A -50 V/100 Amp high frequency switch mode rectifier unit and its application to digital switching system

The authors describe the development of a 20 kW off-line switch mode rectifier system to power a large-capacity digital switching system which is under development. The rectifier unit uses a double forward circuit topology composed of four power MOSFET modules that are controlled by pulse width modulation; this makes it possible to reduce the size and weight of magnetic components. The unit is convection-cooled and uses isolated power modules mounted on one end of a heat-pipe-type heatsink. A well-designed heatsink along with a careful choice of parts and components yields an overall efficiency of typically 90%. Four rectifier units are housed in a rack cabinet, together with a total control unit which includes distribution, protection, control, and alarm functions. This rack cabinet can be paralleled in modular fashion to any required power level, and installed along with the digital switching system in a switch room. This eliminates the need for separate power rooms and distribution busbar layouts