Conducted EMI Suppression Using Power Semiconductor Filter With Dynamic Ramp Modulation to Regulate Series Pass Device Voltage

The concept of the power semiconductor filter (PSF) is based on utilizing a series pass device (SPD) operated in linear mode to regulate the input current of switching converters. In order to avoid input current oscillation, a fixed-frequency dynamic ramp modulator has been proposed. It is based on operating the converter at a fixed switching frequency and setting the switching frequency away from the grid-side resonant frequency. Regardless of the input variation, the voltage across the SPD is also maintained at a low level by a dynamic ramp, resulting in low power dissipation in the SPD. An optimized fast-current regulation circuit is designed to achieve high conducted electromagnetic interference (EMI) suppression. A method to predict the EMI suppression performance of the PSF has been proposed. Furthermore, the ground loop inductance in the fast-current regulation circuit has been analyzed, and PCB layout guidelines have been given to mitigate the performance degradation of the PSF caused by this inductance. A 100-W, 90-264 Vac/200 Vdc buck-boost PFC prototype has been built and evaluated; the prototype with the PSF satisfies EMC standard EE55015 class B in the whole range of 150kHz to 30MHz.