PURPOSE:To obtain an output of 12V battery specification (8-16V) from an input voltage of 24V battery specification (16-32V) by providing the 1st and the 2nd resistors for voltage reduction and turning on and off the current flowing through the 2nd resistor. CONSTITUTION:When the input voltage is at 16V, a switch circuit 3 is on and the resistors 1 and 2 are inserted between an input and an output in prallel. When the resistance value of the resistors 1 and 2 is R, resistance R/2 is provided between the input and output. At this time, when the input voltage Vin rises, an output voltage Vout rises and attains to 16V at the input voltage of 24V. Then, the resistors 401 and 402 and a Zenor voltage are set so that a Zener diode 403 turns on at said time, and consequently a transistor (TR) 405 turns on and a TR301 turns off. At this time, the resistance value between the input and output is only R by the resistaor 1 and the output voltage drops to 8V and reaches the output voltage 16V at the input of 32V.