| Abstract |
High-frequency DC-DC converters are nowadays widely used in a diversity of power electronic applications. High-operating frequencies, entail a reduction in size of the passive components, such as inductors, capacitors and power transformers. By moving to higher operating frequencies with conventional hard-switching (square-current waveforms) topologies, the transistor switching losses increase at both turn-on and turn-off. High-dissipation spikes occur more often and as a result the average transistor losses are increased. Circuit parasitics such as semiconductor junction capacitance, transformer leakage inductance and winding capacitance, are major factors hindering high-frequency operation of the conventional hard-switched PWM converters. Lower switching losses can be achieved by associating a resonating L-C tank. Current and/or voltage waveforms become more or less sinusoidal and with a proper control strategy, the switching losses can be dramatically reduced. This paper is reffered to high-power aplications. High-voltage input of some tens of KV is considered on the primary side meanwhile high-current of some hundreds of ampere is considered on the secondary side. The operating frequency is in the rate of some KHz and the power rating is in the scale of some MW. The major objective of this paper is to propose alternatives with lower production cost and with better operating characteristics compared with the conventional configurations. The scope of this paper is to identify the optimum topologies and evaluate them taking into consideration their operational behaviour and the component stress parameters as obtained by simulations and in some cases by laboratory measurements. |
