Patent ID: 7417413

Claim:
A self-oscillation ripple converter comprising: a switching element arranged to switch an input direct-current voltage; a choke coil and a smoothing capacitor arranged to smooth the switched direct-current voltage; a flywheel device arranged to cause a current to flow through the choke coil when the switching element is turned off; and a control circuit arranged to perform feedback control as to whether the switching element is on or off according to ripple in an output voltage; wherein the control circuit includes a waveform converter arranged to convert a waveform of a signal that is proportional to the output voltage and output a resulting signal, and a comparing unit arranged to compare the output of the waveform converter with a reference voltage and output a result of the comparison to the switching element; the waveform converter includes a current detector arranged to detect a waveform of the current that flows through the choke coil and output an output signal that is proportional to the waveform of the current, and a signal processor arranged to process the signal that is proportional to the output voltage according to the output signal of the current detector; the current detector uses a resistive component of the choke coil; the waveform converter includes a plurality of resistors and a plurality of capacitors; and at least one of the plurality of resistors and at least one of the plurality of capacitors of the waveform converter are connected in parallel with the choke coil.