Flyback Converter Controller Using Resonant Tank Current
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Solution Overview
Problem
Flyback converters face challenges in monitoring and regulating output current without breaking galvanic isolation, especially when operating with a wide input voltage range and varying output voltages, as existing solutions often require direct electrical connections that compromise isolation.
Innovation Solution
A power converter controller that uses the resonant tank current, measured during phases with no reflected current, as a proxy for output current, allowing for effective monitoring and regulation without breaching galvanic isolation by controlling switches in a half-bridge configuration and employing a current measurement circuit coupled to the power converter controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct electrical connection is used to monitor output current, then output current monitoring is achieved, but galvanic isolation is compromised
Solution Approach 1:
The patent uses resonant tank current as an intermediary parameter to indirectly measure output current. By measuring the current in the resonant tank circuit during specific phases when no reflected current is present, the system obtains output current information without direct electrical connection to the output side, thus maintaining galvanic isolation while achieving monitoring capability
Solution Approach 2:
The patent replaces direct electrical measurement (mechanical/electrical connection) with electromagnetic field-based indirect measurement. By utilizing the relationship between resonant tank current and output current through electromagnetic coupling in the transformer, the system substitutes direct contact measurement with field-based measurement, preserving isolation
2Reliability
If resonant tank current is used to measure output current, then galvanic isolation is maintained, but measurement accuracy may be affected by reflected current
Solution Approach 1:
The patent applies preliminary action by timing the measurement of resonant tank current to occur specifically during phases when reflected current is absent. The control logic identifies and selects measurement windows in the switching cycle where only resonant tank current flows, eliminating interference from reflected current before the measurement is taken
Solution Approach 2:
The patent uses feedback by continuously monitoring the switching phases and reflected current status to determine the appropriate measurement timing. The control logic adjusts the measurement window based on the current phase of operation, ensuring measurements are always taken when reflected current is absent, thereby maintaining measurement accuracy
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
Enables accurate output current monitoring and regulation across a wide input voltage range while maintaining galvanic isolation, improving the operational efficiency and adaptability of flyback converters.
Implementation Method 1
A flyback converter is provided with a primary side comprising at least two switches connected in series in a half bridge configuration and a resonant tank coupled to a connection node between the at least two switches, and a secondary side inductively coupled to the primary side
Data Source
AI summary
Power converter controllers, flyback converters and methods are provided which use a resonant tank current of the flyback converter as a measure for an output current of the flyback converter. A power converter controller includes a control logic circuit that is configured to use, as a measure of an output current of the flyback converter, the resonant tank current indicated by the signal at a time in a phase where there is no reflected current to the primary side of the flyback converter.