Capacity discharge method and circuit

Abstract

The invention discloses capacity discharge method and circuit which are applied to a switch power supply. The capacity discharge method includes that a detecting circuit detects voltage of one end of an X capacitor in the switch power supply to generate a first voltage signal, the first voltage signal is monitored, if the first voltage signal is kept at low-level null state within preset time, detection signals output by the detecting circuit are at high-level effective state, and thus an input end of the switch power supply is indicated as power off. Then, the discharge circuit receives detection signals so as to discharge the X capacitor after the input end of the switch power supply is powered off. The capacity discharge circuit has no need for devices such as discharge resistors, power loss of the system is reduced, no-load power consumption and standby power consumption are also reduced, and requirements for power consumption of new standards are met.

Description

technical field [0001] The invention relates to the field of power supplies, more specifically, to a capacitor discharge method and a discharge circuit applied to switching power supplies. Background technique [0002] At the input end of the AC power supply of the switching power supply, an X capacitor is generally connected in parallel between the live wire and the neutral wire as a safety capacitor to suppress EMI conduction interference (mainly to suppress differential mode interference). In some occasions, due to actual needs, The capacitance of the X capacitor is often relatively large, so that after the AC power is cut off, the X capacitor will store high-voltage electric energy for a long time, and the safety standard stipulates that within two seconds after the AC power is cut off, the voltage of the input terminal of the power supply must drop to 30% of the original rated working voltage, so in order to meet the requirements of safety standards, the X capacitor nee...

AI Technical Summary

Problems solved by technology

[0004] In view of this, the present invention provides a capacitor discharge method and a discharge circuit, which are applied to switching power supplies to solve the problem of high energy consumption caused by X capacitor discharge circuits in switching power supplies in the prior art

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