What makes LED efficient?

LEDs has a lot of benefits and has been very popular for some time now. This is among other things because of the high efficiency of LEDs which is significantly higher than conventional lighting technologies. In normal language, when we talk about the efficiency of light sources, we generally mean their luminous efficacy, which is measured in lumens per watt (lm/W). This metric takes the sensitivity of the human eye into account. Another measure is efficiency characterized by radiometric power.

The efficiency of LEDs depends on many different factors, some of them we will look on in this article.

The color temperature

One of the factors which have a major influence on luminous efficacy is the choice of color temperature. It can be used within the framework of existing lighting regulations as a control for the efficient planning of lighting solutions. Generally, LEDs with a correlated color temperature (CCT) on e.g. 5000K, which is characterized as high, have a higher efficiency than those with e.g. 3000K CCT, characterized as low.

Normally, a semiconductor chip that emits blue light is used in LED lighting. In order to produce white light with LEDs, phosphor is used. Some of the light will then be converted into light with longer wavelengths which enable the human eye to see other colors. This conversion process involves losses, as some of the light is turned into heat when converted. In order to minimize the losses, we need a precise alignment of the absorption and emission wavelengths of the converter.

Color rendering

As already mentioned when we discussed color temperature, the composition of the color spectrum based on a suitable converter has a crucial influence on the efficiency of the LED. The converter mix is developed specifically for different color rendering index (CRI) and is optimized for the CRI and for efficiency. The differences between the CRIs can be seen very clearly in the red light, which is the color that involves the highest losses.

The choosing of color temperature and CRI of an LED is restricted by specifications, guidelines, and the particular requirements of a specific application.

A light source with adjustable efficiency

In terms of color and brightness, LEDs are usually grouped. Therefore, it is possible to adjust the LEDs to fit the application or desired level of luminous efficacy when varying the current density. This is due to the LED opto-semiconductor, which offers the luminaire manufacturer a further dimension in which the efficiency or luminous efficacy can be adjusted. This is not possible with conventional light sources. The LEDs efficiency also depends on parameters such as maximum operating conditions or the operating temperature.

How to reduce system costs?

As LEDs has been developed, they have become brighter which makes them more efficient. But some applications do not necessarily need greater efficiency. This makes one wonder, why is there such huge demand for brighter light-emitting diodes with greater efficiency? One reason is, without a doubt, that more efficient LEDs can lead to significant cost reductions at the SSL system level.

All the above shows that a lot of factors have an influence on the luminous efficacy of an LED. The higher the color temperature, the greater the luminous efficacy, and the higher CRI, the lower the luminous efficacy. Furthermore, there is a crucial difference between LEDs and conventional light sources as LEDs can be adjusted via the operating current and this can lead to significant savings in LED systems.

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