Overvoltage protection circuit

Abstract

According to the overvoltage protection circuit provided by the utility model, an overvoltage protection point is set through the reference electrode R of the three-end adjustable shunt reference source U1 and the divider resistors R5 and R7, when the voltage input by the voltage sampling point V1 is detected to be too high, the optocoupler PC1 is conducted, and the VCC is pulled down, so that the overvoltage protection circuit is shut down, and the overvoltage protection function is realized; the overvoltage protection point is set through the reference electrode R of the three-end adjustable shunt reference source U1 and the divider resistors R5 and R7, the overvoltage protection point is not affected by temperature changes, the stability of the overvoltage protection point at different environment temperatures can be ensured, and then the precision stability of the overvoltage protection circuit is achieved; meanwhile, the overvoltage protection circuit is simple in structure, low in implementation cost and more practical.

Description

Technical Field

[0001] The utility model relates to the technical field of overvoltage protection, in particular to an overvoltage protection circuit. Background Art

[0002] As an important component, power supply equipment is used in various electronic equipment systems. Power supply equipment is generally required to be safe and reliable, and timely protection should be provided under abnormal circumstances to avoid significant losses caused by damage to the back-end equipment. One of the more important methods is overvoltage protection. For example, the patent with application number CN202110884379.7 is a three-terminal fixed positive output voltage regulator that our company has produced. The safe operating area protection unit 6 of the voltage regulator includes overcurrent and overvoltage protection circuits. However, the overvoltage protection circuit disclosed herein uses a voltage regulator to set the overvoltage protection point, and the value of the voltage regulator will change with temperature, so the accuracy is not high. Summary of the invention

[0003] In order to solve the problem in the prior art that the overvoltage protection point is set based on a voltage regulator tube, which leads to low accuracy as the ambient temperature changes, the utility model provides an overvoltage protection circuit, which can effectively protect the power supply equipment when the voltage becomes abnormally high, and can maintain the stability of the overvoltage protection point at different ambient temperatures.

[0004] The structure of the utility model is as follows: an overvoltage protection circuit, characterized in that it includes: resistors R1, R2, R3, R4, R5, R7, capacitors C1, C2, C3, a unidirectional thyristor SCR1, a three-terminal adjustable shunt reference source U1, an optical coupler PC1 and a voltage stabilizing diode ZD1;

[0005] The A pole of the unidirectional thyristor SCR1 is connected to the cathode of the voltage-stabilizing diode ZD1 and then connected to the power supply voltage. The K pole of the unidirectional thyristor SCR1 is connected to one end of the capacitor C1 and then grounded. The other end of the capacitor C1 is connected to the G pole of the unidirectional thyristor SCR1 and one end of the resistor R1. The other end of the resistor R1 is connected to the 3rd pin of the optical coupler PC1, the 4th pin of the optical coupler PC1 is connected to the positive pole of the voltage-stabilizing diode ZD1, the 1st pin of the optical coupler PC1 is connected to one end of the resistor R3 and one end of the resistor R4, and the 2nd pin of the optical coupler PC1 is connected to One end of the capacitor C3, the cathode K of the three-terminal adjustable shunt reference source U1, the other end of the resistor R4 and one end of the capacitor C2, the other end of the capacitor C3 is connected to the anode A of the three-terminal adjustable shunt reference source U1, one end of the resistor R7 and then grounded, the reference electrode R of the three-terminal adjustable shunt reference source U1 is connected to the other end of the resistor R7, the other end of the capacitor C2 and one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the resistor R3 and one end of the resistor R2, and the other end of the resistor R2 is connected to the detection voltage sampling point V1.

[0006] It is further characterized by:

[0007] The resistor R2 is connected in parallel with a voltage divider diode;

[0008] The resistor R5 and the resistor R7 are each connected in parallel with a resistor;

[0009] The three-terminal adjustable shunt reference source U1 is implemented based on the TL431 chip; the unidirectional thyristor SCR1 is implemented based on the unidirectional thyristor triode BT169.

[0010] The utility model provides an overvoltage protection circuit, which sets the overvoltage protection point through a three-terminal adjustable shunt reference source U1 reference pole R and voltage-dividing resistors R5 and R7. When the voltage input to the detection voltage sampling point V1 is too high, the optocoupler PC1 is turned on, and VCC is pulled down, thereby shutting down and realizing the overvoltage protection function. In the present application, the overvoltage protection point is set through a three-terminal adjustable shunt reference source U1 reference pole R and voltage-dividing resistors R5 and R7, which is not affected by temperature changes and can ensure the stability of the overvoltage protection point at different ambient temperatures, thereby realizing the stability of the accuracy of the overvoltage protection circuit. At the same time, the overvoltage protection circuit of the present application has a simple structure and a low implementation cost, and is more practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the circuit diagram of the overvoltage protection circuit. DETAILED DESCRIPTION

[0012] like Figure 1As shown, the utility model includes an overvoltage protection circuit, characterized in that it includes: resistors R1, R2, R3, R4, R5, R7, capacitors C1, C2, C3, a unidirectional thyristor SCR1, a three-terminal adjustable shunt reference source U1, an optical coupler PC1 and a voltage regulator diode ZD1; in specific implementation, the three-terminal adjustable shunt reference source U1 is implemented based on the TL431 chip; the unidirectional thyristor SCR1 is implemented based on the unidirectional thyristor triode BT169.

[0013] The A pole of the unidirectional thyristor SCR1 is connected to the cathode of the voltage-stabilizing diode ZD1 and then connected to the power supply voltage. The K pole of the unidirectional thyristor SCR1 is connected to one end of the capacitor C1 and then grounded. The other end of the capacitor C1 is connected to the G pole of the unidirectional thyristor SCR1 and one end of the resistor R1. The other end of the resistor R1 is connected to the 3rd pin of the optocoupler PC1, the 4th pin of the optocoupler PC1 is connected to the positive pole of the voltage-stabilizing diode ZD1, the 1st pin of the optocoupler PC1 is connected to one end of the resistor R3 and one end of the resistor R4, and the 2nd pin of the optocoupler PC1 is connected to One end of capacitor C3, cathode K of three-terminal adjustable shunt reference source U1, the other end of resistor R4 and one end of capacitor C2, the other end of capacitor C3 is connected to anode A of three-terminal adjustable shunt reference source U1, one end of resistor R7 and then grounded, the reference electrode R of three-terminal adjustable shunt reference source U1 is connected to the other end of resistor R7, the other end of capacitor C2 and one end of resistor R5, the other end of resistor R5 is connected to the other end of resistor R3 and one end of resistor R2, and the other end of resistor R2 is connected to detection voltage sampling point V1.

[0014] The overvoltage protection circuit of the present application uses the reference pole R of the three-terminal adjustable shunt reference source U1 as the voltage reference point. In this embodiment, the reference voltage of the R terminal is 2.5v. When the voltage of the detection voltage sampling point V1 increases, the reference voltage of U1 and the voltage of R increase accordingly. When the voltage of the R terminal is higher than the voltage reference, the anode A and cathode K of U1 are turned on; then the 1st and 2nd pins of the optocoupler PC1 are turned on, and after the light-emitting diode of the optocoupler emits light, the 3rd and 4th pins receive the light signal and are turned on; after the gate value of the unidirectional thyristor SCR1 is reached, the anode A and cathode K of the unidirectional thyristor SCR1 are turned on, and VCC is grounded, so that the machine is shut down and stops working, and overvoltage protection is achieved.

[0015] In the overvoltage protection circuit of the present application, resistors R2, R5 and R7 are voltage-dividing resistors, and the accuracy of the voltage-dividing resistors will affect the accuracy of the overvoltage protection point. In order to further improve the accuracy of the overvoltage protection point, in real time, R2, R5 and R7 are implemented based on high-precision resistors, and according to actual needs, a high-precision resistor can be connected in parallel to resistors R5 and R7, respectively, to further improve the accuracy of the overvoltage protection point. At the same time, when the voltage input to the detection voltage sampling point V1 is high, in order to be compatible with different output voltages, a voltage regulator tube can be connected in parallel to R2 to reduce the voltage input to R3 and R5, thereby realizing overvoltage protection for different output voltages.

[0016] After using the technical solution of the utility model, the overvoltage protection circuit can utilize the reference of U1 to set the overvoltage protection point through high-precision resistors, and it is very stable under different ambient temperatures; the overvoltage protection circuit based on the thyristor circuit can effectively protect when the voltage of the power supply equipment becomes abnormally high, preventing damage to the back-end equipment, and the circuit cost of the present application is low and more practical.

Claims

1. An overvoltage protection circuit, characterized in that: It includes: resistors R1, R2, R3, R4, R5, R7, capacitors C1, C2, C3, unidirectional thyristor SCR1, three-terminal adjustable shunt reference source U1, optocoupler PC1 and voltage stabilizing diode ZD1; The A pole of the unidirectional thyristor SCR1 is connected to the cathode of the voltage-stabilizing diode ZD1 and then connected to the power supply voltage. The K pole of the unidirectional thyristor SCR1 is connected to one end of the capacitor C1 and then grounded. The other end of the capacitor C1 is connected to the G pole of the unidirectional thyristor SCR1 and one end of the resistor R1. The other end of the resistor R1 is connected to the 3rd pin of the optical coupler PC1, the 4th pin of the optical coupler PC1 is connected to the positive pole of the voltage-stabilizing diode ZD1, the 1st pin of the optical coupler PC1 is connected to one end of the resistor R3 and one end of the resistor R4, and the 2nd pin of the optical coupler PC1 is connected to One end of the capacitor C3, the cathode K of the three-terminal adjustable shunt reference source U1, the other end of the resistor R4 and one end of the capacitor C2, the other end of the capacitor C3 is connected to the anode A of the three-terminal adjustable shunt reference source U1, one end of the resistor R7 and then grounded, the reference electrode R of the three-terminal adjustable shunt reference source U1 is connected to the other end of the resistor R7, the other end of the capacitor C2 and one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the resistor R3 and one end of the resistor R2, and the other end of the resistor R2 is connected to the detection voltage sampling point V1.

2. The overvoltage protection circuit according to claim 1, characterized in that: The resistor R2 is connected in parallel with a voltage divider diode.

3. The overvoltage protection circuit according to claim 1, characterized in that: The resistor R5 and the resistor R7 are respectively connected in parallel with a resistor.

4. The overvoltage protection circuit according to claim 1, characterized in that: The three-terminal adjustable shunt reference source U1 is implemented based on the TL431 chip; the unidirectional thyristor SCR1 is implemented based on the unidirectional thyristor triode BT169.

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