1. The relationship between the spectrum of visible light and white light of LED. As everyone knows, the wavelength range of the visible light spectrum is 380nm ~ 760nm, which is the seven colors of light that can be felt by the human eye - red, orange, yellow, green, cyan, blue, purple, but the light of each of the seven colors is A monochromatic light. For example, the peak wavelength of red light emitted by an LED is 565 nm. There is no white light in the spectrum of visible light, because white light is not monochromatic light, but composite light synthesized by a variety of monochromatic lights, just as sunlight is white light synthesized by seven monochromatic lights, while in color televisions White light is also composed of three primary colors red, green, and blue. Thus, to make the LED emit white light, its spectral characteristics should include the entire visible spectral range. However, it is impossible to manufacture LEDs of this performance under the current process conditions. According to people's research on visible light, white light that can be seen by human eyes requires at least two kinds of light mixing, that is, two-wavelength light (blue light + yellow light) or three-wavelength light (blue light + green light + red light) mode. . The above two modes of white light require blue light, so the ingestion of blue light has become a key technology for manufacturing white light, that is, the "blue light technology" currently chased by major LED manufacturing companies. At present, there are only a few manufacturers that have mastered "Blu-ray technology" in the world, so the promotion and application of white LEDs, especially the promotion of high-brightness white LEDs in China, has a process.
2. Process structure of white LED and white light source. For general illumination, white LEDs are usually formed by two methods in the process structure. The first one uses "blue light technology" to form white light with phosphors; the second is a variety of monochromatic light mixing methods. Both methods have successfully produced white light devices. The first method to produce white light is shown in Figure 1. In the figure, the LED GaM chip emits blue light (λp = 465 nm), which is packaged with YAG (yttrium aluminum garnet) phosphor, which is emitted when the phosphor is excited by blue light. Yellow light, as a result, blue light and yellow light mix to form white light (the structure of the LED is shown in Figure 2). The second method uses a chip of different color light to be packaged together, and white light is generated by mixing various colors of light.
3. The application prospect of white light LED lighting new light source. To illustrate the characteristics of white LEDs, let's look at the current state of the lighting source. Incandescent and tungsten halogen lamps have a luminous efficacy of 12 to 24 lumens per watt; fluorescent lamps and HID lamps have a luminous efficacy of 50 to 120 lumens per watt. For white LEDs: In 1998, the efficacy of white LEDs was only 5 lumens per watt. By 1999, it had reached 15 lumens per watt. This indicator is similar to general household incandescent lamps. In 2000, the efficacy of white LEDs was similar. Has reached 25 lumens / watt, this indicator is similar to the tungsten halogen lamp. Some companies predict that by 2005, the luminous efficacy of LEDs can reach 50 lumens / watt, by 2015, LED light efficiency is expected to reach 150 ~ 200 lumens / watt. At that time, the working current of the white LED could reach the amperage level. It can be seen that the development of lighting sources for white LED writers will become a possible reality.
Incandescent lamps and tungsten halogen lamps for general lighting are inexpensive, but the luminous efficacy is low (the thermal effect of the lamp is vainly consumed), the life is short, and the maintenance workload is large. However, if the white LED is used for illumination, not only the light effect is high, but also the life is long. Long (continuous working time of 10,000 hours or more), almost no maintenance. At present, Hella of Germany has developed aircraft reading lights using white LEDs; a street in Canberra, Australia, has used white LEDs for street lighting; China's urban traffic management lights are also replacing white traffic lights with white LEDs. It is foreseeable that in the near future, white LEDs will enter the home to replace existing lights.
LED light source has the advantages of using low-voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, multi-color illuminating, etc. Although the price is more expensive than existing lighting equipment, it is still considered to be Inevitably replace existing lighting devices.
Led-feature
LED features and benefits
The intrinsic characteristics of the LED determine that it is the most ideal light source to replace the traditional light source, and it has a wide range of uses.
small volume
The LED is basically a small chip that is encapsulated in epoxy, so it is very small and very light.
Low power consumption
LED power consumption is very low, generally the operating voltage of the LED is 2-3.6V. The operating current is 0.02-0.03A. This means that it consumes no more than 0.1W.
long lasting
LEDs have a service life of up to 100,000 hours at the right current and voltage
High brightness, low heat
Environmental protection
LEDs are made of non-toxic materials, unlike mercury-containing fluorescent lamps that can cause contamination, and LEDs can be recycled.
strong and sturdy
The LED is completely encapsulated in epoxy, which is stronger than both the bulb and the fluorescent tube. There are no loose parts in the lamp body. These features make the LEDs hard to damage.
Color temperature and color application
(1) Color temperature of the light source: The color temperature of the light source (the color seen by the human eye when directly observing the light source) is also described by the absolute temperature of the complete radiator equal to or similar to the color temperature of the light source, which is also called the color temperature of the light source. The color temperature is expressed by the absolute temperature K. Different color temperatures can cause people to react differently in emotions. We generally divide the color temperature of light sources into three categories:
a. Warm color light: The color temperature of warm color light is below 3300K. The warm color light is similar to the incandescent light color, and the red light component is more, giving people a warm, healthy and comfortable feeling. It is suitable for families, houses, dormitories, hospitals, hotels. Such places, or places with relatively low temperatures.
b. Warm white light: also called the middle color, its color temperature is between 3300K-5300K. The warm white light is soft, which makes people feel happy, comfortable and serene. It is suitable for shops, hospitals, offices, restaurants, restaurants, waiting rooms and other places.
c. Cool color light: also known as daylight color, its color temperature is above 5300K, the light source is close to natural light, has a bright feeling, makes people concentrate, suitable for reading in offices, conference rooms, classrooms, drawing rooms, design rooms, libraries. Room, exhibition window and other places.
Color rendering: The degree to which the light source appears to the color of the object is called color rendering, which is the realistic degree of color. The light source with high color rendering performs better on color. The color we see is closer to natural color, color rendering. Low light sources perform poorly on color, and the color deviations we see are also large.
Why is there a color rendering? The key is the spectral characteristics of the light. The wavelength of visible light is in the range of 380 nm to 780 nm, which is the red, orange, yellow, green, blue, and blue we see in the spectrum. The range of purple light, if the proportion of the light contained in the light emitted by the light source is close to the natural light, the color seen by our eyes is more realistic.
We generally characterize color rendering by color rendering index. The standard color is set to 100 under the radiation of a standard light source. When the color scale is illuminated by the test light source, the degree of visual distortion of the color is the color rendering index of the light source. The larger the color rendering index, the less the distortion. Conversely, the larger the distortion, the smaller the color rendering index. The color rendering index requirements of the light source are different in different places. In the International Lighting Association, the color rendering index is generally divided into five categories:
Category Ra Scope of application
1A >90 Art galleries, museums and printing industries and places
2B 80-90 Family, restaurant, high-grade textile technology and similar industries
2 60-80 office, school, outdoor street lighting
3 40—60 Heavy industry factory, outdoor street lighting
4 20-40 Outdoor road lighting and some places where the requirements are not high
LED development history
The basic knowledge of the ability of semiconductor materials to generate light was known 50 years ago. The first commercial diode was born in 1960. The core of the LED is a wafer consisting of a p-type semiconductor and an n-type semiconductor. There is a transition layer between the p-type semiconductor and the n-type semiconductor, called a pn junction. In some PN junctions of semiconductor materials, the injected minority carriers recombine with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. The PN junction adds a reverse voltage, and minority carriers are difficult to inject, so they do not emit light. Such a diode fabricated by the principle of injection electroluminescence is called a light-emitting diode, and is generally called an LED. When it is in the forward working state (ie, the forward voltage is applied to both ends), when the current flows from the anode of the LED to the cathode, the semiconductor crystal emits light of different colors from ultraviolet to infrared, and the intensity of the light is related to the current. High-efficiency, low-light-loss high-power LED has been widely used in many lighting fields such as street lamps, mining lamps, tunnel lights, spotlights, fluorescent lamps, etc., and has been well received by the industry.
1. The self-encapsulation of solid-state semiconductor device wafers has high luminous efficiency. The brightness of 1W can reach the effect of ordinary fluorescent lamps of 3W, saving 60% of electricity, good light decay performance, and high temperature resistant pc plastic materials.
2. The lower vf value (3.1v-3.5v) can reduce the power dissipation and reduce the heat generation, and extend the working time of the LED.
3. Using the original epoxy resin encapsulation process to emit energy in the form of electrons, the lumen value of white and white can be almost the same. The product has no spot color, high color and good consistency.
4. The lens is treated by special methods to ensure that it will not fall.
5. Use
LED street light, LED light. LED lighting, led spotlight high power 60W 80W 120W 160W 180W LED decorative light LED lighting LED street light LED industrial and mining lights LED lighting LED stage lights.
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