Charge/discharge control circuit and battery assembly
View Patent ↗There is provided a charge/discharge control circuit and a battery assembly including an accurate overcurrent protecting circuit with low consumption current characteristics. The charge/discharge control circuit comprises a current protecting circuit including: a reference voltage circuit having a reference transistor for detecting overcurrent flowing through a control transistor to turn it on, and a constant current circuit; and a comparison circuit for comparing voltage on the reference voltage circuit with voltage generated by overcurrent flowing through the control transistor, wherein when no overcurrent flows, the electric current flowing through the reference voltage circuit is interrupted to reduce power consumption.
1. 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.
2. The charge/discharge control circuit according to claim 1 , wherein the overcurrent protecting circuit comprises one or both of a discharge overcurrent protecting circuit for detecting discharge overcurrent flowing through the control transistor, or a charge overcurrent protecting circuit for detecting charge overcurrent flowing through the control transistor.
3. A battery assembly comprising:
a secondary battery capable of being charged and discharged;
the control transistor of claim 1 in a charge and discharge path of the secondary battery to control charge and discharge of the secondary battery; and
the charge/discharge control circuit according to claim 1 , which controls the control transistor to control the charge and discharge of the secondary battery.
4. A battery assembly comprising:
a secondary battery capable of being charged and discharged;
the control transistor of claim 1 in a charge and discharge path of the secondary battery to control charge and discharge of the secondary battery; and
the charge/discharge control circuit according to claim 2 , which controls the control transistor to control the charge and discharge of the secondary battery.