Combined Hybrid and Local Dimming Control of Light Emitting Diodes

An apparatus comprising:

• master control paths configured to control master light emitting diode backlight illumination of a display, comprising:
• a first master control path configured to generate a hybrid digital modulation control signal in digital modulation control paths of light emitting diode drivers of the display;
• a second master control path configured to generate a hybrid current control signal in string current control paths of the light emitting diode drivers of the display;
• and
• a local control path configured to selectively perform local dimming control of a light emitting diode driver associated with a selected light emitting diode string associated with a selected local display region of the display, the local control path configured to generate a local digital modulation control signal in the digital modulation control path of the light emitting diode driver associated with the selected local display region and configured to combine the local digital modulation control signal with the hybrid digital modulation control signal to generate a composite local digital modulation control signal, controlling the light emitting diode driver associated with the selected local display region.

A liquid crystal display system with controlled light emitting diode dimming, comprising:

• a plurality of strings of backlight light emitting diodes arranged to provide backlight illumination to the liquid crystal display, each controlled by an light emitting diode driver, and at least some arranged to provide backlight illumination to respective local display regions of the liquid crystal display;
• a local light emitting diode driver control unit configured to:
• generate, for a predefined range of range of lower light emitting diode master brightness values, a hybrid digital modulation control signal in a digital modulation control path associated with a digital modulation setting corresponding to a desired light emitting diode brightness value associated with a master brightness control signal, up to a specified maximum digital modulation setting, while maintaining string current and string voltage substantially constant;
• generate, for a predefined range of range of higher light emitting diode master brightness values above the light emitting diode brightness value associated with the maximum digital modulation setting, a hybrid current control signal in a current control path associated with a string current corresponding to a desired light emitting diode brightness value associated with the master brightness control signal;
• and
• selectively perform local dimming and illumination control for a light emitting diode driver associated with a light emitting diode string associated with a selected local display region of the liquid crystal display by generating a local digital modulation control signal in the digital modulation control path associated with a digital modulation setting corresponding to a desired light emitting diode brightness value for the selected local display region, and combining the local digital modulation control signal with the hybrid digital modulation control signal to generate a composite local digital modulation control signal used to control the associated light emitting diode driver, the composite digital modulation control signal corresponding to the desired light emitting diode brightness value for the selected local display region.