Resonant Converter Control Using Protected Power Thresholds
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Solution Overview
Problem
Resonant converters face challenges in preventing capacitive mode operation, which can lead to unstable behavior and reduced performance.
Innovation Solution
A controller for a resonant converter that sets upper and lower voltage threshold values based on a protected power signal, which is determined by a time delay between switch state changes and zero-crossings of the measured current signal, thereby preventing capacitive mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the resonant converter operates at high power levels, then productivity is improved, but the risk of entering capacitive mode increases causing instability
Solution Approach 1:
The controller proactively determines protected power levels and sets voltage threshold values before the resonant converter enters capacitive mode. By calculating the time delay between switch state changes and current zero-crossings in advance, the system establishes safety margins that prevent instability while allowing high power operation.
Solution Approach 2:
The controller continuously monitors the resonant tank voltage and compares it against dynamically adjusted threshold values. When the voltage approaches these thresholds, the controller modifies switch timing to maintain a safe distance from capacitive mode, creating a closed-loop feedback system that ensures stable operation at high power levels.
2Reliability
If voltage threshold values are set conservatively to prevent capacitive mode, then reliability is improved, but the power output capability is reduced
Solution Approach 1:
The voltage threshold values are not fixed but dynamically adjusted based on the protected power signal, which is determined by the measured time delay between switch state changes and current zero-crossings. This dynamic adjustment allows the system to maximize power output while maintaining reliable prevention of capacitive mode entry.
Solution Approach 2:
The controller changes the voltage threshold parameters adaptively by selecting between different protected power signal values. This allows the system to optimize the balance between reliability and productivity by adjusting threshold levels according to real-time operating conditions and measured electrical characteristics.
Data Source
AI summary
A controller for a resonant converter. The controller is configured to: receive a measured current signal that represents current flowing in the resonant tank; receive a measured voltage signal that represents the voltage at a predetermined point in the resonant tank; receive a power setting signal, which defines a requested power level for the load; set a protected power signal based on a time delay between a change in state of one of first and second switches and a subsequent zero-crossing of the measured current signal; set an upper voltage threshold value and a lower threshold value based on the lower of: i) the protected power signal; and ii) the power setting signal; in response to the measured voltage signal exceeding the upper voltage threshold value, open the first switch and close the second switch; and in response to the measured voltage signal dropping below the lower voltage threshold value, open the second switch and close the first switch.