LED Backlight Systems

KOE provides several back light technology solutions for our customers including electro-luminescent back lights (EL), cold cathode fluorescent luminescent back lights (CCFL)  and light emitting diode back lights (LED). Most of our displays are offered with LED technologies. LED technology provides our customers with many advantages.

• a cleaner solution (mercury free)
• a more durable solution (no glass bulbs)
• a more energy efficient display solution in a smaller package (space and energy inefficient inverter not needed)
  
• an easier time passing regulatory constraints (No high frequency high voltage systems for EMI and safety concerns)
• a greater range of dimming control (0-100% in LED as compared to 50-100% for CCFL) which translates into a more comfortable user experience and improved energy efficiency in low light conditions

We currently provide 3 technology solutions, consumer grade, low power, and long life (70K LED) back light systems. Each of these have opportunity costs and your back light system selection will depend on the application in which you will be using your display device.

Long Life LED (LLLED) Back light system

Most of our industrial customers provide products that are in service for many

years and are interested in long display product life. For this reason we design mid power LEDS into our displays. Not only do we apply this technology to our displays’ back light systems but we also design the back light system themselves to properly provide for long product life. LED life is determined by the power utilization and the junction temperature in the device itself. We design our 70K rated back lit displays as a total unit to ensure that the LED junction temperature meets our supplier’s requirements to ensure 70Khours (8 years) of continuous use at room temperature with greater than 50% initial luminance.

Many other display suppliers merely use the same LED as Hitachi and claim the same life performance. If you are looking for a 70K life LED back lit display, be cognizant of the difference.

Warning signs of a poorly designed back light system are.

·         Non-uniform temperature or particularly warm areas of the display module body

·         Non-uniformity of contrast and “wash-out” near the sides where the LEDs are located in the display module.

Some back light systems cannot accommodate long back light lifetimes without external heat management systems. Examples of this are

·         After market “high brightened” back light systems

·         Replaceable back light systems

·         Thin lightweight consumer style LCD modules

·         +70^oC (+158^oF) rated backlight used in +80^oC (176^oF) rated displays

 Be particularly aware of exaggerated claims by suppliers such as very long life and long life at elevated ambient temperatures or tricky “specsmanship” where differing criteria of life are used. They may be counting on you buying a replacement from them in a year or so.

We do have a durable display line (Rugged +) which is specially designed to operate at under extreme conditions such as elevated temperatures, but most display suppliers have not made the effort.

Our consumer grade back light systems are rated for 10K hours for devices which have fast product replacement cycles,  very low display utilization ratios (back light on for short periods), or cost sensitive applications. They are not designed for devices where the back light is on continuous and for long periods of time.

Our low power back light systems are rated for 40k hours of continuous use and are used for devices which have power constraints, such as in battery operated mobile devices. Typically to save battery power, such devices turn off the back light at least 50% of the time and long product life (80K hours or more) is achieved indirectly from implementation of power saving techniques.