Accumulation and emission of energy in and from a coil having an intermediate
tap is controlled by switching a DC input voltage from a DC power source on and
off. Controlled voltages generated at a plurality of terminals are rectified and
smoothed to output a plurality of DC output voltages. Connection to a reference
voltage is controlled such that the voltages generated at the plurality of terminals
are not dependent on the DC input voltage during the on-off switching. Therefore,
a switching power supply unit is provided in which a coil having an intermediate
tap is used to allow a simple configuration, to convert a DC input voltage into
a plurality of DC output voltages with high efficiency, and to achieve compactness.
