internally set upper limit, the internal switch device turns off. The inductor current continues to flow through the first and second resistors, the first inductor, the load LED, and the diode, returning to the power supply, but it decays at a rate determined by the forward voltage drop of the load LED and the diode. This decaying current generates a decreasing voltage across the resistor, which is sensed by the main control chip. A voltage proportional to the sensed voltage across the resistor is applied to the input of the internal comparator. When this voltage drops to an internally set lower threshold, the internal switch device turns on again.

[0010] In an example of the present invention, the main control chip further includes a fifth pin and a sixth pin, which are connected to the anode of the diode; wherein the fifth pin and the sixth pin are also connected to the drain of the switching device.

[0011] In one embodiment of the present invention, the constant current driving circuit further includes: a second capacitor, one end of the second capacitor is connected to the eighth pin and the other end is grounded; a fourth capacitor, one end of the fourth capacitor is connected to the power supply and the other end is grounded.

[0012] In an example of the present invention, the constant current driving circuit further includes: a fifth capacitor connected in parallel to both ends of the load; and a sixth capacitor connected in parallel to both ends of the load.

[0013] In one example of the present invention, the main control chip includes a fourth pin, and the constant current drive circuit also includes: a third capacitor, one end of the third capacitor is connected to the fourth pin, and the other end is grounded; wherein the fourth pin receives the first current signal and the PWM signal of the switching device.

[0014] In one embodiment of the present invention, the constant current driving circuit further includes: a third resistor and a seventh capacitor; the third resistor is connected between the seventh capacitor and the fifth pin; one end of the seventh capacitor is connected to the third resistor, and the other end is grounded.

[0015] In an example of the present invention, the model of the main control chip is AL8860.

[0016] In a specific embodiment, the present invention further provides a constant current driving board for automobile lights, comprising any of the above constant current driving circuits.

[0017] Compared with the prior art, the technical effect achieved by adopting this technical solution is that the constant current driver board in this embodiment has all the beneficial effects of the constant current driver circuit in any embodiment of the present utility model, which will not be repeated here. Using the constant current driver circuit in the above-mentioned embodiment 1 on the constant current driver board, the modular universal design can reduce design pressure on the one hand, and on the other hand, unified materials can be produced in batches without being batched with the project, thereby increasing the product reliability of the constant current driver board and reducing product costs.

[0018] After adopting the technical solution of the utility model, the following technical effects can be achieved:

[0019] (1) Compared with the traditional driver board-level integrated DCDC-BUCK type LED driver of the adaptation project, the integration level is further improved, the standardization level is further improved, the performance test is more stable and reliable, and the one-time test pass rate is improved;

[0020] (2) Modular design achieves partial decoupling of projects and designs, and partial decoupling of production and projects, enabling mass production and mass procurement to reduce procurement costs;

[0021] (3) The modular universal design can reduce design pressure on the one hand, and on the other hand, the unified materials can be produced in batches without following the project, thereby increasing the product reliability of the constant current driver board and reducing product costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a framework diagram of a constant current drive circuit for a car lamp provided in the first embodiment of the present utility model;

[0023] Figure 2 for Figure 1 Circuit diagram of the constant current drive circuit.

[0024] Description of reference numerals:

[0025] 10 - BUCK topology module; 100 - main control chip; 201 - high-side current sampling unit; 202 - low-side current sampling unit; 30 - load; 210 - first resistor; 220 - second resistor; 230 - third resistor; 310 - first inductor; 400 - diode; 510 - first capacitor; 520 - second capacitor; 530 - third capacitor; 540 - fourth capacitor; 550 - fifth capacitor; 560 - sixth capacitor; 570 - seventh capacitor; 580 - eighth capacitor. DETAILED DESCRIPTION

[0026] To make the above-mentioned purposes, features, and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0027] [Example 1]

[0028] See also Figure 1 The utility model provides a constant current drive circuit for automobile lights, combined with Figure 2 The constant current drive circuit includes: a power supply, a BUCK topology module 10, a constant current module and a load 30; the power supply is used to output a power signal; the BUCK topology module is connected between the power supply and the constant current module, and the BUCK topology module 10 is used to convert the power signal into a low-voltage signal; the constant current module includes a main control chip 100 and a current sampling unit, the main control chip 100 is used to convert the low-voltage signal into a first current signal, and the current sampling unit is used to convert the first current signal into a first voltage signal and feed it back to the main control chip 100; wherein, a switching device is provided in the main control chip 100; when the load 30 changes, the main control chip 100 adjusts the switching device to keep the first current signal unchanged.

[0029] In a specific embodiment, when designing a traditional DCDC-BUCK type LED driver, the circuit scheme design often changes with the project on different driver boards, and there is duplication of work in dealing with experimental problems such as EMC, resulting in increased design costs. In order to solve this problem and reduce design pressure, the constant current drive circuit of the present invention, compared with the traditional DCDC-BUCK type LED driver with board-level integration for the adaptation project, has further improved integration and standardization, and the performance experiment is more stable and reliable, which improves the one-time experimental pass rate; at the same time, the modular design realizes partial decoupling of the project and the design, and realizes partial decoupling of production and the project, which can be mass-produced and purchased in large quantities to reduce procurement costs. The constant current module is used to provide a constant current for the subsequent load 30. The main control chip 100 uses a step-down constant current chip, and the current sampling unit includes a high-side current sampling unit 201 and a low-side current sampling unit 202. The working principle is as follows: after the power flows through the BUCK topology module 10, it outputs a stable low-voltage signal that enters the main control chip 100. After the low-voltage signal is converted by the main control chip 100, it outputs a stable current to power the load 30. After sampling by the high-side and low-side current sampling units 202, the current signal flows through the resistor to convert it into a voltage signal, which is then fed back to the main control chip 100. When the load 30 changes, the main control chip 100 continuously adjusts the switching frequency and duty cycle of the switching device to keep the first current signal unchanged, thereby maintaining the stability of the output current.

[0030] Furthermore, the main control chip 100 includes a first pin and an eighth pin, the first pin is connected to the load 30, and the eighth pin is connected to the power supply. The constant current drive circuit also includes: a first resistor 210, the first resistor 210 is connected between the first pin and the eighth pin; a second resistor 220, the second resistor 220 is connected between the first pin and the eighth pin; a first inductor 310, one end of the first inductor 310 is connected to the first pin, and the other end is connected to the eighth pin.

[0031] Specifically, the first pin is the SET pin, which connects resistor RS to VIN to define the nominal average output current. The eighth pin is the VIN pin, which is the power input. R1 is the first resistor 210, and R2 is the second resistor 220. The first and second resistors 210 and 220 are sense resistors, and the output average current can be adjusted by the sense resistors R1 and R2. L1 is the first inductor 310.

[0032] Preferably, in this embodiment, R1 and R2 are both milliohm precision resistors with a resistance value of 0.2R, and the model is R0805.

[0033] The specific working principle of this design is as follows Figure 1As shown in the figure: ① The power supply VIN is initially filtered by a capacitor. The filtered power signal enters the step-down constant current chip, where the switching device inside the main control chip 100 converts it into a high-frequency pulse signal. ② The high-frequency pulse signal is filtered and transformed by the inductor, turning it into a stable low-voltage output signal. During this process, the chip continuously adjusts the switching frequency and duty cycle of the switching device to maintain output current stability.

[0034] Furthermore, the constant current driving circuit further includes: a diode 400 , which is connected between the first inductor 310 and the main control chip 100 , with the anode of the diode 400 connected to the first inductor 310 and the cathode of the diode 400 connected to the eighth pin.

[0035] Specifically, D1 is diode 400, and D2 is a Schottky diode 400. During normal operation, when a normal input voltage is applied to VIN, the internal switch of the main control chip 100 turns on. Current begins to flow through the sense resistors R1 and R2, the inductor L1, and the load 30LED. The current increases linearly, with the rate of increase determined by the input voltage VIN and the inductor L1. This rising current creates a voltage ramp across the resistors. The internal circuitry of the main control chip 100 senses the voltage between R1 and R2 and applies a proportional voltage to the input of the internal comparator. When this voltage reaches an internally set upper limit, the internal switch turns off.

[0036] The inductor current continues to flow through R1, R2, L1, load 30LED, and diode 400D1, returning to the power supply. However, it decays at a rate determined by the forward voltage drop of load 30LED and diode 400D1. This decaying current generates a decreasing voltage across the resistor, which can be sensed by the main control chip 100. A voltage proportional to the sensed voltage across the resistor is applied to the input of the internal comparator. When this voltage drops to an internally set lower threshold, the internal switching device turns on again.

[0037] Furthermore, the main control chip 100 further includes a fifth pin and a sixth pin, which are connected to the anode of the diode 400 ; wherein the fifth pin and the sixth pin are also connected to the drain of the switching device.

[0038] Specifically, the fifth pin is the SW2 pin, and the sixth pin is the SW1 pin. Both the fifth pin and the sixth pin are SW pins. The SW pin is connected to the drain of the internal switching device. The switching device is NDMOS, which is often used for pull-down driving.

[0039] Furthermore, the constant current driving circuit further includes: a second capacitor 520, one end of the second capacitor 520 is connected to the eighth pin, and the other end is grounded; a fourth capacitor 540, one end of the fourth capacitor 540 is connected to the power supply, and the other end is grounded.

[0040] Specifically, C2 is the second capacitor 520, C4 is the fourth capacitor 540, and C2 and C4 are input capacitors; the second capacitor 520 and the fourth capacitor 540 can filter out high-frequency and low-frequency noise on the voltage signal, making the output DC signal smoother.

[0041] Preferably, C2 is 100nF and C4 is 2.2uF.

[0042] Furthermore, the constant current driving circuit further includes: a fifth capacitor 550 , which is connected in parallel to both ends of the load 30 ; and a sixth capacitor 560 , which is connected in parallel to both ends of the load 30 .

[0043] Specifically, C5 is the fifth capacitor 550, and C6 is the sixth capacitor 560. C5 and C6 are output capacitors. The fifth and sixth capacitors 550 and 560 also filter out high- and low-frequency noise from the voltage signal, smoothing the output DC signal. In addition to filtering noise, large capacitors also provide voltage regulation, preventing sudden voltage fluctuations that could cause system instability.

[0044] Preferably, C5 is 10nF and C6 is 4.7uF.

[0045] Furthermore, the main control chip 100 includes a fourth pin, and the constant current drive circuit also includes: a third capacitor 530, one end of the third capacitor 530 is connected to the fourth pin, and the other end is grounded; wherein the fourth pin receives the first current signal and the PWM signal of the switching device.

[0046] Specifically, the fourth pin is the CTRL pin. Dimming can be achieved by applying an external control signal to the CTRL pin, and the CTRL pin will receive a DC voltage signal or a PWM signal. C3 is a third capacitor 530, one end of C3 is connected to the CTRL pin, and the other end is grounded.

[0047] Furthermore, the constant current driving circuit also includes: a third resistor 230 and a seventh capacitor 570; the third resistor 230 is connected between the seventh capacitor 570 and the fifth pin; one end of the seventh capacitor 570 is connected to the third resistor 230, and the other end is grounded.

[0048] Specifically, R3 is the third resistor 230, C7 is the seventh capacitor 570, one end of R3 is connected to the SW pin and the anode of the diode 400, and the other end is connected to C7; one end of C7 is connected to R3, and the other end is grounded.

[0049] Preferably, R3 is a resistor with a resistance value of 6R, model R0805; C7 is 100pF.

[0050] Furthermore, the model of the main control chip 100 is AL8860.

[0051] Specifically, AL8860 is a step-down DC / DC converter.

[0052] Preferably, the main control chip 100 is further provided with a second pin, a third pin and a seventh pin, the second pin is a GND1 pin, the third pin is a GND2 pin, and the seventh pin is an NC pin; GND1 and GND2 are both grounded, and the NC pin is an empty pin.

[0053] Preferably, the constant current drive circuit further includes a first capacitor 510 and an eighth capacitor 580, C1 being the first capacitor 510 and C8 being the eighth capacitor 580, one end of C1 and C8 being connected to the SET pin and the other end being grounded. In this embodiment, C1 and C8 are both 10nF capacitors, model C0603.

[0054] [Example 2]

[0055] This embodiment further provides a constant current driving board for automobile lights, comprising the constant current driving circuit of the above-mentioned embodiment 1.

[0056] Specifically, this embodiment can achieve the technical effects corresponding to any of the technical solutions in the above-mentioned embodiment 1, which will not be described in detail here. Using the constant current drive circuit in the above-mentioned embodiment 1 on the constant current drive board, the modular universal design can reduce design pressure on the one hand, and on the other hand, unified materials can be produced in batches without project, thereby increasing the product reliability of the constant current drive board and reducing product costs.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A constant current drive circuit for automobile lights, characterized in that: The constant current driving circuit comprises: a power supply, a BUCK topology module (10), a constant current module and a load (30); The power supply is used to output a power signal; The BUCK topology module (10) is connected between the power supply and the constant current module, and the BUCK topology module (10) is used to convert the power supply signal into a low voltage signal; The constant current module comprises a main control chip (100) and a current sampling unit, wherein the main control chip (100) is used to convert the low voltage signal into a first current signal, and the current sampling unit is used to convert the first current signal into a first voltage signal and feed it back to the main control chip (100); Wherein, a switch device is provided in the main control chip (100); when the load (30) changes, the main control chip (100) adjusts the switch device to keep the first current signal unchanged.

2. The constant current driving circuit according to claim 1, characterized in that: The main control chip (100) comprises a first pin and an eighth pin, the first pin being connected to the load (30), and the eighth pin being connected to the power supply, and the constant current drive circuit further comprising: a first resistor (210), the first resistor (210) being connected between the first pin and the eighth pin; a second resistor (220), the second resistor (220) being connected between the first pin and the eighth pin; A first inductor (310), one end of the first inductor (310) is connected to the first pin, and the other end is connected to the eighth pin.

3. The constant current driving circuit according to claim 2, characterized in that: The constant current drive circuit further includes: A diode (400) is connected between the first inductor (310) and the main control chip (100), with the positive electrode of the diode (400) connected to the first inductor (310) and the negative electrode of the diode (400) connected to the eighth pin.

4. The constant current driving circuit according to claim 3, characterized in that: The main control chip (100) further includes a fifth pin and a sixth pin, wherein the fifth pin and the sixth pin are connected to the positive electrode of the diode (400); The fifth pin and the sixth pin are also connected to the drain of the switching device.

5. The constant current driving circuit according to claim 2, characterized in that: The constant current drive circuit further includes: a second capacitor (520), one end of the second capacitor (520) being connected to the eighth pin, and the other end being grounded; A fourth capacitor (540), one end of the fourth capacitor (540) is connected to the power supply, and the other end is grounded.

6. The constant current driving circuit according to claim 1, characterized in that: The constant current drive circuit further includes: a fifth capacitor (550), the fifth capacitor (550) being connected in parallel to both ends of the load (30); A sixth capacitor (560) is connected in parallel to both ends of the load (30).

7. The constant current driving circuit according to claim 1, characterized in that: The main control chip (100) includes a fourth pin, and the constant current drive circuit further includes: a third capacitor (530), one end of the third capacitor (530) being connected to the fourth pin, and the other end being grounded; The fourth pin receives the first current signal and the PWM signal of the switching device.

8. The constant current driving circuit according to claim 4, characterized in that: The constant current driving circuit further includes: a third resistor (230) and a seventh capacitor (570); The third resistor (230) is connected between the seventh capacitor (570) and the fifth pin; One end of the seventh capacitor (570) is connected to the third resistor (230), and the other end is grounded.

9. The constant current driving circuit according to claim 1, characterized in that: The model of the main control chip (100) is AL8860.

10. A constant current driver board for automobile lights, characterized in that: The constant current driving board includes the constant current driving circuit according to any one of claims 1 to 9.

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