Driving method for improving luminous efficacy of a light emitting diode

Abstract

A driving method for improving luminous efficacy of a light emitting diode (LED), the method comprising: periodically switching a DC current supplied to the LED between a high current level l [sub H] and a low current level l [sub L], the low current level l [sub L] being fixed at zero or raised above zero to produce a DC offset; and maintaining an average current at a first value I [sub f] by adjusting the duty cycle acting on the high current level l [sub H] and any one from the grouping consisting of: adjusting the high current level l [sub H] and adjusting the low current level l [sub L], and adjusting the high current level l [sub H] or adjusting the low current level l [sub L].