| 摘要 |
A charge/discharge protection circuit and a power supply unit are provided to control charge/discharge of a charger by automatically detecting the connection of a load or a charger even though a secondary battery, the load, or the charger is cut by a double-way semiconductor switching device. A charge/discharge protection circuit includes a double-way semiconductor switching device(1), and a charge/discharge controlling circuit(5). The double-way semiconductor switching device(1) is inserted between an external terminal and a secondary battery(12). The charge/discharge controlling circuit(5) monitors the voltage of the secondary battery(12), and controls the charge/discharge of the secondary battery(12) by switching on and off the double-way semiconductor switching device(1). The charge/discharge controlling circuit includes a first terminal(2) connected to the double-way semiconductor switching device, and a second terminal(3) which monitors which of a charger or a load(4) is connected to the external terminal.
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