Patent ID: 7365998

Claim:
An apparatus, comprising: an unregulated isolated DC/DC converter configured to receive an input signal and to provide an output signal; and a ripple control circuit coupled to the unregulated isolated DC/DC converter, wherein the ripple control circuit is configured to reduce an amount of low frequency ripple transferred to the output signal from the input signal, wherein the ripple control circuit comprises: a filter circuit coupled to the output signal and configured to pass a filtered signal having a low frequency ripple component; a first summing circuit coupled to receive the filtered signal from the filter circuit and configured to subtract the filtered signal from a first reference signal and provide an intermediate signal; a compensator circuit coupled to receive the intermediate signal and configured to regulate a low frequency AC ripple content in the intermediate signal and provide a compensated signal; and a second summing circuit coupled between the compensator circuit and the unregulated isolated DC/DC converter and configured to add the compensated signal to a second reference signal and provide a resulting control signal to the unregulated isolated DC/DC converter.