Switching power supply and over-voltage protection circuit thereof

Abstract

The invention relates to a switching power supply and an over-voltage protection circuit of the switching power supply. The over-voltage protection circuit comprises a varistor RV, a zero sequence current transformer T1, a potentiometer RP1, a bidirectional thyristor VS and a fuse F1, wherein the zero sequence current transformer comprises a first primary coil L1, a second primary coil L2 and a second coil L3, a first electrode of the bidirectional thyristor VS is connected with the first end of a commercial power after being connected with the fuse F1 in series, a second electrode is connected with the second end of the commercial power, and a control pole is connected with a sliding contact end of the potentiometer RP1; L1 is connected between the first electrode and the first input end of a rectifier-filter circuit, L2 is connected between the second electrode and the second input end of the rectifier-filter circuit, and L3 is connected between the second electrode and a first fixed end of the potentiometer RP1; a second fixed end of the potentiometer is connected with a second electrode; the varistor RV is connected between the second electrode and the first input end of the rectifier-filter circuit. The over-voltage protection circuit can cut off the circuit when voltage continuously exceeds standards.

Description

technical field [0001] The invention relates to an overvoltage protection technology, in particular to an overvoltage protection circuit for a switching power supply. Background technique [0002] Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. It is widely used in various fields. [0003] In some situations where the environmental conditions of the power supply are relatively complex and harsh, such as the grid voltage is unstable, and 220V and 380V are not easy to distinguish, etc., it is easy to cause damage to the internal components of the switching power supply due to excessive voltage. In order to protect circuit components, a transient (transient) voltage suppression diode TVS is usually used in the prior art to provide protection, such as figure 1 Shown, shows a common off-line switching power supply input part of the schematic diagra...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a switching power supply and its overvoltage protection circuit in view of the above-mentioned defects in the prior art that cannot protect circuit elements under continuous overvoltage conditions. and continuous overvoltage, automatically cut off the path to protect other components in the circuit from damage

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