Browsing by Author "Liu, Yen-Ming"

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Active-clamping single-stage ac-dc converter with the input current shaper charged in the duty-off time
(2008-04-01)
Chan, Lon-Kou
;
Liu, Yen-Ming
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Single-stage a.c.-d.c. converters employing boost-type input current shapers (ICS) usually suffer from relatively high switch current stress and line current waveform distortion caused by the voltage-follower control. To remedy these drawbacks, this paper presents a novel single-stage soft-switching a.c.-d.c. converter. Unlike the conventional single-stage designs, the proposed ICS scheme is intentionally arranged to be charged in the ditty-off time. With this design, the switch current stress in the duty-on time is greatly reduced. Moreover, this design produces a.c. modulation effect on the charging time of the ICS so that the waveforms of the average charging current and discharging current of the boost inductor can compensate each other automatically. Consequently, the input i-v curve has nearly linear relationship. In the proposed topology, an auxiliary transformer winding is employed to achieve the above functions. By programming the turns ratio between the auxiliary and secondary windings, the proposed converter can be guaranteed to comply with the IEC 1000-3-2 class D specifications at as high efficiency as possible. Experimental results, obtained front a prototype circuit with universal line input and 48 V/100 W output, are given to confirm the predicted performance.
Single-Stage Soft-Switching AC-DC Converter With Input-Current Shaping for Universal Line Applications
(2009-02-01)
Liu, Yen-Ming
;
Chang, Lon-Kou
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a novel single-stage soft-switching ac-dc converter for universal line applications is presented. Unlike the conventional single-stage designs, the proposed input-current shaping scheme is intentionally arranged to be charged in the duty-off time. With this design, the switch current stress in the duty-on time is significantly reduced. Meanwhile, this design produces ac modulation effect on the charging time of the boost inductor so that the input i-v curve drawn by the proposed converter has nearly linear relationship. Moreover, an active-clamp flyback-forward topology is used as the downstream de-de cell to alleviate voltage stress across the bulk capacitor. By deactivating the flyback subconverter and keeping the forward subconverter supplying the output power at light-load condition, the bulk-capacitor voltage can be alleviated effectively and guaranteed below 450 V in wide ranges of output load and line input (90-265 V(rms)). Experimental results, obtained from a prototype circuit with 20-V/100-W output, have verified that three achievements can be obtained simultaneously, including the compliance with the line-current harmonic regulations, the reliable alleviation of the bulk-capacitor voltage stress, and the substantially promoted conversion efficiency.