LCD Current Consumption for a custom segment display
I have addressed LCD current consumption in this article because more and more new product designs are losing their power cord and moving to battery powered.
The LCD current consumption (aka current draw) is the big killer of battery life and LCDs are one of the biggest components for current consumption.
LCDs with the lowest LCD current consumption
There are seven main LCD technologies that Focus Displays offers. The one that offers the lowest LCD current consumption is a segment or static LCD.
Note: Bistable LCD technology does require less current to hold an image, but it does require a step function every time the image changes. Also, the high cost of this technology has made it unaffordable for most products.
So I will address a segment display since it is the next lowest current technology.
The LCD current consumption of a segment LCD module at normal operating temperature is between 1.2uA/square cm to 1.5uA per square cm.
Note: The colder the operating temperature, the more current is required to keep a sharp contrast.
LCD backlight current draw
The majority of segment LCDs are custom and built to the size requested by the customer. Many of these designs need to operate with a backlight so that they are readable in the dark. When adding a LED backlight to the LCD, your power consumption will increase by as much as 10x the current needed to drive the segment LCD only.
If you must have a backlight on your product we suggest the following:
- Build the display with a Transflective polarizer which will allow it to be readable with or without the backlight
- Have the backlight shut off or dim within a few seconds.
LCD current consumption options
Focus Displays offers the following options on a segment display to help reduce current draw.
- 3.3 V LCD driving voltage instead of the standard 5V LCD driving voltage.
- The 5 volt option is better for displays that operate in cold temperatures since the colder the display is, the more power required to hold a sharp contrast.
- Wide temperature fluid
- The display can be built with a wide temperature fluid. This will allow a 3.3V display to operate down to -20C (and in some cases -30C) without the need of a heater or more current draw.
- Wide temperature fluid increases the cost of the overall display by 3% to 5%.
- Fluid type
- There are three main fluid types available for a segment LCD: TN, STN or FSTN
- TN (Twisted Nematic) is the lowest cost and operates better in the cold. The one disadvantage of TN is that is does not have as wide of viewing angle as STN and FSTN.
Need a display with low current consumption for your next design? Contact Focus LCDs with your questions at 480-503-4295.