Single-stage Isolated Full-bridge Power Factor Correction Converter

The subject does research on Single-Phase Single-Stage Isolated Power-Factor-Corrected Converter. In the dissertation, status quo and trends of single-stage isolated PFC converters are presented. Puzzles or challenges such as precision of small-signal modeling, voltage of dc-link capacitor and magnetic biasing are discussed and illuminated. Converters are classified based on the factor that whether the DC-link capacitor is involved or not in the topology.In the dissertation, the basic conceptions on PFC technology are explained systematically. The properties of ideal rectifier are explored, and a model is described which is also called a loss-free resistor (LFR). Operating principle of boost PFC converter are explored and characteristics of the small-signal model are indicated. Merits and limitations of different kind converters are assessed. Some outstanding topologies are demonstrated. A Novel Zero-Voltage-Transition Full-Bridge PWM Converter with Active Clamp is presented.The new topology is based on current-fed full-bridge structure. There is no dc link capacitor problem. It is a favorable topology for isolated PFC converters in medium-high power applications field. Average current control method is adapted to achieve near unit power factor.A simple auxiliary circuit which includes two active switches provides a soft-switching condition to all semiconductor devices and voltages of them are well clamped. All the power mosfets are zero-voltage-switching(ZVS) on or zero-current-switching(ZCS) on, and all the power diodes are ZCS off. The problem of overshoot and ring induced by the transformer leakage is well resolved. EMC of the whole system is greatly optimized.The ZVS is achieved for wide line and load ranges with minimum device voltage and current stresses. The conduction loss and switching loss are minimized. A prototype was built to show the feasibility of the single stage scheme. The experiment result reveal that efficiency of the novel converter is higher than 93%(half load to full load), heat sink volume is rapidly reduced and high power density is achieved. Theoretically, the novel single-phase single-stage isolated PFC converter can uprate the power level of previous converters and is suitable for medium-high power applications.