LED Lighting: Technical Analysis of the Technology, Advantages and Applications

Introduction

LED (Light Emitting Diode) lighting has transformed the modern lighting landscape thanks to its high energy efficiency, long lifespan and versatility in applications. This white paper provides a detailed analysis of the physical principles governing the operation of LEDs , their technical characteristics, advantages and disadvantages, as well as their diverse applications in different sectors.

Principles of Operation

LED Diode Structure

An LED diode is a semiconductor device that emits light when an electric current passes through it. The basic structure includes:

• Semiconductor Material : LEDs are made from compound semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP) or gallium nitride (GaN). The choice of material determines the emission spectrum and wavelength of the light produced.

• PN Junction : The junction is formed by combining two types of semiconductors:

  • Type P : Contains holes (positive carriers) due to doping with elements such as boron.
  • Type N : Contains free electrons due to doping with elements such as phosphorus.

When a forward bias voltage is applied across the diode, electrons on the N side recombine with holes on the P side, releasing energy in the form of photons. The wavelength (λ) and therefore the emitted colour depend on the bandgap (the difference between the energies of the highest occupied level and the lowest unoccupied level) of the semiconductor material used.

Emissive Spectrum

LEDs can emit different colors depending on the semiconductor material used. For example:

• Red : Gallium arsenide (GaAs)
• Green : Gallium phosphide (GaP)
• Blue : Gallium nitride (GaN)

To obtain white light, two main approaches can be used:

1. Additive Mixing : Combination of red, green and blue LEDs.
2. Photoluminescent Conversion : Use of a phosphor that converts part of the blue light emitted by a blue LED into yellow light, resulting in a mixture that we perceive as white.

Key Technical Parameters

1. Luminous Efficiency (η) : Measured in lumens per watt (lm/W), it indicates how much visible light an LED produces for each watt consumed. Modern LEDs can achieve efficiencies greater than 200 lm/W.

2. Colour Rendering Index (CRI) : Measures the ability of a light source to faithfully reproduce colours compared to a standard source. A CRI greater than 80 is generally acceptable for commercial applications.

3. Correlated Color Temperature (CCT) : Measured in Kelvin (K), it indicates the apparent color of the light emitted by an LED. Low values ​​(<3000 K) correspond to warm tones; high values ​​(>5000 K) correspond to cool tones.

4. Useful Life : Usually specified as L70, which indicates the time in hours until the light output decreases to 70% of the initial value; typically between 25,000 and 50,000 hours.

Technical Advantages

1. Superior Energy Efficiency : LEDs convert approximately 80-90% of the energy consumed into visible light, while incandescent bulbs only convert about 10%. This results in a significant reduction in operating costs and energy consumption.

2. Long Lifespan : With an average lifespan of 25,000 to 50,000 hours, LEDs require less replacement and maintenance compared to traditional technologies.

3. Low Heat Emission : LEDs generate less waste heat due to their high energy efficiency; this reduces the risk associated with burn-in and improves the overall thermal efficiency of the system.

4. Physical Robustness : Solid construction without fragile filaments makes LEDs more resistant to mechanical shocks and vibrations.

5. Lower Environmental Impact : By not containing mercury or other toxic materials present in some fluorescent bulbs, their use contributes to less generation of hazardous waste.

6. Advanced Controllability : LED systems allow precise control over light intensity through technologies such as dimmers or DMX/RDM controllers for professional applications.

Technical Disadvantages

1. High Initial Cost : Although prices have decreased significantly in recent years, the initial cost to purchase LED technology can be higher than other traditional options.

2. Thermal Sensitivity : Some models may be adversely affected by extreme temperatures; it is crucial to select products suitable for specific environments.

3. Chromatic Deviations : Not all LEDs offer adequate color rendering; it is essential to choose products with a high CRI rating for applications where color accuracy is critical.

4. Flicker : Some LED systems may exhibit noticeable flickering under certain electrical conditions or inappropriate drivers; this may cause eye fatigue or discomfort.

Applications

The technical versatility and advanced functionality of LED lighting allows its use in various applications:

Residential

• General Lighting : LED bulbs for lamps and ceiling lights.