Application of PWM techniques to realize a 2MHz off-line switching regulator, with hybrid implementation

Abstract

A high frequency, 2Mhz, off-line switching regulator intended for applications in military use environments, has been implemented with PWM techniques. This paper describes the design trade-offs made in selecting the PWM approach for this relatively high frequency application, and provides an overview of the performance characteristics of the circuit and key critical components. This is an off-line power supply which must operate over a wide range of MIL-STD-704 aircraft prime power interface conditions. This power supply delivers three output voltages, each f u l l y regulated, at up to 50 watts total delivered power. The design will be implemented in a high density, hybrid configuration of approximately 10 watts per cubic inch, and will include the power processor and all filtering and bypass functions, except for rectification of the AC input lines, which is done external to the module. The circuits and components used to implement the power processing stage, the feedback control and stabilization network, and the overall supervisory circuit are discussed. Performance under high frequency load conditions is covered, as well as general regulator performance. A brief comparison of operating characteristics and complexity between this topology and an equivalent series resonant circuit is also given. This paper concludes with highlights of advanced packaging techniques similar to those to be used to implement this circuit in the high density configuration.