Apparatus and method for valley bottom locking in quasi-resonant switching power supply

Abstract

The invention relates to an apparatus and a method for valley bottom locking in a quasi-resonant switching power supply. The apparatus for valley bottom locking in the quasi-resonant switching power supply includes: an encoding module for generating an encoded signal based on a received input signal; and a valley bottom locking state generation module used for generating a valley bottom locking state of a power tube in the quasi-resonant switching power supply based on the coded signal, wherein the valley bottom locking state indicates a valley bottom position where a drain resonance voltage of the power tube is located when the power tube is conducted, the valley bottom locking state comprises full conduction at the Nth valley bottom, partial conduction at the Nth valley bottom, partial conduction at the (N + 1)th valley bottom and full conduction at the (N + 1)th valley bottom, and N is a positive integer.

Description

technical field [0001] The present disclosure relates to integrated circuits, and more particularly, to apparatus and methods for valley locking in quasi-resonant (QR) switching power supplies. Background technique [0002] With the increasing demand for switching power supplies with small size, high frequency and high power density, quasi-resonant switching power supplies with zero voltage and low voltage turn-on (for example, quasi-resonant flyback switching power supplies) are becoming more and more widely used . The transformer of the flyback converter in the quasi-resonant flyback switching power supply has a parasitic leakage inductance L leak , power transistor S1 (for example, metal oxide semiconductor field effect transistor (MOSFET), bipolar junction NPN transistor (BJT-NPN), insulated gate bipolar transistor (IGBT), and gallium nitride (GaN) transistor, etc.) , and the parasitic capacitance C between the source and drain of the power transistor S1 p ,Such as f...

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Problems solved by technology

[0004] However, the existing methods for valley locking will generate a large frequency difference and feedback voltage foldback when cutting the valley, which will easily cause large fluctuations in the feedback voltage and the risk of failure of the valley locking state, resulting in low-frequency unwanted Periodic adjacent valley switching states generate large audio noise and output ripple. This problem is more prominent in quasi-resonant switching power supplies with small volume, high frequency and high power density, and needs to be solved urgently

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