Control circuit of constant current power supply

Abstract

The utility model provides a control circuit of a constant current power supply, which realizes accurate control of output current and output voltage by utilizing hardware characteristics of MOS (Metal Oxide Semiconductor) tubes. According to an accurate load V-I curve, a required output voltage is fitted through a set output current, the required output voltage is output through a controller DA to serve as a control quantity of a voltage outer loop, the control quantity is compared with an actual sampling voltage, conduction of a preceding-stage MOS tube is controlled, and closed-loop control over the output voltage is achieved. Through comparison of the set current and the sampling current, conduction of a post-stage MOS tube is controlled, and closed-loop control of the output current is realized. By comparing the set terminal voltage threshold of the back-stage MOS tube with the voltage of the MOS tube, the conduction of the front-stage MOS tube is controlled, so that the terminal voltage of the back-stage MOS tube is within a certain threshold range, and the output power consumption is reduced. According to the circuit structure and the control strategy, the output current response is faster, the stability is higher, and the overall power consumption is smaller.

Description

Technical Field

[0001] This application relates to the field of power electronic power supply control technology, and more specifically, to a control circuit for a constant current power supply. Background Technology

[0002] With the continuous development of digital chips, digital control technology is increasingly widely used in the control of power electronic converters. Compared with analog control, digital control technology simplifies hardware control circuits and improves the reliability and anti-interference capability of control circuits. However, digital control suffers from control delay, which affects the dynamic performance of the converter. Digital control delay includes calculation delay and modulation delay. The traditional control strategy of current sampling plus controller processing to adjust the PWM duty cycle to achieve closed-loop control of output current has many shortcomings, resulting in slow output current response, poor stability, large ripple, and high power consumption. In constant current power supply design, the control idea mostly adopted for stable current output is to use PID (Proportional Integral Derivative) control strategy to achieve continuous adjustment of output current. However, due to the long response time, large overshoot, steady-state error, and the dependence of calculation parameters on empirical data and expert experience, experimental debugging is cumbersome and lengthy.

[0003] Utilizing the hardware characteristics of MOSFETs to achieve precise control of output voltage and output current can effectively avoid the above-mentioned shortcomings, resulting in faster output current response, higher stability, smaller ripple, and stronger anti-interference capability. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model proposes a control circuit for a constant current power supply, which utilizes the hardware characteristics of MOSFETs to achieve precise control of output voltage and current, as well as to achieve fast and stable current output.

[0005] This invention proposes a control circuit for a constant current power supply.

[0006] The control circuit includes an output current control unit, an output voltage control unit, and a Buck circuit. The output current control unit includes a first emitter follower circuit, a first comparator circuit, a Class B complementary power amplifier circuit, and a current control circuit at the VT2 terminal of the subsequent MOSFET. The output voltage control unit includes a second emitter follower circuit, a second comparator circuit, a voltage sampling circuit at the VT2 terminal of the subsequent MOSFET, a voltage regulation protection circuit, a voltage comparison circuit at the VT2 terminal of the subsequent MOSFET, and a conduction control circuit for the VT1 terminal of the preceding MOSFET.

[0007] The control circuit compares the control quantity of the outer voltage loop with the actual sampled voltage value based on the load VI curve and then controls the conduction of the front-stage MOSFET VT1 to achieve closed-loop control of the output voltage. It also compares the set current with the sampled current and then controls the conduction of the rear-stage MOSFET VT2 to achieve closed-loop control of the output current. In the Buck circuit, the gate control voltage of the front-stage MOSFET VT1 is jointly controlled by the voltage comparison circuit and the second comparison circuit at the terminal of the rear-stage MOSFET VT2.

[0008] As a further optimized technical solution of this utility model, the current control circuit of the VT2 terminal of the subsequent MOS transistor includes a sampling resistor R8. The output current forms a voltage signal through the sampling resistor R8 in the current control circuit of the VT2 terminal of the subsequent MOS transistor, and after amplification, it is used as the reference voltage of the comparator in the first comparison circuit.

[0009] As a further optimized technical solution of this utility model, the first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, the second comparator circuit, the voltage sampling circuit at the VT2 terminal of the subsequent MOSFET, the voltage comparison circuit at the VT2 terminal of the subsequent MOSFET, and the conduction control circuit of the VT1 terminal of the preceding MOSFET all include operational amplifier modules, and all use LM324. The power supplies of the first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, and the second comparator circuit are connected to positive 12V and ground, and the power supplies of the voltage sampling circuit at the VT2 terminal of the subsequent MOSFET and the voltage comparison circuit at the VT2 terminal of the subsequent MOSFET are connected to positive 6V and negative 6V.

[0010] As a further optimized technical solution of this utility model, the output of the second comparison circuit is divided by a voltage divider resistor and enters the non-inverting input terminal of the comparator in the conduction control circuit of the front-stage MOSFET VT1, and the output of the voltage comparison circuit of the rear-stage MOSFET VT2 is connected to the inverting input terminal of the comparator in the conduction control circuit of the front-stage MOSFET VT1.

[0011] As a further optimized technical solution of this utility model, the first emitter follower circuit receives the set current signal and inputs it to the non-inverting input terminal of the first comparator circuit. The voltage of the sampling resistor is input to the inverting input terminal of the first comparator circuit for comparison and output. After passing through the Class B complementary power amplifier circuit, it is connected to the gate G pin of the current control circuit at the VT2 terminal of the subsequent stage MOS transistor.

[0012] The beneficial effects of this invention are: through dual closed-loop control of voltage and current, the output voltage and output current can be precisely matched, reducing power loss. At the same time, it avoids the traditional digital control method of using PWM to control the duty cycle of the MOSFET, and the hardware circuit design avoids digital control delays, ensuring the speed and stability of the output voltage and output current. Attached Figure Description

[0013] Figure 1 The block diagram of the constant current output circuit of the control circuit of the constant current power supply proposed in this utility model.

[0014] Figure 2 This is the current stabilization control logic diagram of this utility model.

[0015] Figure 3 This is a circuit diagram of a Buck converter.

[0016] Figure 4 This is a circuit diagram for precise control of the output current of a MOSFET in this utility model.

[0017] Figure 5 This is the output voltage closed-loop control circuit diagram of this utility model.

[0018] In the diagram: 1. First emitter follower circuit 1; 2. First comparator circuit; 3. Class B complementary power amplifier circuit; 4. Current control circuit for the subsequent MOSFET VT2; 5. Second emitter follower circuit; 6. Second comparator circuit; 7. Voltage sampling circuit for the subsequent MOSFET VT2; 8. Voltage regulation protection circuit; 9. Voltage comparison circuit for the subsequent MOSFET VT2; 10. Turn-on control circuit for the preceding MOSFET VT1. Detailed Implementation

[0019] To facilitate understanding, the technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0020] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0021] Figure 1 The block diagram of the constant current output circuit of the control circuit of the constant current power supply proposed in this utility model is as follows: Figure 1As shown, the control circuit includes an output current control unit, an output voltage control unit, and a Buck circuit. The output current control unit includes a first emitter follower circuit 1, a first comparator circuit 2, a Class B complementary power amplifier circuit 3, and a current control circuit 4 at the VT2 terminal of the subsequent MOSFET. The output voltage control unit includes a second emitter follower circuit 5, a second comparator circuit 6, a voltage sampling circuit 7 at the VT2 terminal of the subsequent MOSFET, a voltage regulation protection circuit 8, a voltage comparison circuit 9 at the VT2 terminal of the subsequent MOSFET, and a conduction control circuit 10 for the VT1 terminal of the preceding MOSFET.

[0022] The controller's DA outputs the set current signal, which is then input to the non-inverting input of the first comparator circuit 2 after passing through the first emitter follower circuit 1. The voltage of the sampling resistor is input to the inverting input of the first comparator circuit 2 for comparison and output. The output is then connected to the gate G pin of the current control circuit 4 after passing through the class B complementary power amplifier circuit 3 and the subsequent MOSFET VT2, thereby controlling the on / off state of the MOSFET VT2 in real time.

[0023] Based on the load VI curve, the current value is set to fit the required voltage of the load. The controller outputs DAC-Vref, which is then input to the non-inverting input of the second comparator circuit 6 after passing through the second emitter follower circuit 5. The actual output voltage signal is input to the inverting input of the second comparator circuit for comparison and output. The on / off state of MOSFET VT1 is controlled in real time to achieve closed-loop control of the output voltage. The set current is compared with the sampled current and then the conduction of the subsequent MOSFET VT2 is controlled to achieve closed-loop control of the output current.

[0024] The gate control voltage of the switching MOSFET VT1 in the Buck circuit is jointly controlled by the voltage comparison circuit 9 at the terminal of the subsequent MOSFET VT2 and the second comparison circuit 6.

[0025] The output of the comparator in the second comparator circuit 6 (the comparator's power supply is connected to +12V and ground, such as an LM324 comparator) serves as the non-inverting input of the comparator in the pre-stage MOSFET VT1 turn-on control circuit 10. The output of the voltage sampling circuit 7 at the terminal of the subsequent MOSFET VT2 is compared with a set threshold voltage by the voltage comparison circuit 9 at the terminal of the subsequent MOSFET VT2. The output of this comparison circuit is then fed into the inverting input of the comparator in the pre-stage MOSFET VT1 turn-on control circuit 10. The output of the pre-stage MOSFET VT1 turn-on control circuit 10 is connected to the gate (G) pin of the pre-stage MOSFET VT1 turn-on control circuit. The current control circuit 4 at the terminal of the subsequent MOSFET VT2 includes a sampling resistor R8. The output current passes through the sampling resistor to form a voltage signal, which is amplified and used as the reference voltage for the comparator in the first comparator circuit 2. The first emitter follower circuit 1 includes an operational amplifier used to isolate the controller from the power devices. If the voltage at the terminal of MOSFET VT2 is higher than the threshold voltage, MOSFET VT1 is turned off, causing the output voltage to drop, thus reducing power loss while ensuring stable output voltage.

[0026] In this embodiment, the current control circuit at the VT2 terminal of the subsequent MOSFET includes a sampling resistor R8. The output current passes through the sampling resistor R8 in the current control circuit at the VT2 terminal of the subsequent MOSFET to form a voltage signal, which is then amplified and used as the reference voltage of the comparator in the first comparator circuit.

[0027] The first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, the second comparator circuit, the voltage sampling circuit at the VT2 terminal of the subsequent MOSFET, the voltage comparator circuit at the VT2 terminal of the subsequent MOSFET, and the turn-on control circuit for the VT1 terminal of the preceding MOSFET all include operational amplifier modules, all using LM324. The first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, and the second comparator circuit are powered by +12V and ground. The voltage sampling circuit at the VT2 terminal of the subsequent MOSFET and the voltage comparator circuit at the VT2 terminal of the subsequent MOSFET are powered by +6V and -6V. The output of the second comparator circuit is divided by a voltage divider resistor and fed into the non-inverting input of the comparator in the turn-on control circuit for the VT1 terminal of the preceding MOSFET. The output of the voltage comparator circuit at the VT2 terminal of the subsequent MOSFET is connected to the inverting input of the comparator in the turn-on control circuit for the VT1 terminal of the preceding MOSFET. During the voltage fine-tuning stage, when the voltage at the terminal of the subsequent MOSFET is greater than the threshold voltage and the actual output voltage during the pre-charging stage is greater than the calculated voltage corresponding to the set current, the preceding MOSFET will be cut off. Since the terminal voltage of the subsequent MOSFET VT2 will only be divided when the output voltage is higher than the actual load voltage, the terminal voltage of MOSFET VT2 will increase.

[0028] like Figure 1-2 As shown, the control method of this utility model includes a pre-charge control stage, a current stabilization control stage, and a fine-tuning output voltage stage to reduce power loss, and specifically includes the following steps:

[0029] During the pre-charging phase, based on the set current value, the output voltage is calculated according to the accurate load VI curve, and the corresponding digital signal is given to the DAC-Vref value. After being electrically isolated by the second emitter follower circuit, it passes through the second comparator circuit and is compared with the load terminal voltage to form a pre-charging MOSFET control signal α. After passing through the front-stage MOSFET VT1 turn-on control circuit, a high level is output to turn on MOSFET VT1. When the load terminal voltage reaches and exceeds the voltage calculated according to the VI curve, it indicates that the pre-charging is complete. At this time, the α signal is 0V and the β signal is 6V. After passing through circuit 10, a low level is output to turn off VT1. The pre-charging operation is realized through the above cycle.

[0030] During the current stabilization control phase, based on the set current value, the corresponding digital signal DAC-Iref value is electrically isolated by the first emitter follower circuit, and then compared with the sampled current by the first comparator circuit. The output controls the base voltage of the two transistors, realizes the conduction control of MOSFET VT2, and stabilizes the output current at the set current.

[0031] During the stage of fine-tuning the output voltage to reduce power loss, the output voltage is stabilized at the voltage value calculated according to the VI curve, and the output current is stabilized at the set current value. If the MOSFET terminal voltage Vmos signal is higher than the set MOSFET terminal voltage threshold signal, the duty cycle of MOSFET VT1 is reduced so that the front-stage MOSFET VT1 turn-on control circuit outputs a low level, MOSFET VT1 is turned off, and the output voltage decreases. If the MOSFET terminal voltage Vmos signal is lower than the set MOSFET terminal voltage threshold signal, the duty cycle of MOSFET VT1 is increased so that the front-stage MOSFET VT1 turn-on control circuit outputs a high level, MOSFET VT1 is turned on, and the output voltage increases.

[0032] Figure 4 This is a circuit diagram for precise control of the output current of a MOSFET in this utility model, as shown below. Figure 4 As shown, the current control section of the MOSFET is controlled by a control voltage (DAC-Iref, i.e., a voltage signal corresponding to the set current) in the second comparator circuit. The voltage at the non-inverting input of the comparator and the voltage at the inverting input of the sampling resistor are simultaneously input to the second comparator circuit (the comparator power supply is connected to positive 12V and ground, such as LM324 as a comparator). The output is connected to the gate G pin of the subsequent MOSFET through a Class B complementary power amplifier circuit. If the control voltage is lower than the reference voltage, the MOSFET VT2 is controlled to conduct and output current.

[0033] In the Buck circuit, the gate control voltage of the switching MOSFET VT1 is jointly controlled by the voltage comparison circuit of the subsequent MOSFET VT2 and the second comparison circuit. The output of the second comparison circuit is divided by a voltage divider resistor and enters the non-inverting input of the comparator in the conduction control circuit of the preceding MOSFET VT1. The output of the voltage comparison circuit of the subsequent MOSFET VT2 is connected to the inverting input of the comparator in the conduction control circuit of the preceding MOSFET VT1. When the voltage of the subsequent MOSFET VT2 is greater than the voltage threshold of the subsequent MOSFET VT2 and the actual output voltage is greater than the set voltage corresponding to the set current, the preceding MOSFET VT1 will be turned off.

[0034] In this design, the output voltage closed-loop control is performed based on the relatively accurate VI curve of the load. The required voltage value of the load is calculated by setting the output current. In this calculation process, the VI curve does not need to be strictly accurate, because the calculated voltage can be appropriately higher than the actual required voltage. This can serve as a pre-charging function and ensure that the output voltage value meets the power supply requirements of the load. Later, the voltage at the terminal of the subsequent MOSFET VT2 is compared with the threshold voltage to control the cutting off of the preceding MOSFET VT1, and then the output voltage is reduced to form a closed loop.

[0035] In the closed-loop control of the output current, the output current passes through the sampling resistor R8 in the current control circuit 4 of the subsequent MOSFET VT2 to form a voltage signal. After amplification, this signal serves as the reference voltage for the comparator. The control voltage comes from a voltage parameter calculated proportionally by the controller based on the set current value. After passing through the D / A output and the first emitter follower circuit 1, it enters the comparator in the first comparator circuit 2. The first emitter follower circuit 1 utilizes the high common-mode rejection ratio of the operational amplifier to achieve isolation, isolating the controller from the power devices. Initially, the current is very small, so the control voltage is higher than the output voltage. At this time, pin G is basically 12V, which allows the transistor to conduct quickly. After a very short time, as the current gradually increases and reaches a certain value, the output voltage rises rapidly. When it approaches and exceeds the control voltage, the comparator outputs a low level (close to 0V), cutting off the transistor and reducing the current. Then, as the current decreases, the reference voltage drops, the transistor conducts again, and the current increases again, repeating the cycle to achieve inner-loop current control.

[0036] like Figure 3 and 5As shown, in the Buck circuit, the gate control voltage of the switching MOSFET VT1 is jointly controlled by the voltage comparison circuit 9 at the terminal of the subsequent MOSFET VT2 and the second comparison circuit 6. All operational amplifier modules use LM324, with power supplies connected to +12V and ground. The output of the second comparison circuit 6 is divided by a voltage divider resistor and fed into the non-inverting input of the comparator in the MOSFET VT1 turn-on control circuit 10. The output of the voltage comparison circuit 9 at the terminal of the subsequent MOSFET VT2 is connected to the inverting input of the comparator in the MOSFET VT1 turn-on control circuit 10. When the voltage at the terminal of the subsequent MOSFET is greater than the threshold voltage and the actual output voltage is greater than the set voltage corresponding to the set current, the preceding MOSFET will be turned off. Since the voltage at the terminal of the subsequent MOSFET VT2 only increases when the output voltage is higher than the actual load voltage, this ensures that the output voltage reaches the preset voltage value and that the preset voltage matches the actual load voltage, reducing power loss.

[0037] The current signal is set to pass through the DA output of the controller, and after passing through the first emitter follower circuit 1, it is output to the non-inverting input of the comparator of the second comparator circuit 2. The voltage idcs of the sampling resistor is input to the inverting input of the comparator of the second comparator circuit 2. After comparison, the output is connected to the gate G pin of the subsequent MOSFET 4 through the Class B complementary power amplifier circuit 3, and the on and off of the MOSFET VT2 is controlled in real time.

[0038] Based on the load VI curve, the required voltage of the load is fitted by setting the current value. The controller outputs DAC-Vref, which is then output to the non-inverting input of the comparator in the second comparator circuit 6 after passing through the second emitter follower circuit 5. The actual output voltage signal is input to the inverting input of the comparator in the second comparator circuit 6 for comparison and output, thereby controlling the on / off state of the MOSFET VT1 in real time.

[0039] The voltage at the terminals of VT2 is sampled, and the differential amplifier (subtractor) of the voltage sampling circuit 7 of the subsequent MOSFET VT2 subtracts the voltage value at both ends of VT2. The result is then fed into the non-inverting input of the comparator through the voltage regulation protection circuit 8 and compared with the set threshold voltage of the MOSFET. This allows for real-time adjustment of the conduction of the preceding MOSFET VT1, achieving adaptive voltage output and reducing energy consumption.

[0040] Example 1:

[0041] In this embodiment, a step-down DC-DC power supply module with a large load current output is designed, with dimensions of 50mm*50mm*25mm. The parameters are as follows: input voltage 48V, continuously adjustable output current of 20A, and adaptive output voltage. All comparators are LM324 operational amplifiers. The pre-stage MOSFET VT1 is a CSD19531Q5A, and the post-stage MOSFET VT2 is an IPB020N10N5. The threshold voltage of VT2 is set to 0.05V. The power supply module is designed and tested using the aforementioned control method and circuit design. Ultimately, precise and stable current control and low power consumption are achieved. Furthermore, this power supply module exhibits fast output current response, good stability, low ripple, strong anti-interference capability, and lower overall power consumption and higher efficiency.

[0042] This design employs dual closed-loop control of voltage and current to precisely match the output voltage and current, reducing power loss. Furthermore, the hardware-based circuit design avoids digital control delays, ensuring the speed and stability of the output voltage and current. This design offers greater application prospects, better economic benefits, and significant potential for wider adoption.

[0043] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0044] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of this application.

[0045] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A control circuit for a constant current power supply, characterized in that, The control circuit includes an output current control unit, an output voltage control unit, and a Buck circuit. The output current control unit includes a first emitter follower circuit, a first comparator circuit, a Class B complementary power amplifier circuit, and a current control circuit at the VT2 terminal of the subsequent MOSFET. The output voltage control unit includes a second emitter follower circuit, a second comparator circuit, a voltage sampling circuit at the VT2 terminal of the subsequent MOSFET, a voltage regulation protection circuit, a voltage comparison circuit at the VT2 terminal of the subsequent MOSFET, and a conduction control circuit for the VT1 terminal of the preceding MOSFET. The control circuit compares the control quantity of the outer voltage loop with the actual sampled voltage value based on the load VI curve and then controls the conduction of the front-stage MOSFET VT1 to achieve closed-loop control of the output voltage. It also compares the set current with the sampled current and then controls the conduction of the rear-stage MOSFET VT2 to achieve closed-loop control of the output current. In the Buck circuit, the gate control voltage of the front-stage MOSFET VT1 is jointly controlled by the voltage comparison circuit and the second comparison circuit at the terminal of the rear-stage MOSFET VT2.

2. The control circuit according to claim 1, characterized in that, The current control circuit at the VT2 terminal of the subsequent MOSFET includes a sampling resistor R8. The output current passes through the sampling resistor R8 in the current control circuit at the VT2 terminal of the subsequent MOSFET to form a voltage signal, which is then amplified and used as the reference voltage of the comparator in the first comparator circuit.

3. The control circuit according to claim 1, characterized in that, The first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, the second comparator circuit, the voltage sampling circuit at the VT2 terminal of the subsequent MOSFET, the voltage comparison circuit at the VT2 terminal of the subsequent MOSFET, and the conduction control circuit of the VT1 terminal of the preceding MOSFET all include operational amplifier modules, and all use LM324. The power supplies of the first emitter follower circuit, the first comparator circuit, the second emitter follower circuit, and the second comparator circuit are connected to positive 12V and ground, and the power supplies of the voltage sampling circuit at the VT2 terminal of the subsequent MOSFET and the voltage comparison circuit at the VT2 terminal of the subsequent MOSFET are connected to positive 6V and negative 6V.

4. The control circuit according to claim 1, characterized in that, The output of the second comparator circuit is divided by a voltage divider resistor and enters the non-inverting input of the comparator in the conduction control circuit of the preceding MOSFET VT1. The output of the voltage comparison circuit of the following MOSFET VT2 is connected to the inverting input of the comparator in the conduction control circuit of the preceding MOSFET VT1.

5. The control circuit according to claim 1, characterized in that, After receiving the set current signal, the first emitter follower circuit inputs it to the non-inverting input of the first comparator circuit. The voltage of the sampling resistor is input to the inverting input of the first comparator circuit. The signal is compared and output. The signal is then connected to the gate G pin of the current control circuit through the VT2 terminal of the subsequent MOSFET.

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