Patent ID: 7750614

Claim:
A switching regulator for inputting a power source, supplying output power to an external circuit, and adjusting an output voltage supplied to the external circuit to a target voltage, comprising: a switching regulator circuit having a coil that receives current from the power source and accumulates energy, a first transistor that is connected to one end of the coil and is turned ON when energy accumulates in the coil, and a second transistor connected to one end of the coil and is turned ON when output power is supplied to an external circuit; a feedback circuit that receives the output voltage of the switching regulator circuit, and outputs a control pulse signal at a frequency in accordance with the received output voltage; a PLL circuit unit having a PLL circuit that receives the control pulse signal from the feedback circuit, receives a first control signal inputted to the first transistor, and generates a PLL output pulse having a frequency in accordance with a phase difference between the two received signals, and a first control signal generating circuit that is controlled by the rise and fall of the PLL output pulse and the signal of one end of the coil and outputs the first control signal for controlling a conduction of the first transistor; a drive circuit that outputs a second control signal that controls a conduction of the second transistor; and a control circuit that monitors a period of the PLL output pulse and a period of the control pulse signal, and supplies a timing control signal to the drive circuit to variably control OFF timing of the second transistor by the second control signal when a difference of not less than a predetermined reference value is generated between the period of the PLL output pulse and the period of the control pulse signal, wherein the control circuit supplies a reset signal to the PLL circuit to reset the PLL circuit when a difference of not less than the predetermined reference value is generated between the period of the PLL output pulse and the period of the control pulse signal.