DC to DC Power for Driving LED-Backlit LCDs

by Michael Keene, Design Engineer Endicott Research Group, Inc. Abstract As LED backlights continue to displace CCFLs in LCDs, display manufacturers have to deal with several important decisions regarding the choice and arrangement of these LEDs and how best to drive them. One major decision is whether to use a large number of low-power LEDs, or a smaller number of mediumto high-power LEDs. The use of low-power LEDs results in a lower cost per LED, but requires a higher quantity of LEDs to properly backlight the LCD. The electrical configuration of these LEDs is also critical because some configurations can lead to impractical, expensive, or inefficient driver designs. With the use of mediumto high-power LEDs, the driver electronics are more simplified, but the optics can become more challenging, requiring more elaborate schemes to turn a small number of point sources into a single, uniform backlight.