The led commercial lightings development

The fire began the first revolution in the field of human commercial lighting. In 1879, Edison invented the first tungsten light bulb, opening up a second revolution in the field of human commercial lighting. Since then, incandescent lamps have been illuminated for more than 130 years. We know that tungsten filament lamps still belong to blackbody radiation. The temperature is more ambiguous, the spectrum shifts toward the blue light. The temperature of tungsten filament in tungsten filament lamp is about 2000. When the temperature is low, most of the spectrum is infrared spectrum, which becomes heat dissipation. out. From an environmental point of view, tungsten lamps are not energy-saving products, their energy efficiency is very low, only 5% of the electricity is used to illuminate, and the remaining 95% is used for heating. A tungsten halogen lamp is a kind of incandescent lamp. The principle is to inject a halogen gas such as iodine or bromine into the bulb. At high temperatures, the evaporated tungsten chemically reacts with the halogen, and the evaporated tungsten re-solidifies on the tungsten wire to form a balanced cycle that prevents premature rupture of the tungsten wire.

Therefore, tungsten halogen lamps last longer than incandescent lamps. The third revolution in commercial lighting was the gas discharge lamp. Fluorescent lamps, high-pressure mercury lamps, sodium lamps and metal halide lamps are the most widely used gas discharge lamps for lighting. The basic process of luminescence of a gas discharge lamp is divided into the following three stages.

1 After the discharge lamp is connected to the working circuit, a stable self-sustaining discharge is generated, and the electrons emitted by the cathode are accelerated by the external electric field, and the electric energy is converted into the kinetic energy of the free electrons.

2 The fast moving electrons collide with the gas atoms, the gas atoms are excited, and the kinetic energy of the free electrons is converted into the internal energy of the gas atoms.

3 The excited gas atoms return to the ground state from the excited state, and the internal energy obtained is released as optical radiation.

The above process is repeated and the lamp continues to emit light. The light radiation and current density of the discharge lamp, the type of gas.

The level of air pressure is related. Certain types of gas atoms can only radiate spectral lines of certain wavelengths. At low air pressure, the radiation spectrum of the discharge lamp is mainly the characteristic line of the atom. When the air pressure rises, the radiation spectrum of the discharge lamp broadens and develops toward the long wave. When the air pressure is high, there is a strong continuous spectral component in the radiation spectrum of the discharge lamp.

Fluorescent lamps are low-pressure discharge lamps. The mercury vapor in the fluorescent tubes is excited by ultraviolet light, which excites the phosphor on the fluorescent tube wall to generate visible light.

The LED lamp belongs to electroluminescence. Under the action of the applied forward electric field, the carrier transitions from the low energy state to the high energy state, that is, the electrons in the N region migrate to the P region. When they return from the high energy state to the low energy state, according to the energy The principle of conservation, the excess energy will be expressed in the form of light. The luminous efficiency of high-power LED lighting has significantly exceeded that of fluorescent lamps, and beyond the metal halide lamps, the luminous efficiency of low-power LED lamps has exceeded that of high-pressure sodium lamps. A comparison of the luminous efficiencies of LED illumination with other white illumination sources is shown in Figure 1-6:

Comparison of luminous efficiency between LED Commercial Lightings and other white light illumination sources

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