Engineering LED Drivers for Incandescent Bulb Replacement is a BOM Challenge

Cutaway view of a typical LED replacement bulb.

LED-based bulbs that replace their incandescent counterparts require a significant amount of engineering. In the 60 W range the LED driver board can take up about 15% of the overall cost of the bulb. Consumer price pressure on the LED driver IC manufacturer has forced its designers to work with one hand on a calculator and the other hand on an oscilloscope.

Power Electronics' February issue reports that LED replacement of incandescent lighting for residential use involves IC design that requires “penny pinching” to a degree not found in many other areas. For example, designers have a choice between using a power MOSFET or bipolar junction transistor (BJT) to power the LEDs. The MOSFET may cost $.12 where the BJT is only $.07. Therefore, the BJT wins the fight for a lower bill of materials (BOM)....