| 摘要 |
A battery pack BP is constructed by terminals T1, T2, and T3, a detecting circuit 1, a signal generating circuit 2, a temperature, voltage, and current detecting circuit 3, a switching circuit SW, and a secondary battery BT. An external signal generating unit 4 is connected to the terminals T1 and T2. An external signal generating unit 5 is connected to the terminals T2 and T3. The detecting circuit 1 detects that the external signal generating unit 4 or 5 has been connected. The on/off operations of the switching circuit SW are controlled in accordance with a detection result. The temperature, voltage, and current detecting circuit 3 detects a temperature of the battery pack BP and a terminal voltage and a current of the secondary battery BT. The on/off operations of the switching circuit SW are controlled on the basis of the detected temperature, voltage, and current. A signal is supplied to the signal generating circuit 2 on the basis of the detected temperature, voltage, and current. In the signal generating circuit 2, a signal is supplied to an electronic apparatus connected through the terminal T2 on the basis of the supplied signal. A load 105 of the electronic apparatus is connected to terminals T21 and T23. A power source unit 106 of a power source which is obtained from a charging device is connected to terminals T22 and T23. The secondary battery BT and switching circuit SW are serially connected between the terminals T21 and T23. In a power supply circuit 101, the power source supplied from the power source unit 106 through the terminal T22 can be supplied as a constant voltage and a constant current to a control circuit 102. A signal detecting circuit 103detects the voltage and current of the power source which is supplied from the power source unit 106 through the terminal T22. The detected voltage and current are supplied from the signal detecting circuit 103 to a signal circuit 104. The signal circuit 104 supplies a signal for forming the signal to the control circuit 102 in accordance with the detected voltage and current. The control circuit 102 controls the switching circuit SW in accordance with the signal from the signal circuit 104.
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