Abstract: A phase-locked loop circuit comprises first and second charge pumps which apply charge and discharge voltages to a control voltage generator. The control voltage generator applies a control voltage which is dependent on the charge and discharge voltages to a voltage controlled oscillator. The voltage controlled oscillator generates an oscillation frequency dependent on the control voltage. The oscillation frequency is compared with a reference frequency to detect a difference therebetween. The first charge pump supplies a charge or discharge voltage to the control voltage generator intermittently for a first period, and the second charge pump, in parallel with the first charge pump, supplies a charge or discharge voltage to the control voltage generator continually for a second period subsequently to the first period, so that a time by which the difference becomes zero is shortened by use of the second charge pump as compared to a case where the first charge pump is only used.

Abstract: An automatic frequency sweeping method for controlling frequency synthesizing type autotuners for broadcasting receivers comprises a first intermediate frequency counting method in which the intermediate frequency is counted for a relatively short first time and the presence or absence of the received signal is judged in a first range having a relatively wide intermediate frequency width and a second intermediate frequency counting method in which the intermediate frequency is counted for a second time longer than the first time and the presence or absence of the received signal is judged in a second range having a intermediate frequency width narrower than that of the first range. Thus, a high speed frequency sweeping is ordinarily executed by using the first intermediate frequency counting method, and when the presence of the received signal is judged in the first intermediate frequency counting method, a more precise judgement is made in accordance with the second intermediate frequency counting method.