Combined Hybrid and Local Dimming Control of Light Emitting Diodes

摘要

An LED backlight controller combines global/hybrid and local brightness/dimming control for an LED backlight illuminator with local regions illuminated by associated LED strings. Global/hybrid brightness/dimming control performs hybrid digital modulation control for a predefined lower range of brightness levels, with string current maintained at a substantially constant level associated with a predefined maximum brightness for the lower range (controlling brightness by adjusting digital modulation, such as PWM duty cycle, up to a maximum), and performs hybrid string current control for a predefined higher range of brightness levels (controlling brightness by adjusting string current). Local dimming control is performed by introducing a local digital modulation signal into a hybrid digital modulation control path for the associated string, so that digital modulation for the associated string is a combination of local digital modulation and global/hybrid digital modulation.