The power supply unit is provided with a power supply circuit adapted to generate
an output voltage in accord with an instruction voltage, an output condenser Co
connected to the output end of the power supply circuit, and an auxiliary output
voltage setting circuit adapted to compare the instruction voltage and the output
voltage and to cause the output condenser to discharge its electric charge when
the instruction voltage becomes lower than the output voltage. Because of the auxiliary
output voltage setting circuit, the power supply circuit quickly generates an output
voltage in accord with the instruction voltage if the instruction voltage is lowered.
