Power Factor Correction Control System Stabilizing Oscillation
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Solution Overview
Problem
Conventional power factor correction circuits face issues with unstable oscillation and varying switching frequency due to changes in AC power source voltage, leading to inefficiencies and complex control circuits.
Innovation Solution
A control system for power factor correction circuits that includes a voltage error amplifier, current command value generator, comparator, timer circuit, and reset-set type flip-flop, which sets off-periods for the switching element proportionally to AC power source values, and incorporates maximum and minimum frequency limiting circuits to stabilize oscillation and maintain constant switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional peak current control system with constant frequency pulse generator is used, then switching element can be turned on at constant frequency, but unstable sub-harmonic oscillation occurs
Solution Approach 1:
The patent applies preliminary action by generating a fixed off-time signal before the switching element is turned off. The off-time signal generation circuit produces a predetermined off-time period that forces the switching element to remain off for this fixed duration, preventing sub-harmonic oscillation before it can develop. This proactive timing control stabilizes the switching frequency without requiring complex feedback mechanisms.
2Adaptability or versatility
If AC power source voltage changes, then power factor correction circuit must adapt, but switching frequency varies causing inefficiency
Solution Approach 1:
The patent implements feedback by detecting the AC power source voltage and using this information to control the off-time of the switching element. The off-time signal generation circuit receives the detected voltage information and adjusts the off-time period accordingly, creating a closed-loop control system that maintains constant switching frequency despite voltage variations, thereby preserving conversion efficiency.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the off-time period of the switching element based on the detected AC power source voltage. When voltage changes are detected, the off-time parameter is modified to compensate, ensuring that the switching frequency remains constant. This dynamic parameter adjustment maintains optimal conversion efficiency across different voltage conditions.
3Reliability
If complex control circuits are used to stabilize oscillation, then switching frequency can be controlled, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by extracting the off-time control function into a separate, dedicated off-time signal generation circuit. This circuit independently generates the fixed off-time signal without requiring complex interaction with other control components. By separating this critical stabilization function, the overall control circuit complexity is reduced while maintaining oscillation stability.
Solution Approach 2:
The patent implements self-service by designing the off-time signal generation circuit to autonomously generate the predetermined off-time signal based on simple voltage detection. The circuit self-regulates the switching element's off-time without requiring complex external control or adjustment mechanisms, thereby stabilizing oscillation with minimal circuit complexity.
Data Source
AI summary
A control system for a power factor correction circuit performs stabilized oscillation operation and suppresses switching frequency variation due to change of the AC power source. A control system includes a voltage error amplifier for outputting a voltage error signal obtained by amplifying a difference between a DC output voltage Vo and a command value Vref of the DC output voltage, a current command value generating circuit for outputting a current command value Vi for controlling the input current Iin, a comparator comparing an inductor current signal obtained by detecting an inductor current running in the switching element by a current detecting resistor with a magnitude of the output signal Vi from the multiplier, a timer circuit for setting an off-period of the switching element corresponding to the voltage Vd, and a reset-set type flip-flop circuit for setting an off-timing of the switching element after an elapse of the off-period.