| 摘要 |
A switching mode power supply is described. The switching mode power supply includes a power supply unit, a mode setting unit, a feedback circuit, and a switching controller. The switching controller controls a main switch to carry out a switching operation at a predetermined duty according to feedback voltage charged in a first capacitor in the normal operation mode, and controls the main switch to repeat a switching on state and a switching off state in the standby mode. The current inputted to the switching controller varies with the operation mode. Accordingly, the minimum voltage for operating the switching controller can be maintained even if output voltage is decreased in the standby mode, and unnecessary power consumption in the switching controller can be reduced.
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