A Survey of Low-power Techniques for Liquid Crystal Display Systems with Light Emitting Diode Backlight Units

As the technology evolves, end-users are stuffed with many kinds of handheld devices along with an enormous number of interactive multimedia applications and communication functionalities. These devices consume much power, especially for displaying their services or functions. In contrast, the battery, which is the main power supplier for such devices, has a much lower capacity growth compared to the power demands. This gap has inspired many researchers to study low-power display techniques. In the mean time, there came the invention of a light emitting diode (LED) as a new backlight source for a display panel. LEDs have been adopted in the most widely used Liquid Crystal Display (LCD) system. This paper focuses on recent noticeable low-power display techniques based on LCD systems, especially associated with an LED backlight unit as its light source. We categorize these techniques into four groups: 1) low-power techniques with backlight dimming, 2) low-power techniques with dynamic voltage scaling, 3) software-based low-power techniques, and 4) hardware-based low-power techniques, and review the core of each technique briefly. Among many techniques, concurrent brightness and contrast scaling technique in a color sequential LED-backlit display system achieved the largest power saving ratio by up to 90% of the total system power with a small distortion level. As future research, it is one of important methods to combine the pros from each beneficial technique into one synergistically in the aspect of the whole system power.