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Zero voltage switching flyback converter for primary switch turn-off transitions

A switch and capacitor technology, applied in the field of flyback converters, can solve problems such as power loss of flyback converters

Active Publication Date: 2018-05-01
ALPHA AND OMEGA SEMICONDUCTOR (CAYMAN) LIMITED
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Flyback converters experience power loss when switching transitions occur at non-zero voltages of the power switches

Method used

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  • Zero voltage switching flyback converter for primary switch turn-off transitions
  • Zero voltage switching flyback converter for primary switch turn-off transitions
  • Zero voltage switching flyback converter for primary switch turn-off transitions

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Embodiment Construction

[0034] The invention can be implemented in various ways, including as a process; an apparatus; a system; and / or a composition of matter. In this specification, these implementation manners or any other manners that may be adopted by the present invention may be referred to as technologies. In general, the order of the process steps described can be varied within the scope of the invention.

[0035] The detailed description of one or more embodiments of the invention and the accompanying drawings explain the principles of the invention. Although, the present invention is presented with these embodiments, the scope of the present invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention embraces various alternatives, modifications and equivalents. In the following description, various specific details are set forth in order to provide a thorough understanding of the invention. These details are illustrative and the ...

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Abstract

A flyback converter implements a Forced Zero Voltage Switching (ZVS) timing control by detecting a positive current excursion of the secondary winding current as the synchronous rectifier turn off trigger. The synchronous rectifier switch is turned on near the end of the switching cycle or the on duration is extended to develop a current ripple on the secondary winding current. The control circuitof the flyback converter detects a positive current excursion on the secondary winding current to turn off the synchronous rectifier and to start the next switching cycle. At this point, the voltageacross the primary switch has been discharged and the primary switch can be turned on with zero drain-to-source voltage. In other embodiments, zero voltage switching for the off-transition of the primary switch is realized by coupling a capacitor across the primary switch or by coupling a capacitor across the primary winding, or both.

Description

technical field [0001] The invention relates to the field of flyback converters. Background technique [0002] A flyback converter is an isolated power converter commonly used for ac-to-dc and dc-to-dc conversions with galvanic isolation between an input and one or more outputs. More precisely, a flyback converter is a step-up-buck converter with an inductive split forming a transformer that multiplies the voltage ratio with the added benefit of isolation. Synchronous rectification is often used in place of diode rectifiers to improve efficiency. Figure 1 shows an example of a flyback converter using synchronous rectification. As shown in Figure 1, the typical structure of a flyback converter consists of a primary switch (SW), coupled to the primary transformer winding of transformer Lm, and a synchronous rectifier switch (SR), coupled to the secondary transformer winding of transformer Lm. Through the primary winding and the primary switch, the input voltage V IN . Con...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/335H02M7/537
CPCH02M3/33592H02M7/537H02M1/0058Y02B70/10H02M1/0009H02M1/346
Inventor 张光铭陈霖黄启洪
Owner ALPHA AND OMEGA SEMICONDUCTOR (CAYMAN) LIMITED