Resonant Converter Control for Symmetrical Mode Transition
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Solution Overview
Problem
Existing resonant converter controllers face challenges in efficiently transitioning between current-controlled and voltage-controlled modes, particularly in maintaining symmetrical operation and avoiding asymmetrical hangup situations.
Innovation Solution
The proposed controller for a resonant converter includes a power reduction mode that adjusts the upper and lower voltage threshold values based on measured current and voltage signals, allowing the converter to transition from current-controlled to voltage-controlled operation while maintaining symmetrical switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the controller uses fixed voltage threshold values for switch control, then the switching operation is simple to implement, but the converter cannot recover from dynamic asymmetrical situations and may enter asymmetrical hangup
Solution Approach 1:
The controller dynamically adjusts the upper and lower voltage threshold values based on the detected asymmetrical conditions and power level, rather than using fixed thresholds. This allows the switching control to adapt to changing operating conditions and recover from asymmetrical hangup situations while maintaining simplicity in implementation.
Solution Approach 2:
The controller implements a feedback mechanism that monitors the resonant tank voltage and current to detect asymmetrical conditions. Based on this feedback, the controller adjusts the voltage thresholds to restore symmetrical operation, ensuring reliability while keeping the control logic straightforward.
2Reliability
If the controller dynamically adjusts voltage threshold values to maintain symmetrical operation, then the converter reliability is improved, but the control mechanism becomes more complex
Solution Approach 1:
The controller changes the voltage threshold parameters dynamically based on the detected asymmetrical conditions and power level. By adjusting these parameters rather than adding complex control circuitry, the solution maintains reliability while minimizing the increase in device complexity.
3Ease of operation
If the controller uses current-controlled mode only, then the switching operation is straightforward, but the converter cannot efficiently transition to voltage-controlled mode under varying power conditions
Solution Approach 1:
The controller is designed to operate in both current-controlled and voltage-controlled modes, with the ability to transition between them based on power level and asymmetrical conditions. This multi-functionality allows the converter to maintain straightforward operation while adapting to varying power conditions efficiently.
Data Source
AI summary
A controller for a resonant converter. The controller is configured to: compare a measured current signal with a positive current threshold; compare the measured current signal with a negative current threshold; and set a power reduction mode as active if either or both: the measured current signal is less than the positive current threshold at the end of the preceding high-side switch half cycle; and the measured current signal is greater than the negative current threshold at the end of the preceding low-side switch half cycle. While the power reduction mode is active: the controller gradually decreases the value of a reduced power signal. While the power reduction mode is inactive: the controller gradually increases the value of the reduced power signal. the controller sets an upper voltage threshold value and a lower voltage threshold value based on the lower of: i) the reduced power signal; and ii) a power setting signal.