Asymmetric Half-Bridge Flyback Converter With ZVS Winding Control
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Solution Overview
Problem
Current asymmetric half-bridge flyback power converters face inefficiencies and false turn-on issues during discontinuous conduction mode, particularly due to the control of auxiliary switches leading to synchronous rectifier switch false turn-ons, which reduce operational efficiency and increase failure risks.
Innovation Solution
The implementation of a ZVS winding with a winding direction opposite to the primary winding, coupled to a ZVS switch that is turned on prior to the main switch, allowing zero-voltage switching while preventing false turn-ons of the synchronous rectifier switch, and adaptive on-time adjustment of the ZVS switch based on output voltage to enhance efficiency and reduce electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary switch is controlled in conventional asymmetric half-bridge flyback converters, then the converter can operate, but false turn-ons of the synchronous rectifier switch occur during discontinuous conduction mode
Solution Approach 1:
The ZVS winding is configured to generate a voltage that turns on the ZVS switch before the main switch turns off. This preliminary action ensures that the main switch achieves zero-voltage switching and prevents false turn-on of the synchronous rectifier switch by controlling the timing of switch operations in advance
2Productivity
If conventional switching operation is used, then the converter can function, but switching losses increase and electromagnetic interference is generated
Solution Approach 1:
The patent changes the switching parameter by implementing zero-voltage switching through the ZVS winding and ZVS switch. This parameter change allows the main switch to turn on when its voltage is zero, eliminating switching losses and reducing electromagnetic interference while improving power conversion efficiency
3Productivity
If the ZVS switch on-time is fixed, then the circuit is simple, but efficiency cannot be optimized under varying load conditions
Solution Approach 1:
The patent implements dynamic control of the ZVS switch on-time based on the operating conditions. The controller adjusts the on-time of the ZVS switch according to the load conditions and output voltage, optimizing efficiency under varying loads while maintaining relatively simple circuit structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables zero-voltage switching of the main switch under all conditions, improves light load efficiency, reduces switching losses, and minimizes electromagnetic interference, thereby enhancing the operational efficiency and reliability of the power converter.
Implementation Method 1
a first winding having a winding direction that is opposite to that of the primary winding and being electromagnetically coupled to the primary winding
Data Source
AI summary
A circuit is disclosed. The circuit includes a transformer having a primary winding extending between a first terminal and a second terminal, and further including a secondary winding extending between a third terminal and a first output terminal; a first switch having a first gate terminal, a first source terminal and a first drain terminal, the first drain terminal coupled to the second terminal and the first source terminal coupled to a power source; a second switch having a second gate terminal, a second source terminal and a second drain terminal, the second source terminal coupled to the second terminal, and the second drain terminal coupled to the power source; and a third switch having a third gate terminal, a third source terminal and a third drain terminal, the third source terminal coupled to the third terminal and the third drain terminal coupled to a second output terminal.