Design of a direct converter for high power RF applications

This paper presents practical results from a new type of power supply for high power RF applications for CW operation. The converter is a direct topology, utilising a high frequency resonant link and a high frequency transformer. High operating frequency reduces the transformer and filter size. Soft switching is employed to reduce losses. Two variants of this topology are presented. The first incorporates the high frequency transformer into the resonant circuit. The principle feature of this topology is that parasitic elements associated with all transformers are employed in operation of the converter. However, this requires that the circulating current in the resonant tank flows in the transformer windings. The second topology does not incorporate the transformer into the resonant circuit, therefore requires a smaller transformer. However, the topology will be affected by the parasitic elements of the transformer. Advantages of both these topologies over conventional approaches are discussed. The RF power generated by both topologies is stable and predictable, whilst reduced energy storage in filter components removes the need for crowbar circuits.