Dual-Mode Resonant Converter Control Under Frequency Limits
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Solution Overview
Problem
Resonant converter circuits face inefficiencies at high switching frequencies, leading to increased losses and limited gain range due to varying load conditions, which existing technologies struggle to regulate effectively without compromising output voltage stability.
Innovation Solution
A resonant converter with a switching controller that employs pulse-frequency modulation (PFM) and phase-difference modulation to adjust switching signals based on load conditions, clamping the switching frequency at a maximum value to maintain regulation and reduce losses, while shifting between control modes to maintain output voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching frequency is increased to regulate output voltage under varying load conditions, then the output voltage regulation is improved, but the converter losses increase and efficiency deteriorates
Solution Approach 1:
The patent implements dynamic switching between two control modes (PFM and phase-difference modulation) based on operating conditions. The controller dynamically selects PFM for light-load conditions to minimize losses, and phase-difference modulation for heavy-load conditions to maintain voltage regulation, thereby dynamically optimizing the trade-off between regulation performance and energy efficiency
Solution Approach 2:
The patent changes the control parameter from frequency modulation alone to a hybrid approach where the modulation type itself becomes a variable parameter. By changing the control mode parameter based on load conditions, the system achieves both efficient light-load operation and effective heavy-load regulation without continuously varying switching frequency
2Adaptability or versatility
If the switching frequency is increased to extend gain range, then the adaptability to load variations is improved, but the converter enters high-frequency operation region with increased losses
Solution Approach 1:
The patent segments the operating range into two distinct regions: light-load region controlled by PFM and heavy-load region controlled by phase-difference modulation. This segmentation allows each mode to operate within its optimal frequency range, avoiding the need to extend into high-frequency region and thereby eliminating high-frequency losses while maintaining adequate gain range
3Device complexity
If pulse frequency modulation is used for control, then the simplicity of control is maintained, but the maximum switching frequency is reached limiting further regulation capability
Solution Approach 1:
The patent merges PFM control with phase-difference modulation control into a unified dual-mode control system. The phase-difference modulation component is added to extend the regulation range beyond what PFM alone can achieve, while maintaining relatively simple control logic through systematic mode selection based on predefined criteria
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
The solution allows for a large gain range without the limitations of high-frequency operation, maintaining zero-voltage switching and improving loop-response for faster transient recovery, enabling efficient operation across varying load conditions.
Implementation Method 1
the resulting square wave is applied to a resonant network. The resonant network is configured to filter the square wave in order to generate an alternating current (AC) signal
Implementation Method 2
maintaining zero-voltage switching and improving loop-response for faster transient recovery
Data Source
AI summary
It may be desirable to limit the switching frequency of a pulse frequency modulated (PFM) resonant converter, however certain load conditions and/or startup condition require high switching frequencies to regulate an output voltage. The disclosed resonant converter can limit a maximum switching frequency while regulating an output voltage by shifting from PFM to phase-difference modulation based on a load condition. The appropriate modulation can be applied based on a comparison between a charge-control signal and a load-control signal.