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Leds history

- Aug 24, 2016 -

1, define,

LED (Light Emitting Diode) is short for light-emitting diodes in English, it is made of semiconductor material, it has a positive and a negative, put the positive and negative dc access corresponding is negative, it will shine under the given voltage.

The history of 2,

3, luminous principle

LED the core technology of the semiconductor material made of light-emitting chip, as shown in the figure below, the chip is composed of p-type and n-type semiconductor semiconductor, P and N pole when the chips according to the graphic access dc power supply, the chip will glow.

P-type and n-type semiconductor semiconductor PN junction, the light emitting chip p-n junction voltage is higher, heralding the electronic energy is high, when the p-type material within the hole and the N type semiconductor electronic outside under the action of electric field on the PN junction compound, the compound of energy is released into light energy, which is LED light-emitting mechanism of different semiconductor materials the wavelength of the light is different, different wavelengths in our eyes is felt different colors of light.

LED chip light wavelength range is very wide, covering ultraviolet, visible, infrared this range, we often see are uv LED, infrared LED and red LED, green LED, blue LED, amber light LED.

LED chip can only single wavelength of light, the LED chip is not emit white light, red, green and blue three wavelength combination together, white light produced due to the discontinuous spectrum, narrow range, can't be used for lighting.

4, white LED

We often see the LED lamp bead can be all kinds of light color, among them, there is also a white LED lamp bead, the following figure, mentioned above, the LED chip is not emit white light, so, how to emit white light is LED lamp bead?

Originally, LED white light bead is the lamp bead inside the blue chip with yellow phosphor powder made from the first LED to the birth of white LED, the human experience for 31 years, October 7, 2014, the royal Swedish academy of sciences announced the 2014 Nobel Prize for physics to Japanese scientists red battery yong, amano hao and the Japanese American scientists at the university of California, Santa Barbara, nakamura to fix two (Japan) is the original technical experts and chemical corporation), for in their creations new type high efficiency and energy saving light source technology (blue light emitting diode), the contribution of the Nobel Prize marked the lighting of a quarter of the world electricity consumption will enter a new milestone.

According to the principle of three primary colors, white is the mixture of these three colors red, green and blue, for example, red and green mixed into yellow, then mixed with blue becomes white, primary colors is illustrated below.

Leds emit white light is also using this principle, namely the light emitting chip is blue light, covered with yellow phosphor powder in the chip as shown in the figure below, the blue light through yellow phosphor, yellow phosphor powder will be blue, light yellow, the yellow light and then mixed with blue light, and become the white light, this is the white LED the luminous principle.

Blue chip yellow phosphor (figure particles said red phosphors)

In order to increase the LED white light, the color to yellow phosphor to join the red phosphors.

Below is the LED packaging process, the chip with yellow phosphor, phosphor powder is mixed with the glue after injection.

Phosphor powder quality is good or bad, directly affect the quality of light and light failure, at present, the LED phosphors mainly adopts aluminate and silicate, aluminum acid salt is the most stable, is the main application of phosphor.

Add a small amount of red phosphors in yellow phosphor, can adjust the color temperature of white light LED, along with the increase in red phosphor powder added, the white light color temperature changes from cool to warm color. Pictured above red phosphor particles, particles, the more light is warm, yellow fluorescent lamp after adding red phosphor powder, fluorescent powder mixture color looks will be fairer.

LED phosphors is covered by as little as possible, brand LED coated powder amount is very few, can almost see the outline of blue chip, some LED coated powder amount is large, and even some large manufacturers also to powder coating area as propaganda, the characteristics of the LED brightness coated phosphors powder amount may be greatly stimulate the efficiency is low, large amount of powder coating is easy to cause the light failure.

Is the white light: 4000 k to 6000 k

Warm white: 2800 k to 4000 k

Light color said white light is not accurate, just a range, light color of LED products, procurement emitting light colors tend to vary widely.

Lighting light source color temperature uniformity is an important symbol of lighting quality, LED white light color temperature uniformity is a technical problem of white light LED manufacturing process, there is a temperature with different color (color temperature values are the same, light color different) and same color different temperature with different values (the same color of light, color temperature), expressed in cold white, warm white LED color temperature, is a kind of a disguise for other color temperature difference, the right LED Bai Guangguang representation of color is the color temperature.

5, LED light source compared with other light source

LED lighting light source is a industry developed rapidly in recent years, compared with other light source, LED lighting light source is the most notable features of energy saving and environmental protection, human is the product of energy saving technical progress most performance index, so it is with the LED lighting technology, below is contrast figure luminous efficiency of various kinds of light source.

Environmental characteristics of the LED is in LED consisting of various materials, won't produce pollution to the environment, at the same time, the LED lighting is very high luminous efficiency, can save a lot of electricity, which is around the world compete to development of the important reasons of lighting technology, as the LED cost further reduce, the LED will be widely used in various fields of lighting.

6, LED characteristics

1, high luminous efficiency, energy saving effect is good.

2, good quality of white light spectrum, no ultraviolet and infrared spectrum, belong to healthy light source.

3, long service life: luminous flux decay to 70% of the theoretical service life of up to 5-100000 hours.

4, short response time, suitable for frequent switching and the occasion of high-frequency operation.

5, green environmental protection, LED material without harmful ingredients and pollution environment.

6, flexible control, easy to move light, can achieve a variety of color effects.

7, good color rendering, the object's color reduction effect is good.

8, emitting, single LED is an ideal light source to prevent light pollution.

7, LED species

According to the power size:

1, low power, 0.1 W.

2, the power, 0.5 W.

3, high power, more than 1 w.

According to the packaging form points:

Upright type (DIP) and patch type (SMD).

The emergence of blue LED, changed the human lighting technology, mainly LED lighting changes are happening in our lives, LED lights also over the years become a common word, in the field of public life, everywhere have LED, LED TV, LED backlight, mobile phone, LED traffic light, LED flashlight, LED lamp, LED landscape lighting, LED indoor lighting.

The exact name of the LED lighting is: semiconductor solid-state lighting (SSL).

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