LED – WHAT IS IT?

And how does an LED light source actually work?

LED = LIGHT-EMITTING DIODE

Light-emitting diodes consist of two layers of semiconductor material with different charges. Semiconductor crystals are neutral; the different charges are created by adding charged atoms, such as silicon or boron. The n-layer has an excess of electrons and is therefore negatively charged; conversely, the p-layer is positively charged and contains so-called electron holes. When both layers are brought together, the charges balance out in a boundary layer and NOTHING happens.

If we now apply a voltage – even a very small one is sufficient – the electrons from the n-layer begin to ‘jump’ into the electron holes of the p-layer. There, the electrons combine with the positively charged atoms and release their excess energy in flashes of light. This is what we perceive as visible light. The more voltage we apply, the stronger the effect and the more light is emitted. This is known as the ‘principle of semiconductor electroluminescence’.

Knowledge Base | What is an LED? | Diagram: Light and Heat Emission

The wavelength of the light varies depending on the semiconductor material and the additives used. Typically, however, the wavelength range is very limited – the emitted light is monochromatic, meaning it has only one color. Red, or blue, or green. There is NO white light, which we nevertheless need for artificial lighting. We can produce this by coating the diodes with a fluorescent layer. The composition of this layer (usually phosphor) produces different colors of light.

THE HEAT SINK

Electroluminescence generates not only light but also heat. Admittedly, not as much as with a tungsten filament, but still enough to damage the sensitive semiconductors. To protect them, they are mounted on a heat sink or enclosed by it. This ensures a long service life and, above all, largely consistent luminous intensity with minimal heat generation.

TYPES OF LED

There are essentially two types of LED: ‘High Power’ and ‘Low Power’. High Power LEDs are those diodes that operate at more than 10mA. They enable high luminosity in a small space, but are also prone to heat and have a shorter service life.

DIP LED (
Dual-in-line-package) – the earliest type of light-emitting diode. This LED is soldered onto a circuit board with two leads and emits light at a single wavelength. It is frequently used as an indicator on electrical devices.
SMD LED
(Surface-Mounted Device) is still the most widely used type of LED. The semiconductor and heat sink form a single unit. The diodes are soldered onto a circuit board in a circuit. The semiconductor itself is soldered into the heat sink; this solder joint serves both as a heat transfer point and an electrical connection. The second electrical component is the so-called bond wire, through which the voltage is applied.

Knowledge Base | What is an LED? | Diagram: SMD LED

COB (
Chip-On-Board) LED. In this technology, the semiconductor is soldered directly onto the circuit board within its own housing. This housing can be made from various materials and also serves as a heat sink. Ceramic is a good material, as its thermal conductivity is excellent. The voltage is generated here via two bonding wires. This technology is becoming increasingly widespread. SEGULA light sources are now exclusively fitted with COB LEDs.

Knowledge Base | What is an LED? | Diagram: COB LED

COB technology has made the development of modern filaments possible. This is not only groundbreaking in terms of technology, but also pioneering in terms of design. The patented Soft Filament delivers outstanding properties and a stunning appearance!