Flyback Converter Secondary Switch Timing for Primary ZVS
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Solution Overview
Problem
Existing power converters face challenges in achieving zero voltage switching (ZVS) for the primary switch without relying on primary to secondary communication.
Innovation Solution
The method involves controlling a secondary switch to achieve zero voltage switching of the primary switch by calculating the required secondary switch hold time based on measurements such as forward pin voltage or the ratio of discharge time to charge time, eliminating the need for primary to secondary communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If primary to secondary communication is used to achieve ZVS of the primary switch, then ZVS can be implemented, but the system complexity increases due to communication requirements
Solution Approach 1:
The patent extracts the communication requirement from the ZVS implementation by using only secondary side measurements (forward pin voltage, discharge time, charge time) to calculate the secondary switch hold time. This eliminates the need for primary to secondary communication while maintaining ZVS capability through secondary side autonomous control.
Solution Approach 2:
The secondary controller autonomously determines the secondary switch hold time using measurements taken on the secondary side itself (forward pin voltage, discharge time, charge time ratio). The system serves itself by eliminating external communication requirements and using only locally available information to achieve ZVS.
Data Source
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AI summary
Zero voltage switching with a secondary switch (e.g., a synchronous rectifier) is described herein. The method allows a secondary side controller to dynamically calculate during a switching period a required secondary switch hold time to effectuate ZVS of a primary switch. By measuring a charge time and a discharge time during a switching period, the required secondary switch hold time may be determined without the need for primary to secondary communication.