| 摘要 |
A switching mode power supply is provided to protect an electronic circuit by quickly detecting a short-circuit state at an output stage by using a duty ratio of a main switch and a feedback voltage. A switching mode power supply includes a power supply unit(100), a feedback circuit unit(300), and a switching controller(400). The power supply unit includes a main switch which is coupled with a primary coil of a transformer. The power supply unit supplies power to a secondary portion of the transformer according to an operation of the main switch. The feedback circuit unit generates a feedback voltage corresponding to an output voltage from the secondary portion of the transformer. The switching controller compares a first voltage with a first reference voltage and selectively turns off the main switch based on the compared result. The first voltage corresponds to a current which flows through the main switch. The first reference voltage corresponds to the feedback voltage. The main switch is turned off, when the feedback voltage has a level higher than a second reference voltage and a duty ratio of the main switch is smaller than a reference value.
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