| 摘要 |
A switch-mode power supply for selectively providing power from a main power source and a standby power source to an electronic device is provided. The switch-mode power supply includes a signal input, a first transistor, a second transistor, a driving circuit, and a switching circuit. The signal input is used for receiving a control signal. The driving circuit and switching circuit connect the signal input to the gate of the second transistor in series. When the driving circuit detects the first transistor is switched off, the gate of the second transistor is immediately pulled up to open the second transistor, and when the driving circuit detects the first transistor is switched on, the gate of the second transistor is immediately pulled down to close the second transistor.
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