To provide a battery pack and a power supply circuit which can improve significantly the precision of a current to be cut off when they are, for instance, applied to a system using a lithium ion battery and the current is detectd by on-resistances of switching devices to cut off the current.

When a current IL is detected by on-resistances of switching devices 5 and 6 and cut off, the temperature characteristics of the on-resistances are compensated by the temperature characteristics of a reference voltage Vref side.