A Deconstruction of LED Lights

Curiosity for light

Curiosity for light

What goes into making a common LED light? What are its component parts?




Components of a LED downlight


So, there’s various shapes and sizes of LEDs or light engines. Some of the most common LEDs are the COB type or Chip on board technology, these were created to produce a higher lumen density from a single point source, essentially these work by having a number of smaller die on a single circuit board with a single phosphor coating.

The next ones are the middle power LEDs, which are becoming increasingly popular because of their high efficacy and lower heat output and minimal heat sink requirement. These work in a similar way to the CoB style but on a smaller scale and generally with only a single die underneath.

Other variants are the single high power chips which the Philips Lumiled company make – named the Rebel, and Multi Die high power chips like Cree’s MCE LED.

There are also light engines which are mostly complete components that often comprise of a range of smaller LEDs – in the case of CREEs true white technology, different colour LEDs including yellow and red are mixed to produce a high CRI and high output engine.

The LED chip sets the colour temperature and colour rendering index of the light and also sets forth the luminous flux or brightness.

Since LED technology is a semiconductor, heat is a byproduct of it’s use, and along with this in general a heat sink is employed to help dissipate the heat produced.

Although they run significantly cooler than traditional forms of lighting, LEDs still need a heat sink to prevent the light source from degrading too rapidly – Higher temperatures will cause the LED to shift colour and shorten its lifespan. As a general rule we can say, the larger the heat sink the closer to optimal temperature the LED will run, the more it’s life and colour will be preserved. But heat sink can’t always be enormous – their size is constrained by the housing it needs to squeeze in to Therefore case temperatures can still become quite high, but typically with a maximum of 85 degree Celsius which is still no where near that of an incandescent or halogen.

The heat sink generally adds to the aesthetic design of the fitting as well when piecing the mechanical aspects of the light together.

Following on from the heat sink, the optical properties are another important factor, again these are built into the design of the product and are used for shaping the light from the LED. There are a few different ways these optics are used, for example – reflectors are generally used for directional light sources such as down lights with single point sources. These reflectors are usually quite efficient and generally provide a nice spill light that produce arcs against the wall as well.

Typically Lenses are even more efficient, but these are a bit more complex to design, though they do offer much more control over the shaping of light. An example of this could be a street light where the light needs to be spread over a wider area between light fittings but much more narrow across the roads width. With the use of lenses this can reduce the overall losses of light.

The final super important component is the LED driver. These also come in varied forms and sizes, but they all roughly do the same thing, these are designed to transform the mains power into a suitable constant current or in some cases constant voltage for the selected LED chip or light engine.

The driver can also contain additional equipment like integrated dimming circuits, which can allow you to use triac or phase shift dimmers, 0-10v analogue dimmers or integrate with building control systems such as DALI or digitally addressable lighting interface.

They can also contain power surge or spike protection, thermal management and can also be integrated with motion sensors, photo electric sensors and so on.

The driver is THE most important factor to LEDs achieving their long life span because if it stops working then it all stops working. There are a number of factors that which affect a driver’s life span of which the obvious one is heat, the components used inside the driver – capacitors, transistors, resistors and integrated circuits should all be designed correctly and if substandard components are used then it will be hard to reach the long life expectancy of the LED.

The last part of what goes into a LED light which doesn’t necessarily go INTO the light is the certification or verification and testing process, once the goals have been determined and the design completed along with any prototypes the product must then be tested to confirm it’s accuracy and conformity to any relevant standards such as safety testing and light output accuracy.

These are generally done by third party testing labs, and in some cases larger manufacturers test in house.

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