CIRCUIT FOR CONTROLLING CONSTANT POWER OF SMPS

摘要

PURPOSE: A circuit for controlling constant power of SMPS is provided to output the constant power by reducing the output voltage when the output current exceeds the predetermined range. CONSTITUTION: A circuit for controlling constant power comprises a current detecting resistor for detecting the variation of current of an output side. The current detecting resistor is positioned at a secondary feed back power line of a trans. An output current comparing portion(30) is provided to output a control signal by comparing the output current detected by the current detecting resistor with a predetermined current. A switching control portion(10) is provided to increase/decrease the duty ratio of a power switching device based on the variation of the current so as to control the constant power.