Pulse constant current power supply circuit

Abstract

The utility model relates to the technical field of power supply circuits, in particular to a pulse constant-current power supply circuit, a voltage-adjustable Boost power supply module of the pulse constant-current power supply circuit comprises an oscillator, a power supply management chip U1, a first-path error amplifier and a second-path error amplifier, and the first-path error amplifier is used for adjusting the duty ratio of a PWM (Pulse-Width Modulation) signal; the second path error amplifier is used for limiting the maximum current; the pulse constant current module supplies power through an internal BOOST boost power supply or an external constant voltage source; and the processor module is used for controlling the pulse width and detecting pulse input. The oscillator is matched with the power management chip U1 to generate sawtooth wave oscillation signals, the two error amplifiers are used for jointly controlling output, the two error amplifiers are responsible for voltage feedback and current limitation respectively, stability and safety of the system are ensured, the first error amplifier is adjusted through voltage signals output by the MCU DAC, and the second error amplifier is used for adjusting the voltage signals output by the MCU DAC. And the second error amplifier is used for current detection to prevent an overcurrent condition.

Description

Technical Field

[0001] This utility model relates to the field of power supply circuit technology, and in particular to a pulse constant current power supply circuit. Background Technology

[0002] In existing technologies, traditional pulse power supply designs often struggle to meet the demands of high-frequency, high-precision control. This limitation is particularly pronounced in applications requiring precise current control, such as camera flash control, laser driving, and LED lighting. These applications typically demand high efficiency, fast response time, stable output, and multi-channel synchronous or asynchronous control capabilities. Specifically, traditional pulse power supplies suffer from several key problems: Insufficient frequency response: Traditional designs often fail to provide a sufficiently high frequency response to meet high-speed control requirements. Low current control accuracy: Due to the lack of sophisticated feedback mechanisms and control algorithms, the accuracy and stability of current control are difficult to guarantee. Difficulty in multi-channel synchronization: Ensuring synchronization and independent adjustment capabilities across all channels is a challenge when controlling multiple loads simultaneously. Summary of the Invention

[0003] This invention provides a pulse constant current power supply circuit to address the problems of existing technologies. It generates a sawtooth wave oscillation signal by cooperating with the power management chip U1 through an oscillator, and uses two error amplifiers to jointly control the output. The two error amplifiers are responsible for voltage feedback and current limiting, respectively, to ensure system stability and safety. The first error amplifier is finely adjusted by the voltage signal output by the MCU DAC, while the second error amplifier is used for current detection to prevent overcurrent.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This utility model provides a pulse constant current power supply circuit, which includes:

[0006] An adjustable voltage Boost power supply module includes an oscillator, a power management chip U1, a first error amplifier, and a second error amplifier. The oscillator works with the power management chip U1 to generate a sawtooth wave oscillation signal. The first error amplifier receives a voltage signal from an external MCU and inputs it to the inverting input of a comparator to adjust the duty cycle of the PWM signal. The second error amplifier limits the maximum current.

[0007] The pulse constant current module is powered by an internal BOOST boost power supply or an external constant voltage source.

[0008] The processor module is used to control the pulse width and detect the pulse input;

[0009] The adjustable voltage Boost power supply module and the pulse constant current module are respectively connected to the processor module.

[0010] The oscillator includes a resistor R10 and a capacitor C8. The power management chip U1 is a TL494. One end of the resistor R10 is connected to the RT pin of the power management chip U1, and one end of the capacitor C8 is connected to the CT pin of the power management chip U1. The other ends of the resistor R10 and the other ends of the capacitor C8 are connected to ground.

[0011] The adjustable voltage Boost power module further includes a half-bridge gate driver chip U2 and a resistor R4. The half-bridge gate driver chip U2 is used to receive the PWM output of the power management chip U1 and provide built-in dead time protection. The HIN pin and LIN# pin of the half-bridge gate driver chip U2 are connected to the E2 pin of the power management chip U1 and one end of the resistor R4. The other end of the resistor R4 is grounded. The E2 pin of the power management chip U1 is connected to the E1 pin of the power management chip U1.

[0012] The adjustable voltage Boost power module further includes a MOSFET Q3, a capacitor C7, resistors R9, R12, and R13. The DTC pin of the power management chip U1 is connected to one end of resistor R9, and the other end of resistor R9 is grounded. The gate of MOSFET Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the processor module. The source and drain of MOSFET Q3 are connected in parallel with resistor R13. Capacitor C7 is connected in parallel with resistor R13. The source of MOSFET Q3 is connected to the DTC pin of the power management chip U1.

[0013] The processor module includes a central processing unit AX58200, which communicates with an external host computer via an EtherCAT interface.

[0014] The processor module also includes a BUCK step-down chip U4, a transient voltage suppressor D5, resistors R19 and R20. The BUCK step-down chip U4 is used to reduce the 24V input voltage to 6.8V. The 12th pin of the central processing unit AX58200 is connected to one end of resistor R20. The other end of resistor R20 is connected to one end of resistor R19 and the cathode of transient voltage suppressor D5. The anode of transient voltage suppressor D5 is grounded. The other end of resistor R19 is connected to an external MCU.

[0015] The pulse constant current module includes a digital-to-analog converter U7 and four independent channels. The model of the digital-to-analog converter U7 is AD5696. The digital-to-analog converter U7 is connected to the load through the four independent channels, and the digital-to-analog converter U7 is connected to the central processing unit AX58200 through the SCL pin and the SDA pin.

[0016] The four independent channels include a first ADC channel, a second ADC channel, a third ADC channel, and a fourth ADC channel; the first ADC channel includes resistors R37, R40, R45, R49, R54, R58, and R62; capacitors C34, C38, C47, C51, C54, and C55; comparator U9.1 and comparator U9.2; switch Q20; fuse F2; capacitors C18, C22, C26, and C30; resistors R21, R25, R29, and R33; switch Q4, Q8, Q12, and Q13; and Zener diode D6. The digital-to-analog converter U7 is connected to one end of resistor R37 via the VOUTA pin. The other end of resistor R37 is connected to one end of resistor R45, one end of capacitor C34, and the positive input terminal of comparator U9.1. The other ends of resistor R45 and capacitor C34 are grounded. The output terminal of comparator U9.1 is connected to one end of resistor R40 and one end of capacitor C37. Capacitor C38 is connected in parallel with resistor R40. The other end of resistor R40 is connected to the gate of switching transistor Q20. The other end of capacitor C47 is connected to the negative input terminal of comparator U9.1 and one end of resistor R49. The other end of resistor R49 is connected to the positive input terminal of comparator U9.2, one end of capacitor C51, and the positive input terminal of switching transistor Q20. The source of Q20 is connected to one end of resistor R54, and the other end of capacitor C51 and the other end of resistor R54 are grounded. The negative input of comparator U9.2 is connected to one end of resistor R61 and one end of resistor R58. Capacitor C355 is connected in parallel with resistor R58, and the other end of resistor R62 is grounded. The output of comparator U9.2 is connected to the PB.0 pin of processor AX58200 and the other end of resistor R58. A load is connected between the drain of switching transistor Q20 and the drain of switching transistor Q4. The cathode of diode D7 is connected to one end of capacitor C22, and the other end of capacitor C22 is connected to the drain of switching transistor Q4. The source of switching transistor Q4 is connected to the anode of diode D7, the cathode of Zener diode D6, and the fuse. One end of F2 is connected, and the other end of the fuse F2 is connected to the power supply; resistor R21 is connected in parallel with diode D7; the gate of switching transistor Q4 is connected to one end of resistor R25; the other end of resistor R25 is connected to the anode of Zener diode D6, one end of resistor R29, and one end of capacitor C26, respectively; the other end of capacitor C26 is grounded; the other end of resistor R29 is connected to the drain of switching transistor Q8; the source of switching transistor Q8 is grounded; the gate of switching transistor Q8 is connected to one end of capacitor C30, the drain of switching transistor Q12, one end of resistor R33, and the drain of switching transistor Q13, respectively; the other end of capacitor C30 is grounded; the source of switching transistor Q12 is grounded; the gate of switching transistor Q12 is connected to PB of processor AX58200.The circuit has 6 pins; the source of transistor Q13 is grounded, and the gate of transistor Q13 is connected to the PWM output of the external MCU.

[0017] The beneficial effects of this utility model are:

[0018] This invention features an ingenious design. During operation, it generates a sawtooth wave oscillation signal through an oscillator in conjunction with the power management chip U1. Two error amplifiers jointly control the output, with one responsible for voltage feedback and the other for current limiting, ensuring system stability and safety. The first error amplifier is finely adjusted using the voltage signal output from the MCU DAC, while the second error amplifier is used for current detection to prevent overcurrent. This invention provides a highly efficient, flexible, and reliable synchronously triggered pulse-type current source, particularly suitable for applications requiring high-precision control, such as camera flashes or similar applications. It not only improves system reliability and flexibility but also significantly enhances the controllability of image quality. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of the adjustable voltage Boost power supply module of this utility model.

[0020] Figure 2 This is a circuit diagram of the processor module of this utility model.

[0021] Figure 3 This is the circuit diagram of the digital-to-analog converter U7 of this utility model.

[0022] Figure 4 This is the circuit diagram of the first ADC channel of this utility model.

[0023] Figure 5 This is the circuit diagram of the second ADC channel of this utility model.

[0024] Figure 6 This is the circuit diagram of the third ADC channel of this utility model.

[0025] Figure 7 This is the circuit diagram of the fourth ADC channel of this utility model. Detailed Implementation

[0026] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0027] A pulse constant current power supply circuit, such as Figures 1 to 7As shown, it includes: an adjustable voltage Boost power supply module, which includes an oscillator, a power management chip U1, a first error amplifier, and a second error amplifier. The oscillator works with the power management chip U1 to generate a sawtooth wave oscillation signal. The first error amplifier receives a voltage signal from an external MCU and inputs it to the inverting input of a comparator to adjust the duty cycle of the PWM signal. The second error amplifier limits the maximum current. A pulse constant current module is powered by an internal BOOST boost power supply or an external constant voltage source. A processor module is used to control the pulse width and detect the pulse input. The adjustable voltage Boost power supply module and the pulse constant current module are respectively connected to the processor module. The oscillator includes a resistor R10 and a capacitor C8. The power management chip U1 is a TL494. One end of the resistor R10 is connected to the RT pin of the power management chip U1, and one end of the capacitor C8 is connected to the CT pin of the power management chip U1. The other ends of the resistor R10 and the other ends of the capacitor C8 are connected to ground. Specifically, this invention features an ingenious design. During operation, it generates a sawtooth wave oscillation signal through an oscillator in conjunction with the power management chip U1. Two error amplifiers jointly control the output, with the two amplifiers responsible for voltage feedback and current limiting, respectively, ensuring system stability and safety. The first error amplifier is finely adjusted using the voltage signal output from the MCU DAC, while the second error amplifier is used for current detection to prevent overcurrent. This invention provides a highly efficient, flexible, and reliable synchronously triggered pulse-type current source, particularly suitable for applications requiring high-precision control, such as camera flashes or similar applications. It not only improves system reliability and flexibility but also significantly enhances the controllability of image quality.

[0028] In this embodiment, the oscillator circuit consists of R10 and C8, forming an RC oscillation circuit, which determines the basic oscillation frequency.

[0029] In this embodiment of the application, the adjustable voltage Boost power supply module further includes a half-bridge gate driver chip U2 and a resistor R4. The half-bridge gate driver chip U2 is used to receive the PWM output of the power management chip U1 and provide built-in dead time protection. The HIN pin and LIN# pin of the half-bridge gate driver chip U2 are connected to the E2 pin of the power management chip U1 and one end of the resistor R4. The other end of the resistor R4 is grounded. The E2 pin of the power management chip U1 is connected to the E1 pin of the power management chip U1.

[0030] In this embodiment, the adjustable voltage Boost power module further includes a MOSFET Q3, a capacitor C7, resistors R9, R12, and R13. The DTC pin of the power management chip U1 is connected to one end of resistor R9, and the other end of resistor R9 is grounded. The gate of the MOSFET Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the processor module. The source and drain of the MOSFET Q3 are connected in parallel with resistor R13. The capacitor C7 is connected in parallel with resistor R13. The source of the MOSFET Q3 is connected to the DTC pin of the power management chip U1. Specifically, the oscillator in the adjustable voltage Boost power supply module consists of an RC oscillator composed of resistor R10 and capacitor C8, oscillated by a TL494, forming a sawtooth wave oscillation. The error amplifier input is controlled by two inputs. The first error amplifier uses its output Vout, which is divided by resistors and connected to the non-inverting input of the comparator. The inverting input uses the MCU's DAC as amplified by a gain of 100 and then input to the comparator's output. The output voltage of the TL494 error amplifier ranges from 0.5V to 3.5V, and the output pulse width varies from 97% of the period to 0, which limits the inverting input to DAC_VREF to DAC_VREF + (3.5 - DAC_VREF / 100). The DAC output is designed to be 0.8V to 1.5V. Using a 0.8V reference voltage, the output voltage accuracy can also be controlled within ±1. The output voltage is adjustable from 24.8V to 46.5V. The second error amplifier uses a resistor as the current detection input connected to the non-inverting input of the comparator, and the inverting input is set to 0.5V. If the peak current of the output BOOST exceeds 6.25A, the PWM output will be limited, thus achieving the effect of limiting the maximum current. When the gate input of the switching transistor Q3 is low, the switching transistor Q3 is cut off, ensuring that the DTC input is 0.5V. At this time, the PWM controller output is 50%, which can be used as a PWM controller with a period of 250KHz. The PWM output is adjusted from 97% to 0% according to the error amplifier input. When the gate input of the switching transistor Q3 is high, the switching transistor Q3 is turned on, and the DTC input is higher than 1V. At this time, the PWM controller output is 0%, and the PWM output is not affected by other signals.

[0031] The U2 half-bridge gate driver chip is a half-bridge gate driver chip. The PWM output of the TL494 is input to the high-side input and the low-side input inverted input. It has a built-in dead time to protect the high and low-side NMOS from being fully turned on.

[0032] In this embodiment, the processor module includes a central processing unit (CPU) AX58200, which communicates with an external host computer via an EtherCAT interface. Specifically, the processor communicates with the host via the EtherCAT bus, modifies parameters such as pulse width and current magnitude according to the host, and resets the timer when an external pulse is input, which can synchronize the output of the four channels. Zener diode D5 and resistor R20 clamp the external input to a voltage not exceeding 3.6V to ensure that the MCU input does not exceed a safe voltage. After a 24V input, Zener diode D4 (transient voltage suppressor) and F1 (resetting fuse) are added to ensure that the input current does not exceed 1.1A and the input voltage does not exceed 26V.

[0033] In this embodiment, the processor module further includes a BUCK buck chip U4, a transient voltage suppressor D5, resistors R19 and R20. The BUCK buck chip U4 is used to reduce the 24V input voltage to 6.8V. The 12th pin of the central processing unit AX58200 is connected to one end of resistor R20. The other end of resistor R20 is connected to one end of resistor R19 and the cathode of transient voltage suppressor D5. The anode of transient voltage suppressor D5 is grounded. The other end of resistor R19 is connected to an external MCU. Specifically, with the above configuration, the BUCK buck chip U4 reduces the 24V input voltage to 6.8V. Combined with transient voltage suppressor D5 and an appropriate resistor network, this protects the central processing unit AX58200 from overvoltage damage. This configuration ensures the stability of the power supply voltage and also improves the system's resistance to abnormal conditions (such as overvoltage).

[0034] In this embodiment, the pulse constant current module includes a digital-to-analog converter (DAC) U7 and four independent channels. The DAC U7 is model AD5696. The DAC U7 is connected to the load through the four independent channels, and it communicates with the central processing unit AX58200 through the SCL and SDA pins. Specifically, the DAC AD5696 is connected to the load through four independent channels, and each channel can independently control the current magnitude. The SCL and SDA pins communicate with the AX58200 to achieve precise current regulation. This realizes high-precision current control across multiple channels and supports complex multi-channel synchronous control requirements.

[0035] Furthermore, the four independent channels include a first ADC channel, a second ADC channel, a third ADC channel, and a fourth ADC channel; the first ADC channel includes resistors R37, R40, R45, R49, R54, R58, and R62; capacitors C34, C38, C47, C51, C54, and C55; comparator U9.1 and U9.2; switch Q20; fuse F2; capacitors C18, C22, C26, and C30; resistors R21, R25, R29, and R33; switch Q4, Q8, Q12, and Q13; and Zener diode D. 6 and diode D7, the digital-to-analog converter U7 is connected to one end of resistor R37 via the VOUTA pin, the other end of resistor R37 is connected to one end of resistor R45, one end of capacitor C34, and the positive input terminal of comparator U9.1, the other ends of resistor R45 and capacitor C34 are grounded, the output terminal of comparator U9.1 is connected to one end of resistor R40 and one end of capacitor C37, capacitor C38 is connected in parallel with resistor R40, the other end of resistor R40 is connected to the gate of switching transistor Q20, the other end of capacitor C47 is connected to the negative input terminal of comparator U9.1 and one end of resistor R49, the other end of resistor R49 is connected to the positive input terminal of comparator U9.2, one end of capacitor C51, and the positive input terminal of switch U9.1. The source of transistor Q20 is connected to one end of resistor R54, and the other end of capacitor C51 and the other end of resistor R54 are grounded. The negative input of comparator U9.2 is connected to one end of resistor R61 and one end of resistor R58. Capacitor C355 is connected in parallel with resistor R58, and the other end of resistor R62 is grounded. The output of comparator U9.2 is connected to pin PB.0 of processor AX58200 and the other end of resistor R58. A load is connected between the drains of switching transistors Q20 and Q4. The cathode of diode D7 is connected to one end of capacitor C22, and the other end of capacitor C22 is connected to the drain of switching transistor Q4. The source of switching transistor Q4 is connected to the anode of diode D7, the cathode of Zener diode D6, and the fuse. One end of F2 is connected, and the other end of the fuse F2 is connected to the power supply; resistor R21 is connected in parallel with diode D7; the gate of switching transistor Q4 is connected to one end of resistor R25; the other end of resistor R25 is connected to the anode of Zener diode D6, one end of resistor R29, and one end of capacitor C26, respectively; the other end of capacitor C26 is grounded; the other end of resistor R29 is connected to the drain of switching transistor Q8; the source of switching transistor Q8 is grounded; the gate of switching transistor Q8 is connected to one end of capacitor C30, the drain of switching transistor Q12, one end of resistor R33, and the drain of switching transistor Q13, respectively; the other end of capacitor C30 is grounded; the source of switching transistor Q12 is grounded; the gate of switching transistor Q12 is connected to PB of processor AX58200.The circuit has 6 pins. The source of the switching transistor Q13 is grounded, and the gate of Q13 is connected to the PWM output of the external MCU. The 36V input can be from an external constant voltage source or the internal boost circuit. When using the internal boost power supply, the maximum current is 6A, shared by all four channels.

[0036] Specifically, TRI serves as both a camera trigger signal and a hardware synchronization mechanism. The processor detects the input to TRI, using it as both a clock synchronization signal and a PWM clock synchronization signal input. EN acts as the MCU's PWM output, controlling the pulse conduction time. Zener diode D6 acts as a voltage clamp, protecting the PMOS gate voltage from exceeding 13V and ensuring sufficient conduction voltage for switch Q4 when switch Q8 is on. Resistor R29 acts as a current-limiting resistor, protecting Zener diode D6 from burning out due to excessive current. Furthermore, diode D7, resistor R21, and capacitor C22 suppress current overshoot when switch Q4 begins to conduct. Comparator U9.1 and switch Q20 form a current source. The MCU controls the current magnitude by controlling the AD5696 to output different DAC values. The current magnitude is amplified by comparator U9.1 and then fed into the MCU's ADC for detection.

[0037] When CH+ / CH- is connected to the load, the voltage input DA_CH1 controls the voltage input to be 0–2.5V. After proportional voltage division, the voltage at the non-inverting input of comparator U9.1 is 0–1.2V. The gate of Q20 is connected to the output of comparator U9.1, forming a negative feedback loop. The addition of R40, R49, C38, and C47 reduces op-amp oscillation, making the current more stable. At this time, the output current is controlled by DA_CH1, and the current is DA_CH1 / 2.5V*1.2V / 1Ω.

[0038] With the above configuration, the first ADC channel contains a series of components such as resistors, capacitors, comparators, and switching transistors, forming a complete current control loop. During the conversion from DAC output to actual current, the accuracy of the current is ensured by a precision operational amplifier and sampling resistor. It provides high-resolution current regulation capability, ensuring the accuracy and stability of the current output, and is suitable for applications requiring fine control.

[0039] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the present utility model without departing from the scope of the present utility model shall fall within the scope of the present utility model.

Claims

1. A pulse constant current power supply circuit, characterized by, The adjustable voltage Boost power module comprises an oscillator, a power management chip U1, a first error amplifier and a second error amplifier, the oscillator cooperates with the power management chip U1 to generate a sawtooth wave oscillation signal, the first error amplifier is used for receiving a voltage signal from an external MCU and inputting to a comparator inverting input end to adjust a PWM signal duty cycle, and the second error amplifier is used for limiting a maximum current. The pulse constant current module is powered by an internal BOOST voltage boosting power supply or an external constant voltage source. The processor module is used for controlling a pulse width and detecting a pulse input. The adjustable voltage Boost power module and the pulse constant current module are connected with the processor module respectively. The oscillator comprises a resistor R10 and a capacitor C8, the power management chip U1 is a TL494, one end of the resistor R10 is connected with an RT pin of the power management chip U1, one end of the capacitor C8 is connected with a CT pin of the power management chip U1, and the other end of the resistor R10 and the other end of the capacitor C8 are connected and grounded.

2. A pulse constant current power supply circuit according to claim 1, characterized in that: The adjustable voltage Boost power module further comprises a half-bridge gate drive chip U2 and a resistor R4, the half-bridge gate drive chip U2 is used for receiving a PWM output of the power management chip U1 and providing a built-in dead time protection, an HIN pin and a LIN# pin of the half-bridge gate drive chip U2 are connected and connected with an E2 pin of the power management chip U1 and one end of the resistor R4, the other end of the resistor R4 is grounded, and the E2 pin of the power management chip U1 is connected with an E1 pin of the power management chip U1.

3. A pulse constant current power supply circuit according to claim 2, wherein: The adjustable voltage Boost power module further comprises a MOS tube Q3, a capacitor C7, a resistor R9, a resistor R12 and a resistor R13, a DTC pin of the power management chip U1 is connected with one end of the resistor R9, the other end of the resistor R9 is grounded, a gate of the MOS tube Q3 is connected with one end of the resistor R12, the other end of the resistor R12 is connected with the processor module, a source and a drain of the MOS tube Q3 are connected with the resistor R13 in parallel, the capacitor C7 is connected with the resistor R13 in parallel, and the source of the MOS tube Q3 is connected with the DTC pin of the power management chip U1.

4. A pulse constant current power supply circuit according to claim 2, wherein: The processor module comprises a central processor AX58200, and the central processor AX58200 is connected with an external host computer in communication through an EtherCAT interface.

5. The pulse constant current power supply circuit according to claim 1, wherein: The processor module further comprises a BUCK voltage reduction chip U4, a transient voltage suppressor D5, a resistor R19 and a resistor R20, the BUCK voltage reduction chip U4 is used for reducing a 24V input voltage to 6.8V, a twelfth pin of the central processor AX58200 is connected with one end of the resistor R20, the other end of the resistor R20 is respectively connected with one end of the resistor R19 and a cathode of the transient voltage suppressor D5, an anode of the transient voltage suppressor D5 is grounded, and the other end of the resistor R19 is connected with an external MCU.

6. A pulse constant current power supply circuit according to claim 5, wherein: ​ 7. A pulse constant current power supply circuit according to claim 5, wherein: The pulse constant current module comprises a digital-to-analog converter U7 and four independent channels, the model number of the digital-to-analog converter U7 is AD5696; the digital-to-analog converter U7 is connected with the load through the four independent channels respectively, and the digital-to-analog converter U7 is in communication connection with the central processing unit AX58200 through an SCL pin and an SDA pin.

8. A pulse constant current power supply circuit according to claim 7, wherein: The four independent channels include a first ADC channel, a second ADC channel, a third ADC channel and a fourth ADC channel; the first ADC channel includes resistors R37, R40, R45, R49, R54, R58, R62, capacitors C34, C38, C47, C51, C54, C55, comparators U9.1, U9.2, a switch tube Q20, a fuse F2, capacitors C18, C22, C26, C30, resistors R21, R25, R29, R33, switch tubes Q4, Q8, Q12, Q13, a voltage stabilizing diode D6 and a diode D7, the digital-to-analog converter U7 is connected with one end of the resistor R37 through a VOUTA pin, the other end of the resistor R37 is connected with one end of the resistor R45, one end of the capacitor C34 and a positive input end of the comparator U9.1, the other end of the resistor R45 and the other end of the capacitor C34 are grounded respectively, one end of the resistor R40 and one end of the capacitor C37 are connected with the output end of the comparator U9.1, the capacitor C38 is connected with the resistor R40 in parallel, the other end of the resistor R40 is connected with a gate of the switch tube Q20, the other end of the capacitor C47 is connected with a negative input end of the comparator U9.1 and one end of the resistor R49 respectively, the other end of the resistor R49 is connected with a positive input end of the comparator U9.2, one end of the capacitor C51, a source of the switch tube Q20 and one end of the resistor R54 respectively, the other end of the capacitor C51 and the other end of the resistor R54 are grounded, a negative input end of the comparator U9.2 is connected with one end of the resistor R61 and one end of the resistor R58, the capacitor C355 is connected with the resistor R58 in parallel, the other end of the resistor R62 is grounded, the output end of the comparator U9.2 is connected with a PB.0 pin of the processor AX58200 and the other end of the resistor R58 respectively; a load is connected between a drain of the switch tube Q20 and a drain of the switch tube Q4, a cathode of the diode D7 is connected with one end of the capacitor C22, the other end of the capacitor C22 is connected with the drain of the switch tube Q4, a source of the switch tube Q4 is connected with an anode of the diode D7, a cathode of the voltage stabilizing diode D6 and one end of the fuse F2 respectively, the other end of the fuse F2 is connected with a power supply; the resistor R21 is connected with the diode D7 in parallel, a gate of the switch tube Q4 is connected with one end of the resistor R25, the other end of the resistor R25 is connected with an anode of the voltage stabilizing diode D6, one end of the resistor R29 and one end of the capacitor C26 respectively, the other end of the capacitor C26 is grounded, the other end of the resistor R29 is connected with a drain of the switch tube Q8, a source of the switch tube Q8 is grounded, a gate of the switch tube Q8 is connected with one end of the capacitor C30, a drain of the switch tube Q12, one end of the resistor R33 and a drain of the switch tube Q13 respectively, the other end of the capacitor C30 is grounded, a source of the switch tube Q12 is grounded, a gate of the switch tube Q12 is connected with a PB.6 pin connection, switch tube Q13 source is connected with ground, switch tube Q13 gate and external MCU PWM output end is connected.

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