Inventors:
Victor Borgogno - Nevada City CA
Brad Borgogno - Nevada City CA
Mark Bevington - Grass Valley CA
Assignee:
IllumaGraphics, LLC - Sparta MI
International Classification:
H05B 3702
US Classification:
3151693, 315156, 315158, 315308
Abstract:
Electronic sensing circuits monitor multiple sized EL cells, referred to as a lamp, and compensate for variations in contrast between cells, while maintaining a fixed contrast between the luminance of the cells and the ambient lighting. In one embodiment, three separate feedback loops monitor the ambient lighting, cell-luminance, and frequency of the excitation voltage and make appropriate adjustments to an adjustable luminance reference. In another embodiment the circuit which drives the EL cells includes a timer and a microprocessor. The timer measures the elapsed time during which the EL display has been operating. The microprocessor adjusts the drive signal to the EL display to correct for aging, based on the elapsed time measured by the timer and an empirically-determined aging parameter. All these adjustments are accomplished while a microprocessor sequences through a large assortment of electroluminescent cells of various sizes.