A novel technique for smoothing DC ripple in rectifier circuits

If smooth DC is required from a rectifier, an output filter is needed. This normally consists of a series inductance and shunt capacitor. The author suggests a filter which offers certain advantages over the conventional circuit. The smoothing inductance is retained, but the capacitor is connected in parallel with the inductance. The capacitor varies continuously with time, this gives the filter the property that it can be tuned to more than one frequency simultaneously and so can act as a high impedance to several harmonics driven by the AC voltage drops across the inductance. An analysis of the system is presented together with theoretical predictions supported by measured results from an experimental system