To provide a battery driving device that can effectively use a battery as a power source and suppress the consumption of the battery.

This battery driving device which drives a load 6a with electric power from the battery 1 is provided with: a step-up converter 3 that converts a voltage Vb of the battery 1 into a different voltage to supply it to the load 6a; a bus switch 4 that supplies the voltage Vb of the battery 1 directly to the load 6a; an AD converting portion 17 that detects the voltage Vb of the battery 1; a microcomputer 12 that controls the switching of the power supply to the load 6a through either the step-up converter 3 or the bus switch 4 in response to the voltage Vb of the battery 1 detected by the AD converting portion 17; and a series power source circuit 18 that, with its own output portion connected to the load 6a, outputs a voltage automatically from the output portion in such a way that a voltage value impressed to the load 6a does not become lower than a lower limit value of the input rated voltage of the load 6a.

COPYRIGHT: (C)2006,JPO&NCIPI