Resonant Converter Threshold Control for Stable Zero-Load Switching
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Solution Overview
Problem
Existing resonant converters face challenges in achieving stable no-load operation while switching, particularly at high frequencies, due to delays and inaccuracies in power control, leading to irregular switching and audible noise.
Innovation Solution
A controller for a resonant converter that uses slope compensation and adaptive threshold settings based on measured current and power setting signals to ensure stable trajectories and efficient power delivery, even at zero load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power control is used in resonant converters, then power delivery is achieved, but stable no-load operation cannot be maintained due to delays and inaccuracies
Solution Approach 1:
The controller performs preliminary actions by setting adaptive voltage thresholds before the switching event based on the measured current signal. This anticipatory adjustment compensates for control delays and ensures accurate power delivery even at no-load conditions, preventing the instability that would otherwise occur.
Solution Approach 2:
The voltage thresholds are made dynamic rather than fixed. The controller continuously adapts the voltage thresholds based on the measured current signal, allowing the system to maintain stability across varying load conditions including no-load operation, where conventional fixed-threshold controllers fail.
2Loss of energy
If high switching frequency is used to improve efficiency, then power conversion efficiency increases, but audible noise increases due to irregular switching
Solution Approach 1:
The controller uses feedback from the measured current signal to continuously adjust the voltage thresholds. This feedback mechanism ensures regular and predictable switching behavior even at high frequencies, eliminating the irregular switching that causes audible noise while maintaining high conversion efficiency.
Solution Approach 2:
The controller changes the voltage threshold parameters dynamically based on the measured current signal. This parameter adaptation ensures that switching occurs at precise moments regardless of frequency, preventing the irregular switching patterns that generate audible noise while allowing high-frequency operation for improved efficiency.
3Ease of operation
If fixed voltage thresholds are used for switching control, then control simplicity is maintained, but stable operation at zero load cannot be achieved
Solution Approach 1:
The controller transitions from fixed to dynamic voltage thresholds. By making the thresholds adaptive based on the measured current signal, the system maintains the simplicity of threshold-based control while achieving the complexity needed for stable zero-load operation through continuous adaptation.
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 stable zero-load operation and reduced magnetizing current, improving efficiency and reducing audible noise by forcing the resonant tank to follow stable low-load or zero-load trajectories.
Implementation Method 1
a resonant tank that is electrically connected to the first and second switches, wherein the resonant tank comprises a resonant capacitor
Data Source
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Figure 2
AI summary
A controller for a resonant converter. If a measured current signal is greater than an upper-low-load-current-threshold, then the controller sets an upper-voltage-threshold-value based on the measured current signal. If the measured current signal is not greater than the upper-low-load-current-threshold, then the controller sets the upper-voltage-threshold-value based on the power setting signal but independent of the measured current signal. If the measured current signal is less than a lower-low-load-current-threshold, then the controller sets a lower-voltage-threshold-value based on the measured current signal. If the measured current signal is not less than the lower-low-load-current-threshold, then the controller sets the lower-voltage-threshold-value based on the power setting signal but independent of the measured current signal. In response to a measured voltage signal exceeding the upper-voltage-threshold-value, the controller opens the first switch and closes the second switch. In response to the measured voltage signal dropping below a lower-voltage-threshold-value, the controller opens the second switch and closes the first switch.