The development of power electronics make it possible to fabricate a power system with high power density, high efficiency, fast dynamic response, high power quality, and low cost. A typical power converter consists of a power factor corrector (PFC) which converts the AC main voltage into a fixed DC voltage, followed by DC-DC converter or a DC-AC inverter. Normally, two power processing stages are used, and two controllers are adopted, which results in lower power efficiency and high cost. A single-stage power supply will have only one power processing stage, hence the power efficiency and power density are improved. Higher switching frequency is preferred because of the increased power efficiency and the reduced size of the power supply. The soft-switching technique is being utilized in the more commercial power supplies.; This dissertation first presents a novel resonant-boost topology to convert AC main voltage to DC voltage with low current distortion and a high power factor. The high-frequency current source set up by the resonant inductor, input capacitors, and switches helps shape the input current so it follows the voltage. The concept of single-stage power originally proposed for a single is extended to the three-phase case. A single-stage AC-DC-DC converter is presented to convert a three-phase AC voltage into low, adjustable DC voltage. Two control variables, switching frequency and duty cycle, are used to provide stable operation. By changing the control scheme to the full bridge, a new AC-DC-AC converter is explored to convert three-phase AC voltage into a single phase AC voltage with variable frequency. The converter can be used in the ultrasonic instrumentation and induction heating. This dissertation will present a new application of a Power MOSFET where electronic load is developed by using power devices. Over-current protection and adequate cooling are provided to ensure the reliability of the electronic load.
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