PURPOSE: To make it possible to set a load current limit value automatically by initially setting an allowable overcurrent value by an arrangement wherein the load current of a power supply is limited below the sum of a measured load current and an allowable overcurrent based on a current limit reference signal obtained by adding a measured load current value signal to an allowable overcurrent signal.

CONSTITUTION: A current measuring circuit 1 measures the load current of a power supply. Output 11 from a current measuring circuit 1 is fed to a low pass filter 2 and the variation rate of signal is limited below a predetermined level. An adder 4 then adds an output 12 to an overcurrent limit signal 13 thus producing a current limit reference signal 14, i.e. a load current limit value for operating a current limit circuit 5. If the output 11 is larger than the reference signal 14, a comparator 3 provides a control signal 15 to the current limit circuit 5. Furthermore, the current limit circuit 5 limits the load current of power supply below the load current limit value represented by the reference signal 14.