Low cost input anti-overvoltage protection circuit

Abstract

The invention discloses a low-cost input anti-overvoltage protection circuit capable of real-time monitoring the magnitude of an AC input voltage and controlling on-off of a switching device in a chopper circuit through a control circuit. When the AC input voltage is increased abnormally, the control circuit can quickly detect and control the switching device in the chopper circuit to be in the on-of state, maintain the energy storage capacitor voltage, so as to quickly and effectively protect a back stage circuit, prevent an energy storage capacitor and a switch tube of the back stage circuitfrom being damaged due to high voltage, and the back stage circuit can continue to work normally. Compared with the prior art, the anti-overvoltage protection circuit of the invention is applicable to the situation and the condition that the power network voltage abnormal overvoltage can occur caused by a grounding fault, and the like, the reaction speed is high, the circuit is simple and reliable, the cost is low, the EMC performance is excellent, the design is flexible, and the protective valve value can be adjusted.

Description

technical field [0001] The invention relates to the field of circuits, in particular to an input anti-overvoltage protection circuit used in a three-phase four-wire and feeder network automatic power supply system. Background technique [0002] In the three-phase four-wire power meter and switching power supply in the feeder automation industry, problems such as ground faults and high-power equipment interference are often encountered, resulting in abnormally high grid voltage for a period of time. At this time, the grid voltage will exceed the switching power supply. The upper limit of the withstand voltage can easily cause damage to the switching power supply or even cause a fire, posing a huge safety hazard. [0003] There are mainly two methods for the existing switching power supply to solve the problem of high grid voltage. One is to increase the input overvoltage protection circuit, and the other is to increase the upper limit of the operating voltage range that the p...

AI Technical Summary

Problems solved by technology

Among them, increasing the upper limit of the input voltage is mainly to use high withstand voltage devices or multi-stage series-parallel connection. The advantage is that the circuit can still work normally when the overvoltage occurs. The cost of the capacitor has increased by about four times, the cost of the switch tube has increased by more than two times, and the overvoltage working time is very short. This method has serious overdesign and wastes resources; another method is to increase the input overvoltage protection circuit. When the grid voltage is too high, the control chip will stop working. This method can only be used in the case of small overvoltage. When the grid voltage is higher than the original 1.5 times, the voltage after rectification has exceeded the withstand voltage of the large capacitor. Even the withstand voltage of the switch tube is essentially just to stop working when overvoltage, and it cannot protect the subsequent circuit

[0004] In the three-phase four-wire power meter and feeder automation industry, there are only a few switching power supplies on the market today that have anti-ground fault and input overvoltage protection functions. When overvoltage occurs, electrolytic capacitors and switching tubes are often hard-resistant beyond specifications, and there is a huge safety hazard. Hidden danger

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