a phase comparison circuit includes phase comparison device for generating an output signal corresponding to the difference in phase between a first input signal and a second input signal . the phase comparison device has an active mode , and a standby mode in which power consumption is reduced . a phase - difference detecting device is connected to the phase comparison device for outputting a control signal when the phase difference between the first and second input signals is smaller than a predetermined value . the phase comparison device is switched from the standby mode to the active mode in response to the control signal .