Quasi-resonant controlled switch voltage stabilizing circuit and method

Abstract

The invention discloses a quasi-resonant controlled switch voltage stabilizing circuit and a method. By setting minimum limit time, a switching frequency is limited, and the minimum limit time is changed when the time of minimum voltage is close to the terminal time of the minimum limit time so that the purpose of preventing audio-frequency noise can be achieved. The circuit thereof comprises an energy storage element, a switch, a control circuit and a frequency limit circuit, wherein the energy storage element can store energy; the switch is electrically coupled with the energy storage element; when the switch is turned on, the energy storage element stores energy; when the switch is turned off, the energy stored in the energy storage element is transferred to the load; the control circuit is electrically coupled with the switch, controls the switch to be turned on or turned off, and turns on the switch when resonant voltage on both sides of the switch are lowered to minimum voltage;and the frequency limit circuit is electrically coupled with the control circuit, and limits the switching frequency of the switch by setting the minimum limit time, wherein when the time of the minimum voltage is close to the terminal time of the minimum limit time, the frequency limit circuit changes the minimum limit time.

Description

technical field [0001] The invention relates to a switching voltage stabilizing circuit, in particular to a quasi-resonance controlled switching voltage stabilizing circuit. Background technique [0002] Many electronic devices today require DC voltage to be powered, and this DC supply voltage usually comes from an adapter. The adapter obtains AC voltage from the wall socket (grid), converts the AC voltage into an uncontrolled DC voltage through a rectifier bridge, and converts the uncontrolled DC voltage into the required DC power supply voltage through a switching power supply. [0003] Switching power supplies usually use transformers or inductors as energy storage elements. For example, a transformer is used as an energy storage element in a flyback converter. A switch is electrically coupled to the primary side of the transformer, and the control circuit controls the switch to be turned on and off, so that energy is alternately stored or transmitted in the transformer....

AI Technical Summary

Problems solved by technology

It can be seen from the above that even if the load and input remain unchanged, due to the existence of disturbances in the system, the switch off time will also change, such changes will cause the switching frequency to jump within a few switching cycles, resulting in audio noise

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