| 摘要 |
PURPOSE:To intercept a battery and prevent power consumption due to a voltage stabilizing circuit by supplying a power source to an output terminal through only a switching circuit between the battery and the output terminal upon using the battery. CONSTITUTION:Upon using a battery 21, the transistor 51 of a switching circuit 5 is put ON. The voltage of the battery 21 is supplied to an output terminal without any drop of the voltage substantially. The conduction of the transistor 41 of a voltage stabilizing circuit 4 is prevented by the balance of the value of resistance between a resistor 52 and another resistor 44 to prevent power consumption. When the plug of an AC adaptor is mounted to a power source jack 1, a first contact 12 is separated from another first contact 11. The flow of the base current Ib1 of the transistor 51 of the switching circuit 5 is stopped and the battery 21 is separated from the output terminal 3. On the other hand, a voltage from the first contact 11 is supplied to the output terminal 3 through the voltage stabilizing circuit 4 to prevent overvoltage. In this case, the conduction of the transistor 51 is prevented by the balance of said resistances the larger value of resistance of the resistor 44 is preferable upon using the AC adaptor). |
