Application of RF Circuit Design Principles to Distributed Power Converters

The application of RF circuit design principles to high-frequency power converters is described. Compared to conventional converter design, emphasis is placed on obtaining sinusoidal-type waveforms (instead of rectangular-type waveforms) to minimize device switching time requirements and alleviate transforming requirements. A 25-W 48-V to 5-V dc-to-dc converter design using a 5-MHz switching frequency is presented illustrating these principles, using a Class E power amplifier, an L section impedance transformer, and a shunt-mounted harmonically tuned rectifier circuit. Computer simulation results are presented that indicate the feasibility of the proposed design approach, specify required circuit parameters and indicate that line and load regulation can be achieved with narrow-band frequency control. Experimental results on a low power 5-W, 25-V to 5-V dc-to-dc converter breadboard using a 10-MHz switching frequency with the described circuit topology are presented. An efficiency of 68 percent was obtained and load regulation by frequency control demonstrated. Inductor Q requirements limit the conversion efficiency of the proposed converter, and will probably be the limiting factor in obtaining high efficiency with similar design approaches.