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A bilevel driving approach was proposed in the literature for mitigating the energy wastage associated with driving LEDs at high peak current. The main idea is to introduce two drive parameters, i.e., high/low PWM current levels and duty cycles, that give rise to a 2-D luminosity control capability. The same idea was later generalized to an n-level driving approach for maximizing the electrical-to-light conversion efficiency of LEDs. Although previous uses of the n-level driving approach have been focusing on improving the luminous efficacy of LEDs, it is shown in this paper that its 2-D luminosity control feature can also lead to a significant improvement in color resolution when applied to driving RGB LEDs, hence making it well suited for applications in large-area LED display panels. In comparison to the first prototype driver proposed by the inventor of the driving approach, a more practical implementation of the complex 2-D driving approach with digital microcontroller is demonstrated. The various technical aspects of the driving approach, including luminous efficacy, color resolution, and color stability over dimming, are discussed in this paper with the aid of experimental results.
Date of Publication: Dec. 2012