Quasi-Resonant Converter Frequency Reduction via Valley Detection
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Solution Overview
Problem
Quasi-resonant power converters face inefficiencies and audible noise due to increased switching frequency under lightly loaded conditions, which violates energy efficiency regulations and generates noise during burst mode operations.
Innovation Solution
The implementation of a controller that detects valley points in the resonant waveform to extend blanking times and reduce primary and secondary current peaks, maintaining or reducing the operation frequency to prevent excessive switching losses and noise, while adjusting blanking times and current levels based on output loading to maintain efficient energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the output loading is reduced, then the energy packet amplitude and duration are reduced, but the switching frequency increases causing larger switching losses
Solution Approach 1:
The patent implements dynamic frequency adjustment by detecting valley points in the resonant waveform and switching to a new frequency coincident with these valleys. This dynamic approach allows the system to adapt the switching frequency to the current loading conditions, preventing excessive frequency increases under light loads while maintaining efficient energy transfer under heavier loads.
Solution Approach 2:
The patent changes the operating frequency parameter based on detected valley points in the resonant waveform. By switching frequency coincident with valley detection, the system modifies the frequency parameter to maintain optimal efficiency across varying load conditions, preventing the frequency from rising too high when output loading is reduced.
2Reliability
If the energy packet width is increased to control frequency increase, then the frequency stability improves, but the energy transfer efficiency decreases
Solution Approach 1:
The patent employs feedback by detecting the valley point of the resonant waveform and using this information to determine when to switch to a new frequency. This feedback mechanism ensures that frequency transitions occur at optimal moments, maintaining both frequency stability and energy transfer efficiency by coordinating frequency changes with the natural resonant characteristics of the system.
Solution Approach 2:
The patent performs preliminary action by detecting the valley point before switching frequency. This advance detection allows the system to prepare for frequency transition at the optimal moment, ensuring smooth frequency changes that maintain stability while minimizing energy transfer disruption.
3Speed
If the switching frequency is increased under lightly loaded conditions, then the response time improves, but audible noise increases violating energy efficiency regulations
Solution Approach 1:
The patent implements dynamic frequency control that adapts to loading conditions. Under lightly loaded conditions, the system maintains lower switching frequencies by switching coincident with detected valley points, thereby reducing audible noise while still providing adequate response time. This dynamic adjustment prevents the system from operating at excessively high frequencies when full response speed is not required.
Solution Approach 2:
The patent changes the switching frequency parameter based on load conditions and valley point detection. By adjusting the frequency parameter dynamically, the system maintains acceptable response times under various loads while preventing high-frequency operation under light loads that would generate excessive audible noise and violate efficiency regulations.
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
This approach reduces switching losses and minimizes audible noise, ensuring efficient operation across wide input and output ranges, meeting energy efficiency standards and reducing noise levels.
Implementation Method 1
Quasi-resonant (QR) power converters transfer energy packets from a primary-side of a transformer to the secondary-side of the transformer
Implementation Method 2
the frequency is switched coincident with a minimum level, or valley, of a resonant waveform on the primary-side
Data Source
AI summary
A method for frequency reduction of a quasi-resonant (QR) converter includes detecting a valley point of a resonant waveform of the QR converter, by detecting a voltage level of the resonant waveform falling below a first threshold voltage. A blanking time is formed from the beginning of a QR conversion cycle to the valley point. The blanking time is extended in response to a first reduction of an output loading of the QR converter, while maintaining a primary current of the QR converter at a first current level. The primary current is reduced to a second current level being less than the first current level, while maintaining the blanking time at a maximum blanking time, in response to a second reduction of the output loading.