Adaptive Synchronous Rectification Controller for Resonant Converters
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Solution Overview
Problem
Resonant mode power converter circuits face inefficiencies due to reliance on separate SR controllers for synchronous rectification, which can lead to premature SR MOSFET turn-off and additional voltage drops across parasitic inductance, reducing power conversion efficiency.
Innovation Solution
A controller device for resonant mode power converters uses current at the primary side winding to determine synchronous rectification signals, reducing power loss by controlling the synchronous rectification module directly, rather than relying on voltage monitoring across the SR MOSFET.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If separate SR controllers are used for synchronous rectification, then the rectification function is achieved, but power conversion efficiency deteriorates due to premature SR MOSFET turn-off and voltage drops across parasitic inductance
Solution Approach 1:
The patent combines the primary side controller and secondary side SR controller into a single integrated controller device. This merging eliminates communication delays and coordination issues between separate controllers, enabling precise control of SR MOSFET switching based on primary side current information, thereby reducing premature turn-off and improving power conversion efficiency
Solution Approach 2:
The patent implements a feedback mechanism where the controller monitors primary side winding current and uses this information to dynamically adjust SR MOSFET turn-off timing. The controller continues to drive the SR MOSFET on during the body diode conduction period, as indicated by the current feedback, preventing premature turn-off and reducing voltage drops across parasitic inductance
2Loss of energy
If voltage monitoring across SR MOSFET is used for control, then rectification is achieved, but device complexity increases and power loss occurs due to additional voltage drops
Solution Approach 1:
The patent uses primary side winding current as an intermediary signal to control SR MOSFET switching, replacing direct voltage monitoring across the SR MOSFET. This intermediary approach provides indirect control that reduces voltage drops and power loss while simplifying the control circuit by eliminating the need for secondary side voltage sensing and isolation
Data Source
AI summary
In an example, a controller device for a resonant converter includes processing circuitry configured to output a first switching signal and a second switching signal. A switching module is configured to electrically couple a primary side winding of a transformer to a voltage source during an activated state of the first switching signal and to electrically couple the primary side winding to a reference node during an activated state of the second switching signal. The processing circuitry is further configured to determine a first synchronous rectification signal and a second synchronous rectification signal. A synchronous rectification module is configured to generate a first channel for a first secondary side winding of the transformer during an activated state of the first synchronous rectification signal and to generate a second channel for a second secondary side winding of the transformer during an activated state of the second synchronous rectification signal.