Resonant Power Converter Burst-Off Control for Light-Load Efficiency
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Solution Overview
Problem
Existing resonant power converters face inefficiencies in light-load conditions due to high switching frequencies and imprecise capacitor voltage control, leading to unbalanced current delivery and reduced power efficiency.
Innovation Solution
A conversion control circuit that includes a sensing circuit to detect resonant parameters, a PWM control circuit to generate driving signals based on feedback, and a full-wave rectification circuit to offset DC components, enabling a burst OFF period when feedback falls below a threshold, and adjusting duty cycles for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst mode is used to reduce power loss in light load conditions, then power efficiency is improved, but light load power consumption remains significant due to high switching frequency
Solution Approach 1:
The patent applies periodic action by implementing burst mode operation where the resonant power converter operates in periodic bursts rather than continuously. The control circuit enables the power converter to enter a sleep mode between bursts, periodically blocking switching signals to reduce power consumption during light load and standby operations while maintaining the ability to quickly resume normal operation when load increases.
2Speed
If resonant capacitor voltage control is used to achieve fast dynamic response, then control speed is improved, but DC component offset in sensing can affect duty cycle and lead to improper functioning
Solution Approach 1:
The patent extracts and removes the DC component from the resonant capacitor voltage sensing signal using a coupling capacitor. This allows the control circuit to sense only the AC component of the resonant capacitor voltage, eliminating the DC offset that would otherwise affect duty cycle accuracy. The coupling capacitor blocks the DC component while allowing the AC signal to pass through to the control circuit.
Solution Approach 2:
The patent introduces a coupling capacitor as an intermediary element between the resonant capacitor and the control circuit. This intermediary component serves as a DC block that separates the DC component from the sensing signal, allowing accurate AC voltage sensing without being affected by DC offsets in the resonant capacitor voltage.
3Stability of the object's composition
If 50% duty cycle operation is used to balance current delivery, then current balance is improved, but the DC value of resonant capacitor voltage becomes sensitive to sensing offsets
Solution Approach 1:
The patent extracts the DC component from the resonant capacitor voltage sensing signal using a coupling capacitor. This allows the control circuit to sense only the AC component, eliminating the DC offset that would otherwise affect duty cycle accuracy and current balance, while still maintaining stable current delivery through proper AC voltage control.
4Measurement precision
If voltage difference sampling is used to avoid DC component offset, then sensing accuracy is improved, but the method faces challenges under light load conditions due to small voltage difference
Solution Approach 1:
The patent applies preliminary action by using a full-wave rectification circuit to process the resonant capacitor voltage signal before it reaches the control circuit. This rectification converts the AC voltage into a pulsating DC signal that maintains sufficient amplitude even under light load conditions, allowing the control circuit to accurately sense voltage variations without being limited by small voltage differences.
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
Improves power efficiency by reducing conduction losses and maintaining balanced current delivery across light and heavy loads, enhancing the overall performance of resonant power converters.
Implementation Method 1
a resonant circuit including at least one resonant inductor and a resonant capacitor, wherein the high-side transistor and the low-side transistor are configured to switch the resonant circuit to convert the input voltage into an output voltage; wherein the sensing circuit is configured to sense a resonant-related parameter with a resonant state
Data Source
AI summary
A conversion control circuit for controlling a resonant power converter which includes a high-side and a low-side transistor which are coupled to convert an input voltage into an output voltage, and a resonant circuit including at least one resonant inductor and a resonant capacitor. The conversion control circuit includes: a sensing circuit for sensing a resonant-related parameter related to the resonance produced by the resonant circuit to generate a sensed signal; and a PWM control circuit for generating a high-side and a low-side driving signal according to the sensed signal and a feedback signal related to the output voltage. When the feedback signal falls below a low-power threshold, the resonant power converter enters a burst OFF period, during which both the high-side and the low-side transistors are turned OFF. A lower limit of the burst OFF period is equal to a switching period of the high-side and the low-side driving signals.