This patent applications describes several methodologies of decreasing the size of the input bulk capacitor, of increasing the power factor and reducing the RMS current through the input bulk capacitor. Some of these methodologies do not require any hardware change from the conventional AC -DC adapters and all is accomplished just through the modulation of the input current drawn by the isolated DC-DC converter. Others methodologies described in this patent application do require small changes in the hardware and that will amplify the effect of current modulation in reduction of the input bulk capacitor and will significantly improve the power factor.