A High-Efficiency Single-Stage Single-Switch

A High-Efficiency Single-Stage Single-Switch - IEEE...

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Unformatted text preview: IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 13, NO. 4, JULY 1998 699 A High-Efficiency Single-Stage Single-Switch High-Power-Factor AC/DC Converter with Universal Input Jinrong Qian, Member, IEEE, and Fred C. Y. Lee, Fellow, IEEE Abstract— A single-stage single-switch power-factor-correction (PFC) ac/dc converter with universal input is presented in this paper. The PFC can be achieved based upon the charge-pump concept, and the PFC stage operates in the continuous current mode (CCM). The switch has less current and voltage stresses over a wide range of load variation so that a low-voltage rating device can be used. The presented converter features high power factor, high efficiency, and low cost. An 80-W prototype was implemented to show that it has 85% efficiency with low-voltage stress from 0.5% to 100% load variation over universal line input. Index Terms— Power converter, power factor correction. I. INTRODUCTION P OWER-FACTOR-correction (PFC) techniques have be- come attractive since several regulations have been ef- fected recently. Many PFC converters have been presented. They usually can be divided into two categories: the two-stage and single-stage approach. The two-stage approach actually includes two power conversion processes. The first stage is a PFC stage like a boost converter and followed by a dc/dc converter or dc/ac converter to tightly regulate the output voltage. This approach has good electrical characteristics of high power factor and fast output-voltage regulation. The main disadvantage is the high cost due to an increase of the device count. The single-stage approach [1]–[9] combines the PFC stage with a dc/dc converter into one stage with sharing one switch. In order to get tight output regulation, an internal energy storage capacitor is needed so that the output voltage is free of line ripple. The high power factor is usually obtained by operating the PFC stage like a boost converter in the discontinuous current mode (DCM) with constant duty-cycle control. If the dc/dc stage operates in continuous current mode (CCM) to minimize the losses, the duty ratio does not change when the load varies. Therefore, there exists power unbalance between the input and output when the load becomes light. The unbalanced power has to be stored in the bulk capacitor, which increases the bus voltage. The duty ratio has to decrease to keep the output voltage constant. As a result, input power decreases and new power balance is reached at the penalty of the high bus voltage. Thus, high-voltage stress across the bulk Manuscript received December 30, 1996; revised October 20, 1997. Rec- ommended by Associate Editor, F. D. Tan. The authors are with the Virginia Power Electronics Center, Bradley Department of Electrical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0111 USA....
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A High-Efficiency Single-Stage Single-Switch - IEEE...

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