One of the major Achilles heels of smartphones and tablets is battery life. As almost any consumer satisfaction survey can attest too, users generally view battery life of their device as poor as best. Battery makers have been increasing their storage capabilities by ~11% a year—while host system battery requirements are expanding well beyond that.
The biggest consumer of battery life in a mobile device is the display. Displays consume an average of 50% of system power resources; and as they grow in resolution and size, this percentage grows. Within the display, the amount of power consumed is greatly linked to the brightness. A brighter display will be traditionally be more visible, but will consume more power than a dimmer display.
Display panel makers, along with smartphone and tablet OEMs, have explored many ways to decrease power consumption. For instance, a commonly-used method of power savings is known as ‘auto-brightness’, which is found in most mobile products. This method simply adjusts display brightness according to ambient lighting—the brighter the viewing environment, the brighter the display. While this method will save power, it does nothing to actually increase the user experience. In fact, because brightness is adjusts globally, this method can actually reduce the contrast ratio of the display, resulting in the loss the details in the image. Other methods of power savings, such as CABC (Content Adaptive Brightness/Backlight Control) do lead to modest battery savings, but also have negative effects such as loss of details due to its global adjustments.
QuickLogic’s Display Power Optimizer (DPO) technology can extend system battery life, in some cases by as much as 50%, without negatively affecting the user experience. DPO works with QuickLogic’s VEE. As VEE gathers statistical information on a pixel-by-pixel, frame-by-frame basis to adjust the value of individual pixels contrast ratio, dynamic range, and color characteristics, DPO uses that same information to adjust the display brightness. In essence, VEE can increase the viewability of the display to such a degree that brightness can be significantly lowered while still providing a much better viewing experience. This lowering of display brightness results in system battery savings.
The degree to which the display brightness is lowered is completely at the discretion of the OEM. If power savings is the top priority (‘DPO design emphasis’), then display brightness can be greatly lowered by DPO while VEE insures that the viewing experience is still as good, or slightly better than before. If the OEM desires the best possible viewing experience in all lighting conditions (‘VEE design emphasis’), DPO operates to a lesser extent, lowering the display brightness less than with a power-savings centric approach. However, even the most viewing experience-centric OEM will still experience double-digit power savings with DPO (See figure 1).
An additional feature of DPO is its unique ‘Intelligent Brightness Control’ (IBC) feature, which allows for additional reduction in display brightness when the displayed content is of lower contrast and dynamic range, such as a movie being streamed or mobile TV. IBC does not negatively impact display viewability, preserving the user experience. IBC-based power savings, which can be as high as 10%, are in addition to the power savings that DPO can provide.
Display Power Optimizer has been implemented on numerous production and pre-production customer systems. Figure 1 illustrates what battery life extensions have been OEM-proven.
|Form Factor||Display Size/Type||Original Brightness Level||Original System Power||Design Emphasis||DPO-enabled Brightness Level||DPO-enabled System Power||System Power Savings||Battery Live Improvement|
Note: Figure 1 does not account for content-based savings that can be garnered with IBC.