LED constant-current control circuit based on direct-current power supply acquisition principle
Through the LED constant current control circuit based on the DC power supply acquisition principle, the PWM signal duty cycle is monitored and adjusted in real time, and combined with the PID program to correct the voltage value, the problems of LED driving current limitation and voltage fluctuations in the prior art are solved, and a stable and controllable LED driving current is achieved.
Patent Information
- Application Number
- CN202421428538.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-21
- Publication Date
- 2025-07-22
- Estimated Expiration
- 2034-06-21
AI Technical Summary
The existing LED driving circuit is costly and electromagnetic radiation is difficult to control, the driving current is limited, and it cannot be further increased, and the LED current fluctuates with voltage.
The LED constant current control circuit based on the DC power supply acquisition principle is adopted to monitor the supply voltage in real time through the resistor voltage divider circuit. The main control chip adjusts the PWM signal duty cycle of the MOS tube driving circuit, and uses the PID program to correct the voltage value to achieve closed-loop control.
The closed-loop precise control of LED driving current is realized, and the stable and controllable driving current is provided, which overcomes the limitations of the prior art.
Smart Images
Figure CN223142176U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of LEDs, and particularly relates to an LED constant current control circuit based on the principle of DC power supply acquisition. Background Technique
[0002] With the wide application of in-vehicle LED headlights, the cost and reliability of LED drive circuits have become the focus of attention in the industry. Currently, the mainstream LED drive solutions mostly adopt buck-boost circuits with a BUCK architecture. This solution integrates a high-frequency DCDC circuit, resulting in a relatively high cost and difficult control of electromagnetic radiation.
[0003] Existing LED drive solutions based on discrete devices usually utilize the characteristics of triodes. By connecting a high-precision sampling resistor in series with the emitter and feeding back the sampled voltage to control the base current, the constant current of LED low-side drive is achieved. However, under this solution, the drive current of the LED is restricted by the collector current of the triode, usually only reaching below 150 mA, and it is impossible to further increase the drive current. If MOS transistors are cascaded to increase the drive current, it will cause the problem that the LED current fluctuates with the voltage more severely when the drive voltage increases. Summary of the Utility Model
[0004] To achieve the constant current drive of LEDs and meet the power usage requirements at the same time, the utility model proposes an LED constant current control circuit based on the principle of DC power supply acquisition, including:
[0005] A resistor voltage division circuit for real-time monitoring of the DC power supply voltage at the power supply port and feeding back the voltage acquisition value to the main control chip;
[0006] A main control chip for adjusting the duty cycle of the PWM signal output to the MOS transistor drive circuit according to the voltage acquisition value, and performing correction adjustment of the PWM signal duty cycle according to the feedback real-time voltage value and the preset voltage value;
[0007] A MOS transistor drive circuit for maintaining the constant current of the LED drive current according to the duty cycle of the PWM signal input to the MOS transistor gate and feeding back the real-time voltage value to the main control chip.
[0008] Further, the main control chip includes a VDD port, a first I / O port, a second I / O port, a PWM port, a serial programming port, and a VSS port.
[0009] Further, the VDD port is used to connect to the power supply voltage, the first I / O port is used to receive the voltage acquisition value, the second I / O port is used to receive the real-time voltage value, the PWM port is used to output the PWM signal, the serial programming port is used to burn the program, and the VSS port is grounded.
[0010] Further, the resistive voltage division circuit includes a low dropout linear regulator.
[0011] The input end of the low dropout linear regulator is connected to the supply voltage output from the power supply port, and is simultaneously connected to one ends of a first resistor and a second capacitor. The other end of the first resistor outputs a voltage acquisition value to the first I / O port of the main control chip, and is grounded through a second resistor and a first capacitor connected in parallel. The other end of the second capacitor is grounded; the grounding end of the low dropout linear regulator is grounded; the output end of the low dropout linear regulator is grounded through a third capacitor and outputs a regulated supply voltage to the VDD port of the main control chip.
[0012] Further, the MOS transistor drive circuit includes a first MOS transistor.
[0013] The gate of the first MOS transistor is connected to the PWM signal output from the PWM port of the main control chip through a third resistor; the source of the first MOS transistor feeds back a real-time voltage value to the second I / O port of the main control chip, and is grounded through a fourth capacitor and a fifth resistor connected in parallel; the drain of the first MOS transistor is connected to the negative electrode of the LED, and the positive electrode of the LED is connected to the supply voltage output from the power supply port through a sixth resistor.
[0014] Further, the main control chip adjusts the duty cycle of the PWM signal based on the comparison between the real-time voltage value and the preset voltage value through a pre-programmed PID program.
[0015] Compared with the prior art, the present utility model has at least the following beneficial effects:
[0016] The LED constant current control circuit based on the DC power supply acquisition principle described in the present utility model can collect the supply voltage in real time through the MCU, drive the power MOS transistor according to the preset PWM duty cycle data, and simultaneously synchronously collect the actual value of the LED drive current for data comparison and regulation, and adjust the PWM signal successively, thereby realizing the closed-loop precise control of the LED drive current. This method can effectively overcome the limitations of the prior art and provide a more stable and controllable LED drive current. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a circuit schematic diagram of an LED constant current control circuit based on the DC power supply acquisition principle. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0018] The following are specific embodiments of the present utility model in combination with the drawings, and the technical solutions of the present utility model are further described, but the present utility model is not limited to these embodiments.
[0019] In view of the deficiencies of existing simple triode drive circuits and MOS transistor drive circuits when driving LED lights, such as Figure 1 shown, the present utility model proposes an LED constant current control circuit based on the principle of DC power supply acquisition, comprising:
[0020] A resistor voltage division circuit for real-time monitoring of the DC power supply voltage at the power supply port and feeding back the voltage acquisition value to the main control chip;
[0021] A main control chip for adjusting the duty cycle of the PWM signal output to the MOS transistor drive circuit according to the voltage acquisition value, and performing correction adjustment of the PWM signal duty cycle according to the feedback real-time voltage value and the preset voltage value;
[0022] A MOS transistor drive circuit for maintaining a constant current of the LED drive current according to the duty cycle of the PWM signal input to the MOS transistor gate, and feeding back the real-time voltage value to the main control chip.
[0023] Among them, the main control chip includes a VDD port (VDD), a first I / O port (I / O1), a second I / O port (I / O2), a PWM port (PWM), a serial programming port (ICSPDAT, ICSPCLK), and a VSS port (VSS). The VDD port is used to connect to the power supply voltage, the first I / O port is used to receive the voltage acquisition value, the second I / O port is used to receive the real-time voltage value, the PWM port is used to output the PWM signal, the serial programming port is used to burn the program, and the VSS port is grounded.
[0024] The resistor voltage division circuit realizes the power supply to the main control chip through a low-dropout linear regulator. On this basis, the present utility model realizes the equal-ratio acquisition of the voltage value of the DC power supply voltage through the design of the voltage division resistor and feeds it back to the main control chip. Specifically, the circuit connection mode of the resistor voltage division circuit is as follows:
[0025] The input end (IN) of the low-dropout linear regulator (5V LDO) is connected to the power supply voltage (DCV) output from the power supply port, and is simultaneously connected to one end of the first resistor (R1) and the second capacitor (C2). The other end of the first resistor (R1) outputs the voltage acquisition value (VAD) to the first I / O port (I / O1) of the main control chip, and is grounded through the parallel-connected second resistor (R2) and the first capacitor (C1). The other end of the second capacitor (C2) is grounded; the ground end (GND) of the low-dropout linear regulator is grounded; the output end (OUT) of the low-dropout linear regulator is grounded through the third capacitor (C3), and outputs the regulated power supply voltage to the VDD port (VDD) of the main control chip.
[0026] When the supply voltage changes, the voltage across the second resistor (R2) will change proportionally. At this time, the voltage signal received by the first I / O port (I / O1) of the main control chip will change synchronously. At this time, the main control chip identifies and matches the supply voltage corresponding to the feedback voltage based on the pre-burned program, so as to obtain the duty cycle requirement of the PWM signal corresponding to the current supply voltage, and then outputs the corresponding PWM signal from the PWM port to the MOS transistor drive circuit.
[0027] Here, compared with using a triode to cascade-control the MOS transistor, since the MOS transistor is a voltage-controlled component and the resistance of Rds (between the drain and the source) is very small, as long as the gate voltage of the MOS transistor reaches the turn-on voltage, the current passing through the source and drain of the MOS transistor will fluctuate greatly following the supply voltage.
[0028] If the MOS transistor is directly used, it is a large voltage input and Vds is very large, directly reaching the saturation region. At this time, Rds has become very small and no longer changes, which causes the current to completely follow the change of the input voltage of Vds synchronously, and the purpose of constant current cannot be achieved.
[0029] In the present utility model, the overall conduction amount is adjusted by adjusting the duty cycle of the PWM signal. Since the peak value of the PWM signal remains unchanged and does not reach the saturation region, and at the same time, the adjustment of the duty cycle can well control the conduction amount. Therefore, it can initially ensure the constancy of the LED drive current. On this basis, the present utility model also monitors the real-time voltage value (IAD), compares it with the preset voltage value, and uses the burned PID program to perform secondary correction on the PWM signal, so that the actual voltage value gradually approaches the preset voltage value, while ensuring the stability of the LED drive current, gradually approaching the normal operating voltage.
[0030] Specifically, the MOS transistor drive circuit includes a first MOS transistor, whose gate is connected to the PWM signal output from the PWM port of the main control chip through a third resistor (R3); the source of the first MOS transistor feeds back the real-time voltage value to the second I / O port (I / O2) of the main control chip and is grounded through a parallel-connected fourth capacitor (C4) and a fifth resistor (R5); the drain of the first MOS transistor is connected to the negative electrode of the LED, and the positive electrode of the LED is connected to the supply voltage (DCV) output from the power supply port through a sixth resistor (R6).
[0031] In summary, for the LED constant current control circuit based on the DC power supply acquisition principle described in this utility model, the MCU is used to collect the supply voltage in real time, and the power MOS transistor is driven according to the preset PWM duty cycle data. At the same time, the actual value of the LED drive current is synchronously collected for data comparison and regulation, and the PWM signal is adjusted successively, thereby realizing the closed-loop precise control of the LED drive current. This method can effectively overcome the limitations of the prior art and provide a more stable and controllable LED drive current.
[0032] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of this utility model are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If this specific posture changes, the directional indication will also change accordingly.
[0033] In addition, in this utility model, descriptions such as "first", "second", and "one" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this utility model, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.
[0034] In this utility model, unless otherwise clearly specified and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.
[0035] In addition, the technical solutions between the various embodiments of this utility model can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by this utility model.
Claims
1. An LED constant current control circuit based on the principle of DC power supply acquisition, characterized in that, It includes: A resistive voltage divider circuit for real-time monitoring of the DC supply voltage at the power supply port and feeding back the voltage acquisition value to the main control chip; The main control chip for adjusting the duty cycle of the PWM signal output to the MOS transistor drive circuit according to the voltage acquisition value and performing correction adjustment of the PWM signal duty cycle based on the feedback real-time voltage value and the preset voltage value; The MOS transistor drive circuit for maintaining a constant LED drive current according to the duty cycle of the PWM signal input to the MOS transistor gate and feeding back the real-time voltage value to the main control chip.
2. The LED constant current control circuit based on the DC power supply acquisition principle according to claim 1, characterized in that, The main control chip includes a VDD port, a first I / O port, a second I / O port, a PWM port, a serial programming port, and a VSS port.
3. The LED constant current control circuit based on the DC power supply acquisition principle according to claim 2, wherein The VDD port is used to connect to the supply voltage, the first I / O port is used to receive the voltage acquisition value, the second I / O port is used to receive the real-time voltage value, the PWM port is used to output the PWM signal, the serial programming port is used for program burning, and the VSS port is grounded.
4. The LED constant current control circuit based on the DC power supply acquisition principle according to claim 2, wherein, The resistive voltage divider circuit includes a low-dropout linear regulator, The input end of the low-dropout linear regulator is connected to the supply voltage output from the power supply port and is simultaneously connected to one end of a first resistor and a second capacitor. The other end of the first resistor outputs the voltage acquisition value to the first I / O port of the main control chip and is grounded through a parallel-connected second resistor and a first capacitor. The other end of the second capacitor is grounded; the ground end of the low-dropout linear regulator is grounded; the output end of the low-dropout linear regulator is grounded through a third capacitor and outputs the regulated supply voltage to the VDD port of the main control chip.
5. The LED constant current control circuit based on the DC power supply acquisition principle according to claim 2, wherein, The MOS transistor drive circuit includes a first MOS transistor, The gate of the first MOS transistor is connected to the PWM signal output from the PWM port of the main control chip through a third resistor; the source of the first MOS transistor feeds back the real-time voltage value to the second I / O port of the main control chip and is grounded through a parallel-connected fourth capacitor and a fifth resistor; the drain of the first MOS transistor is connected to the negative electrode of the LED, and the positive electrode of the LED is connected to the supply voltage output from the power supply port through a sixth resistor.
6. The LED constant current control circuit based on the DC power supply acquisition principle according to claim 1, characterized in that, The main control chip adjusts the duty cycle of the PWM signal under the comparison of the real-time voltage value and the preset voltage value through a pre-burned PID program.