Development and testing of a high voltage direct converter for high power RF applications

This paper is concerned with the development of a novel direct power converter for high energy physics CW applications. The converter consists of a direct (matrix) converter driving a high frequency resonant link. Operation at high frequency reduces transformer and filter size. The high frequency output is used to excite a resonant tank at its resonant frequency. Losses are minimised by switching at zero current. A high voltage, high frequency transformer is used to step up to the required voltage. The transformer is incorporated into the resonant circuit and uses the latest nano-crystalline materials to further reduce losses. Consequently design of this transformer to provide VA rating, dielectric strength and resonant operation is non-trivial. The RF supply generated is stable and predictable at 20 kV DC, whilst the reduced energy storage removes the need for crowbar circuits. Potential benefits of this converter when compared to conventional approaches are discussed. These include reduced energy storage, reduced size, and reduced turn on time. Simulation results are presented along with output practical results obtained from a prototype (16 kW) converter.