Understanding LED Technology – How do LEDs Work?
Chapter 1: What are LEDs and how do they work?
The first step to understanding LED lighting technology is understanding what LEDs are. LED stands for light emitting diodes. These diodes are semiconductor in nature, which means that they can conduct electrical current. When electrical current is applied across a light emitting diode, the result is the release of energy in the form of photons (light energy).
Due to the fact that LEDs fixtures use a semiconductor diode to produce light, they are referred to as solid state light devices. Other solid-state lights include organic light emitting diodes and polymer light-emitting diodes, which also use a semiconductor diode.
Chapter 2: LED light color and color temperature
Most LED fixtures produce light that is white in color. The white light is classified into various categories depending on the warmth or coolness of each fixture (hence the color temperature). These color temperature classifications include:
- Warm White – 2,700 to 3,000 Kelvins
- Neutral white – 3,000 to 4,000 Kelvins
- Pure White – 4,000 to 5,000 Kelvins
- Day White – 5,000 to 6,000 Kelvins
- Cool White – 7,000 to 7,500 Kelvins
In warm white, the color produced by LEDs has a yellow hue, similar to that of incandescent lamps. As the color temperature rises, the light becomes whiter in appearance, until it reaches day white color, which is similar to the natural light (daytime light from the sun). As the color temperature continues to increase, the light beam starts having a blueish hue.
One thing you should, however, note about light emitting diodes is that they do not produce white light. The diodes are available in the three primary colors: red, green, and blue. The white color that is found in most LED fixtures comes about by mixing these three primary colors. Basically, color mixing in LEDs involves combining the different light wavelengths of two or more diodes. Therefore, through color mixing, it is possible to achieve any of the seven colors that are found in the visible light spectrum (the rainbow colors), which produce a white color when they are all combined.
Chapter 3: LED and energy efficiency
One important aspect of LED lighting technology is their energy efficiency. As already mentioned, almost everyone knows that LEDs are energy efficient. However, a good number of people do not realize how the energy efficiency comes about.
The thing that makes LED more energy efficient than other lighting technologies is the fact that LEDs convert nearly all of the inputted power (95%) into light energy. On top of that, LEDs do not emit infrared radiation (invisible light), which is managed by mixing the color wavelengths of the diodes in each fixture to achieve only the white color wavelength.
On the other hand, a typical incandescent lamp converts only a small portion (about 5%) of the consumed power into light, with the rest being wasted through heat (about 14%) and infrared radiation (about 85%). Therefore, with traditional lighting technologies, a lot of power is needed in order to produce enough brightness, with LEDs needing significantly less energy to produce similar or more brightness.
Chapter 4: Luminous flux of LED fixtures
If you have bought incandescent or fluorescent light bulbs in the past, you are familiar with wattage. For a long time, the wattage was the accepted way of measuring the light produced by a fixture. However, since the coming of LEDs fixture, this has changed. The light produced by LEDs is measured in luminous flux, which is defined as the amount of energy emitted by a light source in all directions. The unit of measure of the luminous flux is lumens.
The reason for changing the measure of brightness from wattage to brightness is due to the fact that LEDs are low power devices. Therefore, it makes more sense to determine brightness using the luminous output instead of the power output. On top of that, different LED fixtures have different luminous efficacy (the ability to convert electrical current into light output). Therefore, fixtures that consume the same amount of power might have a very different luminous output.
Chapter 5: LEDs and heat
A common misconception about LED fixtures is that they do not produce heat- due to the fact that they are cool to the touch. However, this is not true. As already mentioned above, a small portion of the power fed into light emitting diodes is converted into heat energy.
The reason why LED fixtures are cool to the touch is that the small portion of energy converted to heat energy is not too much. On top of that, LED fixtures to come with heat sinks, which dissipate this heat, which prevents the overheating of the light emitting diodes and the electrical circuits of the LED fixtures.
Chapter 6: The lifetime of LED fixtures
In addition to being energy efficient, LEDs light fixtures are also famous for their energy efficiency. Some LED fixtures can last between 50,000 and 70,000 hours, which is about 5 times (or even more) longer compared to some incandescent and fluorescent fixtures. So, what makes LED lights last longer than other types of light?
Well, one of the reasons has to do with the fact that LED is solid state lights, while incandescent and fluorescent lights use electrical filaments, plasma, or gas to emit light. The electrical filaments burn out easily after a short period due to heat degradation, while the glass casings that house the plasma or gas are very susceptible to damage due to impact, vibration, or falling. These light fixtures are thus not durable, and even if they survive long enough, their lifetime is significantly shorter compared to LEDs.
One thing to note about LEDs and lifetime is that they do not burn out like fluorescent or incandescent bulbs (unless the diodes overheat). Instead, the luminous flux of an LED fixture degrades gradually over time, until it reaches 70% of the original luminous output.
At this point (which is referred to as L70), the luminous degradation becomes noticeable to the human eye, and the degradation rate increases, making the continued use of the LED fixtures impractical. The fixtures are thus considered to have reached the end of their lifetime at this point.