A low-voltage direct-current input buck type LED constant current driving circuit and method based on a single-chip microcomputer

Abstract

This invention relates to the field of LED driver power supply technology, specifically a low-voltage DC input Buck-type LED constant current driving circuit and method based on a microcontroller. It includes a current sampling module electrically connected to the LED load, used to acquire the load current value of the LED load and obtain a corresponding voltage feedback signal based on the load current value. Simultaneously, the current sampling module is electrically connected to a microcontroller module, used to determine the corresponding PWM signal based on the voltage feedback signal, and send the PWM signal through a driving module to a Buck main power module electrically connected to a low-voltage DC input power supply. The Buck main power module is also electrically connected to the LED load. This invention achieves high-precision constant current, flexible dimming, and protection functions while ensuring high conversion efficiency and small size, effectively solving the shortcomings of existing low-voltage DC Buck-type LED driver circuits in terms of efficiency, flexibility, and integration.

Description

Technical Field

[0001] This invention relates to the field of LED driver power supply technology, specifically a low-voltage DC input Buck-type LED constant current driving circuit and method based on a microcontroller. Background Technology

[0002] With the rapid development of LED lighting technology, LEDs are widely used in commercial lighting, home lighting, automotive lighting, and industrial equipment due to their advantages such as high efficiency, energy saving, long lifespan, and environmental friendliness. Since LEDs are essentially current-driven devices, their luminous intensity is directly proportional to the forward current and they are extremely sensitive to current fluctuations. Therefore, stable constant current driving is crucial to ensuring the optical performance, color temperature consistency, and lifespan of LEDs. In low-voltage DC power supply scenarios (such as solar systems, vehicle power supplies, and battery power), it is usually necessary to convert lower DC voltages (e.g., 12V / 24V) into driving voltages and currents suitable for LED strings using a buck topology. However, traditional RC buck or linear constant current solutions suffer from low efficiency, high heat generation, and inability to adapt to wide voltage input ranges, making it difficult to meet the demands of modern lighting for high energy efficiency and compact designs.

[0003] Currently, common implementations of constant current drives for low-voltage DC input Buck-type LEDs include using dedicated constant current control chips (such as peak current mode-based PWM controllers) or building feedback loops using general-purpose switching power supply chips. However, these existing solutions generally have the following limitations: First, dedicated chips typically have fixed functions, limiting dimming methods (such as analog dimming or PWM dimming) and protection mechanisms (over-temperature, over-voltage, under-voltage), making it difficult to flexibly adapt to diverse application requirements. Second, traditional analog control loops rely on discrete components (such as operational amplifiers, comparators, timers, etc.), resulting in complex peripheral circuits, a large number of components, a large PCB area, and poor parameter consistency, making it difficult to balance yield and cost in mass production. Furthermore, for applications requiring high-precision dimming (such as 0.1% deep dimming), multi-channel independent control, or intelligent communication (such as DALI, DMX512), pure hardware solutions are almost impossible to meet.

[0004] To address the issues of insufficient efficiency, flexibility, and integration in the aforementioned low-voltage DC Buck-type LED driver circuits, the industry has recently begun to explore the introduction of microcontrollers (MCUs) as the control core, implementing constant current closed-loop and dimming logic digitally. However, existing MCU-driven solutions often simply replace analog PWM generators without fully utilizing the MCU's processing capabilities. For example, low-precision resistor dividers or direct reliance on internal ADCs are still used in the current sampling stage, resulting in constant current accuracy being significantly affected by temperature drift and power supply noise. The lack of adaptive algorithms in Buck topology loop compensation leads to slow response and oscillations during load changes. Furthermore, existing solutions do not adequately consider the peripheral driver circuitry, level matching, and anti-interference design of the MCU, resulting in low system reliability. Therefore, there is an urgent need for a low-voltage DC input Buck-type LED constant current driver circuit and method based on a MCU, capable of achieving high-precision constant current, flexible dimming, and comprehensive protection functions while ensuring high conversion efficiency and small size, thus overcoming the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a low-voltage DC input Buck-type LED constant current driving circuit and method based on a microcontroller, so as to solve the problems mentioned in the background art.

[0006] The technical solution of this invention is: a low-voltage DC input Buck-type LED constant current driving circuit based on a microcontroller, comprising a current sampling module electrically connected to an LED load, used to acquire the load current value of the LED load, and to acquire a corresponding voltage feedback signal based on the load current value; simultaneously, the current sampling module is electrically connected to a microcontroller module, used to determine a corresponding PWM signal based on the voltage feedback signal, and to send the PWM signal through a driving module to a Buck main power module electrically connected to a low-voltage DC input power supply, and the Buck main power module is electrically connected to the LED load.

[0007] Furthermore, the Buck main power module includes a switching transistor electrically connected to the driver module and the LED load. The Buck main power module regulates the conduction state of the switching transistor according to the PWM signal, thereby adjusting the average current of the LED load.

[0008] Furthermore, the Buck main power module includes two symmetrically arranged step-down branches. Each step-down branch includes an energy storage inductor electrically connected to a switching transistor and a low-voltage DC input power supply. The energy storage inductor is connected in parallel with a freewheeling diode and a filter capacitor. The filter capacitor is electrically connected to the LED load.

[0009] Furthermore, the switching transistor is configured as a MOSFET, with its drain electrically connected to an energy storage inductor, its source grounded through a current sampling module, and its gate electrically connected to a driving module.

[0010] Furthermore, the current sampling module includes a sampling resistor, which is electrically connected to the switching transistor and the differential amplifier circuit. The voltage difference across the sampling resistor is sent to the microcontroller module through the differential amplifier circuit.

[0011] Furthermore, it also includes a dimming signal module electrically connected to the microcontroller module, used to set an external dimming signal and adjust the target constant current setting value in the microcontroller module according to the external dimming signal. At the same time, the input signal of the dimming signal module is set to one or more of PWM dimming signal, 0-10V analog dimming signal or thyristor dimming signal.

[0012] Furthermore, the microcontroller module is equipped with a digital PID control unit, which is electrically connected to the dimming signal module and the current sampling module. It is used to determine the corresponding PWM signal based on the comparison result between the voltage feedback signal and the target constant current set value.

[0013] Furthermore, the microcontroller module includes an analog-to-digital conversion unit and a PWM unit. The analog-to-digital conversion unit is electrically connected to a current sampling module to obtain the voltage difference of the sampling resistor. The PWM unit is electrically connected to the Buck main power module through a drive module to send PWM signals to the Buck main power module.

[0014] Furthermore, the driving module includes a transistor electrically connected to a PWM unit and a switching transistor. The PWM unit sends a PWM signal to the transistor, and the transistor sends a driving voltage to the switching transistor according to the PWM signal. The driving voltage is set to the turn-on voltage of the switching transistor.

[0015] A microcontroller-based method for driving a low-voltage DC input Buck-type LED with constant current, using any one of the microcontroller-based low-voltage DC input Buck-type LED constant current driving circuits described above.

[0016] This invention provides an improved low-voltage DC input Buck-type LED constant current driving circuit and method based on a microcontroller, which has the following improvements and advantages compared with the prior art:

[0017] Firstly, this invention introduces single-chip microcomputer digital control and combines it with a current sampling module, a drive module, and a Buck main power module. While ensuring high conversion efficiency and small size, it achieves high-precision constant current, flexible dimming, and protection functions. It effectively solves the shortcomings of existing low-voltage DC Buck LED driver circuits in terms of efficiency, flexibility, and integration. At the same time, through the efficient voltage reduction of the Buck topology, it overcomes the defects of traditional RC voltage reduction or linear constant current schemes, such as low efficiency, high heat generation, and inability to adapt to wide voltage input. It is suitable for commercial lighting, home lighting, automotive lights, and industrial equipment.

[0018] Secondly, the current sampling module of this invention converts the LED load current into a voltage feedback signal through a sampling resistor and a differential amplifier circuit. At the same time, the microcontroller module is equipped with a digital PID control unit, which adjusts the PWM signal in real time according to the comparison result between the voltage feedback signal and the target constant current set value. Thus, the problem of poor parameter consistency and large temperature drift caused by the reliance on discrete components in the traditional analog scheme can be overcome through digital closed-loop control, thereby improving the constant current accuracy, ensuring the consistency of LED luminous intensity and color temperature, and extending the service life.

[0019] Thirdly, this invention, through a dimming signal module, can accept one or more of PWM dimming signals, 0-10V analog dimming signals, or thyristor dimming signals, and can dynamically adjust the target constant current setting value in the microcontroller according to the external dimming signal. Compared with the shortcomings of dedicated constant current chips with fixed functions and limited dimming methods, by utilizing the flexibility of microcontroller software, high-precision dimming (even deep dimming) can be achieved, and it can be expanded to multi-channel independent control or intelligent communication, thereby adapting to diverse application needs.

[0020] Fourthly, this invention uses a microcontroller as its core, integrating constant current closed-loop, dimming logic, protection functions, etc. into a single chip, which can reduce the number of external components, shrink the system size, and improve the consistency and cost-effectiveness of mass production.

[0021] Fifthly, the drive module of this invention uses a transistor and a resistor network to form an inverting drive stage, which converts the 3.3V or 5V PWM signal output by the microcontroller into a gate drive voltage that can fully turn on the switching transistor and provides instantaneous charging and discharging current to achieve fast switching. At the same time, the Buck main power module uses two symmetrical step-down branches, each of which includes an energy storage inductor, a freewheeling diode and a filter capacitor, thereby effectively suppressing voltage spikes and high-frequency ripples. In addition, the microcontroller module can also be connected to a temperature sensor and an overvoltage / overcurrent detection circuit, which reduces the duty cycle or turns off the switching transistor in case of abnormality, thereby providing a complete protection function.

[0022] Sixth: The microcontroller module of this invention can collect the voltage difference of the sampling resistor in real time through the analog-to-digital conversion unit and use the digital PID algorithm for loop compensation. Therefore, it has stronger processing power than the pure hardware solution, and can avoid the problems of slow response and easy oscillation when the load changes suddenly, so that the system can work stably under various working conditions. Attached Figure Description

[0023] The present invention will be further explained below with reference to the accompanying drawings and embodiments:

[0024] Figure 1 This is a system block diagram of the low-voltage DC input Buck-type LED constant current drive circuit according to Embodiment 1 of the present invention;

[0025] Figure 2 This is a circuit diagram of the driving module in Embodiment 2 of the present invention;

[0026] Figure 3 This is a circuit diagram of the Buck main power module according to Embodiment 3 of the present invention;

[0027] Figure 4 This is a circuit diagram of the microcontroller module in Embodiment 4 of the present invention;

[0028] Figure 5 This is a circuit diagram of the power supply management module in Embodiment 5 of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] refer to Figure 1This embodiment provides a low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller. This circuit includes a current sampling module, a microcontroller module, a drive module, a Buck main power module, and a dimming signal module. Specifically, the current sampling module is electrically connected to the LED load to acquire the load current value of the LED load and converts it into a corresponding voltage feedback signal based on the acquired load current value. The current sampling module is also electrically connected to the microcontroller module, which is electrically connected to the dimming signal module. The dimming signal module is used to set an external dimming signal, and the microcontroller module determines the corresponding PWM signal based on the voltage feedback signal acquired by the current sampling module and the external dimming signal set by the dimming signal module. Simultaneously, the microcontroller module is electrically connected to the Buck main power module via the driver module. This means the microcontroller module sends the determined PWM signal to the Buck main power module through the driver module, and the Buck main power module, based on the received PWM signal, electrically connects to the LED load to adjust the average current of the LED load, thereby stabilizing the LED load current at the target constant current setpoint. The Buck main power module is also electrically connected to a low-voltage DC input power supply to provide energy to the Buck main power module.

[0032] Furthermore, the Buck main power module includes two symmetrically arranged buck branches. Each buck branch includes an energy storage inductor electrically connected to a switching transistor and the low-voltage DC input power supply. The switching transistor is electrically connected to the driver module and the LED load. Simultaneously, the Buck main power module regulates the conduction state of the switching transistor according to the PWM signal to adjust the average current of the LED load. Specifically, the switching transistor is a MOSFET, with its drain electrically connected to the energy storage inductor, its source grounded through a current sampling module, and its gate electrically connected to the driver module. A freewheeling diode and a filter capacitor are connected in parallel to the energy storage inductor, and the filter capacitor is electrically connected to the LED load.

[0033] In other words, when the switching transistor is turned on, the low-voltage DC input power supply is electrically connected to the drain of the switching transistor through the energy storage inductor, and the drain of the switching transistor is electrically connected to the sampling resistor through the source of the switching transistor, and the sampling resistor is grounded. At this time, the current in the energy storage inductor rises linearly, and the current flowing through the sampling resistor generates a voltage drop. Furthermore, when the switching transistor is turned off, the energy storage inductor continues to flow through the freewheeling diode, and the current in the energy storage inductor flows through the LED load to the filter capacitor. The current in the filter capacitor flows to the ground terminal and the sampling resistor, while the current in the sampling resistor flows to the energy storage inductor; that is, the current still flows through the sampling resistor. In other words, through the switching transistor configuration, all the load current (i.e., the inductor current) flows through the sampling resistor, generating a small voltage difference (typically tens to hundreds of millivolts) across the sampling resistor that is proportional to the load current of the LED load.

[0034] Furthermore, the current sampling module includes a sampling resistor, which is electrically connected to the switching transistor and the differential amplifier circuit. Specifically, the voltage difference across the sampling resistor in the current sampling module is sent to the microcontroller module via the differential amplifier circuit. In this embodiment, the microcontroller module includes a digital PID control unit, an analog-to-digital converter (ADC), and a PWM unit. The ADC is electrically connected to the current sampling module to acquire the voltage difference across the sampling resistor. The digital PID control unit is electrically connected to the dimming signal module and the current sampling module to determine the corresponding PWM signal based on the comparison between the voltage feedback signal (i.e., the voltage difference across the sampling resistor) acquired by the current sampling module and the target constant current setpoint. The PWM unit is electrically connected to the Buck main power module via the driver module to send the PWM signal to the Buck main power module.

[0035] It is worth noting that the microcontroller module in this embodiment is electrically connected to a temperature sensor and / or an overvoltage / overcurrent detection circuit, which is used to set the PWM duty cycle to be reduced or the switching transistor to be turned off when the temperature exceeds the threshold or the voltage / current is abnormal, thereby realizing the corresponding protection function.

[0036] Furthermore, the dimming signal module is used to set an external dimming signal and, based on the set external dimming signal, adjust the target constant current setting value in the microcontroller module, thereby achieving brightness adjustment of the LED load. Simultaneously, the input signal of the dimming signal module is set to one or more of the following: PWM dimming signal, 0-10V analog dimming signal, or SCR dimming signal.

[0037] To elaborate further, the driver module includes a transistor. This transistor is electrically connected to the PWM unit and the switching transistor. Specifically, the PWM unit sends a PWM signal to the transistor, and the transistor sends a drive voltage to the switching transistor based on the PWM signal. This drive voltage is set to the switching transistor's turn-on voltage. In other words, the driver module converts the 3.3V or 5V PWM signal output from the microcontroller module into a gate drive voltage (e.g., 10V-12V or higher, depending on the specific model of the switching transistor) capable of fully turning on the switching transistor, and provides instantaneous charging and discharging current for rapid switching.

[0038] This embodiment also provides a microcontroller-based method for driving low-voltage DC input Buck-type LEDs with constant current, which uses the aforementioned microcontroller-based circuit for driving low-voltage DC input Buck-type LEDs with constant current.

[0039] Example 2

[0040] This embodiment provides a low-voltage DC input Buck-type LED constant current driving circuit based on a microcontroller. Its specific implementation method is the same as that of Embodiment 1, except that the specific implementation method of this embodiment is explained in conjunction with the circuit diagram of the driving module.

[0041] refer to Figure 2 The driver module includes a transistor QV1. The base of transistor QV1 is electrically connected to the cathode of diode DW1 and resistor RV1 via resistor RV2. Resistor RV1 and the emitter of transistor QV1 are electrically connected to resistor RS2, capacitor C11, and ports 5 and 2 of the TYPE-C interface (i.e., low-voltage DC input power supply). Capacitor C11 is used for power filtering, and diode DW1 is a Zener diode to provide overvoltage protection, preventing input voltage spikes from damaging downstream circuitry. Resistor RS2 is electrically connected to capacitor CS2, and resistor RV1 is electrically connected to resistor RV2 and the cathode of diode DW1.

[0042] Specifically, port 1 of the TYPE-C interface is electrically connected to port 6 of the TYPE-C interface, and is electrically connected to ports 5 and 2 of the TYPE-C interface through capacitor C11. Port 3 of the TYPE-C interface is electrically connected to resistor R30, and port 4 of the TYPE-C interface is electrically connected to resistor R31. At the same time, ports 1 and 6 of the TYPE-C interface, capacitor C11, resistor R30, resistor R31, the anode of diode DW1, and capacitor CS2 are all grounded, and capacitor CS2 is electrically connected to ports 1 and 6 of the TYPE-C interface, capacitor C11, resistor R30, and resistor R31.

[0043] Furthermore, the collector of transistor QV1 is electrically connected to resistors RV3 and RV4, and the gate of switching transistor QM1. Resistor RV3 is electrically connected to the emitter of transistor QV1 and the source of switching transistor QM1, while resistor RV4 is electrically connected to the gate of switching transistor QM1 and is grounded. In other words, in this embodiment, transistor QV1, in conjunction with resistors RV1 / RV2 and RV3, forms an inverting drive stage. Specifically, when the microcontroller module outputs a high level, transistor QV1 conducts, pulling the subsequent circuit low. When the microcontroller module outputs a low level, transistor QV1 is cut off, thus completing the first inversion and current amplification of the logic signal.

[0044] In this embodiment, the drain of transistor QM1 is electrically connected to the Buck main power module, the drain of transistor QM3, the gate of transistor Q13, and resistor RD1 via the input power supply voltage VCC port. Resistor RD1 is electrically connected to the drain of transistor QM3 and the gate of transistor Q13. Both resistor RD1 and the source of transistor Q13 are grounded, and the drain of transistor Q13 is electrically connected to resistor RA1 and the gate of transistor QM3. Specifically, the source of transistor QM3 and resistor RA1 are both electrically connected to the Buck main power module via the switching power output VOUT port. That is, when transistor QV1 is turned on, the gate voltage of transistor QM1 drops. At this time, the voltage difference between the gate and source of transistor QM1 is negative, meaning transistor QM1 is turned on, and current flows to the LED load. When transistor QV1 is turned off, the gate of switching transistor QM1 is pulled up to a voltage value close to the input power supply voltage VCC port by the voltage divider of resistors RV3 and RV4, at which point switching transistor QM1 is turned off.

[0045] Example 3

[0046] This embodiment provides a low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller. Its specific implementation method is the same as that in Embodiment 1, except that the specific implementation method of this embodiment is explained in conjunction with the circuit diagram of the Buck main power module.

[0047] refer to Figure 3The Buck main power module includes switching transistors Q2 and Q3. The sources of both transistors Q2 and Q3 are electrically connected to the switching power output VOUT port. Specifically, the switching power output VOUT port is electrically connected to the source of transistor Q2 and resistor R15. Resistor R15 is electrically connected to the PWM unit of the microcontroller module through resistor R13, grounded through resistor R17, and also electrically connected to the gate of transistor Q2. The drain of transistor Q2 is electrically connected to the cathode of diode D5, resistor RC1, and inductor L1. The anode of diode D5 is electrically connected to capacitors CD1 and CD3. Capacitor CD1 is electrically connected to resistor RC1, capacitor CD3 is electrically connected to resistor RC3, and resistor RC3 is electrically connected to inductor L1 and port 1 of output terminal block P1 (i.e., LED load, model MHDR1X3). Meanwhile, the series circuit composed of capacitor CD1 and resistor RC1, the series circuit composed of capacitor CD3 and resistor RC3, and diode D5 are connected in parallel. The parallel circuit is electrically connected to inductor L1 and port 1 of output terminal block P1 and grounded.

[0048] Furthermore, the switching power output VOUT port is electrically connected to the source of the switching transistor Q3 and resistor R16. Resistor R16 is electrically connected to the PWM unit of the microcontroller module through resistor R14, and grounded through resistor R18. Resistor R16 is also electrically connected to the gate of the switching transistor Q3. The drain of the switching transistor Q3 is electrically connected to the cathode of diode D6, resistor RC2, and inductor L2. The anode of diode D6 is electrically connected to capacitors CD2 and CD4. Capacitor CD2 is electrically connected to resistor RC2, capacitor CD4 is electrically connected to resistor RC4, and resistor RC4 is electrically connected to inductor L2 and port 2 of output terminal block P1 (i.e., the LED load, model MHDR1X3). Simultaneously, the series circuits formed by capacitors CD2 and RC2, and the series circuits formed by capacitors CD4 and RC4, are connected in parallel with diode D6. These parallel circuits are electrically connected to inductor L2 and port 2 of output terminal block P1, and grounded. Port 3 of output terminal block P1 is also grounded.

[0049] In other words, diodes D5 and D6 are both freewheeling diodes. When switching transistors Q2 and Q3 are turned off, they provide freewheeling paths for the current in inductors L1 and L2, respectively, thus preventing voltage spikes from damaging the switching transistors. Meanwhile, capacitors CD1 and CD2 are both output filter capacitors. Through their cooperation with inductors L1 and L2, they filter out high-frequency ripple, thereby providing a stable DC current to the LED load.

[0050] Specifically, the Buck main power module includes two symmetrical buck branches. Each buck branch includes a switching transistor, an energy storage inductor, and a freewheeling diode. The source of the switching transistor is electrically connected to the switching power output VOUT port, the gate is electrically connected to the PWM unit, and the drain is electrically connected to the energy storage inductor, which in turn is connected to the LED load. Simultaneously, the freewheeling diode is connected in parallel between the energy storage inductor and the ground port to provide a freewheeling path when the switching transistor is turned off. This allows for independent constant current control of multiple LED loads through dual independent buck branches.

[0051] It is worth noting that this embodiment uses the switching control of one of the step-down branches as an example for specific explanation. Specifically, when the PWM signal received by switch Q2 is low, switch Q2 is turned on. The corresponding current path is: power output port VOUT → switch Q2 → inductor L1 → port 1 of output terminal block P1 → ground. In this case, inductor L1 stores energy. When the PWM signal received by switch Q2 is high, switch Q2 is turned off. In this case, inductor L1 generates a reverse electromotive force, and the current freewheels through diode D5, thus maintaining continuous current to the LED load. In other words, by adjusting the PWM duty cycle, the on-time of switch Q2 can be controlled, thereby changing the average current flowing through inductor L1 and port 1 of output terminal block P1, thus achieving constant current drive.

[0052] Example 4

[0053] This embodiment provides a low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller. Its specific implementation method is the same as that in Embodiment 1, except that the specific implementation method of this embodiment is explained in conjunction with the circuit diagram of the microcontroller module.

[0054] refer to Figure 4 The microcontroller module includes a microcontroller chip U2 (model CA51F152S1). Port 1 of the microcontroller chip U2 is electrically connected to the power output VOUT port of the switch via resistors R11 and R12. Port 2 is grounded via capacitor C7. Port 3 is electrically connected to capacitors CF2 and CF1, and resistor RF2. Specifically, capacitors CF1 and CF2 are connected in parallel, as are capacitors CL1 and CL2. All three capacitors (CF1, CF2, CL1, and CL2) are electrically connected to resistor RF2. Simultaneously, capacitors CL1 and CL2 are also electrically connected to resistor RF1. Resistor RF1 is electrically connected to resistors RL1, RL2, and RL3, and is grounded. Furthermore, resistors RL1, RL2, and RL3 are connected in parallel, and the parallel circuits formed by resistors RL1, RL2, and RL3, and capacitors CF1, CF2, CL1, and CL2 are all electrically connected and grounded.

[0055] In other words, resistors RF1 and RF2, capacitors CF1, CF2, CL1, CL2, RL1, RL2, and RL3 form an RC filter network. The signal output from the current sampling module enters through the input of this RC filter network, and after processing by the network, high-frequency noise is filtered out.

[0056] Furthermore, pin 4 of the microcontroller chip U2 is grounded, pin 5 is electrically connected to resistor R13 of the Buck main power module, and pin 6 is electrically connected to capacitors C4, C5, and C6, resistor RM2, and the cathode of diode DZ1. Capacitors C4, C5, and C6 are connected in parallel, forming a parallel circuit with diode DZ1. The anodes of capacitors C4, C5, C6, and diode DZ1 are all grounded, and the cathodes of capacitors C4, C5, C6, and diode DZ1 are all electrically connected to the switching power output VOUT port through resistors RM2 and RM1. Simultaneously, pin 7 of the microcontroller chip U2 is electrically connected to resistor R14 of the Buck main power module, and pin 8 is electrically connected to resistor RTK, which is grounded through capacitor Ck1.

[0057] In other words, capacitors C4, C5, and C6, along with resistor RM2, form a buffer network that slows down the edge speed of the PWM signal and reduces EMI interference. Meanwhile, diode DZ1 is a Zener diode used to clamp the output voltage, preventing excessively high PWM signal voltage output from the microcontroller chip U2 (e.g., damage from electrostatic discharge or accidental high voltage connection) from damaging the gate of the switching transistor, thus ensuring that the gate voltage is controlled within a safe range.

[0058] Example 5

[0059] This embodiment provides a low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller. Its specific implementation is the same as in Embodiment 4, except that port 1 of the microcontroller module is electrically connected to the gate of the switching transistor Q11 through resistor R11. The source of the switching transistor Q11 is grounded, and its drain is electrically connected to the power management module. The power management module is electrically connected to the switching power output VOUT port and the input power supply voltage VCC port. The specific implementation of this embodiment is described below with reference to the specific circuit diagram.

[0060] refer to Figure 5The power supply management module includes charging management chip U1, charging management chip U11, and lithium battery protection chip U3. Ports 1 and 3 of charging management chip U1 are grounded. Port 2 is electrically connected to resistors R1 and R7, with R1 grounded. Resistor R7 is electrically connected to the drain of switching transistor Q11 and resistor R27, and resistor R27 is electrically connected to port 2 of charging management chip U11. Port 4 of charging management chip U1 is electrically connected to capacitor C1 and the input power supply voltage VCC port, with capacitor C1 grounded.

[0061] Furthermore, port 5 of the charging management chip U1 is grounded through capacitor C2. Simultaneously, port 5 of the charging management chip U1 is electrically connected to resistor R3, port 5 of the charging management chip U11, the drain of the switching transistor Q1, port 1 of the external lithium battery interface CN2, and port 1 of the external lithium battery CN3. Both ports 2 of the external lithium battery interface CN2 and port 2 of the external lithium battery CN3 are grounded. Specifically, resistor R3 is electrically connected to port 3 of the lithium battery protection chip U3. The gate of the switching transistor Q1 is electrically connected to the input power supply voltage VCC port through resistor R5 and grounded through resistor R6. The source of the switching transistor Q1 is electrically connected to capacitors CE1, C8, C9, and the switching power output VOUT port. Capacitors CE1, C8, and C9 are connected in parallel, and this parallel circuit is grounded.

[0062] Furthermore, port 6 of charging management chip U1 is electrically connected to port 6 of charging management chip U11 and the cathode of diode D7. The anode of diode D7 is electrically connected to the source of switching transistor Q12. The gate of switching transistor Q12 is electrically connected to the cathode of diode D3, port 7 of charging management chip U1, port 7 of charging management chip U11, and resistor RS1. The drain of switching transistor Q12 is electrically connected to the cathode of diode D4. Specifically, the anode of diode D3 is electrically connected to the anode of diode D4, and both the anodes of diode D3 and diode D4 are electrically connected to port 8 of charging management chip U1, the input power supply voltage VCC port, and resistor RS1 through resistor R2.

[0063] In this embodiment, ports 1, 2, 4, and 5 of the lithium battery protection chip U3 are all grounded. Port 3 is electrically connected to ports 5 of the charging management chip U1 and U11 through resistor R3. Meanwhile, port 3 of the lithium battery protection chip U3 is grounded through capacitor C3, and capacitor C3 is electrically connected to ports 4 and 5 of the lithium battery protection chip U3 through resistor NC.

[0064] Furthermore, ports 1 and 3 of the charging management chip U11 are grounded, and port 2 is grounded through resistor R21. At the same time, port 2 of the charging management chip U11 is electrically connected to the drain of the switching transistor Q11 and resistor R7 through resistor R27. Ports 4 and 8 of the charging management chip U11 are electrically connected to the input power supply voltage VCC port, port 5 is electrically connected to port 5 of the charging management chip U1, port 6 is electrically connected to port 6 of the charging management chip U1, and port 7 is electrically connected to resistor RS1 and the gate of the switching transistor Q12.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller, characterized in that, The device includes a current sampling module electrically connected to an LED load, used to acquire the load current value of the LED load and obtain a corresponding voltage feedback signal based on the load current value. Simultaneously, the current sampling module is electrically connected to a microcontroller module, used to determine the corresponding PWM signal based on the voltage feedback signal, and send the PWM signal through a drive module to a Buck main power module electrically connected to a low-voltage DC input power supply. The Buck main power module is electrically connected to the LED load.

2. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 1, characterized in that, The Buck main power module includes a switching transistor, which is electrically connected to the driver module and the LED load. The Buck main power module regulates the conduction state of the switching transistor according to the PWM signal, thereby adjusting the average current of the LED load.

3. A low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 1 or 2, characterized in that, The Buck main power module includes two symmetrically arranged step-down branches. Each step-down branch includes an energy storage inductor electrically connected to a switching transistor and a low-voltage DC input power supply. The energy storage inductor is connected in parallel with a freewheeling diode and a filter capacitor. The filter capacitor is electrically connected to an LED load.

4. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 3, characterized in that, The switching transistor is configured as a MOSFET, with its drain electrically connected to an energy storage inductor, its source grounded through a current sampling module, and its gate electrically connected to a driving module.

5. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 4, characterized in that, The current sampling module includes a sampling resistor, which is electrically connected to a switching transistor and a differential amplifier circuit. The voltage difference across the sampling resistor is sent to the microcontroller module through the differential amplifier circuit.

6. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 5, characterized in that, It also includes a dimming signal module electrically connected to the microcontroller module, used to set an external dimming signal and adjust the target constant current setting value in the microcontroller module according to the external dimming signal. At the same time, the input signal of the dimming signal module is set to one or more of PWM dimming signal, 0-10V analog dimming signal or thyristor dimming signal.

7. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 6, characterized in that, The microcontroller module is equipped with a digital PID control unit, which is electrically connected to the dimming signal module and the current sampling module. It is used to determine the corresponding PWM signal based on the comparison result between the voltage feedback signal and the target constant current set value.

8. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 6, characterized in that, The microcontroller module includes an analog-to-digital converter (ADC) unit and a PWM unit. The ADC unit is electrically connected to a current sampling module to obtain the voltage difference of the sampling resistor. The PWM unit is electrically connected to the Buck main power module through a driver module to send PWM signals to the Buck main power module.

9. The low-voltage DC input Buck-type LED constant current drive circuit based on a microcontroller according to claim 8, characterized in that, The driving module includes a transistor, which is electrically connected to a PWM unit and a switching transistor. The PWM unit sends a PWM signal to the transistor, and the transistor sends a driving voltage to the switching transistor according to the PWM signal. The driving voltage is set to the turn-on voltage of the switching transistor.

10. A constant current driving method for low-voltage DC input Buck-type LEDs based on a microcontroller, characterized in that, The low-voltage DC input Buck-type LED constant current drive circuit based on a single-chip microcomputer, as described in any one of claims 1-9, is used.

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