Active filter circuit supporting or replacing smoothing capacitor for DC power supply

摘要

An active filter circuit for suppressing harmonics, especially for supporting the action of a smoothing capacitor of DC supply works as a step-down voltage converter (t2,d1) when the alternating component of the voltage exceeds a reference voltage and as a step-up voltage converter (t1,d2) when the reference is not exceeded. The circuit comprises two controlled electronic switches in series. One switch is in parallel with a storage unit formed by an inductance (ls) in series with a capacitance (cs). A charging capacitor (cl) is in parallel to the combined switch path. There is a control unit (st) for the antiphase signals for the switches.