Battery and Solar-Powered Low Voltage LCD Displays
Engineers looking for low voltage LCD displays are on the rise. I am thinking of buying stock in battery companies. I am not suggesting that you should make the same investment, but I am seeing more and more designs for battery powered LCD applications come across my desk.
Low voltage LCD Displays for mobile devices:
People are more mobile now than ever, and they want to take everything with them. This includes games, spread sheets, digital cameras, calendars and thousands of books. All of which can be kept in the palm of your hand thanks to low voltage LCD displays that are located in tablets and other electronic products.
With more electronic products converting from power cord to battery or solar, there is an increasing demand for designs to incorporate low voltage LCD display modules. In short, extending battery life is critical and has become the primary requirement in new mobile devices.
One of the highest power consuming components in a circuit is the Liquid Crystal Display. For many years color and monochrome LCD display panels required 12 volts, 7 volts, 5 volts or even dual operating voltages. Now much of that has given way to 3.3V custom LCD Displays and 3V custom LCD display modules. It is all part of the drive to reduce power consumption in LCD displays.
3.0V and 3.3V custom LCD Displays:
Why are 3.3V custom LCD Displays and 3V custom LCD display modules so popular?
One reason is that AA batteries can produce between 1.2V to 1.65V per cell. When combined in pairs, they are able to supply between 3.0V and 3.3V. AA batteries are much smaller than the older, heaver ‘C’ and ‘D’ batteries that were required to operate older, portable electronics.
What made lower voltages for LCDs possible?
- One reason why LCD modules have been able to lower their operating voltage is because the LCD module is integrated with a power saving controller chip from companies such as NXP, Microchip and others.
- A second reason is that they incorporate low power ITO LCD glass that reduces the amount of power (VLCD) necessary to drive the segments.
- The third reason is the addition of charge pumps. Charge pumps, also referred to as bump circuits or booster circuits, allow the designer to supply a lower LCD input voltage (VDD) and have it ‘bumped’ up to the voltage necessary to drive the LCD (VLCD).
Charge pumps and custom LCD Modules:
There are some concerns with custom LCD modules incorporating a charge pump. Although they allow the design engineer to work with a VDD of 3V or 3.3V, they do not behave very well in some environments.
The challenge is that they can arc (or spark) and this can be a very bad thing. Products that will be operating in explosive situations need to stay clear of charge pumps. (Also, they need to stay clear of capacitive touch screens, but this is a whole different subject.)