PROTECTION CIRCUIT FOR BATTERY AND POWER SUPPLY DEVICE PROVIDED WITH SAID PROTECTION CIRCUIT

A protection circuit for a battery includes a discharge FET, a control circuit, a first small-signal FET, and a second small-signal FET. The discharge FET connected in series to a battery interrupts an electric current. The control circuit switches on or off the discharge FET. The first small-signal FET connected in parallel between a gate (G) and a source (S) of the discharge FET is switched to an ON state, to set a gate voltage of the discharge FET to an OFF-state voltage. The second small-signal FET connected in parallel between G and S of the discharge FET detects a voltage between a drain (D) and S of the discharge FET. When the voltage between D and S of the discharge FET exceeds a preset voltage, the second small-signal FET is switched to an ON state to set the gate voltage of the discharge FET to the OFF-state voltage.