Patent ID: 7545127

Claim:
A power supply controller disposed between a power source and a load for controlling power supply from said power source to said load, said power supply controller comprising: a semiconductor switching element disposed on a current supply line connected between said power source and said load; and a PWM signal generator including an oscillator circuit for outputting an oscillator signal, and further including a comparator circuit for receiving said oscillator signal and a reference signal and outputting an output signal that is level-inverted according to a magnitude relation between a level of said oscillator signal and a level of said reference signal, said PWM signal generator being configured to provide an output signal of a pulse train from said comparator circuit, as a PWM signal for pulse width modulation control, to said semiconductor switching element in order to cause ON/OFF operation, wherein said oscillator circuit includes: a parallel circuit having a first resistive element and a capacitor which are arranged parallel to each other; a first switching element disposed on a path of a charging current for charging said capacitor; a charge/discharge control circuit for turning said first switching element from ON to OFF when a charging voltage for said capacitor reaches a first voltage that changes depending on a power supply voltage of said power source, and for turning said first switching element from OFF to ON when said charging voltage is the same as a second voltage that changes depending on said power supply voltage; and a current changing circuit for changing said charging current depending on said power supply voltage.