To provide a PLL circuit and a method of control thereof which implement a wide range of changes in the oscillation frequency of a VCO while suppressing an increase in circuit scale.
A PLL circuit 1 includes a VCO 11, control logic 14 and a phase comparator 13. The VCO 11 has a variable capacitive element having a variable capacitance value depending on a potential difference between both ends, and outputs an output signal of an oscillation frequency depending on the potential difference. With a predetermined voltage applied to one end of the variable capacitive element, the control logic 14 determines a control voltage Vtc to be applied to the other end of the variable capacitive element on the basis of a frequency difference of an output signal from a reference signal. With a voltage at the other end of the variable capacitive element fixed at the control voltage Vtc determined by the control logic 14, the phase comparator 13 determines a control voltage Vta to be applied to the one end of the variable capacitive element on the basis of a phase difference of an output signal from the reference signal.