| 摘要 |
PURPOSE: A SMPS(switching mode power supply) having a low voltage protection circuit is provided to protect a SMPS and circuit components from the over current caused by the low AC input voltage by including simple configuration protection circuit. CONSTITUTION: A SMPS having a low voltage protection circuit comprises a first rectification and smoothing circuit, a driving power, a PWM controller, a switching transistor, a switching transformer, a second rectification and smoothing circuit, a third rectification and smoothing circuit, a constant voltage circuit, a protection circuit(80,90) for being applied the output voltage of the first rectification and smoothing circuit and controlling not to drive the driving power if the output voltage of the first rectification and smoothing circuit is less than the set value, an input rectification and smoothing unit(10) for smoothing and rectifying the input AC voltage, a first voltage detecting unit for outputting a reset signal if the output voltage of the input rectification and smoothing unit is less than the set value, a constant controller for outputting a control signal to increase the output voltage of the constant voltage unit on applying the reset signal, and a feedback controller.
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