Tips To Maximize Battery Life In Designs With Displays

LCD (Liquid Crystal Display)
LCD (Liquid Crystal Display)

Portable and remote systems which rely on battery power have strict design requirements to extend the operational time between charges.

The typical approach in system optimization is to start with the largest power users and work towards the point of diminishing returns.

A display is often one of the top three energy consumers and deserves special consideration.

The first tips revolve around the initial selection process. It’s best to select the smallest possible screen size. The smaller the screen, the fewer elements which need to be powered.

Next is to choose the technology which fits the application as well as the cost considerations. This can be as simple as a fixed character LCD (liquid-crystal display), to a Monochrome LCD, through to OLED (Organic Light Emitting Diode) and full-color TFT LCD (thin-film-transistor). A back-light may also be required, which is an additional power drain when in operation.

For power optimization, LCD solutions are preferred as their maximum electrical usage occurs only when a pixel changes state.

This brings us to the next tip: Only update the pixels on the screen which have changed. It’s not necessary to completely blank the display and refresh it on each cycle. This does require that the system have sufficient memory to store a complete screens’ worth of data, as well as the updated information. In many cases, it’s often easier to have a memory size which can accommodate two full screens of data.

The associated benefit to only updating the elements which have changed is that the graphics controller or processor can use fewer cycles to “refresh” the image. The less time that power hungry devices are operating in the active mode, and the quicker they can return to sleep mode, the less drain it will be on the battery.

Along these same lines, a lower refresh rate for the display will also help maximize the battery life. Even if the display information has not changed between refresh cycles, the underlying system must still power up to an active mode and determine if it needs to update the screen.

The next tip is to match the processing speed to maximum peripheral interface speeds, since the display update speed is often limited to the interface speed.  Any processor performance beyond the rate it can communicate is wasted and just consuming power.

A final tip is to scale the system operations to match whatever application is running. Many systems often run multiple applications, each with unique power curves and duty cycles. By matching the system performance to the application requirements, rather than designing for the maximum case, it’s possible to further maximize battery life.

The device specification is only the starting point to maximize battery life. And always keep in mind that “Power Off” is the ultimate low power state, so  look for those opportunities to turn off the display and anything else whenever possible.

(Image Credit – Free Photos)

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