To reduce the cost of LCD backlight unit (BLU) and raise efficiency, a direct LED BLU consisted of double-triangular
structures was proposed to control the light from RGB side emitting LEDs. A genetic algorithm was used to search the
optimal parameters of the shape of the double-triangular structures and the layout of the LEDs. A switch mode constant
current control driver with a PWM controlled converter switch was used to maintaining the constant current output for
the variable numbers of the LEDs in this paper. From the simulation results showed that without the diffuser, the
brightness uniformity on the 25-point test was 93.44% for a 22" direct LED backlight unit with a thickness of 30mm
with the optimized double-triangular structure. And the experiment result showed that the brightness uniformity and
color uniformity were 85.61% and 0.021 for a small size test unit.