A feedback circuit for controlling a chip

Abstract

The present application relates to the field of electronic circuit design, especially to a feedback circuit for controlling chip. The output voltage of the voltage output terminal is determined by the ninth resistor, the tenth resistor and the feedback compensation circuit, wherein when the normal output voltage, the third resistor and the second resistor electrically connected with the triode are properly adjusted to make the triode work in the linear region. When the circuit works, the fourth resistor and the fifth resistor provide steady-state working current for the working state of the three-terminal adjustable shunt reference source, and the fourth resistor provides working current for the voltage reference source of the three-terminal adjustable shunt reference source. When working normally, the current passes through the three-terminal adjustable shunt reference source to break down, the three-terminal adjustable shunt reference source provides a 2.5V reference voltage, and then the sixth resistor and the seventh resistor proportionally amplify the output voltage. The high-precision feedback circuit loop is stable, and the output voltage precision, load regulation and linear regulation of the product are greatly improved.

Description

[0001] This case is a divisional application based on the invention patent filed on December 24, 2018, with application number 201811578757.3 and title "A High-Precision Feedback Circuit". Technical Field

[0002] This invention relates to the field of electronic circuit design, and more particularly to a high-precision feedback circuit. Background Technology

[0003] In current switching power supply products, smaller size has become a development trend, and chip integration is increasing. More and more power chip manufacturers are integrating voltage reference sources and control chips together, such as PI's INNO series chips. Figure 1 As shown, when this series of chips is used, a bias resistor is added to the reference voltage pin FB (i.e., a bias resistor is applied to the reference voltage pin FB). Figure 1 The resistors R1 and R2 in the figure are used to achieve output voltage feedback. However, due to the low voltage accuracy of the reference voltage pin FB, which is generally around 3%, and the accuracy of the upper and lower bias resistors of the reference voltage pin FB, the overall output voltage accuracy of the product is close to 5%. This is far from sufficient for the output voltage accuracy requirements of existing products, which require the output voltage accuracy to be controlled within 1%.

[0004] Therefore, a high-precision feedback circuit is needed to meet the application requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-precision feedback circuit to improve the accuracy of the output voltage and meet application requirements.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A high-precision feedback circuit includes a control chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a transistor, and a three-terminal adjustable shunt reference source.

[0008] The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and one end of a first resistor, respectively. The other end of the ninth resistor is electrically connected to a voltage output terminal, the other end of the tenth resistor is electrically connected to a ground terminal, and the other end of the first resistor is electrically connected to the collector of a transistor.

[0009] One end of the second resistor, one end of the third resistor, one end of the fourth resistor, and one end of the sixth resistor are electrically connected to the voltage output terminal, respectively. The other end of the second resistor is electrically connected to the emitter of the transistor. The other end of the third resistor is electrically connected to the base of the transistor and one end of the fifth resistor, respectively. The other end of the fifth resistor, the other end of the fourth resistor, one end of the second capacitor, and one end of the eighth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source, respectively. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The other end of the eighth resistor is electrically connected to one end of the first capacitor. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor, the other end of the second capacitor, the other end of the first capacitor, and one end of the seventh resistor, respectively. The other end of the seventh resistor is electrically connected to the ground terminal.

[0010] Another technical solution adopted in this invention is:

[0011] A high-precision feedback circuit includes a control chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a MOSFET, and a three-terminal adjustable shunt reference source.

[0012] The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and one end of a first resistor, respectively. The other end of the ninth resistor is electrically connected to a voltage output terminal, the other end of the tenth resistor is electrically connected to a ground terminal, and the other end of the first resistor is electrically connected to the source of a MOSFET.

[0013] One end of the second resistor, one end of the third resistor, one end of the fourth resistor, and one end of the sixth resistor are electrically connected to the voltage output terminal, respectively. The other end of the second resistor is electrically connected to the drain of the MOSFET. The other end of the third resistor is electrically connected to the gate of the MOSFET and one end of the fifth resistor, respectively. The other end of the fifth resistor, the other end of the fourth resistor, one end of the second capacitor, and one end of the eighth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source, respectively. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The other end of the eighth resistor is electrically connected to one end of the first capacitor. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor, the other end of the second capacitor, the other end of the first capacitor, and one end of the seventh resistor, respectively. The other end of the seventh resistor is electrically connected to the ground terminal.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention provides a high-precision feedback circuit. The output voltage at the voltage output terminal is determined by a ninth resistor, a tenth resistor, and a feedback compensation circuit. During normal output voltage operation, the third resistor (connected to the base of the PNP transistor) and the second resistor (connected to the emitter of the PNP transistor) are appropriately adjusted to allow the PNP transistor to operate in the linear region. The first resistor serves as a current-limiting resistor for the feedback current. When the circuit is operating, the fourth and fifth resistors provide a steady-state operating current for the three-terminal adjustable shunt reference source. Simultaneously, the fourth resistor provides operating current to the voltage reference source of the three-terminal adjustable shunt reference source. During normal operation, the current breaks down through the three-terminal adjustable shunt reference source, providing a 2.5V reference voltage, which is then proportionally amplified by the sixth and seventh resistors. The eighth resistor, the first capacitor, and the second capacitor form the loop compensation network of the circuit. Compared to traditional solutions, this high-precision feedback circuit offers stable loop operation, significantly improving the output voltage accuracy, load regulation, and linearity adjustment of the product. Furthermore, using a MOSFET instead of a PNP transistor can further enhance the accuracy of the output voltage. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an existing output voltage feedback circuit in the background art;

[0017] Figure 2 This is a circuit diagram of a first embodiment of a high-precision feedback circuit according to the present invention;

[0018] Figure 3 This is a detailed circuit diagram of a first embodiment of a high-precision feedback circuit according to the present invention;

[0019] Figure 4 This is a circuit diagram of a second embodiment of a high-precision feedback circuit according to the present invention;

[0020] Figure 5 This is a detailed circuit diagram of a second embodiment of a high-precision feedback circuit of the present invention;

[0021] Label Explanation:

[0022] U1, control chip; FB, reference voltage pin;

[0023] R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; RU, ninth resistor; RL, tenth resistor;

[0024] C1, the first capacitor; C2, the second capacitor;

[0025] Q1, transistor; Q2, MOSFET;

[0026] U2, Three-terminal adjustable shunt reference source; K, Cathode; A, Anode; REF, Reference electrode;

[0027] Vout, voltage output terminal;

[0028] GND, grounding terminal;

[0029] DZ1, diode. Detailed Implementation

[0030] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0031] It should be noted that: Figure 2-5 R1 in the middle is not Figure 1 R1 in the middle, but Figure 2-5 RU in the middle is Figure 1 R1 in the middle; Figure 2-5 R2 in the middle is not Figure 1 R2 in the middle, but Figure 2-5 RL in the middle is Figure 1 R2 in the middle.

[0032] Please refer to Figure 2 as well as Figure 3 The present invention provides a high-precision feedback circuit, including a control chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a transistor, and a three-terminal adjustable shunt reference source.

[0033] The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and one end of a first resistor, respectively. The other end of the ninth resistor is electrically connected to a voltage output terminal, the other end of the tenth resistor is electrically connected to a ground terminal, and the other end of the first resistor is electrically connected to the collector of a transistor.

[0034] One end of the second resistor, one end of the third resistor, one end of the fourth resistor, and one end of the sixth resistor are electrically connected to the voltage output terminal, respectively. The other end of the second resistor is electrically connected to the emitter of the transistor. The other end of the third resistor is electrically connected to the base of the transistor and one end of the fifth resistor, respectively. The other end of the fifth resistor, the other end of the fourth resistor, one end of the second capacitor, and one end of the eighth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source, respectively. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The other end of the eighth resistor is electrically connected to one end of the first capacitor. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor, the other end of the second capacitor, the other end of the first capacitor, and one end of the seventh resistor, respectively. The other end of the seventh resistor is electrically connected to the ground terminal.

[0035] As can be seen from the above description, the beneficial effects of the present invention are as follows:

[0036] This invention provides a high-precision feedback circuit. The output voltage at the voltage output terminal is determined by a ninth resistor, a tenth resistor, and a feedback compensation circuit. During normal output voltage operation, the third resistor (connected to the base of the PNP transistor) and the second resistor (connected to the emitter of the PNP transistor) are appropriately adjusted to ensure the PNP transistor operates in the linear region. The first resistor serves as a current-limiting resistor for the feedback current. When the circuit is operating, the fourth and fifth resistors provide a steady-state operating current for the three-terminal adjustable shunt reference source. Simultaneously, the fourth resistor provides operating current to the voltage reference source of the three-terminal adjustable shunt reference source. During normal operation, the current breaks down through the three-terminal adjustable shunt reference source, providing a 2.5V reference voltage, which is then proportionally amplified by the sixth and seventh resistors. The eighth resistor, the first capacitor, and the second capacitor form the loop compensation network of the circuit. Compared to traditional solutions, this high-precision feedback circuit offers stable loop operation, significantly improving the output voltage accuracy, load regulation, and linearity adjustment of the product.

[0037] Furthermore, it also includes a diode. The other end of the ninth resistor, one end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to each other and then electrically connected to the positive terminal of the diode. The negative terminal of the diode is electrically connected to the voltage output terminal.

[0038] As can be seen from the above description, this diode is a Zener diode. Its purpose is to protect the TL431 device when designing voltages of 36V and above, since the maximum operating voltage of the TL431 is 36V. Without a Zener diode, the TL431 may break down and be damaged.

[0039] Furthermore, the model of the three-terminal adjustable shunt reference source is TL431.

[0040] Continue reading Figure 4 and Figure 5 The present invention also provides a high-precision feedback circuit, including a control chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a MOSFET, and a three-terminal adjustable shunt reference source.

[0041] The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and one end of a first resistor, respectively. The other end of the ninth resistor is electrically connected to a voltage output terminal, the other end of the tenth resistor is electrically connected to a ground terminal, and the other end of the first resistor is electrically connected to the source of a MOSFET.

[0042] One end of the second resistor, one end of the third resistor, one end of the fourth resistor, and one end of the sixth resistor are electrically connected to the voltage output terminal, respectively. The other end of the second resistor is electrically connected to the drain of the MOSFET. The other end of the third resistor is electrically connected to the gate of the MOSFET and one end of the fifth resistor, respectively. The other end of the fifth resistor, the other end of the fourth resistor, one end of the second capacitor, and one end of the eighth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source, respectively. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The other end of the eighth resistor is electrically connected to one end of the first capacitor. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor, the other end of the second capacitor, the other end of the first capacitor, and one end of the seventh resistor, respectively. The other end of the seventh resistor is electrically connected to the ground terminal.

[0043] As can be seen from the above description, the beneficial effect of the present invention is that: further using a MOSFET instead of a PNP transistor can achieve the same technical effect claimed in the first solution, but the first solution is preferred because:

[0044] The control mechanisms of transistors and MOSFETs are different. Transistors are current-controlled devices, while MOSFETs are voltage-controlled devices. Transistors can control the collector current by controlling the base current, while in this design, a MOSFET is essentially a switch, and the current needs to be controlled by a current-limiting resistor. Therefore, the control effect of a MOSFET is slightly worse.

[0045] Furthermore, it also includes a diode. The other end of the ninth resistor, one end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to each other and then electrically connected to the positive terminal of the diode. The negative terminal of the diode is electrically connected to the voltage output terminal.

[0046] Furthermore, the model of the three-terminal adjustable shunt reference source is TL431.

[0047] Please refer to Figure 2-3 Embodiment 1 of the present invention is as follows:

[0048] The present invention provides a high-precision feedback circuit, comprising a control chip U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor RU, a tenth resistor RL, a first capacitor C1, a second capacitor C2, a transistor Q1, and a three-terminal adjustable shunt reference source U2; the three-terminal adjustable shunt reference source U2 is a TL431.

[0049] The control chip U1 includes a reference voltage pin FB, which is electrically connected to one end of the ninth resistor RU, one end of the tenth resistor RL, and one end of the first resistor R1. The other end of the ninth resistor RU is electrically connected to the voltage output terminal Vout, the other end of the tenth resistor RL is electrically connected to the ground terminal GND, and the other end of the first resistor R1 is electrically connected to the collector of the transistor Q1.

[0050] One end of the second resistor R2, one end of the third resistor R3, one end of the fourth resistor R4, and one end of the sixth resistor R6 are electrically connected to the voltage output terminal Vout. The other end of the second resistor R2 is electrically connected to the emitter of transistor Q1. The other end of the third resistor R3 is electrically connected to the base of transistor Q1 and one end of the fifth resistor R5. The other end of the fifth resistor R5, the other end of the fourth resistor R4, one end of the second capacitor R2, and one end of the eighth resistor R8 are electrically connected to the cathode K of the three-terminal adjustable shunt reference source U2. The anode A of the three-terminal adjustable shunt reference source U2 is electrically connected to the ground terminal GND. The other end of the eighth resistor R8 is electrically connected to one end of the first capacitor C1. The reference terminal REF of the three-terminal adjustable shunt reference source U2 is electrically connected to the other end of the sixth resistor R6, the other end of the second capacitor C2, the other end of the first capacitor C1, and one end of the seventh resistor R7. The other end of the seventh resistor R7 is electrically connected to the ground terminal GND.

[0051] The aforementioned high-precision feedback circuit also includes a diode DZ1. The other end of the ninth resistor RU, one end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4 are electrically connected to each other and then electrically connected to the positive terminal of the diode DZ1. The negative terminal of the diode DZ1 is electrically connected to the voltage output terminal Vout.

[0052] Continue reading Figure 4 and Figure 5 Embodiment two of the present invention is as follows:

[0053] The present invention also provides a high-precision feedback circuit, including a control chip U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor RU, a tenth resistor RL, a first capacitor C1, a second capacitor C2, a MOSFET Q2, and a three-terminal adjustable shunt reference source U2; the three-terminal adjustable shunt reference source U2 is model TL431.

[0054] The control chip U1 includes a reference voltage pin FB, which is electrically connected to one end of the ninth resistor RU, one end of the tenth resistor RL, and one end of the first resistor R1. The other end of the ninth resistor RU is electrically connected to the voltage output terminal Vout, the other end of the tenth resistor RL is electrically connected to the ground terminal GND, and the other end of the first resistor R1 is electrically connected to the source of the MOS transistor Q2.

[0055] One end of the second resistor R2, one end of the third resistor R3, one end of the fourth resistor R4, and one end of the sixth resistor R6 are electrically connected to the voltage output terminal Vout. The other end of the second resistor R2 is electrically connected to the drain of the MOSFET Q2. The other end of the third resistor R3 is electrically connected to the gate of the MOSFET Q2 and one end of the fifth resistor R5. The other end of the fifth resistor R5, the other end of the fourth resistor R4, one end of the second capacitor C2, and one end of the eighth resistor R8 are electrically connected to the cathode K of the three-terminal adjustable shunt reference source U2. The anode A of the three-terminal adjustable shunt reference source U2 is electrically connected to the ground terminal GND. The other end of the eighth resistor R8 is electrically connected to one end of the first capacitor C1. The reference terminal REF of the three-terminal adjustable shunt reference source U2 is electrically connected to the other end of the sixth resistor R6, the other end of the second capacitor C2, the other end of the first capacitor C1, and one end of the seventh resistor R7. The other end of the seventh resistor R7 is electrically connected to the ground terminal GND.

[0056] The aforementioned high-precision feedback circuit also includes a diode DZ1. The other end of the ninth resistor RU, one end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4 are electrically connected to each other and then electrically connected to the positive terminal of the diode DZ1. The negative terminal of the diode DZ1 is electrically connected to the voltage output terminal Vout.

[0057] In summary, the high-precision feedback circuit provided by this invention determines the output voltage at the voltage output terminal through a ninth resistor, a tenth resistor, and a feedback compensation circuit. During normal output voltage operation, the third resistor (connected to the base of the PNP transistor) and the second resistor (connected to the emitter of the PNP transistor) are appropriately adjusted to allow the PNP transistor to operate in the linear region. The first resistor serves as a current-limiting resistor for the feedback current. When the circuit is operating, the fourth and fifth resistors provide a steady-state operating current for the three-terminal adjustable shunt reference source. Simultaneously, the fourth resistor provides operating current to the voltage reference source of the three-terminal adjustable shunt reference source. During normal operation, the current breaks down through the three-terminal adjustable shunt reference source, providing a 2.5V reference voltage, which is then proportionally amplified by the sixth and seventh resistors. The eighth resistor, the first capacitor, and the second capacitor form the loop compensation network of the circuit. Compared with traditional solutions, this high-precision feedback circuit offers stable loop operation, significantly improving the output voltage accuracy, load regulation, and linearity adjustment of the product. Furthermore, using MOSFETs instead of PNP transistors can further improve the accuracy of the output voltage.

[0058] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A feedback circuit for controlling a chip, characterized in that, It includes a control chip, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a ninth resistor, a tenth resistor, a transistor, and a three-terminal adjustable shunt reference source; The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and the collector of a transistor, respectively. The other end of the ninth resistor is electrically connected to a voltage output terminal, and the other end of the tenth resistor is electrically connected to a ground terminal. One end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to the voltage output terminal. The other end of the second resistor is electrically connected to the emitter of the transistor. The other end of the third resistor is electrically connected to the base of the transistor and one end of the fifth resistor. The other ends of the fifth resistor and the fourth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the voltage output terminal. The feedback circuit also includes a current-limiting resistor for feedback current, and the reference voltage pin is electrically connected to the collector of the transistor through the current-limiting resistor; The feedback circuit also includes a loop compensation network circuit, which is electrically connected to the cathode of the three-terminal adjustable shunt reference source and the reference electrode of the three-terminal adjustable shunt reference source, respectively. The feedback circuit also includes a voltage amplifier circuit, and the reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the voltage output terminal through the voltage amplifier circuit; The loop compensation network circuit includes an eighth resistor, a first capacitor, and a second capacitor. The eighth resistor is connected in series with the first capacitor and then in parallel with the second capacitor. The two ends of the parallel connection are respectively connected to the cathode of the three-terminal adjustable shunt reference source and the reference electrode of the three-terminal adjustable shunt reference source. The voltage amplification circuit includes a sixth resistor and a seventh resistor; one end of the sixth resistor is electrically connected to the voltage output terminal, the reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor and one end of the seventh resistor, respectively, and the other end of the seventh resistor is electrically connected to the ground terminal. The feedback circuit also includes a diode. The other end of the ninth resistor, one end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to each other and then electrically connected to the positive terminal of the diode. The negative terminal of the diode is electrically connected to the voltage output terminal. The model of the three-terminal adjustable shunt reference source is TL431.

2. A feedback circuit for controlling a chip, characterized in that, It includes a control chip, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a ninth resistor, a tenth resistor, a MOSFET, and a three-terminal adjustable shunt reference source; The control chip includes a reference voltage pin, which is electrically connected to one end of a ninth resistor, one end of a tenth resistor, and the source of a MOSFET. The other end of the ninth resistor is electrically connected to a voltage output terminal, and the other end of the tenth resistor is electrically connected to a ground terminal. One end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to the voltage output terminal. The other end of the second resistor is electrically connected to the drain of the MOS transistor. The other end of the third resistor is electrically connected to the gate of the MOS transistor and one end of the fifth resistor. The other ends of the fifth resistor and the fourth resistor are electrically connected to the cathode of the three-terminal adjustable shunt reference source. The anode of the three-terminal adjustable shunt reference source is electrically connected to the ground terminal. The reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the voltage output terminal. The feedback circuit also includes a current-limiting resistor for feedback current, and the reference voltage pin is electrically connected to the collector of the transistor through the current-limiting resistor; The feedback circuit also includes a loop compensation network circuit, which is electrically connected to the cathode of the three-terminal adjustable shunt reference source and the reference electrode of the three-terminal adjustable shunt reference source, respectively. The feedback circuit also includes a voltage amplifier circuit, and the reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the voltage output terminal through the voltage amplifier circuit; The loop compensation network circuit includes an eighth resistor, a first capacitor, and a second capacitor. The eighth resistor is connected in series with the first capacitor and then in parallel with the second capacitor. The two ends of the parallel connection are respectively connected to the cathode of the three-terminal adjustable shunt reference source and the reference electrode of the three-terminal adjustable shunt reference source. The voltage amplification circuit includes a sixth resistor and a seventh resistor; one end of the sixth resistor is electrically connected to the voltage output terminal, the reference terminal of the three-terminal adjustable shunt reference source is electrically connected to the other end of the sixth resistor and one end of the seventh resistor, respectively, and the other end of the seventh resistor is electrically connected to the ground terminal. The feedback circuit also includes a diode. The other end of the ninth resistor, one end of the second resistor, one end of the third resistor, and one end of the fourth resistor are electrically connected to each other and then electrically connected to the positive terminal of the diode. The negative terminal of the diode is electrically connected to the voltage output terminal. The model of the three-terminal adjustable shunt reference source is TL431.

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