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LED learning center
  • Introduction of commonly-used LEDs
  • 15-09-2010

The LED's are surely the most important quality criteria when it comes to LED video displays. They determine the image quality of the led display and are decisive in determining how the image quality is retained over time. The quality characteristics for LED's are very diverse, and, here too, the maxim applies: the most expensive choice is not always the best choice. To highlight an example from the automobile industry: You are sure to be able to spontaneously list a variety of luxury sedans, though you may not generally consider these when selecting a new vehicle. Price and purpose play major roles in the decision of which model to choose. And also, luxury sedans differ in many ways, although they often all meet the highest quality standards.

The quality of an LED is determined primarily by the chip used. It determines the service life of the LED and how the lighting behavior of the LED changes over time. The mayor Chip manufacturers of LED's are:

  • Nichia (Japan)
  • Cree (USA)
  • AXT (USA)
  • Epistar (Taiwan)
  • Silan (China)

The prevailing opinion on the market today is that LED's made by Nichia are the best for use in LED video displays. However, they are also undeniably the most expensive LED's on the market by a wide margin. The price of LED's varies on average from less than one cent per LED to up to 15 cents and more, depending on the type of LED (RGB LED's with three chips in one housing are often more expensive). An extensive price difference can arise in manufacturing, depending on the LED's used.

The most important factor for purchasing a LED screen and determining which LED's to choose are:

  • Brightness: The brightness of the LED's is measured in mcd (milli-candela). The higher the brightness, the better. You can run the display at a lower brightness, thus increasing the service life or increasing visibility during the day when the sun is shining.
  • Electrostatic Discharge(ESD): The LED chips produced by various manufacturers differentiate themselves through a varying sensitivity to the effects of electrostatic discharge (for example due to contact). Display failures caused by electrostatic discharges can be prevented by implementing safeguarding measures against ESD in the production process. The following LED chips listed are indicating the voltages that the LED's can withstand in case of electrostatic discharges:
    • Cree: 2000V
    • Nichia: 1000V
    • Taiwanese LED Chips: 800V
    • Chinese LED Chips: 200~800V
  • Sensitivity to Temperature Variations: Poor LED chips can fade faster, i.e. their service life can shorten, if they are exposed to high temperature variations. Depending on the country, temperatures can become extremely hot or cold during the summer or winter months, respectively. As a result, a poor LED quality could cause premature fading of the overall, expensive LED display.
  • General Service Life: The general service life of the LED's often lies between 50,000 and 100,000 hours. (100,000 hours equates to 10 years of continuous display operation at full white, if no other factors exist which reduce the service life; such as increased heat in the led display housing, or operating the LED's at overvoltage in order to balance brightness reduction.

Nichia (Japan)

Cree (USA)

AXT (USA)

Silan (China)

Epistar (Taiwan)

Red LED

2.5%

Unknown

Unknown

Unknown

28%

Green LED

2,50%

26%

8%

7%

28%

Blue LED

2,50%

45%

8%

7%

28%

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