Abstract: A power supply circuit that withstands voltages greater than or equal to a voltage capacity and prevents an increase in circuit area and manufacturing costs. The power supply circuit includes a first transistor for receiving a DC voltage and generating an internal power supply voltage. A clamp circuit is connected to the first transistor. The clamp circuit is activated when the DC current voltage is an excessive voltage to clamp the internal power supply voltage at a predetermined voltage that is less than the excessive voltage. A gate voltage control circuit is connected to the first transistor and the clamp circuit to supply the gate of the transistor with a control voltage so that the internal power supply voltage decreases when the clamp circuit is activated.

Abstract: A power supply circuit that withstands voltages greater than or equal to a voltage capacity and prevents an increase in circuit area and manufacturing costs. The power supply circuit includes a first transistor for receiving a DC voltage and generating an internal power supply voltage. A clamp circuit is connected to the first transistor. The clamp circuit is activated when the DC current voltage is an excessive voltage to clamp the internal power supply voltage at a predetermined voltage that is less than the excessive voltage. A gate voltage control circuit is connected to the first transistor and the clamp circuit to supply the gate of the transistor with a control voltage so that the internal power supply voltage decreases when the clamp circuit is activated.

Abstract: A voltage-controlled oscillator outputs a signal of a frequency controlled by a voltage of an input signal, the output signal being used for feedback as an internal change signal. A phase comparator detects a phase difference between the internal change signal and an external reference signal. A charge pump outputs the signal having the voltage based on the phase difference to the voltage-controlled oscillator via a low-pass filter. The charge pump is controlled so that the voltage of the signal input to voltage-controlled oscillator becomes a voltage for oscillating a lock frequency. When instruction of changing the lock frequency is input, and/or a phase inversion of the internal change signal used for feedback in a locking-up operation rendered in response to the instructions is detected, a control is made such that an absolute value of an output current of the charge pump is increased.

Abstract: A voltage-controlled oscillator outputs a signal of a frequency controlled by a voltage of an input signal, the output signal being used for feedback as an internal change signal. A phase comparator detects a phase difference between the internal change signal and an external reference signal.- A charge pump outputs the signal having the voltage based on the phase difference to the voltage-controlled oscillator via a low-pass filter. The charge pump is controlled so that the voltage of the signal input to voltage-controlled oscillator becomes a voltage for oscillating a lock frequency. When instruction of changing the lock frequency is input, and/or a phase inversion of the internal change signal used for feedback in a locking-up operation rendered in response to the instructions is detected, a control is made such that an absolute value of an output current of the charge pump is increased.