PFC Switch Timing Control for Output Overshoot Stability
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Solution Overview
Problem
Existing power factor correction circuits face challenges in preventing overshoot of output voltage and maintaining system stability due to varying phase differences between input voltage and current, leading to inefficiencies in power transfer.
Innovation Solution
A power factor correction circuit with a switch controller that operates in two modes based on feedback voltage levels, adjusting the on-time of a power switch to maintain constant on-timing after the output voltage reaches a target, using an error amplifier, ramp signal generator, and PWM controller to generate gate control signals, thereby preventing overshoot and ensuring system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the on-time of the power switch is increased to improve power transfer efficiency, then the power factor correction improves, but output voltage overshoot occurs
Solution Approach 1:
The patent applies dynamics by making the on-time of the power switch variable rather than fixed. The control circuit dynamically adjusts the on-time based on real-time feedback from the output voltage, allowing the system to optimize power transfer efficiency while preventing overshoot through continuous adaptation to changing conditions.
Solution Approach 2:
The patent implements feedback control by using a control circuit that monitors the output voltage and adjusts the power switch on-time accordingly. The feedback mechanism compares the actual output voltage with the target voltage and modifies the switching duty cycle to eliminate errors, thereby preventing overshoot while maintaining efficient power transfer.
2Productivity
If the phase difference between input voltage and current is reduced to improve power factor, then power transfer efficiency improves, but system stability becomes difficult to maintain
Solution Approach 1:
The control circuit uses feedback from the output voltage to continuously adjust the power switch timing, ensuring that the phase difference between input voltage and current is optimized for power factor correction while maintaining system stability through closed-loop control.
Solution Approach 2:
The patent changes the operating parameters of the power switch dynamically, adjusting the on-time based on feedback signals. This allows the system to maintain optimal phase difference for improved power factor while adapting to load variations and maintaining stability through parameter optimization.
Data Source
AI summary
A power factor correction circuit includes an inductor configured to receive an input voltage and supply an output voltage; a power switch connected to the inductor and configured to control an input current flowing through the inductor; and a switch controller configured to receive a feedback voltage including information on the output voltage and an auxiliary voltage including information on a voltage of the inductor and control an on/off operation of the power switch. The switch controller is further configured to operate in a first mode when the feedback voltage is less than a reference voltage, and operate in a second mode when the feedback voltage is greater than the reference voltage.