Optimal Lowest-Voltage-Switching for Boundary Mode Power Factor Correctors
Date Issued
2014
Date
2014
Author(s)
Cheng, Wei-Chun
Abstract
In recent years, the standard of input harmonic currents of electronic devices has been set to maintain high quality public mains power networks. The power factor correctors have become an essential part of power supply systems. The power factor correctors are mostly implemented with boundary mode switching converters because of its high efficiency. For a boundary mode converter, soft-switching techniques can be applied without additional discrete components, which minimize the switching loss of the power MOSFET. In conventional control methods, the switching timing of the power MOSFET is determined using fixed thresholds. However, for a power factor corrector, the resonant voltage and current waveforms are different in each switching cycle since its input is an AC voltage. It makes the switching timing of the power MOSFET away from the optimal timing, which increases the switching loss and the conduction loss.
Therefore, we proposed the optimal lowest-voltage-switching for boundary mode power factor correctors. Utilizing the symmetric characteristic of the resonant waveforms, the optimal switching for the power MOSFET can be realized in consideration of the gate driver delay. The proposed approach achieves optimal zero-voltage-switching or valley-switching operation automatically to minimize the switching loss. The proposed lowest-voltage-switching technique can be applied to other resonant converters as well. The detailed analyses and circuit implementations are described in this dissertation.
In order to verify the proposed methods and circuits, a 50 W boundary mode boost PFC converter with the proposed optimal switching technique has been implemented using a 0.5um N-well process. Experimental results show that the proposed approach can realize optimal soft switching, and improve the efficiency of the boost PFC converter.
Subjects
功率因數校正器
切換式電源供應器
共振式轉換器
零電壓切換
波谷切換
Type
thesis
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