Power semiconductor filter: Use of series-pass device in switching converters for input filtering

A concept called “Power Semiconductor Filter (PSF)” for performing input filtering in switching converters is proposed. The methodology is based on using a series-pass device (SPD) to control the input current waveform of the converter. The operating point of the SPD is regulated at the boundary between the active and the saturation regions by controlling the input impedance of the converter, so as to minimize the power dissipation in the SPD. The operating principle of the concept is demonstrated on a 48W, 50-80V/12V buck dc-dc converter. Investigations reveal that the PSF allows a substantial size reduction and gives competitive efficiency, as compared to passive inductor-capacitor filter. The proposed technique makes the input filtering section amenable to monolithic integration. The exploration lays a foundation for further investigation into the use of the PSF concept for other power electronic converter systems.