| 摘要 |
A control circuit for selectively allowing a backup battery to be physically connected to a load without being electrically connected to the load includes a bistable multivibrator circuit, a power-to-load switching circuit connected to the multivibrator circuit, a delay circuit and a sleep state switching circuit. The multivibrator circuit is in a first sleep state when the backup battery is connected to the control circuit but no voltage is supplied to the control circuit from the power supply. Under these circumstances, the control circuit provides no power supply voltage or backup battery voltage to the load. The multivibrator circuit changes to a second state from the first state when a power supply voltage is provided to the control circuit after the multivibrator circuit is already in the first state. Then, the control circuit will provide either the power supply voltage or the backup battery voltage to the load. The multivibrator circuit remains in the second state unless it receives a signal from the sleep state switching circuit which places it back into the first sleep state.
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