Study on Input Power Reduction and Frequency Response Improvement of DCPT by Ripple Cancellation Circuit

A novel circuit technology for input power reduction and frequency response improvement of a DCPT was studied. First, proportionality between the DCPT output ripple and the output winding voltage ripple was proved through circuit analysis. Second, a circuit was designed which cancels the output ripple with the winding voltage ripple, and its basic operation was confirmed in experiments using a 60 Hz-drive DCPT (rated input power 80 W, natural frequency of reactor 12 kHz), Because a residual pulse voltage due to the natural oscillation of the reactor was observed in every half-cycle of the 60 Hz oscillation, a time delay of about 60 μs was added to the cancellation circuit to reduce the pulse amplitude. As a result of these modifications, the input power requirements were reduced to 1/5 that of a conventional DCPT, and a frequency response nearly equal to that of an ACPT (i.e. the reactor itself) was attained.