STEPDOWN DC-DC CONVERTER FOR LIGHT EMITTING DIODE, AND POWER SUPPLY DEVICE AND METHOD USING THE SAME

摘要

A stepdown DC-DC converter is adapted to provide a power supply voltage necessary to control the operation of an LED. The stepdown DC-DC converter includes: a reference voltage supplier for providing a reference voltage; a feedback unit for feeding back the power supply voltage on an output line; an operational amplifier for operationally amplifying the reference voltage and the fed-back power supply voltage; a switch unit for switching on/off a DC voltage on an input line toward the output line; and a charging and discharging circuit for selectively performing a charging operation of the switched voltage from the switch unit and a discharging operation of its charged voltage according to the switching operation of the switch unit to provide the power supply voltage to the output line.