What do we usually mean by the word LED? LED is the abbreviation of Light Emitting Diode. It is a solid-state semiconductor device that can directly convert electricity into light.
Since the development of this kind of semiconductor component, it has been generally used as indicator lights and display panels, but with the increase in technology, it has been used as a light source. It can not only directly convert electrical energy into light energy with high efficiency, but also has up to tens of thousands of hours of service life. At the same time, it is not as fragile as traditional bulbs and can save electricity. Meanwhile, LED light is environmentally friendly, mercury-free, small in size, can be used in low-temperature environments. The light source is directional, causing less light damage and rich in color gamut Etc.
With the emergence of white LEDs and the introduction of more technology, the current lighting equipment is flourishing in household appliances and notebook computers, automobile anti-fog lamps, indoor lighting, etc. The application of LEDs is becoming more and more common.
The invention of LED
In 1955, Rubin Braunstein of Radio Corporation of America discovered the infrared radiation effect of gallium arsenide (GaAs) and other semiconductor alloys. In 1962, Nick Holonyak Jr of General Electric Company (GE) Developed visible light LED. However, the real take-off of LED technology was after the emergence of white LEDs in the 1990s, and then they began to be paid more and more attention, and their applications became wider and wider.
LED’s light-emitting principle
So what is the working principle of an LED? LED is an electronic component that can convert electrical energy into light energy, and it also has the characteristics of a diode, that is, it has a positive electrode and a negative electrode. The most special feature of LED is that it will emit light only when it is energized from the positive electrode, so when it is generally given the DC power, the LED will emit light steadily. But if it is connected to the AC power, the LED will flicker, and the flashing frequency depends on the frequency of the input AC power.
The light-emitting principle of LED is to apply a voltage to allow electrons and holes to be combined in a semiconductor to release energy in the form of light. At present, the different types of LEDs developed by the global industry can emit light of different wavelengths from infrared to blue, and the industry also has purple to ultraviolet LEDs. In recent years, the most attractive development of LEDs is to coat blue LEDs with phosphor. A white LED product that converts blue light into white light. The reason why LED is called Century New Light Source is that LED has the characteristics of point light source and solid-state light source, which can save energy, high shock resistance, long life, small size, fast response, and high color saturation.
LED color classification
As LEDs are made of different materials, the generated photons have different energy. Therefore, the industry uses manufacturing materials to control the wavelength of the LED’s light emission, thereby producing various LEDs with different spectra and colors.
The material used in the world’s first LED is arsenic (As) gallium (Ga), with a working voltage of 1.424V, and the light emitted by it is in the infrared spectrum. After that, the industry developed phosphor (P) gallium (Ga) as the material of the LED, the working voltage is 2.261V, and the emitted light is a green light.
Through the materials required for these two types of LEDs, the lighting industry developed LED products of all wavelengths ranging from infrared to green light, including common red LEDs, yellow LEDs, orange LEDs, etc. The three major types of LEDs are called 3-element LEDs because they use gallium, arsenic, and phosphorous, while blue LEDs, green LEDs, and infrared LEDs are called 2-element LEDs. The industry later developed a 4-element LED that mixed aluminum (Al), calcium (Ca), indium (In), and nitrogen (N), which can emit light in all visible light ranges and part of the ultraviolet spectrum.
When discussing LED products, there are 3 units of luminous brightness, which are lux (Lux), luminous unit lumens (Lumen; lm), and luminous intensity unit candle (Candle power; CD).
- CD represents the luminous intensity of a completely radiant object, at the freezing point temperature of platinum, per sixtieth of an area of a square centimeter. It is suitable for use in the field of active light-emitting lamps, such as incandescent light bulbs.
- lm means the amount of light irradiated by 1 CD light on a plane with a distance of 1 cm and an area of 1 cm². It is suitable for use in reflective lamps and penetrating lamps, such as projectors.
- Lux means the illuminance that 1 Lm of light is evenly distributed on an area of 1 square meter. Suitable for use in the field of photography.
Generally speaking, the luminous intensity of a single LED takes CD as the unit, coupled with the viewing angle parameter, and the luminous intensity of the LED ranges from 1mCD to 5,000 mCD. When the manufacturer labels a single LED product, its luminous intensity specification refers to the luminous intensity at the point of maximum luminous intensity at the best viewing angle and at the center position when the LED is lit under a current of 20 mA.
Energy-saving benefits of LED
Based on the environmental protection standpoint and energy conservation demands, governments around the world attach importance to the economic and energy-saving benefits brought by LEDs and energy-saving lamps. Manufacturers are also optimistic about the business opportunities of this lighting revolution and have invested in them. In addition to the phased ban on the use of incandescent bulbs in the European Union and the U.S. Congress, Canada has already announced a total ban on incandescent bulbs in 2010. And some states in the U.S. including California will also ban incandescent bulbs in 2012. Australia announced a total ban on the sale of incandescent light bulbs in 2010, and China and Japan also have LED incentive schemes in the planning.
Although there is already another energy-saving fluorescent lamp (CFL) on the market, its lighting quality is still insufficient, the start-up time is longer than ordinary incandescent bulbs, and the light source output brightness cannot be adjusted, so the popularity is still not enough high. LED has more energy-saving benefits, and through the improvement of technology, the brightness has reached a satisfactory level. However, the high price is a big problem. In the future, as the mass production of global LED manufacturers accelerates, the price reduction can accelerate the popularity of LED lamps.
Generally, LEDs have a long light-emitting life, and most products are marked for more than 100,000 hours, but in fact, the brightness of LEDs will decay. After a period of use, the brightness will decay to half or even less. Fortunately, with the advancement of technology in the industry, there are many solutions to reduce the problem of LED brightness decay. In the production process, the use of 4 element LEC materials can have a longer brightness decay cycle, and the LED technology used by the manufacturer has a great relationship with how long the finished product can last. Color matching is also the key to the production of LED factories.
The service life of LEDs is up to 50,000 hours compared with 1,000 hours for ordinary incandescent bulbs and 10,000 hours for daylight lamps, which greatly reduces the cost of lamp replacement. This feature helps LED lamps win a good advantage in price and is a good reason to replace ordinary bulbs with LEDs. The obvious disadvantage of LED is the heat dissipation problem. Improper heat dissipation will cause the luminosity and service life of LED lamps to be attenuated. Fortunately, this part has gradually improved significantly with the blessing of new technology.
In addition to the LED indicators on various electronic products that we are familiar with, LED screens, LED lighting, LED backlights for LCD screens, LED backlights for buttons on mobile phones, new generation OLED screens, PLED screens, etc. The application of LEDs is gradually developing steadily. Because of the mature market development of LED applications in some areas, the speed of popularization has begun to accelerate, creating amazing business opportunities invisibly.
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