Patent ID: 7342577
Filing Date: 2008-03-11
Classification: G09G,H05B,Y02B

Abstract:
1. An apparatus for driving a light source over a luminance range in response to a luminance input, the apparatus comprising: a voltage source having an output configured to couple with the light source, a first input configured to receive the luminance input, and a second input, said voltage source configured to generate an output signal at said output, said output signal having a frequency and having a pulse width based on the luminance input; a photodetector unit configured to logarithmically compress the luminance range and determine a first voltage based on a luminance of the light source in said logarithmically compressed luminance range; a comparator having an input coupled to said photodetector unit and having an output, said comparator configured to determine an error signal based on a comparison of the luminance input with said first voltage; and a signal converter having an input coupled to said output of said comparator and having an output coupled to said second input of said voltage source, said converter configured to exponentially convert said error signal to said frequency.