Integration of a series-pass device into switched-mode power converters for input harmonics filtering

A concept called the power semiconductor filter (PSF) is presented in this paper. It is used to perform input harmonics filtering for switched-mode power converters. The realisation of this concept is based on connecting a series-pass device (SPD) in series with the input of the converter, so that the input current of the entire system can be programmed by the SPD. The power dissipation of the SPD is maintained at a low level through a feedback mechanism that adjusts the input impedance of the converter and makes the voltage across the SPD small. The proposed concept has been applied to two applications: a 75W, 90V to 140V/24V classical buck converter and a 100W, 90V to 265V/400V power factor corrector (PFC). The results show that the PSF concept can significantly reduce the input current harmonics and improve the power factor with a conversion efficiency comparable to traditional passive filters. The major advantages of the PSF are that the filter section is amenable to monolithic integration and that the system will have a high power density.