| 摘要 |
PURPOSE: A burst mode switching mode power supply is provided to reduce power consumption during the standby mode, and costs by eliminating the necessity of using a photo-coupler required for the control of the burst mode. CONSTITUTION: A burst mode switching mode power supply comprises a power supply unit(100) including a main switch(Qsw) coupled to a primary coil(L1) of a transformer, wherein the main switch performs a switching operation at a predetermined duty during a normal operation mode, and the main switch does not perform a switching operation for a first section and performs a switching operation for a second section during a standby mode, thus permitting the power supply unit to supply power to an output unit(500); a mode discrimination unit(400) for sensing the existence of the external synchronous signal, and generating a signals for operating the main switch at the normal operation mode or standby mode in accordance with the existence of the external synchronous signal; a control voltage generating unit(200) including a transistor where a current corresponding to the signal output from the mode discrimination unit is applied, and a capacitor(Cfb) connected in parallel to the first transistor; and a switching control unit(300) for controlling the main switch to perform a switching operation at a predetermined duty in accordance with the control voltage charged in the capacitor of the control voltage generating unit during a normal operation mode, and controlling the main switch to repeatedly perform switching on and off operations during a standby mode.
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