<p>Disclosed is a DC-DC converter using an insulating transformer, the converter including means that reduces/mitigates electromagnetic noise due to voltage/current harmonics, without magnetically saturating the insulating transformer. In order to realize the above, a DC power supply of this invention is constructed so that a pulse turn-on duration in an output voltage waveform of a DC-AC power conversion circuit is controlled to a value corresponding to a DC voltage of a DC voltage source, and so that a switching period in the output voltage waveform of the DC-AC power conversion circuit changes in accordance with a predetermined time-series signal.</p>
