Prevention of discharge in power switches in power converters

By disabling the control of the synchronous rectifier and using an anti-discharge circuit and a state machine to control the enable switch, the problem of parasitic capacitor discharge of the power switch under light load or no load conditions is solved, ensuring the stable operation of the power converter and efficient energy transfer.

CN114762235BActive Publication Date: 2026-03-17POWER INTEGRATIONS INC
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Patent Information

Application Number
CN201980102684.7
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Filing Date
2019-12-12
Publication Date
2026-03-17
Estimated Expiration
2039-12-12

AI Technical Summary

Technical Problem

Under light or no-load conditions, the switching on of the synchronous rectifier causes the parasitic capacitance of the power switch to discharge, resulting in unwanted energy being transferred from the secondary winding to the primary winding, affecting the normal operation of the power converter.

Method used

By disabling control of the synchronous rectifier under light or no-load conditions, and using an anti-discharge circuit and a state machine to control the enable switch, the secondary control signal is prevented from inappropriately turning on the synchronous rectifier, thus avoiding the discharge of parasitic capacitance.

Benefits of technology

It effectively prevents the discharge of parasitic capacitance of the power switch under light or no load conditions, ensuring stable operation and efficient energy transfer of the power converter.

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Abstract

A power converter includes a controller for controlling a synchronous rectifier (SR) switch. The controller includes a request control circuit and a discharge prevention circuit. The request control circuit is configured to generate a request signal in response to the output of the power converter. The request control circuit generates a secondary control signal to control the SR switch. The discharge prevention circuit is configured to prevent the discharge of parasitic capacitance of the power switch caused by the activating of the SR switch. The discharge prevention circuit further generates a prevention signal to: disable the control of the synchronous rectifier switch by the secondary control signal when the period of the request signal is greater than a first time threshold; and enable the control of the synchronous rectifier switch by the secondary control signal when the period of the request signal is less than a second time threshold.
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