Low-power color TFT LCD display for hand-held embedded systems

An LCD (Liquid Crystal Display) is a standard display device for hand-held embedded systems. Today, color TFT (Thin-Film Transistor) LCDs are common even in cost-effective equipments. An LCD display system is composed of an LCD panel, a frame buffer memory, an LCD and frame buffer controller, and a backlight inverter and lamp. All of them are heavy power consumers, and their portion becomes much more dominant when running interactive applications. This is because interactive applications are often triggered by human inputs and thus result in a lot of slack time in the CPU and memory system, which can be effectively used for dynamic power management. In this paper, we introduce low-power LCD display schemes as a system-level approach. We accurately characterize the energy consumption at the component level and minimize energy consumption of each component without appreciable display quality degradation. We develop several techniques such as variable-duty-ratio refresh, dynamic-color-depth control and backlight luminance dimming with brightness compensation or contrast enhancement.