Output power control in a power combiner with class-DE amplifiers

Output power of transistorised high-power high-frequency converters can be controlled utilising their specific structure consisting of a set of amplifiers the power of which is combined. The output power of such a converter can be controlled by varying the number of combined amplifiers versus the control signal. In the controlled power-combining network there can be used class-DE power amplifiers operating in zero-voltage-switching conditions, which assures high efficiency for any nonzero output power. The paper presents a theoretical analysis for a power-combining converter with class-DE amplifiers and experimental results obtained for a five-stage 500kHz/700W laboratory model. Advantages and limitations of the power-control method are also discussed.