Electrical source input overvoltage protection circuit

Abstract

The present invention discloses a power source input overvoltage protection circuit, which comprises an overvoltage comparator and a Darlington transistor controlled by the overvoltage comoparator. The input ends of the overvoltage and the Darlingto transistor are respectively connected with the input ends of the overvoltage protection circuit, therefore the output end of the Darlington transistor is connected with the output end of the overvoltage protection circuit; the overvoltage comparator controls the on and off of the Darlington transistor; upon the power source input voltage surpasses the preset overvoltage value of the overvoltage protection circuit, the Darlington transistor is off, and the overvoltage protection circuit is cut off; otherwise the Darlington transistor is on, the power source input voltage goes through the Darlington transistor and then is output from the output end. The technical plan regarding the present invention adopts pure hardware circuit to realize with simple circuit and at low costs, has commonality, much higher reliability and swift response.

Description

technical field [0001] The invention relates to an overvoltage protection circuit, in particular to a power supply input overvoltage protection circuit. Background technique [0002] Electronic equipment cannot work without a stable power supply. However, in actual use, the input power supply may be abnormal due to various abnormal factors; in addition, it often happens that users use non-standard power supplies, so that the input power supply voltage of the equipment cannot be guaranteed. Once these situations occur, serious consequences are often caused, ranging from the burning of the entire equipment or damage to the input power supply, to causing fires, explosions and other safety accidents. Therefore, it is very important to add a suitable OVP (Over Voltage Protection, overvoltage protection) circuit to the power input terminal of the device. [0003] At present, the commonly used OVP circuits mainly include the following types: [0004] 1. Add PTC (Positive Tempera...

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Problems solved by technology

[0004] 1. Add PTC (Positive Temperature Coefficient, positive temperature coefficient) thermistor and varistor or voltage regulator tube at the input end of the power supply. The advantages are low cost and simple circuit; the disadvantage is that when the input overvoltage time is long, the varistor The resistor or Zener tube will be damaged due to serious heating, and its output voltage will rise with the increase of the input voltage, that is, the output voltage is uncertain

[0005] 2. Adding a dedicated OVP chip at the power input terminal has the advantages of small size and relatively simple circuit; the disadvantage is that due to special use, its scope of use is too narrow, OVP chips of various manufacturers are not compatible, and there is a risk of supply

[0006] 3. Add a DC-DC converter with a wide input range at the input end of the power supply, that is, add a voltage converter that effectively outputs a fixed voltage after changing the input voltage. The advantage is that the device can work normally even if the input is overvoltage; the disadvantage is that the circuit is more complicated , The cost is high, and the products of various manufacturers are not compatible, and there is also a risk of supply

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