Valley Detection in Power Factor Correction Circuits
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Solution Overview
Problem
Conventional power factor correction methods using valley switching face issues such as imprecise valley detection, audible noise, and increased system cost due to the requirement of an auxiliary winding, which affects efficiency and electromagnetic interference.
Innovation Solution
A power factor correction method and apparatus that utilizes valley detection without an auxiliary winding by monitoring the drain terminal voltage of a power transistor, identifying a falling edge in the drain voltage signal, and determining the average voltage of resonant ringing to detect valleys, thereby reducing system complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional valley switching methods are used for power factor correction, then power factor improvement is achieved, but system complexity and cost increase due to the requirement of an auxiliary winding
Solution Approach 1:
The patent extracts and eliminates the auxiliary winding from the power factor correction circuit, using only the existing drain terminal voltage signal for valley detection. This removes the unnecessary component while maintaining the core functionality of valley switching for power factor correction.
Solution Approach 2:
The invention makes the power transistor's drain terminal serve a dual function: both power switching and valley detection. The drain voltage signal inherently contains the valley information needed for timing, eliminating the need for separate detection circuits or auxiliary windings.
2Reliability
If conventional valley switching is implemented, then power factor correction is achieved, but electromagnetic interference and audible noise increase
Solution Approach 1:
The patent implements feedback by continuously monitoring the drain terminal voltage and using this information to precisely time the switching operations. This feedback mechanism ensures switching occurs at optimal moments (valleys), minimizing electromagnetic interference and audible noise while maintaining power factor correction effectiveness.
3Measurement precision
If auxiliary winding is added for valley detection, then valley detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The drain terminal is made multi-functional, serving both as a power switching node and as a valley detection sensor. This universal usage of existing circuit elements provides precise valley detection capability without adding any extra components, thereby reducing manufacturing cost.
4Device complexity
If drain terminal voltage monitoring is used for valley detection, then system complexity is reduced, but measurement precision of valley detection may be affected
Solution Approach 1:
The drain terminal voltage signal inherently contains all necessary information for precise valley detection. By utilizing this self-service capability of the existing signal, the patent achieves accurate valley timing without complex additional measurement circuits, maintaining both simplicity and precision.
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 improves operating efficiency, reduces electromagnetic interference, and eliminates the need for an auxiliary winding, resulting in cost-effective and efficient power factor correction.
Implementation Method 1
determining, by detection circuitry coupled to the drain terminal, an input voltage applied to the inductor based on resonant ringing of voltage at the drain terminal
Data Source
AI summary
A power factor correction circuit includes a power transistor, an inductor, and detection circuitry. The inductor is coupled to a drain terminal of the power transistor. The detection circuitry is coupled to the drain terminal of the power transistor. The detection circuitry is configured to determine an input voltage applied to the inductor based on resonant ringing of voltage at the drain terminal, and to detect a valley in the voltage at the drain terminal based on the input voltage applied to the inductor.