Resonant Converter Charge Control for Light-Load Stability
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Solution Overview
Problem
Traditional series resonance converters face poor dynamic response, low low-frequency DC voltage gain, and instability due to sub-harmonic oscillations, especially under light-load or no-load conditions, which existing charge control methods like BBCC and hybrid hysteresis control fail to adequately address.
Innovation Solution
A dual-mode charge control method that switches between single-band and dual-band charge control based on load conditions, using a resettable integrator and pulse-width modulation to generate control signals for power switches, eliminating the need for a mono-stable trigger and enhancing stability by isolating current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If bang-bang charge control (BBCC) is used to improve dynamic response speed and low-frequency DC voltage gain, then the control resolution is improved, but the circuit becomes unstable and oscillates under light-load or no-load conditions
Solution Approach 1:
The patent implements dynamic switching between dual-band charge control and single-band charge control based on load conditions. When the load is light or no-load, the system switches to single-band control to avoid oscillation; when the load is heavy, it uses dual-band control to maintain fast dynamic response. This dynamic adaptation resolves the contradiction between speed and stability.
Solution Approach 2:
The patent changes the control parameters (threshold voltages) based on load conditions. In single-band control, only an upper threshold voltage is used, while in dual-band control, both upper and lower threshold voltages are employed. This parameter adjustment allows the system to maintain stability under light-load conditions while preserving fast response under heavy-load conditions.
2Reliability
If hybrid hysteresis control is used to increase efficiency and stability under light-load condition, then the control stability is improved, but the control frequency is reduced and control resolution is greatly reduced
Solution Approach 1:
The patent dynamically switches between single-band and dual-band charge control modes based on load conditions. Under light-load conditions, it uses single-band control to maintain stability without adding complex slope compensation circuits, thereby preserving control frequency. Under heavy-load conditions, it transitions to dual-band control to maintain fast dynamic response, thus resolving the contradiction between stability and control frequency.
3Speed
If two limit lines are generated and compared with resonance voltage to control power switches, then the dynamic response is improved, but sub-harmonic oscillation occurs when limit lines are close or exchanged under light-load condition
Solution Approach 1:
The patent extracts and eliminates the lower limit line comparison under light-load conditions by switching to single-band control, which only uses an upper threshold voltage. This removes the source of sub-harmonic oscillation that occurs when the two limit lines are close or exchanged, while still maintaining fast dynamic response through the preserved upper threshold comparison.
4Reliability
If a mono-stable flip-flop is added to avoid SR control error zone, then the control stability is improved, but the device complexity increases and the mono-stable trigger may not be properly triggered under rapid load changes
Solution Approach 1:
The patent uses dynamic mode switching between single-band and dual-band charge control based on load conditions, which inherently avoids the SR control error zone without requiring a mono-stable flip-flop. This dynamic adaptation eliminates the need for additional complex circuitry while maintaining control stability under all load conditions.
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 dual-mode charge control method increases stability and control resolution under light-loading or no-loading conditions, maintaining high frequency response and low-frequency voltage gain while avoiding oscillations and signal errors.
Implementation Method 1
acquiring a resonance voltage by calculating the resonance current by a resettable integrator
Implementation Method 2
generating a second control signal complementary to the first control signal by a pulse-width modulation duplicator
Data Source
AI summary
A dual mode charge control method includes steps of: detecting an input voltage of the resonance tank, a resonance current of the resonance tank, an output current of the load, and an output voltage of the load; performing a single-band charge control when determining a light-load condition or a no-load condition of the load according to the output current; compensating the output voltage to generate an upper threshold voltage in the single-band charge control, and acquiring a resonance voltage by calculating the resonance current by a resettable integrator; comparing the resonance voltage and the upper threshold voltage to generate a first control signal; generating a second control signal complementary to the first control signal by a pulse-width modulation duplicator; providing the first control signal and the second control signal to respectively control a first power switch and a second power switch of the resonance circuit.