A low noise, multi-output and multi-resonant flyback power supply for television application

This paper describes the analysis and design of a multi-output power supply which employs a multi-resonant flyback converter. Due to the multiple resonances, voltage and current waveforms present in the converter are quasi-sine wave. As a result both conducted and radiated EMI associated with high dv/dt and di/dt in conventional PWM TV power supplies are reduced. Analysis of the converter circuit based on the normalized state-plane approach is presented and the design information is derived. A design example as well as computer simulations are presented. A prototype of the multi-resonant flyback converter is implemented and open-loop measurements are presented. This converter topology can be advantageously utilized where low noise performance is required as in power supplies for video, telecommunication or audio equipment. Its main advantages are related to its simple structure and control. Large voltage stresses in the switching transistor and wide range of switching frequency variation are drawbacks of the converter.