Flyback power supply circuit and zvs control circuit and control method thereof

Abstract

The invention provides a flyback power supply circuit and a ZVS (zero voltage switching) control circuit and control method thereof. A ZVS control circuit for controlling a flyback power supply circuit includes: a primary side controller circuit for generating a switching signal, to control a primary side switch; and a secondary side controller circuit for generating a synchronous rectifier (SR) control signal for controlling a synchronous rectifier switch. The SR control signal includes an SR-control pulse and a ZVS pulse. The SR-control pulse controls the synchronous rectifier switch to perform secondary side synchronous rectification. The secondary side controller circuit determines a trigger timing point of the ZVS pulse according to a waveform characteristic of a ringing signal, to control the synchronous rectifier switch to be ON for a ZVS period, thereby achieving zero voltage switching of the primary side switch. The primary side or the secondary side controller circuit includes a jitter controller for generating jitter signals and performing jitter control on the ZVS pulse.

Description

technical field [0001] The invention relates to a flyback power supply circuit and its zero-voltage switching control circuit and control method, in particular to a flyback power supply circuit capable of realizing zero-voltage switching. The invention also relates to a zero-voltage switching control circuit used in a flyback power supply circuit and a control method thereof. Background technique [0002] figure 1 A prior art flyback power supply circuit (flyback power supply circuit 1) is shown, in which the primary side control circuit 85 controls the primary side switch S1 to switch the power transformer 10 to generate an output voltage VO, and the secondary side control circuit 95 is used to generate the synchronous rectification control signal S2C to control the synchronous rectification switch S2 to perform synchronous rectification on the secondary side. [0003] figure 1 The disadvantage of the prior art shown in , is that the synchronous rectification switch S2 c...

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Problems solved by technology

[0003] figure 1 The disadvantage of the prior art shown in , is that the synchronous rectification switch S2 cannot be synchronized with the primary side switch S1 on the primary side in real time and accurately, and the power conversion efficiency of the primary side switch S1 is low without zero-voltage switching. Difference

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