To generate a reference signal at low cost for control over the periodic signal.

A reference signal generation part generates a one-shot signal V1 synchronized with a fall of a pulse signal VO, generates a delay signal which is delayed in synchronism with a fall of the signal V1, and generates a saw-tooth integral signal V4 which is reset each time the signal V1 falls. The peak value of an inverted signal V5 is sampled and held by using the signal V1 as a control signal to generate a sample hold signal V6, and the reciprocal of the sample hold signal V6 is operated to generate an F/V conversion signal V7 which is proportional to the frequency of the signal V1. The F/V conversion signal V7 is generated into a triangular wave signal V8 by a triangular wave generation part 38 through integration based upon the signal V1 as the control signal. The signal V8 after being shifted by Vref/2 is made into a sine wave signal V10 by a sine wave generation part 40 by the polygonal approximation of the triangular wave signal.