Patent ID: 8896268

Claim:
A charge/discharge control circuit for controlling a control transistor in a current path between a secondary battery and a load or a charger to control charge/discharge of the secondary battery, the charge/discharge control circuit comprising: an overcurrent protecting circuit including, a first comparison circuit for comparing voltage, generated by electric current flowing through the control transistor, with a first reference voltage, a second reference voltage circuit for outputting a second reference voltage, wherein an on and off state of the second reference voltage circuit is controlled by output of the first comparison circuit, and the second reference voltage circuit includes a normally-off reference transistor having a gate electrode coupled to an output of the first comparison circuit and a drain connected to a constant current circuit that feeds electric current to the normally-off reference transistor, wherein the normally-off reference transistor is equivalent in temperature and gate-source voltage characteristics to the control transistor, and a second comparison circuit for comparing voltage, generated by the electric current flowing through the control transistor, with the second reference voltage, wherein the first reference voltage is lower than the second reference voltage, and when overcurrent flows through the control transistor, the normally-off reference transistor is first turned on by the output of the first comparison circuit, and when the electric current is further increased, the control transistor is turned off.