Quasi-resonant control switching circuit and switch circuit control method

Abstract

The invention discloses a quasi-resonant control switching power supply circuit and a switching power supply circuit control method. The purpose of preventing the generation of audio noises is achieved by adjusting the corresponding relationship between the peak current and the switching frequency. The quasi-resonant control switching power supply circuit comprises an energy storage element, a switch, a valley bottom detection circuit, a mode detection circuit and a peak signal adjustment circuit; wherein the energy storage element can store energy; the switch is electrically coupled to the energy storage element; the energy storage element stores energy when the switch is on, and the energy stored in the energy storage element is transmitted to the load when the switch is off; the valley bottom detection circuit is used for detecting whether the switching voltage at both sides of the switch is lower than the valley bottom reference signal or not; the mode detection circuit is used for detecting whether the switching power supply circuit is operated in the continuous current mode or not; and the peak signal adjustment circuit is used for adjusting the value of the peak signal under the condition of discontinuous current mode and non valley bottom conduction.

Description

technical field [0001] The present invention relates to a switching power supply, in particular, to the quasi-resonant control of the switching power supply. Background technique [0002] 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. The control circuit controls the switch to be turned on and off, so that energy is alternately stored in the transformer or transferred to the secondary side of the transformer. The secondary side of the transformer generates an output voltage at both ends of the output capacitor through the filter, and the output voltage is the DC output voltage of the flyback converter. The increase and decrease of the DC output voltage are opposite to the power delivered to the load. The increase of the load will cause the DC output voltage to decrease, a...

AI Technical Summary

Problems solved by technology

[0004] However, the opening of the valley bottom will cause the output power of the switching power supply to be discontinuous. After the loop adjustment, the switching frequency will jump within a few switching cycles, which will cause audio noise.

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