Research On A High Input Voltage LED Driver

This paper studies on a kind of high input voltage white Light Emitting Diode (LED) driver. A solusion is proposed after introducing the background of LED driver and reviewing the high input voltage converter. Using the series connected metal-oxide-semiconductor field-effect transistors (MOSFETs) circuit the voltage stress of a single device can be reduced. In the proposed circuit the master switch is directly driven by the control IC while the slave switch is driven by the auxiliary circuit. At the same time, effective voltage sharing is realized by the auxiliary circuit.When applied in a quasi-resonant fly-back DC/DC LED driver, the operation principle of the proposed circuit is analyzed in detail. After that the voltage stress of each MOSFET and the power losses of the auxiliary circuit are discussed. A method is given to reduce the voltage stress of the switch and to improve the whole efficiency of the converter. A prototype is built to verify the performance of this circuit.As the proposed circuit can be used in the wide range input voltage situation, it is suitable for the single-stage power factor correction (PFC) flyback AC/DC LED driver. Power losses of the auxiliary circuit are calculated and then some experiment results are given.Finally a multi-MOSFETs series connected circuit is studied. The operate principle of three MOSFETs connected circuit basic on the single-stage PFC flyback AC/DC LED driver is analysed. After discussing the voltage stresses and power losses of the circuit, design guidelines are shown. A prototype shows that the circuit can reliably share the voltage across the three switches. It will further decrease the voltage stress of every MOSFET compare with the dual MOSFETs series-connected circuit.The series connected MOSFETs circuit can be effectively applied in the quasi-resonant flyback converter, which will save the cost of the high input voltage LED driver. Besides, it is extendable for multi-MOSFETs series connected situation.