Analysis of the Truncation Effects and the Zero-Crossing Distortion of Critical-Mode Power-Factor-Correction Circuits

• Main Authors: Shi-Huang Tang, 唐世煌
• Other Authors: 陳德玉
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/90755097304947112072

碩士 === 國立臺灣大學 === 電機工程學研究所 === 96 === Power factor correction is almost a must nowadays for off-line switching power supplies. Among the various PFC schemes, the critical-mode (or boundary-mode or transition-mode) operation has attracted much attention due to its relative ease of control, less diode reverse-recovery problems and moderate transistor switching losses. However, there are two issues about CRM PFC circuits that deserve further investigation for further improvement. One issue is about a proposed truncated operation of the circuit to improve the light-load efficiency which is a very important consideration nowadays. The other issue is about the zero-crossing distortion of the input waveform commonly encountered in CRM PFC. In this thesis, both issues will be addressed. An analysis of the truncated CRM PFC operation was given with emphasis on the input harmonics performance degradation. Experiments were also conducted to demonstrate the efficiency improvement. An analysis was also given for the explanation of the zero-crossing distortion of the input current waveform. The power MOSFET Cds was been pinpointed as the cause of the distortion. Through the analysis, a scheme was proposed to correct the distortion. This scheme has been verified by simulations. Hardware implementation has not conducted but will be done in the future.