PURPOSE: To reduce loss and improve efficiency and miniaturize a device, by detecting the excess current of a chopper type switching regulator, with an output side rectification diode and a resistance connected to the diode n series.

CONSTITUTION: The output of a switching transistor (Tr1) is fed to a load 2 via a rectification diode D and a resistance R1. The voltage of the load 2 is detected by a control section 1, and the ON/OFF pulse range of the Tr1 is controlled, and output voltage is kept constant. So far as a transistor Tr2 is concerned, the value of voltage at the both ends of the diode D and the resistance R1 is applied between a base and an emitter, and load current is detected, nd when voltage BE between the base and the emitter exceeds a specified value, then the Tr2 is turned ON, and by the control section 1, the ON range of the Tr1 is diminished, and load current is diminished. By this method, the value of the resistance R1 is diminished by internal resistance, and loss is reduced, and efficiency is improved, and the device is miniaturized.