PURPOSE: To realize positive charging of battery or power supply to machine by interrupting output and producing an alarm upon detection of abnormality in the supply voltage or current under any one of charging mode or adapter mode.

CONSTITUTION: If a battery is loaded between output terminals through insufficient contact at the time of charging, charging voltage increases over a correct level. That state is detected through an overvoltage circuit 9a. If a control circuit 18 fails under adapter mode, supply voltage increases over an appropriate level. That state is detected through the overvoltage circuit 9a by detecting a voltage higher than a level set by a setting circuit 13 for a predetermined time. If the adapter current is sustained higher than a level set by a setting circuit 12 for a predetermined time, that state is detected through an overcurrent detecting circuit 8. Upon detection of such abnormality, the control circuit 18 controls an output interrupting circuit 19 to interrupt power supply and to produce an alarm from an alarm circuit 20.