ANALYSIS OF LED DRIVER TOPOLOGIES WITH RESPECT TO POWER FACTOR AND THD

Light Emitting Diodes (LEDs) are fast replacing incandescent lamps and CFLs in most of the developing nations. The reason can be attributed mainly to the enhanced lifetime and less energy consumption as compared to the other mentioned types. However one important aspect needs attention, the impact of driver on LEDs. LEDs are current controlled devices and hence emit maximum light with increase in current input to the device. This feature, boost up the light output but it increases the junction temperature of the device. Hence additional heat sinks are required to vent out the excessive heat generated due to increase current input to the LEDs. Those additional heat sinks are at times difficult to accommodate. So, designers have made arrangements to vent out the heat from the device. This is achieved by designing fins. However this arrangement is not suitable in places where the ambient temperature is more than normal. Thus, design of LED driver with controlled current input is essential in order to maintain the thermal limit of the device. Secondly, the AC-DC LEDs driver circuits, which are available in the market, are seldom equipped with input power factor and THD improvement circuitry as prescribed in IEC61000-3-2. This is essential for maintaining the energy efficiency of the nearest utility services and in addition also improves on the current drawn by the device. The following work envisages these issues and proposes corrective driver circuit based on two different driver topologies, buck-boost topology and flyback topology. Both these topologies are proposed in order to address the aspects of power quality and its impact on the life of the device. The simulation were done using Green Point simulation tool from On Semiconductors.