a ripple converter includes a transistor for switching an input direct - current voltage , a choke coil and a smoothing capacitor for smoothing the switched direct - current voltage , a flywheel diode for causing a current to flow through the choke coil when the transistor is turned off , and a comparing unit for controlling the on / off of the transistor according to ripple in an output voltage . in the ripple converter , a waveform converter is provided on a connecting path between an output terminal and a non - inverting input terminal of a comparator in the comparing unit . a result of converting the waveform of the output voltage is compared with a reference voltage , and a result of the comparison is fed back to the transistor .