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                LED lamp beads knowledge summary
                Visit:7139 Date:2016-06-23

                What is a LED lamp beads?

                    LED lamp is a solid state semiconductor devices, which can be converted directly into electricity to light. The semiconductor light emitting device includes a semiconductor LED lamp beads, LED, symbols, alphanumeric tubes and dot matrix display (referred to as the matrix tube) and the like. In fact, digital, symbols, alphanumeric matrix of tubes and pipes in each light-emitting element is a light emitting diode. LED heart is one end of a semiconductor wafer, the wafer is attached to a bracket, one end is negative, and the other end connected to the positive power supply, so that the whole chip is epoxy encapsulated. The semiconductor chip consists of two parts, part of P-type semiconductor, the hole in it dominates the other end of the N-type semiconductor, here is mainly electronic. But when the two semiconductor connected, they form a "P-N junction" between them.

                    When the current through the wire act on the chip, the electron will be pushed to P zone electron hole recombination, and then will be issued in the form of photon energy in the P zone, which is the principle of LED light. The wavelength of light is the color of the light, it is formed by the material P-N junction decision.


                LED lights glowing pearl is how?

                    LED light-emitting principle called electroluminescent diode is a combination of P-type semiconductor material and the N-type semiconductor material, each end with electronic. Such arrangement allows current flow in one direction only. When the forward current through the PN junction, free electrons in the N-type material are attracted to the negative electrode and a positive electrode electron repulsion electrons, P-type substance in the electron-hole to move to the other direction, the time when the holes and free electrons bound , LED lights will glow beads. This will happen in any diode, when all the diodes emit light, most are not very effective. As in most ordinary diode, the semiconductor material itself to attract a lot of energy and an end. Or that the light emitted by the diode some materials can not be used effectively.


                LED lamp beads How many?

                1, according to the arc tube light color points can be divided into red, orange, green (subdivided green, standard green and pure green), Blu-ray and the like. Also, some light-emitting diodes comprises two kinds or three kinds of color chips. The LED light at the doped or undoped scattering agent, colored or colorless, the above-described various colors of light-emitting diodes can also be divided into colored transparent, colorless and transparent, colored and colorless scattering four types of scattering. Scattering-type light-emitting diodes and LEDs use up to do.

                2, according to the points of the arc tube features a smooth round lights, side lights, rectangular, surface-emitting tube, lateral pipe, surface mount miniature tubes. Divided by diameter circular lamp φ2mm, φ4.4mm, φ5mm, φ8mm, φ10mm and φ20mm like. Foreign φ3mm usually referred to as a light emitting diode T-1; the mind φ5mm make T-1 (3/4); the record φ4.4mm make T-1 (1/4).

                3, by the half-value angle size can be estimated circular luminous intensity angle distribution. From the luminous intensity distribution angle to be divided into three categories:

                (1) high directivity. Generally pointed epoxy encapsulated, or packaged with a metal reflector cavity, without adding scattering agent. Half-value angle of 5 ° ~ 20 ° or less, with high directivity, can be used for local lighting or light detector linked to form an automatic detection system.

                (2) standard. Typically used for light, its half-value angle of 20 ° ~ 45 °.

                (3) scattering. This indicator is larger perspective, half-value angle of 45 ° ~ 90 ° or more, a large amount of scattering agent.


                LED lamp What are the characteristics?

                1, LED lamp beads basic structure: light-emitting diodes referred to as LED, LED main material composition comprising: a die, adhesives, gold, frame and epoxy resins.

                2, the light emitting diode according to the type of light-emitting diodes and SMD LED assembly is divided into two kinds of plug-in LED. The light emitting type can be divided into ordinary monochrome LED, high brightness LED, color LED, flashing LED, voltage-controlled LED, ultraviolet light-emitting diodes.

                3, ordinary monochrome LED having a small size, low operating voltage, operating current filial luminous uniformity and stability, fast response, long life, etc., can be a variety of DC, AC, pulse and other power-driven lighting. It belongs to the current-controlled semiconductor device should be used with a suitable series limiting resistor.

                4, ordinary monochrome LED emission color and emission wavelength, whereas the emission wavelength in turn depends on the semiconductor material used for manufacturing a light emitting diode. The red LED wavelength is generally 650 ~ 700nm, amber light emitting diode wavelength is generally 630 ~ 650nm, the wavelength of orange light-emitting diode is generally about 610 ~ 630nm, the wavelength of the yellow light emitting diode is generally about 585nm, green wavelength light emitting diode generally 555 ~ 570nm.

                5, commonly made of ordinary monochromatic light-emitting diodes have BT (factory standard model) series, FG (Ministry of standard model) series and 2EF series. Common importing ordinary monochromatic light-emitting diodes have SLR series and SLC series.


                How to produce white LED lamp beads?

                     After mixing powdered crystals In one dense adhesives made of. When the LED lamp bead chip emits blue light, the blue light will be part of the crystal is efficiently converted to a broad spectrum (Spectrum approximately 580nm) mainly as a yellow light. (In fact, a single crystal of Ce-doped YAG is regarded as more than a phosphor scintillator.) Since yellow light stimulates the eye of the red and green receptors, remixed blue LED itself, make it look like a white light and its color is often called white moonlight. This white LED production method was developed by NichiaCorporation and since 1996 for use in the production of white LED.

                    To adjust the color of pale yellow light, terbium and gadolinium and other rare earth metals can be used substituted Ce3 +: YAG doped with cerium (Ce), can even replace YAG in part or in its entirety aluminum do. And based on the characteristics of its spectrum, red and green objects in this LED light will look less sharp so when broad-spectrum light. Also due to the variation in production conditions, this LED color temperature of the finished product are not uniform, there, so in the production process to make a distinction from warm yellow to blue cold will come out with its characteristics.

                    Another white LED production is a bit like a lamp, emits near ultraviolet LED is coated with a mixture of two phosphors, one is red and blue light europium, and the other is made of green, doped zinc sulfide (ZnS) of copper and aluminum. However, due to ultraviolet light causes deterioration of adhesive epoxy resin cracking, so the production more difficult, but life is also shorter.

                    Compared with the first method, it is less efficient and produce more heat (StokesShift because the former is larger), but the benefits are preferred characteristic spectrum light generated looks better. And due to the high power UV LED lamp beads, so its efficiency is the first method, although relatively low, it was comparable to the brightness of the latest method of manufacturing a white LED not reuse the phosphor. The new approach is on zinc selenide (ZnSe) substrates grown zinc selenide epitaxial layer. Its active zone emits blue light when energized while the substrate will be issued yellow, white light is mixed


                How to improve light extraction efficiency of UV LEDs?

                    UV LEDs are often used in the medical field, also known as medical violet LED, in a deep ultraviolet light emitting diode plated only 5 nanometers thin aluminum, the aluminum film is not only not the same as the one issued on the device like a traditional mirror more light reflected back to the side of the device but skillfully emitted light was collected through the aluminum layer, magically shot from the front, to achieve the light extraction efficiency. This is because after doing when aluminum is very thin, which makes it different from the traditional effect of nano-mirror reflects the light back, but concentrated absorption of light collection and achieve positive emission.

                    Tests showed that this layer of aluminum "coat" of ultraviolet light-emitting diode light extraction efficiency "contribution" will vary with different wavelengths and different. Generally speaking, the shorter the wavelength, the higher the efficiency. Data show that, with this layer is coated with an aluminum film, a wavelength of about 310 nm ultraviolet light emitting diodes, light extraction efficiency can be increased by about 20%; a wavelength of about 290 nm ultraviolet light emitting diodes, light extraction efficiency can be increased by about 50%; and for a wavelength of about 280 nm deep-UV LEDs, the light extraction efficiency can be increased by 130%.


                How to detect visible light LED lamp beads?

                (1) with a multimeter test. The use of having a × 10kΩ gear multimeter can largely determine the quality of the light emitting diode. Normal, the diode forward resistance value of several tens to 200kΩ, reverse resistance value of α. If the forward resistance value of 0 or ∞, reverse resistance value is very small or 0, the easily damaged. This detection method can not actually see luminescence of the arc tube, because × 10kΩ block does not provide a large forward current to the LED. If there are two pointer multimeter (preferably the same model) can better check the light emitting diode luminescence. With a wire which will be "+" a multimeter terminal and another piece of the table "-" terminal connection. The remaining "-" pen then tested positive light tube (P area), the rest of "+" pen then tested negative light tube (N zone). Two multimeter are set × 10Ω block. Under normal circumstances, be able to normal light after switching. If the brightness is very low, not even light, can be allocated to two multimeter are × 1Ω if, if still dark, not even light, then the poor performance of or damage to the light emitting diode. It should be noted, is not a measure will start two multimeter × 1Ω, in order to avoid excessive current damaging the light emitting diodes.

                (2) external power measurements. With 3V voltage source or battery and multimeter two series (Analog or digital can) can accurately measure the optical and electrical characteristics of the light-emitting diodes. To this end may be connected to the circuit 10 shown in FIG. If the measured VF between 1.4 ~ 3V, and the luminous brightness is normal, the light-emitting normal. If the measured VF = 0 or VF≈3V, not light, the light-emitting tube is bad.


                How to detect ultraviolet (IR) light emitting diode detector?

                    Since ultraviolet light emitting diode that emits 1 ~ 3μm ultraviolet light, the human eye can not usually single ultraviolet light emitting diode power only a few mW, different types of UV LED luminous intensity distribution angle is not the same. UV LED's forward voltage drop is generally 2.5 ~ 3.6V, precisely because of its ultraviolet light emitted by human eye can not see, we can only determine its PN junction forward and reverse electrical properties of normal visible light LED using the above assays, and Unable to determine whether the normal luminous. For this reason, it is preferable to prepare a photosensitive device (e.g. 2CR, 2DR silicon photocell) for a receiver, with the change of the voltage across the battery meter multimeter to determine whether the UV LED emitting ultraviolet light after the forward current and add the appropriate measurement circuitry.


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