过欠压保护电路

Abstract

本实用新型提供了一种过欠压保护电路，包括：线性稳压电路、基准电路、欠压检测电路、过压检测电路以及控制电路；其中，线性稳压电路的输入端连接输入电压，线性稳压电路的输出端为过欠压保护电路提供工作电压；基准电路的输入端输入工作电压，基准电路的输出端分别连接欠压检测电路的输入端和过压检测电路的输入端；欠压检测电路的输出端连接控制电路的输入端；过压检测电路的输出端连接控制电路的输入端；控制电路的输出端连接PWM控制器。如此，通过比较工作电压与基准电压，来判断电路中是否过压或欠压，并通过比较器输出高低电平以控制PWM控制器电源的通断，实现高效、准确保护电路的目的。

Claims

1. An over- and under-voltage protection circuit, characterized in that The application relates to a linear voltage stabilizing circuit, a reference circuit, an under-voltage detection circuit, an over-voltage detection circuit and a control circuit. The input end of the linear voltage stabilizing circuit is connected with an input voltage, and the output end of the linear voltage stabilizing circuit provides a working voltage for the over-voltage and under-voltage protection circuit; the input end of the reference circuit is inputted with the working voltage, and the output end of the reference circuit is respectively connected with the input end of the under-voltage detection circuit and the input end of the over-voltage detection circuit; the output end of the under-voltage detection circuit is connected with the input end of the control circuit; the output end of the over-voltage detection circuit is connected with the input end of the control circuit; and the output end of the control circuit is connected with a PWM controller. The linear voltage stabilizing circuit is used for providing the working voltage for the over-voltage and under-voltage protection circuit; the reference circuit is used for providing a reference voltage for the under-voltage detection circuit and the over-voltage detection circuit; the under-voltage detection circuit and the over-voltage detection circuit are respectively used for detecting whether the input voltage is under-voltage or over-voltage; and the control circuit is used for controlling the power on or off of the PWM controller. The linear voltage stabilizing circuit is composed of a first resistor, a voltage stabilizing diode, a first capacitor and a first triode.

2. The over / under voltage protection circuit of claim 1, wherein, The input end of the first resistor is connected with the input voltage, the output end of the first resistor is respectively connected with the anode of the voltage stabilizing diode and the base of the first triode, the cathode of the voltage stabilizing diode is grounded, the emitter of the first triode is connected with the input end of the first capacitor, the output end of the first capacitor is grounded, the first capacitor is connected with the voltage stabilizing diode in parallel, and the emitter of the first triode is used for inputting the working voltage. The reference circuit is composed of a second resistor and a reference voltage source.

3. The over / under voltage protection circuit according to claim 1 or 2, characterized by The input end of the second resistor is inputted with the working voltage, the output end of the second resistor is connected with the cathode of the reference voltage source, the anode of the reference voltage source is grounded, the reference end of the reference voltage source outputs the reference voltage to a first node, the first node is connected with the inverting end of a first comparator in the under-voltage detection circuit and the non-inverting end of a second comparator in the over-voltage detection circuit. The under-voltage detection circuit comprises a third resistor, a fourth resistor, a fifth resistor and a second capacitor.

4. The overvoltage and undervoltage protection circuit of claim 3, wherein, The input end of the third resistor is connected with the input voltage, the output end of the third resistor is connected with the input end of the fourth resistor, the output end of the fourth resistor is connected with the input end of the fifth resistor, and the output end of the fifth resistor is grounded. The second capacitor is connected with the fifth resistor in parallel, and the connection point of the fourth resistor and the fifth resistor is connected with the non-inverting end of the first comparator. The over-voltage detection circuit comprises a sixth resistor, a seventh resistor, an eighth resistor and a third capacitor.

5. The overvoltage and undervoltage protection circuit of claim 4, wherein, The input end of the sixth resistor is connected with the input voltage, the output end of the sixth resistor is connected with the input end of the seventh resistor, the output end of the seventh resistor is connected with the input end of the eighth resistor, and the output end of the eighth resistor is grounded. The third capacitor is connected with the eighth resistor in parallel, and the connection point of the seventh resistor and the eighth resistor is connected with the non-inverting end of the second comparator. ​ 6. The overvoltage and undervoltage protection circuit of claim 5, wherein, The control circuit is composed of a second transistor and a third transistor; wherein, The base of the second transistor is connected with the second node, the emitter of the second transistor is grounded, and the collector of the second transistor is connected with the base of the third transistor through a ninth resistor; The emitter of the third transistor is connected with the working voltage, and the collector of the third transistor is connected with the VCC pin of the PWM controller through a tenth resistor.

7. The overvoltage and undervoltage protection circuit of claim 6, wherein, The second transistor is NPN type, and the third transistor is PNP type; an eleventh resistor is connected with a fourth capacitor in parallel, one end of which is connected with the collector of the second transistor, and the other end is grounded.

8. The over / under voltage protection circuit according to claim 6 or 7, characterized in that, When the level of the third pin of the first comparator is higher than the reference voltage of the first node, and the level of the sixth pin of the second comparator is lower than the reference voltage of the first node, the first pin of the first comparator and the seventh pin of the second comparator output high level, and the second node is high level, so that the second transistor is turned on, the third transistor is turned on, and the PWM controller is powered.

9. The overvoltage and undervoltage protection circuit of claim 8, wherein, When the level of the third pin of the first comparator is lower than the reference voltage of the first node, the first pin of the first comparator outputs low level, and the second node is low level, so that the second transistor is cut off, the third transistor is cut off, and the power supply of the PWM controller is cut off, realizing under-voltage protection.

10. The overvoltage and undervoltage protection circuit of claim 8, wherein, When the level of the sixth pin of the second comparator is higher than the reference voltage of the first node, the seventh pin of the second comparator outputs low level, and the second node is low level, so that the second transistor is cut off, the third transistor is cut off, and the power supply of the PWM controller is cut off, realizing over-voltage protection.

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