LED

LED

  • Standards
  • LM79 A North American standard defining how LED should be measured for electrical and photometric characteristics.
  • LM80 A North American standard defining how LED should be measured for lumen maintenance characteristics.

The main hazard from LED is blue light which can cause damage to the retina. Under normal lighting conditions, almost all LED are RG0 or RG1. Light is a form of energy and is capable of causing physical harm.

  • Input Power The input power can vary considerably depending upon the LED driver and the LED construction and configuration. Standards indicate that the quoted input power value should be within 10% of the worst case situation (e.g. maximum input power).
  • CCT – Colour Temperature LED may either be colored, typically red/green/blue/amber, or white. However, similar to daylight, white can vary from a warm white with a higher red content to a cool white with higher blue content. This is described by the color temperature where warm white has a lower value (in Kelvin) than cool white. Typically warm white could be considered as 3000K or less, cool white as 5000K or above, and intermediate as between 3000K and 5000K
  • Ra – Colour Rendering, Every light source is characterized according to how well it shows colors. This is described by the Ra number where the higher the number the more accurate colors are shown. For the majority of indoor workplaces, a minimum of Ra80 is required. For general outdoor lighting, Ra70 is more usual. Increasing the Ra number to 90 or above generally comes at the expense of a reduction in efficiency
  • Binning The LED manufacturing process is not accurate enough to ensure that every LED is identical. Therefore the LED are sorted according to specific characteristics such as color, light output, and electrical properties. This sorting is called
  • Reliability LED Driver (LED Control Gear) The reliability of a LED luminaire is also dependant upon the driver. If this fails the luminaire will also fail. Therefore it is important to make sure the driver has a suitable rated life or is easily replaceable.
  • Ambient Temperature Ta When any testing is performed on a product it is for defined surrounding air temperature. This is the ambient temperature and is designated as Ta. The standard Ta defined for testing is 25°C although testing at any other value is permissible as long as the temperature is declared.
  • Lx – Rated life The time in hours during which the LED will produce more than a given percentage of their light output at new. x is the percentage of light output. e.g. L80 at 80,000 hours means that after 80,000 hours the light output from the LED will have dropped to 80% of the light output when new hardware Junction Temperature Inside an LED chip is a junction between two materials, one positively charged and one negatively charged. Light is emitted from this junctions by the exchange of electrons between the two materials, and as a side-effect heat is also generated at the junction. The temperature of the junction needs to be controlled to ensure that the light output and LED lifetime to fulfill the requirements for a given application.
  • Dimming and temperature When dimming is used or products are used at a lower ambient temperature than normal the number of failures may be expected to decrease and the rated life may be expected to increase. However, the size of these changes is technology dependent and there is no standard method to calculate these effects.
  • LED Driver A LED luminaire contains electronics to convert the mains electricity into the correct condition for the LED light source. This is called the driver. Drive Current This is the electrical current supplied through the driver to operate the LED. Over-driving the LED (giving a higher than recommended current) will result in high light output but a reduced lifetime. The drive current should provide the correct balance to ensure the performance and lifetime claims are met.
  • LED Luminaire containing an LED light source, either a LED module or a LED lamp

LED Module One or more LED package with mechanical and optical components but no lamp cap

LED Lamp One or more LED package with mechanical and optical components and a lamp cap

LED Package A LED chip in a form allowing simple electrical connection

White Light For LED white light is generated in one or two ways:

RGB or RGBY As white light is a combination of the colors in the spectrum (or rainbow) colored LED can be similarly used to give the appearance of white light. The colored LED blend on any surface they are lighting, giving white light.

Phosphor Conversion Blue LED is used to light a chemical phosphor, similar to that contained in a normal fluorescent tube, which converts the blue light into white light. This method will generally give superior color rendering as the white light contains more colors within the spectrum.