LED是发光二极管为什么叫发光二极管

1、LED是发光二极管为什么叫发光二极管Semiconductor light-emitting device _ 1, semiconductor light-emitting diode working principle, characteristics and applicationSemiconductor luminescent devices include semiconductor light-emitting diodes (leds), digital tubes, symbolic tubes, meter tubes, and dot matrix displays (f

2、or short, matrix tubes). In fact, every luminous element in a digital tube, a symbol tube, a meter tube, and a matrix tube is a light-emitting diode. one, semiconductor light-emitting diodes (leds) working principle, characteristics and application (one) LED principle leds by - compounds, such as Ga

3、As (gallium arsenide), GaP (gallium phosphide), GaAsP made of semiconductor such as gallium arsenide (p), its core is the p-n junction. Therefore, it has the i-n feature of general p-n junction, which is the positive guide, reverse cut-off, and puncture characteristics. In addition, under certain co

4、nditions, it also has the luminescence characteristic. Under positive voltage, the electron is injected into the P area by N, and the void is injected into N area by P area. A small number of carriers entering the other side of the area (children) are composed of most carriers (many children), as sh

5、own in figure 1. assumption is glowing in the P region, then injected electrons and the valence band hole composite and shine directly, or be luminous center after capture, hole composite luminescence again. In addition, this kind of light composite some electrons are not luminous center (the center

6、 between the conduction band, interface with near middle) capture, then with hole compound, every time the energy released is not big, could not form visible light. The higher the amount of light, the higher the amount of light, the higher the quantum efficiency. Because the composite is glowing in

7、the childrens diffuse region, light is produced only within the mu m near the PN junction. theory and the practice proves that the peak wavelength lambda light with the light emitting area of semiconductor materials forbidden band width of Eg, namely lambda material 1240 / Eg (mm) type of Eg unit fo

8、r electron volts (eV). If visible light can be produced (at a wavelength of 380nm 780nm red), the semiconductor material should be between 3.26 and 1.63 eV. The light that is longer than red wavelengths is red. There are now infrared, red, yellow, green and blue light emitting diodes, but the cost o

9、f the blue leds and the high price are not universal. (2) the characteristics of the ledsThe significance of (1) the limit parameters (1) allow power Pm: allow LED on both ends are dc voltage and current flow through the maximum value of product. More than that, LED heat and damage. maximum positive

10、 dc current IFm (2) : allows to add one of the biggest positive dc current. More than this can damage a diode.Maximum reverse voltage VRm (3) : the biggest reverse voltage is allowed to add. Over this value, leds may be punctured and damaged.Topm (4) work environment: light-emitting diodes (leds) wo

11、rking environment temperature range. Below or above the temperature range, the light-emitting diode will not work properly and the efficiency will be greatly reduced. 2. The significance of electrical parameters (1) spectral distribution, and peak wavelength: a light of the light emitting diode is n

12、ot a single wavelength, the wavelength can press is shown in figure 2. the chart shows, in the light of the luminous tube light intensity, the largest of a wavelength lambda 0 this wavelength for peak wavelength. (2) luminous intensity IV: the luminous intensity of leds, often referred to as normal

13、() refers to the axis of cylindrical luminous tubes on the direction of luminous intensity. If the intensity of radiation in that direction is (1/683) W/sr, then it will be 1 candela (symbol CD). The luminescence intensity is commonly used as a unit of candela (MCD) because the light of a general LE

14、D is small. (3) spectrum halfwidth lambda: spectral purity of luminous tube. It said is refers to the figure 3 1/2 wavelength two peak intensity in between. (4) half value Angle theta 1/2 and perspectives: theta 1/2 refers to half of the axial intensity is a luminous intensity value direction and An

15、gle of optical axis to the (normal). 2 times of the half value Angle view (or a power Angle). figure 3 shows the Angle of two different types of leds luminous intensity distribution. The coordinates of AO are relative luminance (the ratio of luminescence intensity to maximum luminous intensity). Obv

16、iously, south displayed prominently on normal direction estates Cha kang ren? The larger the Angle of departure from the normal, the lower the relative luminance. In this case, a half value Angle or point of view is obtained. (5) positive working current If: it refers to normal light-emitting light-

17、emitting diode when the positive current value. In practice, the IF should be selected under 0.6 IFm as required. (6) is working voltage VF: parameters of the working voltage is given in the table at a given positive electrical flow. Its usually measured at IF = 20mA. Leds are working voltage VF at

18、1.4 3V. The VF will decrease as the outside temperature increases. (7) V - I characteristic: light-emitting diodes (leds) the relationship between voltage and current can be used in figure 4. in forward voltage is less than a certain value (called threshold), small current, light. When the voltage e

19、xceeds a certain value, the forward current increases rapidly with the voltage, emitting light. The v-i curve can derive the positive voltage of the luminous tube, the reverse current and the reverse voltage. Reverse leakage current of the glowing tube is below 10 mu A. (3) the classification of the

20、 LED 1. According to the luminous tube emitting light colors according to the luminous tube light color points, can be divided into red, orange, green, yellow green, standards, green and subdivision and pure green), blue, etc. In addition, some leds contain two or three types of chips. according to

21、leds out light scattering or after adding the agent, colored or colorless, the above all sorts of color of leds can also be divided into colored transparent, colorless, transparent, colored and colorless scattering four types. Scattered light-emitting diodes (leds) are used for indicating lamps. 2.

22、According to the luminous tube smooth feature pointsAccording to the luminescence tube, the lamp, the square lamp, the rectangle, the surface light pipe, the side tube, the surface installation USES the micro-tube. The circular lamp is divided into phi 2mm, phi 4.4 mm, phi 5mm, phi 8mm, phi 10mm and

23、 phi 20mm. Foreign countries usually call the light-emitting diodes of phi 3mm as t-1; Lets call phi 5mm T minus one (3/4); Lets call phi 4.4 mm T minus 1 of 1/4. by half value horn size can estimate the circular luminous intensity distribution. There are three types of light intensity Angle distrib

24、ution: (1) high directivity. It is usually encapsulated by epoxy, or with a metal reflector, which is not a scattering agent. Half value Angle of 5 20 or less, has the very high directivity, can be used for local lighting light source, or with light detector combined to form an automatic test system

25、. (2) standard. Usually used as indicator light, the half value Angle of 20 to 45 . (3) the scattering model. This is a bigger light Angle, half value Angle is 45 90 or greater, the amount of scattering agent is bigger. 3. According to the structure of light emitting diode according to the structure

26、 of the light-emitting diodes (leds) have all epoxy coating, metal base epoxy encapsulation, ceramic base epoxy encapsulation, glass encapsulation structure, etc. 4. According to the luminous intensity and working current according to luminous intensity and working current are normal brightness LED

27、luminescence intensity ( 100mcd); High luminescent leds between 10 and 100 MCD. general LED working current in a dozen mA to dozens of mA, and LED the working current of low current under 2 mA brightness (the same as the ordinary light-emitting tube). apart from the above classification method, and

28、the chip materials classification and classified by function method. (4) the application of the LED due to the light emitting diode luminescence intensity of the color, size, shape, and transparent situation is different, so using light-emitting diodes (leds) should choose according to actual needs

29、appropriately. because the light emitting diode has the biggest forward current VRm IFm, maximum reverse voltage limit, when used, shall ensure that no more than this value.For the sake of safety, the actual current IF should be below 0.6 IFm; Reverse voltage VR 0 is allowed to occur. 6 VRM. LED is

30、widely used in electronic instruments and electronic equipment, can be used as the indicator, level indicator or micro light source. Infrared light-emitting tubes are often used in remote controls such as televisions and video recorders. (1) using high brightness or super high brightness leds made f

31、lashlight circuit as shown in figure 5. The resistance of the resistance R in the graph should ensure that the current of the LED is less than the maximum allowable current IFm when the voltage is highest. (2) the figure 6 (a), (b), (c), respectively, for the dc power supply, rectifier power supply

32、and ac power circuit. figure (a) resistance of the material (E - VF)/IF; figure (b) the R material (1.4 Vi - VF)/IF; figure (c) of the R/IF material Vi type, Vi - ac voltage RMS. (3) single LED level indication circuit. In the output of an amplifier, oscillator, or pulse digital circuit, the LED ind

33、icates that the output signal is normal, as shown in figure 7. R is the current limiting resistance. Leds may only emit light when the output voltage is greater than the threshold voltage of the LED. (4) single LED can be served as a low voltage regulator works. Due to the LED positive, the current

34、changes very rapidly with voltage, and has normal voltage stabilizer. The stable voltage of the light-emitting diode is between 1.4 and 3V, and the VF should be selected according to the need, as shown in figure 8. (5) the level meter. At present, the LED level meter is widely used in audio equipmen

35、t. It is a variation of the output level, which indicates the output signal level of a multi-luminescent tube. Figure 9 is a meter with five light-emitting diodes. When the input signal is low, it doesnt glow. When the input signal level increases, first the LED1 is bright, then the LED2 is brighter

36、. It is. (5) light emitting diode detection 1. Ordinary light-emitting diode detection (1) using a multimeter test. Using pointer with x 10 k block multimeter can roughly judge of light-emitting diodes (leds). Normal, the diode is proposed.theoretical for decades to 200 k, reverse resistance value i

37、s . If the positive resistance value is 0 or infinity, the reverse resistance is small or 0, which can be easily damaged. This kind of detection method, cannot see the luminous tube light field, because x 10 k block cannot provide larger forward current to the LED. if there are two pieces of pointer

38、 multimeter (same) best can better check light-emitting light-emitting diodes (leds). Use a wire to connect the + terminal to the - connection of the other. The rest of the - is the positive electrode of the glowing tube (P), and the remaining + is attached to the negative pole of the glowing tube (

39、N). Two pieces of multimeter all buy x 10 block. Normally, when you are connected, you will be able to glow normally. If the brightness is very low, not even light, can be both block multimeter to x 1 if, if still very dark, not even light, it shows that the light emitting diode performance undesira

40、ble or damage. Should be paid attention to, cant start measuring is put two pieces of multimeter at x 1 , in order to avoid too much electricity, damage the leds. (2) an external power measurement. The light and electrical properties of light-emitting diodes (leds) can be accurately measured with 3V

41、 stable source or by two series of dry cells and multimeter (pointer or digital). You can connect the circuit as shown in figure 10. If the VF is measured between 1.4 and 3V, and the luminescence is normal, it can be indicated that it is normal. If you measure VF = 0 or v f approximately 3V, and it

42、doesnt glow, it means that the glowing tube is broken. 2. Detection of infrared light-emitting diodes (oleds) with infrared light-emitting diodes, it 1 3 microns of infrared light that the human eye cant see. Usually a single infrared LED emitting diode emits only a few mW, and different models of i

43、nfrared leds have different angular distributions. The positive pressure drop of infrared LED is 1.3 2.5 V. And it was because of the sight of the infrared light that it was emitting,Therefore, the detection method of using the above visible LED can only determine whether the PN junction and the rev

44、erse electrical characteristics are normal, and it is impossible to determine whether the luminescence is normal. To do this, it is best to prepare a photosensitive device (such as a 2CR, 2DR silicon cell) for a receiver. Use multimeter to measure the variation of voltage on both ends of the battery

45、. To determine whether infrared leds are combined with appropriate positive current to emit infrared light. It measures the circuit.Semiconductor luminescent devices include semiconductor light-emitting diodes (leds), digital tubes, symbolic tubes, meter tubes, and dot matrix displays (for short, ma

46、trix tubes). In fact, every luminous element in a digital tube, a symbol tube, a meter tube, and a matrix tube is a light-emitting diode. one, semiconductor light-emitting diodes (leds) working principle, characteristics and application (one) LED principle leds by - compounds, such as GaAs (gallium

47、arsenide), GaP (gallium phosphide), GaAsP made of semiconductor such as gallium arsenide (p), its core is the p-n junction. Therefore, it has the i-n feature of general p-n junction, which is the positive guide, reverse cut-off, and puncture characteristics. In addition, under certain conditions, it

48、 also has the luminescence characteristic. Under positive voltage, the electron is injected into the P area by N, and the void is injected into N area by P area. A small number of carriers entering the other side of the area (children) are composed of most carriers (many children), as shown in figur

49、e 1. assumption is glowing in the P region, then injected electrons and the valence band hole composite and shine directly, or be luminous center after capture, hole composite luminescence again. In addition, this kind of light composite some electrons are not luminous center (the center between the

50、 conduction band, interface with near middle) capture, then with hole compound, every time the energy released is not big, could not form visible light. The higher the amount of light, the higher the amount of light, the higher the quantum efficiency. Because the composite is glowing in the children

51、s diffuse region, light is produced only within the mu m near the PN junction. theory and the practice proves that the peak wavelength lambda light with the light emitting area of semiconductor materials forbidden band width of Eg, namely lambda material 1240 / Eg (mm) type of Eg unit for electron v

52、olts (eV). If visible light can be produced (at a wavelength of 380nm 780nm red), the semiconductor material should be between 3.26 and 1.63 eV. The light that is longer than red wavelengths is red. There are now infrared, red, yellow, green and blue light emitting diodes, but the cost of the blue l

53、eds and the high price are not universal. (2) the characteristics of the ledsThe significance of (1) the limit parameters (1) allow power Pm: allow LED on both ends are dc voltage and current flow through the maximum value of product. More than that, LED heat and damage. maximum positive dc current

54、IFm (2) : allows to add one of the biggest positive dc current. More than this can damage a diode.Maximum reverse voltage VRm (3) : the biggest reverse voltage is allowed to add. Over this value, leds may be punctured and damaged.Topm (4) work environment: light-emitting diodes (leds) working enviro

55、nment temperature range. Below or above the temperature range, the light-emitting diode will not work properly and the efficiency will be greatly reduced. 2. The significance of electrical parameters (1) spectral distribution, and peak wavelength: a light of the light emitting diode is not a single

56、wavelength, the wavelength can press is shown in figure 2. the chart shows, in the light of the luminous tube light intensity, the largest of a wavelength lambda 0 this wavelength for peak wavelength. (2) luminous intensity IV: the luminous intensity of leds, often referred to as normal () refers to

57、 the axis of cylindrical luminous tubes on the direction of luminous intensity. If the intensity of radiation in that direction is (1/683) W/sr, then it will be 1 candela (symbol CD). The luminescence intensity is commonly used as a unit of candela (MCD) because the light of a general LED is small. (3) spectrum halfwidth lambda: it said light-emitting tube spectral purity.This is the difference between the two wavelengths of the 1/2 peak in figure 3. (4) half value Angle theta 1/2 and perspectives: