Quasi-Resonant Controller With Dynamic Frequency Limiting
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Solution Overview
Problem
Quasi-resonant power converters experience reduced efficiency under light-load conditions due to increased switching frequency, which leads to higher switching losses.
Innovation Solution
A controller for quasi-resonant power converters that includes a PWM circuit, detection circuit, signal generation circuit, and burst circuit to generate switching signals, enabling signals, and burst signals, which limit the maximum frequency and adjust the off-time of the switching signal based on feedback from the output load, thereby reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is increased to improve efficiency at high load conditions, then the efficiency is improved, but the switching loss increases under light-load conditions
Solution Approach 1:
The patent implements dynamic switching frequency control where the maximum switching frequency is adjusted based on the operating state of the power converter. Under light-load conditions, the maximum switching frequency is limited to reduce switching losses, while under heavy-load conditions, the switching frequency can increase to improve efficiency. This is achieved through a control circuit that dynamically sets the maximum frequency limit according to the load level.
Solution Approach 2:
The patent changes the parameter of maximum switching frequency based on operating conditions. By modifying the maximum frequency parameter according to load levels, the system optimizes performance across different operating states. The control circuit adjusts this parameter to maintain high efficiency while preventing excessive switching losses during light-load operation.
2Adaptability or versatility
If the switching frequency is allowed to vary freely in response to input voltage and output load, then the converter adapts to different conditions, but the efficiency decreases under light-load conditions due to increased switching frequency
Solution Approach 1:
The patent implements dynamic control where the maximum switching frequency is not fixed but changes based on the operating state. Under light-load conditions, the maximum frequency is limited to prevent excessive switching losses, while under heavy-load conditions, the frequency can vary freely to adapt to load changes. This dynamic adjustment maintains both adaptability and efficiency.
Solution Approach 2:
The patent changes the maximum frequency parameter based on load conditions. By dynamically adjusting this parameter, the system maintains adaptability to different load conditions while preventing the switching frequency from becoming excessively high during light-load operation, thereby reducing switching losses.
3Loss of energy
If valley switching is implemented to achieve soft switching, then the efficiency is improved, but the switching frequency may increase under light-load conditions leading to higher switching loss
Solution Approach 1:
The patent combines valley switching with dynamic maximum frequency limiting. While valley switching enables soft switching and improved efficiency, the system dynamically limits the maximum switching frequency under light-load conditions to prevent the switching frequency from becoming excessively high, thereby maintaining low switching losses across all operating conditions.
Solution Approach 2:
The patent changes the maximum frequency parameter based on operating conditions while implementing valley switching. This parameter adjustment ensures that even with soft switching, the switching frequency does not become excessively high during light-load operation, maintaining the balance between efficiency and switching loss reduction.
Data Source
AI summary
A controller for a power converter is provided. The controller includes a PWM circuit, a detection circuit, a signal generation circuit and an oscillation circuit. The PWM circuit generates a switching signal coupled to switch a transformer of the power converter. A feedback signal is coupled to the PWM circuit to disable the switching signal. The detection circuit is coupled to the transformer via a resistor for generating a valley signal in response to a signal waveform of the transformer. The signal generation circuit is coupled to receive the feedback signal and the valley signal for generating an enabling signal. The oscillation circuit generates a maximum frequency signal. The maximum frequency signal associates with the enabling signal to generate a pulse signal. The feedback signal is correlated to an output load of the power converter. The maximum frequency of the pulse signal is limited.