A constant voltage constant current source feedback control circuit and detection method thereof

Abstract

The present invention provides a constant voltage constant current source feedback control circuit in the field of lithium battery testing technology, including an MCU, a proportional integral regulation and integral regulation combined control circuit, a linear regulation circuit and a voltage and current acquisition circuit; the input end of the MCU is connected to the voltage and current acquisition circuit, and the output end is connected to the proportional integral regulation and integral regulation combined control circuit; the proportional integral regulation and integral regulation combined control circuit is connected to the linear regulation circuit and the voltage and current acquisition circuit; the present invention also provides a detection method for a constant voltage constant current source feedback control circuit. The present invention has the advantages of realizing outputting constant voltage and constant current in a step loading mode, being able to respond quickly and without convex waves.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery testing, and in particular to a constant voltage and constant current source feedback control circuit and a detection method thereof. Background Art

[0002] After lithium batteries are assembled into finished lithium battery packs, it is necessary to perform charge and discharge tests on the protection board of the lithium battery pack and the finished lithium battery pack, as well as the on-off test of the MOSFET tube. However, due to the large number of models of lithium battery packs and protection boards and the large number of tests, it is often necessary to change the output loading mode of the test equipment. When the output loading mode of the test equipment is changed, it is necessary to maintain high response and non-surge output of the test equipment.

[0003] Traditionally, the following three control circuits are used to test lithium battery packs and protection boards: the first is an integral regulation feedback control circuit, the second is a proportional integral regulation feedback control circuit, and the third is an integral regulation and proportional integral regulation parallel feedback control circuit.

[0004] However, the traditional method has the following disadvantages: since the capacitance value of the integral capacitor and the resistance value of the integral resistor are immutable, the constant voltage and constant current output in the step loading mode has the defects of slow loading response time and convex waves, which affects the loading performance of the circuit under different forms, and further affects the detection speed of the overcurrent protection value of the protection board, causing impact damage to the protection board. Summary of the invention

[0005] One of the technical problems to be solved by the present invention is to provide a constant voltage and constant current source feedback control circuit to achieve output constant voltage and constant current in a step loading mode, which can respond quickly and without convex waves.

[0006] The present invention achieves one of the technical problems as follows: a constant voltage and constant current source feedback control circuit, including an MCU, a proportional integral regulation and integral regulation combined control circuit, a linear regulation circuit and a voltage and current acquisition circuit;

[0007] The input end of the MCU is connected to the voltage and current acquisition circuit, and the output end is connected to the proportional integral regulation and integral regulation combined control circuit; the proportional integral regulation and integral regulation combined control circuit is connected to the linear regulation circuit and the voltage and current acquisition circuit.

[0008] Further, the proportional integral regulation and integral regulation combined control circuit includes a resistor R1, a resistor R2, a resistor R3, a variable resistor R4, a variable resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R10, a resistor R11, a variable resistor R12, a variable resistor R13, a resistor R14, a resistor R15, an optocoupler U1, an optocoupler U4, a MOSFET tube U2, a MOSFET tube U5, a capacitor C1, a variable capacitor C2, a capacitor C3, a variable capacitor C4, an operational amplifier N1A, an operational amplifier N1B, a diode D1 and a diode D2;

[0009] Pin 1 of the optical coupler U1 is connected to the resistor R1, pin 2 is connected to the drain of the MOSFET tube U2, pin 3 is connected to the capacitor C1, and pin 4 is connected to the variable capacitor C2, resistor R6, the output end of the diode D1 and pin 7 of the operational amplifier N1B; the gate of the MOSFET tube U2 is connected to the resistor R2 and the resistor R3, and the drain is connected to the resistor R3; the resistor R2 is connected to the MCU; the pin 5 of the operational amplifier N1B is connected to the resistor R7, and the pin 6 is connected to the variable resistor R5, the capacitor C1 and the variable resistor R4; the variable resistor R4 is connected to the variable capacitor C2; the variable resistor R5 and the resistor R7 are both connected to the MCU; the resistor R5 is connected to the voltage and current acquisition circuit;

[0010] Pin 1 of the optocoupler U4 is connected to resistor R8, pin 2 is connected to the drain of the MOSFET tube U5, pin 3 is connected to the capacitor C3, pin 4 is connected to the variable capacitor C4, resistor R14, the output end of the diode D2 and pin 4 of the operational amplifier N1A; the gate of the MOSFET tube U5 is connected to resistor R10 and resistor R11, and the drain is connected to the resistor R11 and grounded; the resistor R10 is connected to the MCU; pin 3 of the operational amplifier N1A is connected to resistor R15, and pin 2 is connected to the variable resistor R13, capacitor C3 and variable resistor R12; the variable resistor R12 is connected to the variable capacitor C4; the variable resistor R13 and resistor R15 are both connected to the MCU; the resistor R13 is connected to the voltage and current acquisition circuit; the resistor R6, resistor R14, the input end of the diode D1 and the input end of the diode D2 are all connected to the linear regulation circuit.

[0011] Furthermore, the linear regulation circuit includes a MOSFET tube U3 and a resistor R9;

[0012] The gate of the MOSFET tube U3 is connected to the proportional integral regulation and integral regulation combined control circuit; one end of the resistor R9 is connected to the voltage and current acquisition circuit, and the other end is connected to the voltage and current acquisition circuit and grounded.

[0013] Furthermore, the voltage and current acquisition circuit includes a voltage acquisition circuit and a current acquisition circuit; the voltage acquisition circuit and the current acquisition circuit are respectively connected to the MCU.

[0014] Further, the voltage acquisition circuit includes a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20 and an operational amplifier N2A;

[0015] Pin 2 of the operational amplifier N2A is connected to resistors R19 and R20, pin 3 is connected to resistors R16 and R17, and pin 4 is connected to resistors R18 and R20; the resistor R16 is grounded; the resistor R18 is connected to the MCU and the proportional-integral regulation and integral regulation combined control circuit.

[0016] The current collection circuit includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25 and an operational amplifier N2B;

[0017] Pin 6 of the operational amplifier N2B is connected to resistors R24 and R25, pin 5 is connected to resistors R21 and R22, and pin 7 is connected to resistors R23 and R25; the resistor R21 is grounded; the resistor R23 is connected to the MCU and the proportional-integral regulation and integral regulation combined control circuit.

[0018] Furthermore, the model of the MCU is ADuCM361; the PI-CONI pin of the MCU is connected to the resistor R2, the PI-CONV pin is connected to the resistor R10, the Iset pin is connected to the resistor R7, the Vset pin is connected to the resistor R15, the VFB pin is connected to the resistor R13 and the voltage and current acquisition circuit, and the IFB pin is connected to the resistor R5 and the voltage and current acquisition circuit.

[0019] The second technical problem to be solved by the present invention is to provide a detection method for a constant voltage and constant current source feedback control circuit, so as to realize rapid detection of the overcurrent protection value of the protection board without causing impact damage to the protection board.

[0020] The present invention achieves the second technical problem in the following way: a detection method of a constant voltage constant current source feedback control circuit, the method needs to use the above control circuit, the method comprises the following steps:

[0021] Step S10, obtaining the current parameters of the protection board, and setting the current loading parameters of the control circuit;

[0022] Step S20, gradually adding current to the protection board according to the current parameter and the current loading parameter, and recording the time parameter of the current loading process;

[0023] Step S30, calculating the overcurrent protection value of the protection board according to the current parameter, the current loading parameter and the time parameter.

[0024] Furthermore, the step S10 is specifically as follows:

[0025] Get the lower limit current I1, upper limit current I2 and protection delay T0 of the protection board;

[0026] Set the total time of step-by-step loading to T1 and the number of increments to n;

[0027] Among them, I1, I2, and T0 are all greater than 0, T1=T0, and n is a positive integer.

[0028] Furthermore, the step S20 specifically includes:

[0029] Step S21, setting a percentage p%, quickly loading the lower limit current I1 to the protection board through the control circuit, the MCU records the time T2 when the current value fed back by the voltage and current acquisition circuit reaches I1*p%, and waits for a protection delay T0 when the current value reaches I1*p%;

[0030] Step S22, set a percentage q%, the control circuit increases the load current I3 to the protection board in steps each time, and the time for each step-by-step increase is T3. The MCU records the time T4 taken when the current value fed back by the voltage and current acquisition circuit reaches q% of the input current of the control circuit, and waits for a protection delay T0 after loading until the current value reaches the upper limit current I2; wherein I3 = (I2-I1) / n, T3 = T0 / n.

[0031] Furthermore, the step S30 is specifically as follows:

[0032] The overcurrent protection value of the protection board is I=I1+T5 / T3*I3, T5=T4-T2-T0;

[0033] Wherein T5 represents the time from the step-by-step increase of the lower limit current I1 to the time T4; T5 / T3 represents the number of step-by-step increase in the time T5; and T5 / T3*I3 represents the total current value of the step-by-step increase in the time T5.

[0034] The advantages of the present invention are:

[0035] By setting the resistor of the proportional-integral regulation and integral regulation combined control circuit to a variable resistor and the capacitor to a variable capacitor, the resistor and the capacitor can be adjusted according to the actual output demand, thereby achieving constant voltage and constant current output in the step loading mode and the direct loading mode, and being able to respond quickly and without convex waves, that is, not affecting the output response and the smoothness of the rising curve, meeting the needs of step-by-step detection and ramp detection of the voltage and current protection points, and achieving rapid detection of the overcurrent protection value of the protection board, without causing impact damage to the protection board due to convex waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0037] Figure 1 The invention discloses a circuit principle block diagram of a constant voltage and constant current source feedback control circuit.

[0038] Figure 2 It is a circuit diagram of a proportional integral regulation and integral regulation combined control circuit of the present invention.

[0039] Figure 3 It is a circuit diagram of the linear regulation circuit of the present invention.

[0040] Figure 4 It is a circuit diagram of the voltage and current acquisition circuit of the present invention.

[0041] Figure 5 It is a pin diagram of the MCU of the present invention.

[0042] Figure 6 The present invention is a flow chart of a detection method of a constant voltage and constant current source feedback control circuit. DETAILED DESCRIPTION

[0043] Please refer to Figures 1 to 6 As shown, a preferred embodiment of a constant voltage constant current source feedback control circuit of the present invention includes an MCU, a proportional integral regulation and integral regulation combined control circuit, a linear regulation circuit and a voltage and current acquisition circuit; the MCU, the proportional integral regulation and integral regulation combined control circuit, the linear regulation circuit and the voltage and current acquisition circuit constitute a constant voltage constant current source circuit; the MCU is used to set the output size of the constant voltage constant current source, set the parameters of the proportional integral regulation and integral regulation combined control circuit, and read the voltage value and current value collected by the voltage and current acquisition circuit; the signal collected by the voltage and current acquisition circuit is transmitted to the MCU for monitoring all the way, and is transmitted to the proportional integral regulation and integral regulation combined control circuit all the way; the proportional integral regulation and integral regulation combined control circuit is used to control the linear regulation circuit to output a stable constant voltage and constant current value.

[0044] The input end of the MCU is connected to the voltage and current acquisition circuit, and the output end is connected to the proportional integral regulation and integral regulation combined control circuit; the proportional integral regulation and integral regulation combined control circuit is connected to the linear regulation circuit and the voltage and current acquisition circuit. The linear regulation circuit and the voltage and current acquisition circuit are respectively connected to the load (protection board).

[0045] The proportional integral regulation and integral regulation combined control circuit includes a resistor R1, a resistor R2, a resistor R3, a variable resistor R4, a variable resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R10, a resistor R11, a variable resistor R12, a variable resistor R13, a resistor R14, a resistor R15, an optocoupler U1, an optocoupler U4, a MOSFET tube U2, a MOSFET tube U5, a capacitor C1, a variable capacitor C2, a capacitor C3, a variable capacitor C4, an operational amplifier N1A, an operational amplifier N1B, a diode D1 and a diode D2; the models of the operational amplifier N1A and the operational amplifier N1B are both OPA2277;

[0046] Pin 1 of the optical coupler U1 is connected to the resistor R1, pin 2 is connected to the drain of the MOSFET tube U2, pin 3 is connected to the capacitor C1, and pin 4 is connected to the variable capacitor C2, resistor R6, the output end of the diode D1 and pin 7 of the operational amplifier N1B; the gate of the MOSFET tube U2 is connected to the resistor R2 and the resistor R3, and the drain is connected to the resistor R3; the resistor R2 is connected to the MCU; the pin 5 of the operational amplifier N1B is connected to the resistor R7, and the pin 6 is connected to the variable resistor R5, the capacitor C1 and the variable resistor R4; the variable resistor R4 is connected to the variable capacitor C2; the variable resistor R5 and the resistor R7 are both connected to the MCU; the resistor R5 is connected to the voltage and current acquisition circuit;

[0047] Pin 1 of the optocoupler U4 is connected to resistor R8, pin 2 is connected to the drain of the MOSFET tube U5, pin 3 is connected to the capacitor C3, pin 4 is connected to the variable capacitor C4, resistor R14, the output end of the diode D2 and pin 4 of the operational amplifier N1A; the gate of the MOSFET tube U5 is connected to resistor R10 and resistor R11, and the drain is connected to the resistor R11 and grounded; the resistor R10 is connected to the MCU; pin 3 of the operational amplifier N1A is connected to resistor R15, and pin 2 is connected to the variable resistor R13, capacitor C3 and variable resistor R12; the variable resistor R12 is connected to the variable capacitor C4; the variable resistor R13 and resistor R15 are both connected to the MCU; the resistor R13 is connected to the voltage and current acquisition circuit; the resistor R6, resistor R14, the input end of the diode D1 and the input end of the diode D2 are all connected to the linear regulation circuit.

[0048] The linear regulation circuit includes a MOSFET tube U3 and a resistor R9;

[0049] The gate of the MOSFET tube U3 is connected to the proportional integral regulation and integral regulation combined control circuit; one end of the resistor R9 is connected to the voltage and current acquisition circuit, and the other end is connected to the voltage and current acquisition circuit and grounded. The source of the MOSFET tube U3 and the resistor R9 are both connected to the load.

[0050] The voltage and current acquisition circuit includes a voltage acquisition circuit and a current acquisition circuit; the voltage acquisition circuit and the current acquisition circuit are respectively connected to the MCU.

[0051] The voltage acquisition circuit includes a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20 and an operational amplifier N2A;

[0052] Pin 2 of the operational amplifier N2A is connected to resistors R19 and R20, pin 3 is connected to resistors R16 and R17, and pin 4 is connected to resistors R18 and R20; resistor R16 is grounded; resistor R18 is connected to the MCU and the proportional integral regulation and integral regulation combined control circuit. Resistors R17 and R19 are both connected to the load for collecting the voltage value of the load.

[0053] The current collection circuit includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25 and an operational amplifier N2B; the operational amplifier N2A and the operational amplifier N2B are both OPA2188;

[0054] Pin 6 of the operational amplifier N2B is connected to resistors R24 and R25, pin 5 is connected to resistors R21 and R22, and pin 7 is connected to resistors R23 and R25; resistor R21 is grounded; resistor R23 is connected to MCU and proportional integral regulation and integral regulation combined control circuit; resistor R22 is connected to resistor R9 and load; resistor R24 ​​is connected to resistor R9 and grounded. Resistors R22 and R24 are both connected to the load for collecting the current value of the load.

[0055] The model of the MCU is ADuCM361; the PI-CONI pin of the MCU is connected to the resistor R2, the PI-CONV pin is connected to the resistor R10, the Iset pin is connected to the resistor R7, the Vset pin is connected to the resistor R15, the VFB pin is connected to the resistor R13 and the voltage and current acquisition circuit, and the IFB pin is connected to the resistor R5 and the voltage and current acquisition circuit.

[0056] The working principle of a constant voltage and constant current source feedback control circuit of the present invention is as follows:

[0057] Constant voltage direct loading output: The MCU controls the PI-CONI pin and the PI-CONV pin to output a low level, controls the voltage and current output by the Vset pin and the Iset pin, and then drives the MOSFET tube U5 to output the corresponding voltage and current values. The charge and discharge characteristics of the capacitor and the relationship between charge, capacitance and voltage are used to adjust the electrical values ​​of the variable resistors R12 and R13, and the capacitance value of the variable capacitor C4, so that the integral voltage across the variable capacitor C4 rises quickly and smoothly, so that the constant voltage output responds quickly and without convex waves.

[0058] Constant voltage step loading output: the MCU controls the PI-CONI pin to output a low level and controls the PI-CONV pin to output a high level, so that the capacitor C3 is connected in parallel with the variable resistor R12 and the variable capacitor C4, and the loop is controlled by a combination of proportional integral regulation and integral regulation; the MCU controls the Vset pin to output the voltage Vset0 and controls the Iset pin to output the current, thereby driving the MOSFET tube U5 to output the corresponding voltage and current values, and loading the voltage value ΔVset from the Vset pin in a step form. Since the subsequently loaded ΔVset value is very small, the current ΔVset / R13 value in the loop is very small, that is, the integration time of the variable capacitor C4 is very long; since the capacitor C3 is connected in parallel with the variable resistor R12 and the variable capacitor C4, the total capacitance value is reduced, and the integration time of the variable capacitor C4 is reduced, thereby speeding up the response time, and realizing a fast response and convex-free step output when the voltage difference between the front and rear loadings is small.

[0059] Constant current direct loading output: The MCU controls the PI-CONI pin and the PI-CONV pin to output a low level, controls the voltage and current output by the Vset pin and the Iset pin, and then drives the MOSFET tube U5 to output the corresponding voltage and current values. The charge and discharge characteristics of the capacitor and the relationship between charge, capacitance, and voltage are used to adjust the electrical values ​​of the variable resistors R4 and R5, and adjust the capacitance value of the variable capacitor C2, so that the integral voltage across the variable capacitor C2 rises quickly and smoothly, so that the constant current output responds quickly and without convex waves.

[0060] Constant current step loading output: the MCU controls the PI-CONI pin to output a high level and controls the PI-CONV pin to output a low level, so that the capacitor C1 is connected in parallel with the variable resistor R4 and the variable capacitor C2, and the loop is controlled by a combination of proportional integral regulation and integral regulation; the MCU controls the Vset pin to output the voltage and controls the Iset pin to output the current Iset0, thereby driving the MOSFET tube U2 to output the corresponding voltage and current values, and loads the current value ΔIset from the Iset pin in a step form. Since the subsequent loaded ΔIset value is very small, the voltage ΔIset*R5 value in the loop is very small, that is, the integration time of the variable capacitor C2 is very long; since the capacitor C1 is connected in parallel with the variable resistor R4 and the variable capacitor C2, the total capacitance value is reduced, and the integration time of the variable capacitor C2 is reduced, thereby accelerating the response time, and realizing a fast response and a step output without convex waves when the difference between the currents loaded before and after is small.

[0061] A preferred embodiment of a detection method of a constant voltage and constant current source feedback control circuit of the present invention comprises the following steps:

[0062] Step S10, obtaining the current parameters of the protection board, and setting the current loading parameters of the control circuit;

[0063] Step S20, gradually adding current to the protection board according to the current parameter and the current loading parameter, and recording the time parameter of the current loading process;

[0064] Step S30, calculating the overcurrent protection value of the protection board according to the current parameter, current loading parameter and time parameter. The overcurrent protection value of the protection board is the current value flowing through the protection board when charging triggers protection.

[0065] The step S10 is specifically as follows:

[0066] Get the lower limit current I1, upper limit current I2 and protection delay T0 of the protection board; the protection delay T0 refers to the time the protection board can withstand working under a certain current, and this current is between I1 and I2;

[0067] Set the total time of step-by-step loading to T1 and the number of increments to n;

[0068] Among them, I1, I2, and T0 are all greater than 0, T1=T0, and n is a positive integer; the purpose of setting T1=T0 is to have enough time to trigger the protection when the load current is increased in steps; the value of n affects the accuracy of the protection board detection data, and the larger the value of n, the higher the detection accuracy.

[0069] The step S20 specifically includes:

[0070] Step S21, setting a percentage p%, quickly loading the lower limit current I1 to the protection board through the control circuit, the MCU records the time T2 when the current value fed back by the voltage and current acquisition circuit reaches I1*p%, and waits for a protection delay T0 when the current value reaches I1*p%;

[0071] Step S22, set a percentage q%, the control circuit increases the load current I3 to the protection board in each step, and the time for each step increase is T3, the MCU records the time T4 when the current value fed back by the voltage and current acquisition circuit reaches q% of the input current of the control circuit, and waits for a protection delay T0 after the current value reaches the upper limit current I2; where I3 = (I2-I1) / n, T3 = T0 / n. The purpose of waiting for a protection delay T0 is to have enough time to trigger the protection mechanism of the lithium battery pack when loading the upper limit current I2.

[0072] The step S30 is specifically as follows:

[0073] The overcurrent protection value of the protection board is I=I1+T5 / T3*I3, T5=T4-T2-T0;

[0074] Wherein T5 represents the time from the step-by-step increase of the lower limit current I1 to the time T4; T5 / T3 represents the number of step-by-step increase in the time T5; and T5 / T3*I3 represents the total current value of the step-by-step increase in the time T5.

[0075] In summary, the advantages of the present invention are:

[0076] By setting the resistor of the proportional-integral regulation and integral regulation combined control circuit to a variable resistor and the capacitor to a variable capacitor, the resistor and the capacitor can be adjusted according to the actual output demand, thereby achieving constant voltage and constant current output in the step loading mode and the direct loading mode, and being able to respond quickly and without convex waves, that is, not affecting the output response and the smoothness of the rising curve, meeting the needs of step-by-step detection and ramp detection of the voltage and current protection points, and achieving rapid detection of the overcurrent protection value of the protection board, without causing impact damage to the protection board due to convex waves.

[0077] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A constant voltage and constant current source feedback control circuit, characterized in that: It includes an MCU, a proportional integral regulation and integral regulation combined control circuit, a linear regulation circuit and a voltage and current acquisition circuit; The input end of the MCU is connected to the voltage and current acquisition circuit, and the output end is connected to the proportional integral regulation and integral regulation combined control circuit; the proportional integral regulation and integral regulation combined control circuit is connected to the linear regulation circuit and the voltage and current acquisition circuit; The linear regulation circuit includes a MOSFET tube U3 and a resistor R9; The gate of the MOSFET tube U3 is connected to the proportional integral regulation and integral regulation combined control circuit; one end of the resistor R9 is connected to the voltage and current acquisition circuit, and the other end is connected to the voltage and current acquisition circuit and grounded; The voltage and current acquisition circuit includes a voltage acquisition circuit and a current acquisition circuit; the voltage acquisition circuit and the current acquisition circuit are respectively connected to the MCU.

2. A constant voltage constant current source feedback control circuit as claimed in claim 1, characterized in that: The proportional-integral regulation and integral regulation combined control circuit includes a resistor R1, a resistor R2, a resistor R3, a variable resistor R4, a variable resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R10, a resistor R11, a variable resistor R12, a variable resistor R13, a resistor R14, a resistor R15, an optocoupler U1, an optocoupler U4, a MOSFET tube U2, a MOSFET tube U5, a capacitor C1, a variable capacitor C2, a capacitor C3, a variable capacitor C4, an operational amplifier N1A, an operational amplifier N1B, a diode D1 and a diode D2; Pin 1 of the optical coupler U1 is connected to the resistor R1, pin 2 is connected to the drain of the MOSFET tube U2, pin 3 is connected to the capacitor C1, and pin 4 is connected to the variable capacitor C2, resistor R6, the output end of the diode D1 and pin 7 of the operational amplifier N1 B; the gate of the MOSFET tube U2 is connected to the resistor R2 and the resistor R3, and the drain is connected to the resistor R3; the resistor R2 is connected to the MCU; the pin 5 of the operational amplifier N1 B is connected to the resistor R7, and the pin 6 is connected to the variable resistor R5, the capacitor C1 and the variable resistor R4; the variable resistor R4 is connected to the variable capacitor C2; the variable resistor R5 and the resistor R7 are both connected to the MCU; the resistor R5 is connected to the voltage and current acquisition circuit; Pin 1 of the optocoupler U4 is connected to resistor R8, pin 2 is connected to the drain of the MOSFET tube U5, pin 3 is connected to the capacitor C3, pin 4 is connected to the variable capacitor C4, resistor R14, the output end of the diode D2 and pin 4 of the operational amplifier N1A; the gate of the MOSFET tube U5 is connected to resistor R10 and resistor R11, and the drain is connected to the resistor R11 and grounded; the resistor R10 is connected to the MCU; pin 3 of the operational amplifier N1A is connected to resistor R15, and pin 2 is connected to the variable resistor R13, capacitor C3 and variable resistor R12; the variable resistor R12 is connected to the variable capacitor C4; the variable resistor R13 and resistor R15 are both connected to the MCU; the resistor R13 is connected to the voltage and current acquisition circuit; the resistor R6, resistor R14, the input end of the diode D1 and the input end of the diode D2 are all connected to the linear regulation circuit.

3. A constant voltage constant current source feedback control circuit as claimed in claim 1, characterized in that: The voltage acquisition circuit includes a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20 and an operational amplifier N2A; Pin 2 of the operational amplifier N2A is connected to resistors R19 and R20, pin 3 is connected to resistors R16 and R17, and pin 4 is connected to resistors R18 and R20; resistor R16 is grounded; resistor R18 is connected to MCU and proportional integral regulation and integral regulation combined control circuit; The current collection circuit includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25 and an operational amplifier N2B; Pin 6 of the operational amplifier N2B is connected to resistors R24 and R25, pin 5 is connected to resistors R21 and R22, and pin 7 is connected to resistors R23 and R25; the resistor R21 is grounded; the resistor R23 is connected to the MCU and the proportional-integral regulation and integral regulation combined control circuit.

4. A constant voltage constant current source feedback control circuit as claimed in claim 2, characterized in that: The model of the MCU is ADuCM361; the PI-CONI pin of the MCU is connected to the resistor R2, the PI-CONV pin is connected to the resistor R10, the Iset pin is connected to the resistor R7, the Vset pin is connected to the resistor R15, the VFB pin is connected to the resistor R13 and the voltage and current acquisition circuit, and the IFB pin is connected to the resistor R5 and the voltage and current acquisition circuit.

5. A detection method for a constant voltage and constant current source feedback control circuit, characterized in that: The method needs to use the control circuit as described in any one of claims 1 to 4, and the method comprises the following steps: Step S10, obtaining the current parameters of the protection board, and setting the current loading parameters of the control circuit; Step S20, gradually adding current to the protection board according to the current parameter and the current loading parameter, and recording the time parameter of the current loading process; Step S30, calculating the overcurrent protection value of the protection board according to the current parameter, the current loading parameter and the time parameter.

6. The detection method of a constant voltage and constant current source feedback control circuit as claimed in claim 5, characterized in that: The step S10 is specifically as follows: Get the lower limit current I1, upper limit current I2 and protection delay T0 of the protection board; Set the total time of step-by-step loading to T1 and the number of increments to n; Among them, I1, I2, and T0 are all greater than 0, T1=T0, and n is a positive integer.

7. The detection method of a constant voltage and constant current source feedback control circuit as claimed in claim 6, characterized in that: The step S20 specifically includes: Step S21, setting a percentage p%, quickly loading the lower limit current I1 to the protection board through the control circuit, the MCU records the time T2 when the current value fed back by the voltage and current acquisition circuit reaches I1*p%, and waits for a protection delay T0 when the current value reaches I1*p%; Step S22, set a percentage q%, the control circuit increases the load current I3 to the protection board in steps each time, and the time for each step-by-step increase is T3. The MCU records the time T4 taken when the current value fed back by the voltage and current acquisition circuit reaches q% of the input current of the control circuit, and waits for a protection delay T0 after loading until the current value reaches the upper limit current I2; wherein I3 = (I2-I1) / n, T3 = T0 / n.

8. The detection method of a constant voltage and constant current source feedback control circuit as claimed in claim 7, characterized in that: The step S30 is specifically as follows: The overcurrent protection value of the protection board is I=I1+T5 / T3*I3, T5=T4-T2-T0; Wherein T5 represents the time from the step-by-step increase of the lower limit current I1 to the time T4; T5 / T3 represents the number of step-by-step increase in the time T5; and T5 / T3*I3 represents the total current value of the step-by-step increase in the time T5.

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