Interleaved PFC Control Circuit Light Load Switching Loss
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Solution Overview
Problem
Conventional interleaved PFC power converters with master/slave switching control circuits face challenges in reducing switching loss, especially at light loads, which affects system efficacy and efficiency.
Innovation Solution
A control circuit with a slave reference signal generator is introduced to gradually reduce the switching frequency of the second switch controlled by the slave switching control circuit when the load is in the hysteresis range of a light load, thereby reducing switching loss and enhancing efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the slave switching control circuit operates at the same switching frequency as the master switching control circuit, then the power converter maintains stable operation, but switching loss increases at light loads reducing system efficacy
Solution Approach 1:
The slave switching control circuit dynamically adjusts its switching frequency based on load conditions. When the load is light, the slave switching frequency is reduced or stopped, while the master switching control circuit continues to operate at a higher frequency, thereby reducing switching loss while maintaining stable operation through the master circuit's continued activity.
2Productivity
If the slave switching control circuit operates at high frequency, then power conversion efficiency is maintained under heavy load, but switching loss increases at light load conditions
Solution Approach 1:
The system changes the operating parameters (switching frequency) of the slave switching control circuit based on load conditions. Under heavy load, the slave circuit operates at high frequency to maintain power conversion efficiency. Under light load, the switching frequency is reduced or stopped, thereby reducing switching loss while the master circuit ensures continuous operation.
3Power
If both master and slave switching control circuits operate simultaneously at full frequency, then the power converter handles full load capacity, but switching loss doubles compared to single circuit operation
Solution Approach 1:
The slave switching control circuit operates partially (at reduced frequency or stopped) instead of at full frequency, especially under light load conditions. This partial operation reduces switching loss significantly while the master switching control circuit compensates to maintain the required power handling capacity.
Data Source
AI summary
A control circuit of an interleaved PFC power converter according to the present invention comprises a master switching control circuit, a slave switching control circuit, and a slave reference signal generator. The master switching control circuit generates a control signal and a first switching signal in response to an input voltage and a feedback signal. The first switching signal is utilized to control a first switch of the PFC power converter. The slave reference signal generator generates a slave control signal in response to a load condition of the PFC power converter and the control signal. The slave switching control circuit generates a second switching signal in response to the slave control signal. The slave control signal is utilized to control a second switch of the PFC power converter. The slave reference signal generator adjusts the control signal in response to the load condition for generating the slave control signal correspondingly. The slave control signal drives the slave switching control circuit to adjust the switching frequency of the second switch for reducing the switching loss.