Considerations on the influence of the current ripple and switching frequency towards the differential mode EMI filter

Abstract:
With new semiconductor technologies of outstanding performance each day more accessible, higher power density converters are being developed and introduced in the market, taking advantage of the potential increase on switching frequency offered by such devices without efficiency decrease. Attempting a further inductor size decrease, its value can be reduced, consequently increasing the current ripple up to trade-off between size and magnetic losses. However, the operation with higher switching frequency yields unusual EMI issues, as the higher magnitude harmonics (1st, 2nd, etc) of the generated noise to be attenuated are located close to or within the frequency range limited by current EMC standards. The current ripple also influences the harmonic content, increasing the noise amplitude. Therefore, based on a grid-connected full-bridge inverter, this paper presents an analysis towards the influences of the current ripple and switching frequency on the overall losses, minimization possibility and EMI filter design.