Valley-Lock Switching Controller for Quasi-Resonant Power Converters
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Solution Overview
Problem
Quasi-resonant power converters experience reduced efficiency under light-load conditions and generate acoustic noise due to varying switching frequencies, which existing technologies fail to effectively address.
Innovation Solution
A controller for quasi-resonant power converters that includes a PWM circuit, detection circuit, signal generator, oscillation circuit, valley-lock circuit, and burst circuit to limit maximum switching frequency and implement valley switching operations across full-range load conditions, reducing acoustic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency of QR power converter is increased to achieve higher efficiency under high switching frequency, then efficiency is improved, but acoustic noise is generated during valley switching operation
Solution Approach 1:
The patent implements dynamic switching frequency adjustment through valley-lock switching, where the switching frequency is modulated to lock onto the resonant valley points of the transformer waveform. This dynamic approach allows the system to operate at optimal efficiency points while avoiding fixed-frequency acoustic noise generation. The controller continuously adapts the switching frequency based on real-time detection of transformer voltage valleys, creating a dynamic balance between efficiency and noise reduction.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically to achieve both high efficiency and low noise. By varying the switching frequency to track the resonant characteristics of the transformer, the system can operate at frequencies that maximize efficiency while minimizing acoustic noise generation. The maximum frequency signal limits the upper bound of this parameter change to prevent excessive noise.
2Adaptability or versatility
If the switching frequency is varied in response to input voltage and output load, then adaptability is improved, but efficiency under light-load condition deteriorates
Solution Approach 1:
The patent employs periodic valley switching action where the controller waits for and triggers switching at specific resonant valley points of the transformer waveform. This periodic action creates a natural rhythm in the switching operation that maintains efficiency across different load conditions. The periodic nature of valley detection and triggering ensures consistent efficient operation whether the load is heavy or light, as the switching always occurs at the optimal resonant points.
Solution Approach 2:
The patent implements feedback through the detection circuit that continuously monitors the transformer waveform and provides information to the controller. This feedback mechanism allows the system to adapt to changing load conditions while maintaining efficient operation by detecting valley points and adjusting switching timing accordingly. The feedback loop ensures that even under light-load conditions, the system operates at optimal efficiency points rather than degrading performance.
3Object-affected harmful factors
If valley switching operation is implemented to reduce acoustic noise, then acoustic noise is reduced, but switching frequency control complexity increases
Solution Approach 1:
The patent introduces a detection circuit as an intermediary between the transformer and the controller. This intermediary component simplifies the control complexity by automatically detecting valley points in the transformer waveform and providing clear trigger signals to the controller. Instead of requiring complex algorithms to identify optimal switching points, the detection circuit acts as a mediator that performs this function automatically, reducing the computational burden on the controller while maintaining effective noise reduction through valley switching.
Solution Approach 2:
The valley-lock switching mechanism is self-regulating, where the system automatically locks onto and tracks the resonant valley points without requiring external intervention or complex control algorithms. The detection circuit and controller work together in a self-service manner, with the detection circuit automatically identifying valley points and the controller automatically adjusting switching frequency to maintain lock. This self-service approach reduces control complexity while achieving effective acoustic noise reduction.
Data Source
AI summary
The present invention provides a controller for a power converter. The controller comprises a PWM circuit, a detection circuit, a signal generator, an oscillation circuit, a valley-lock circuit, a timing circuit and a burst circuit. The PWM circuit generates a switching signal coupled to switch a transformer of the power converter. A feedback signal is coupled to control and disable the switching signal. The detection circuit is coupled to the transformer via a resistor for generating a valley signal in response to a waveform obtained from the transformer. The signal generator 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 turning-on signal. The turning-on signal is coupled to enable the switching signal. A maximum frequency of the turning-on signal is limited.