Flyback Primary-Side Valley Switching for EMI and Noise Reduction
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Solution Overview
Problem
Existing power converters face challenges in achieving high efficiency and reduced size while minimizing electromagnetic interference (EMI) and audible noise, particularly in electronic devices like computers and televisions.
Innovation Solution
A flyback power converter with a primary side controller that monitors input power to control resonant voltage valley switching, using a lookup table to determine optimal valley numbers for switching, thereby reducing switching losses and EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional power conversion circuits are used, then basic power conversion function is achieved, but efficiency is low and size is large
Solution Approach 1:
The patent implements dynamic valley selection where the controller dynamically determines the optimal resonant voltage valley number based on real-time input power conditions. This dynamic adaptation allows the circuit to operate at optimal efficiency points across varying load conditions, resolving the contradiction between maintaining basic conversion function and achieving high efficiency.
Solution Approach 2:
The patent changes the operating parameter (resonant voltage valley number) based on input power levels. By selecting different valley numbers corresponding to different input power ranges, the system optimizes efficiency across the operating spectrum, transforming a static conversion circuit into an adaptive high-efficiency power converter.
2Volume of moving object
If switching frequency is increased to reduce size, then power converter size is reduced, but electromagnetic interference and audible noise increase
Solution Approach 1:
The patent utilizes periodic resonant voltage valleys to time the switching action. By synchronizing switch transitions with specific resonant voltage valleys in the periodic waveform, the system achieves soft switching that reduces EMI and audible noise while maintaining compact size through resonant operation.
Solution Approach 2:
The patent exploits electromagnetic resonance and vibration phenomena to achieve soft switching. By timing switch transitions with resonant voltage valleys, the system utilizes the natural oscillation of the circuit to minimize switching losses and reduce harmful electromagnetic radiation and audible noise.
3Loss of energy
If resonant voltage valley switching is implemented, then switching losses are reduced, but control complexity increases
Solution Approach 1:
The patent replaces complex analog control circuits with a digital controller that uses lookup tables and digital processing to determine optimal valley numbers. This substitution simplifies the physical control circuitry while maintaining the ability to reduce switching losses through intelligent digital control based on input power sensing.
4Use of energy by moving object
If dynamic valley selection based on input power is implemented, then efficiency across varying loads is improved, but measurement and control difficulty increases
Solution Approach 1:
The patent pre-calculates and stores optimal valley number selections in lookup tables based on input power ranges. This preliminary action allows the controller to quickly determine the appropriate valley number by simple table lookup rather than complex real-time calculation, reducing measurement and control difficulty while maintaining efficiency optimization across varying loads.
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 solution enhances efficiency and reduces audible noise by accurately selecting resonant voltage valleys for switching, minimizing EMI and improving power converter performance.
Implementation Method 1
a transformer having a primary winding magnetically coupled to a secondary winding
Implementation Method 2
a plurality of resonant voltage valleys occur at the drain terminal
Data Source
AI summary
A circuit is disclosed. The circuit includes a solid state switch controlled by a control circuit, the control circuit arranged to transition the solid state switch from a first on-state to a first off-state, where in response to the transition a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch, the control circuit further arranged to: determine an input power to the power converter circuit and in response, determine a resonant voltage valley number based at least in part on the input power, and transition the solid state switch from the first off-state to a second on-state when a sequential number of the plurality of resonant voltage valleys equals the resonant voltage valley number.