Boost Chopper PFC Control for AC Interruption Overshoot Suppression
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Solution Overview
Problem
Conventional power factor correction circuits face challenges in suppressing overshoot during momentary AC input halts, especially when the control circuit is not reset, and struggle to maintain stable output voltage during sudden input or load changes without increasing system costs.
Innovation Solution
A power factor correction circuit that includes an error signal generation unit, an oscillation unit, a zero current detection unit, a drive signal generation unit, and an input interruption detection unit, which controls the slope of the triangular wave signal to manage the switching element of a boost chopper, ensuring stable output voltage and preventing overshoot during momentary AC input halts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control circuit is not reset during momentary AC input halt, then the circuit can quickly resume operation, but output voltage overshoot occurs
Solution Approach 1:
The patent applies preliminary action by resetting the control circuit before the momentary AC input halt ends. The reset signal is generated based on detection of the AC input interruption, and the control circuit is reset during the interruption period so that when power is restored, the circuit starts fresh without conditions that would cause overshoot, enabling both quick resumption and overshoot prevention
Solution Approach 2:
The patent uses feedback by detecting the AC input voltage state and generating a reset signal accordingly. The detection unit monitors whether the AC input is interrupted, and this feedback information controls the reset timing of the control circuit, ensuring the reset occurs at the appropriate moment to prevent overshoot while maintaining fast response
2Reliability
If the slope of triangular wave signal is increased during AC input interruption, then soft-start function is achieved, but output power is reduced
Solution Approach 1:
The patent applies dynamics by making the slope of the triangular wave signal changeable based on the AC input state. When AC input is detected as interrupted, the slope is increased to provide soft-start protection; when AC input is normal, the slope returns to normal levels, maintaining full output power. This dynamic adjustment resolves the contradiction between reliability and power output
3Ease of operation
If discrete clamp voltages are used for error amplifier, then soft-start control is achieved, but output voltage stability during sudden changes deteriorates
Solution Approach 1:
The patent extracts the soft-start control function from the discrete clamp voltage system and implements it separately through AC input interruption detection and control circuit resetting. This separation allows the clamp voltages to focus on their primary voltage regulation function, improving output voltage stability during sudden changes while the dedicated reset mechanism handles soft-start control
Data Source
AI summary
A power factor correction circuit including: an error signal generation unit configured to output a signal obtained by amplifying an error between the output voltage of a boost chopper and a referential voltage; an oscillation unit configured to output a triangular wave signal; a zero current detection unit configured to detect zero current in an inductor current of the boost chopper; a drive signal generation unit configured to generate a drive signal for the switching element based on a zero current detection signal, the error signal, and the triangular wave signal; and an input interruption detection unit configured to detect an interruption state of an AC input voltage based on the zero current detection signal. When the input interruption detection unit detects an input interruption state, the oscillation unit controls a slope of the triangular wave signal to be larger than the slope when no input interruption state is detected.