A protecting circuit monitors a voltage of a secondary battery and supplies the signal to permit a discharge to a gate terminal of a discharge control FET when the voltage is equal to or more than a lower limit value in a rated voltage range. When the discharge control FET receives this signal, it is connected and passes a discharge current. In the other cases, it shuts off the discharge current. Further, when the voltage is equal to or more than a predetermined value, a signal of a voltage of a battery voltage or more is supplied from a voltage converter to the gate terminal. When the voltage is equal to or less than an upper limit value in the rated voltage range, the protecting circuit supplies the signal to permit a charge to a gate terminal of a charge control FET. Further, when the voltage is equal to or more than a predetermined value, the voltage output from the voltage converter is supplied to the gate terminal. A battery pack in which by applying the voltage of the battery voltage or more to the gate terminal, the discharge control FET and the charge control FET are controlled and an energy loss is suppressed to the minimum is provided.
1. A battery pack having a secondary battery therein, comprising:
one or more voltage converters;
a discharge control FET to permit or shut off a discharge of said secondary battery in accordance with a signal which is supplied to a gate terminal of said discharge control FET;
a protecting circuit to permit output of the signal that permits the discharge to said gate terminal when a voltage of said secondary battery is equal to or more than a lower limit value in a rated voltage range of said secondary battery;
an output terminal of said one or more voltage converters connected to said gate terminal;
a resistor connected between an output terminal of said protecting circuit from which said signal is outputted and the gate terminal of said discharge control FET;
an anode of a diode connected to the output terminal of said one or more voltage converters; and
a cathode connected to the gate terminal of said discharge control FET.
2. A battery pack having a secondary battery therein, comprising:
one or more voltage converters;
a discharge control FET to permit or shut off a discharge of said secondary battery in accordance with a signal which is supplied to a gate terminal of said discharge control FET;
a protecting circuit to permit output of the signal that permits the discharge to said gate terminal when a voltage of said secondary battery is equal to or more than a lower limit value in a rated voltage range of said secondary battery;
an output terminal of said one or more voltage converters connected to said gate terminal;
an anode of a first diode connected to an output terminal of said protecting circuit;
a cathode connected to the gate terminal of said discharge control FET;
an anode of a second diode connected to the output terminal of said one or more voltage converters;
a cathode connected to the gate terminal of said discharge control FET; and
a resistor connected between the gate terminal of said discharge control FET and a source terminal of said discharge control FET.