Zero-crossing protection circuit for switching power supply

Abstract

The invention discloses a zero-crossing protection circuit for a switching power supply, and includes a zero sequence detection module, a delay control module and a bidirectional silicon controlled rectifier connected on an alternating current loop. The zero sequence detection module includes a rectification circuit, a first triode and a phase inverter, an input end of the rectification circuit is connected on the alternating current loop, an output end is connected on a base electrode of the first triode, an emitting electrode of the first triode is connected on an input end of the phase inverter, the delay control module includes a 555 timing chip, an output end of the 555 timing chip is connected on a base electrode of a second triode, the first triode and the second triode form an independent electrical signal loop, a photoelectric coupler is connected in series between the first triode and the second triode, and an output end of the photoelectric coupler is connected on a control electrode of the bidirectional silicon controlled rectifier. The zero-crossing protection circuit for the switching power supply has the beneficial effect that a phenomenon that originally alternating current is directly connected and an electrical element is subjected to impact of alternating current instantaneous current can be prevented.

Description

technical field [0001] The invention relates to a protection circuit of a switching power supply, in particular to a zero-crossing protection circuit of a switching power supply. Background technique [0002] Switching power supply is an electrical component that converts AC into DC. There are many aspects to evaluate the quality indicators of switching power supply devices, but reliability and safety should be the first principles. The switching power supply will have sporadic failures. Therefore, in order to ensure the safety and reliability of the switching power supply output in harsh environments and sudden failures, it is necessary to design circuits with multiple protection functions so that once the switching power supply fails, the switching The power supply will automatically enter the protection state or automatically correct parameters to make it operate under a normal and reasonable working condition. [0003] The input of the switching power supply is alternat...

AI Technical Summary

Problems solved by technology

[0003] The input of the switching power supply is alternating current, and the characteristic of alternating current is that the output polarity is alternately positive and negative. Generally, the switching power supply uses thyristor as the inverter element, and the thyristor is a switching device controlled by a pulse signal. When the conduction angle of the trigger pulse of the thyristor is greater than the threshold value of the thyristor, the thyristor will turn on the circuit, and when the conduction of the thyristor is at the peak and valley of the AC circuit, it will cause The instantaneous impact of the circuit causes damage to electrical components

Images