Patent ID: 7319311

Claim:
A switching regulator that is a step-down switching regulator for converting a voltage applied on an input terminal to a predetermined voltage and outputting the predetermined voltage from an output terminal, said switching regulator comprising: a switching transistor formed from a PMOS transistor configured to switch ON or switch OFF output of the input voltage according to a control signal input to a control electrode; a smoothing circuit configured to smooth the output voltage from the switching transistor and output the smoothed voltage to the output terminal; a selection circuit configured to control connection of a substrate gate of the switching transistor according to the input control signal; and a switching transistor control circuit configured to control a switching operation of the switching transistor so that the voltage output from the output terminal becomes the predetermined voltage; wherein the selection circuit connects the substrate gate to a drain of the switching transistor when the voltage on the input terminal is less than or equal to the voltage on the output terminal, and connects the substrate gate to a source of the switching transistor when the voltage on the input terminal is greater than the voltage on the output terminal.