ABSTRACT
Nowadays the ac/dc converters are widely used in many off-line power supplies. The increasing amount urges researchers to develop more efficient, smaller size, and low cost ac/dc converters. Traditionally, an ac/dc converter consists of a diode-bridge rectifier followed by a bulky capacitor and a high-frequency dc/dc converter. This kind of converter inevitably introduces highly distorted input current, resulting in a large amount of harmonics and a low power factor. paper proposes a single-stage high-power-factor ac/dc converter with symmetrical topology. The circuit topology is derived from the integration of two buck-boost power-factor-correction (PFC) converters and a full-bridge series-resonant dc/dc converter. Switch-utilization factor is improved by using two active switches to serve in the PFC circuits. A high power factor at the input line is assured by operating the buck-boost converters at discontinuous conduction mode. With symmetrical operation and elaborately designed circuit parameters, zero-voltage-switching on all the active power switches of the converter can be retained to achieve high circuit efficiency. The operation modes and design equations for the circuit parameters are proposed.
Thursday 16 June 2011
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