POWER FACTOR COMPENSATING CIRCUIT

摘要

PURPOSE: A power factor compensating circuit is provided to stabilize a system and minimize a power consumption by making the compensating circuit operate with respect to a switching mode power supply and not operate at a standby mode. CONSTITUTION: A power supply part(100) includes a main switch(Qsw) coupled to the first coil(L11) of a primary side of a transformer(T) and performs power factor compensation when the main switch performs a switch operation by a turn-on duty ratio. A switch control part(201) include the second coil of the primary side coupled to the first coil. The switch control part receives a feedback signal from an external load supplied with a power induced at the primary side and generates the first drive high voltage by controlling a switch element so as to be switched by a predetermined duty ratio at a normal operation mode. The switch control part generates the first drive low voltage by controlling at a burst mode where the switch element repeats an on-state and an off-state by a constant ratio. An output part(500) includes a secondary coil(L12) supplied with a power from the primary side and is connected to the external load. A power factor compensation control part(300) controls the main switch and is supplied with the second drive voltage coupled with the first drive high voltage or the first drive low voltage. A drive voltage applying part(400) controls such that the second drive voltage is dropped below an operating voltage at the standby mode.