Patent ID: 6462970
Filing Date: 2002-10-08
Classification: H02M,Y02B

Abstract:
An SMPS protection circuit in an electronic appliance, comprising:a power supply section for receiving and converting an AC voltage to a driving voltage to output the driving voltage; a pulse generating section for receiving the driving voltage outputted by the power supply section and generating pulses of a predetermined frequency; a frequency oscillating section for providing a time constant for setting the frequency of the pulses from the pulse generating section; an SMPS transformer having a primary winding for applying an input DC power thereto, and a secondary winding for inducing an AC power therein; a switching section for switching the DC voltage inputted to the primary winding in accordance with the pulses generated from the pulse generating section; an output rectifying section for rectifying the output DC power of the SMPS transformer, and supplying the rectified power to a load; an output current detecting section for outputting a predetermined signal corresponding to a difference between the DC power source outputted from the output rectifying section and the voltage descended due to the load; an output current feedback section for outputting a voltage corresponding to the predetermined signal outputted from the output current detecting section; a frequency down section for reducing the output power of the SMPS transformer by downing the frequency of the output pulses from the pulse generating section through variation of the time constant of the frequency oscillating section, if the voltage outputted from the output current feedback section is within a first set voltage range representing that the voltage outputted from the output current feedback section is in a light load region; and a power intercepting section connected between an output terminal of the driving voltage of the power supply section and the pulse generating section for ceasing operation of the SMPS transformer by ceasing operation of the pulse generating section through by-passing the driving voltage of the pulse generating section.