Functional characteristics and market development of LED used in stage lighting 1. LED is the latest substitute of traditional light source. Their advantages include long service life, compact size, vibration resistance, low voltage (LVDC) operation, minimal maintenance costs and minimal environmental impact. LEDs are not affected by the mercury disposal issues that plague fluorescent tubes.
However, manufacturers have been working hard to further improve the energy efficiency of LED chips. Here we start by understanding LEDs. Understanding LEDs compares LEDs to traditional light sources, explains the relevance and importance of LED parameters, and highlights new products that drive LED design and functionality. 1, LED classification We use Philips lumileds official products to explain, see the picture below, from the power point, it can be high power, medium and small power, high voltage, COB, modules, etc. In terms of color: infrared wavelength: greater than 800nm, red wavelength: 620~630nm; orange wavelength: 600~620 nm; yellow wavelength: 585-600 nm; green wavelength: 555~585 nm; blue wavelength: : 440-480nm Purple wavelength: 350-440nm Pink wavelength: 360-380nm Ultraviolet: less than 350nm (UV).
Now everyone is making LED tri-primary swatches (LED flat lights) with low and medium power, which are mainly used to illuminate ambient light and LED strobe lights. High power is mainly used to make LED dyed par light (LEDPAR), LED effect lights, LED moving head lights, COB. Mainly make COBPAR lights, two-eye, four-eye, eight-eye audience lights. High-power modules are mainly used to make LED moving head beam lights, LED moving head pattern lights, LED moving head three-in-one lights, and LED moving head cutting lights. At present, some LED moving head lights can be seen with 30W patterns, 60W patterns, 80W beams, 120W pattern, 150W pattern, 350W three-in-one, 400W cutting, 500W cutting, 600W cutting, etc. 2. To make LED products, you must know the chromaticity diagram. The chromaticity diagram is a plan view of various chromaticity represented by points at different positions.
It was formulated by the International Commission on Illumination (CIE) in 1931, so it is called the CIE chromaticity diagram. Some people call it the spectral diagram and the chromaticity diagram. In the figure, the x coordinate is the ratio of the red primary color, the y coordinate is the ratio of the green primary color, and the coordinate z representing the blue primary color can be derived from x+y+z=1. Each point on the arc in the figure represents a pure spectral color, and this arc is called a spectral locus.
The straight line from 400nm (violet) to 700nm (red) is the violet-red color series (non-spectral colors) not on the spectrum. The center point C represents white, which is equivalent to the color of sunlight at noon, and its chromaticity coordinates are x=0.3101, y=0.3162. If you give a little S on the chromaticity diagram, you can immediately get the hue and saturation of the color represented by the S point.
Connect CS, its extended line intersects the spectral locus at point O, the wavelength at point O is the dominant wavelength of color S, which determines the hue of color S. The ratio CS/CO of the distances from C to points S and O is the saturation of the color. If a straight line is drawn from any point on the spectral locus through point C to another point on the opposite spectral locus, the colors at both ends of the straight line are complementary colors.
Draw a straight line from any point P on the straight line representing the non-spectral color series through point C, and intersect the spectral locus at point Q. The color at point Q is the complementary color of the non-spectral color at point P. The non-spectral color is expressed by adding a letter c after its complementary color wavelength, for example, 528c represents the complementary color of green with a wavelength of 528 nanometers, that is, purple. When any two colors are mixed, the color point of the mixed color must be on the connecting line of the first two color points.
It can be seen from the chromaticity diagram that the three primary colors of red, green and blue can be synthesized into any color. The CIE chromaticity diagram has great practical value. Any color, whether it is the color of the light source or the surface color, can be calibrated in the chromaticity diagram, which makes the description of the color simple and accurate, and the synthesis route of each color light is also clear at a glance. In order to ensure the correct identification of colors, CIE published the "Visual Signal Surface Color" standard in 1983. This document specifies the specific range of visual signal surface color on the CIE chromaticity diagram.
3. LED forward current characteristics 4. LED light output characteristics and current 5. LED light output characteristics and temperature 6. Relationship between LED life and temperature 7. LED optical parameters, unit a, luminous intensity (I, Intensity): T unit Candela, that is, cd. The luminous flux emitted by a light source in a unit solid angle in a given direction is defined as the (luminous) intensity (degree) of the light source in that direction. The luminous intensity is for a point light source, or the size of the illuminant is compared with the irradiation distance small occasions. This quantity indicates the converging ability of the luminous body emitted in space.
It can be said that the luminous intensity describes how "bright" the light is, because it is a common description of light power and convergence ability. The greater the luminous intensity, the brighter the light source looks, and the brighter the object illuminated by the light source under the same conditions. Therefore, this parameter was used to describe the flashlight earlier. b. LED luminous flux (F, Flux): T unit lumen, ie lm.
The amount of light emitted by a light source per unit time is called the luminous flux of the light source. Similarly, this amount is for the light source, and it describes the total amount of light emitted by the light source, which is equivalent to the light power. The greater the luminous flux of the light source, the more light is emitted. For isotropic light (that is, the light from the light source is emitted with the same density in all directions), then F = 4πI.
That is to say, if the I of the light source is 1cd, the total luminous flux is 4π =12.56 lm. Compared with the mechanical unit, the luminous flux is equivalent to the pressure, and the luminous intensity is equivalent to the pressure. In order to make the irradiated point appear brighter, we not only need to increase the luminous flux, but also increase the means of convergence, which is actually to reduce the area, so as to obtain greater intensity.
c. LED illuminance (E, Illuminance): T unit lux is lx (formerly called lux). The illuminance produced by the luminous flux of 1 lumen evenly distributed on the surface of 1 square meter. We usually don’t use this parameter a lot, so we won’t introduce it in detail here. d. Color rendering: The degree to which the light source presents the color of the object itself is called color rendering, that is, the degree of color fidelity; the color rendering of the light source is indicated by the color rendering index, which indicates that the color of the object under the light is better than the reference light (Sunlight) The color deviation during lighting can fully reflect the color characteristics of the light source.
A light source with high color rendering performance is better in color, and the colors we see are close to natural colors. A light source with low color rendering performance is poor in color performance, and the color deviation we see is also large. The CIE of the International Commission on Illumination sets the color rendering index of the sun as 100, and the color rendering index of various light sources is different, such as: high pressure sodium lamp color rendering index Ra=23, fluorescent tube color rendering index Ra=60~90. There are two types of color rendering: Faithful color rendering: To correctly express the original color of the material, a light source with a high color rendering index (Ra) must be used. The value is close to 100, and the color rendering is the best.
Common light source color rendering index Ra: incandescent lamp 97, white fluorescent lamp 75-85, warm white fluorescent lamp 80-90, halogen tungsten lamp 95-99, high pressure mercury lamp 22-51, high pressure sodium lamp 20-30, metal halide lamp 60- 65.8. Heat dissipation analysis of LED products Thermal conductivity Thermal conductivity refers to the thermal conductivity of a material with a thickness of 1m and a temperature difference of 1 degree (K, ℃) on both sides of a material under stable heat transfer conditions. The heat transferred by a square meter area, the unit is watts/meter degree (W/(m K), where K can be replaced by ℃). Thermal conductivity is only for the form of heat transfer in which heat conduction exists. When there are other forms of heat transfer, such as radiation, convection, and mass transfer, the composite heat transfer relationship is often called apparent heat transfer. Coefficient, apparent thermal conductivity or effective thermal conductivity (thermal transmissivity of material).
In addition, the thermal conductivity is for homogeneous materials. In reality, there are porous, multi-layer, multi-structure, and anisotropic materials. The thermal conductivity obtained by such materials is actually a performance of comprehensive thermal conductivity. , also known as the average thermal conductivity. The basic formula of heat transfer is: Φ=KA⊿T.Φ: heat flow. WK: total thermal conductivity.
W/(M2.℃)A: heat transfer area. M2⊿T: The temperature difference between the hot fluid and the cold fluid. The necessary condition for heat conduction is that there is a temperature difference inside the object, so heat is transferred from the high temperature part to the low temperature part.
The heat transfer process is commonly known as heat flow. The physical meaning of λ is: when the temperature gradient is 1K/m, the heat conducted through the heat conduction area of 1m2 per second, and its unit is W/m·K or W/m·℃. The λ of various substances can be determined experimentally.
Generally speaking, metals have the largest lambda value, solid non-metals have smaller lambda values, liquids have smaller lambda values, and gases have the smallest lambda values.