【 iyashi 】
Use the lamps and lanterns of LED materials as raw materials
LED (Light Emitting Diode), light-emitting Diode, is a kind of to electric energy into visible Light solid state of semiconductor devices, it can directly put DianZhuan into Light.
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【 principle term 】
The heart of the LED is a semiconductor chip, chip attached to a bracket on the end, the end is negative, the other end connected to the power of the anode, the whole chip is encapsulated by epoxy resin.
Semiconductor chip consists of two parts, one part is a p-type semiconductor, dominated by holes in it, the other end is N type semiconductor, here mainly electronic. But this two kinds of semiconductor connected, forming a p-n junction between them.
When a current flows through a wire to the chip, the electron will be pushed to P, electron and holes in the P zone compound, then will be issued in the form of photon energy.
The wavelength of light, that is, the color of the light, it is determined by the formation of the p-n junction material.
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【 classification Term 】
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1. [Press the luminotron light emitting color]
(red, orange, green and yellow green segment, the standard green and pure green, blue, etc.
In addition, some leds included in two or three kinds of color chip.
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2. [Press the light-emitting tube out of the smooth features]
Circular lights, side lights, rectangular, surface light-emitting tube, lateral tube, install with micro tube surface, etc.
Circular lamp according to the diameter of divided into from 2 mm, 4.4 mm, 5 mm, 8 mm phi phi is, from 10 mm and 20 mm, etc.
Abroad usually write phi is 3 mm leds for T - 1; The phi is 5 mm as T - 1 (3/4); Write phi is 4.4 mm for T - 1 (1/4).
Can be estimated by half value Angle size round Angle of luminous intensity distribution.
Light-emitting diodes (leds) out of the light on or after adding the scattering 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. Scattering type leds light and up to do.
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3. [Press the Angle of luminous intensity distribution map]
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(1) high directivity
Is commonly pointed epoxy encapsulation, or with metallic reflective cavity encapsulation, scattering agent and all the time.
Angle of half value of 5 ° ~ 20 ° or less, has the very high directivity, and can be used for local lighting light source, light detector or combined to form automatic detection system.
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(2) standard
Often used as indicator light, the half value Angle of 20 ° to 45 °.
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(3) scattering type
This is a bigger light perspective, half value Angle is 45 ° ~ 90 ° or greater, the amount of scattering agent is bigger.
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4. [Press thelight-emitting diode structure]
The epoxy coating, metal base epoxy encapsulation, ceramic base epoxy encapsulation, glass encapsulation structure, etc.
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5. [Press the luminous intensity and working current]
Normal brightness LED luminous intensity (100 MCD); The luminous intensity between 10 ~ 100 MCD is high brightness leds.
General LED working current in a dozen mA to dozens of mA, and low current LED working current in under 2 mA (brightness is the same as the ordinary light-emitting tube).
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"Source term"
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1. [cold light source]
Cold light source is the use of chemical energy, electrical energy, biomass of excitation light source (fireflies, neon signs, LED, etc.).
Has the very good optical and flash features.
Luminous objects, its temperature is not higher than the environment temperature, cold light, this light is called for if the LED is the use of electron hole pair recombination luminescence.
Strictly speaking, LED LED lights is electroluminescent heat is also produced, is relatively lower compared with incandescent lamp light source, such as. LED electro-optic conversion efficiency is about 30%, of which about 70% internal quantum efficiency (close to theoretical limits), external quantum efficiency is about 50%. (this is only the experimental data is not accurate)
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2. [Heat source]
Using thermal excitation light source, such as incandescent lamp in 3000-4000 K temperature thermal radiation. Incandescent light bulb 80-90% of the energy conversion to heat energy, about 10% of the energy converted into light energy. So luminous efficiency is low. We are not defined according to the shell of lamps and lanterns temperature of cold light source, light or heat.
The surrounding temperature of lamps and lanterns, can evaluate the superiority of the lamps and lanterns of the cooling measures.
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3. [] difference between
Cold light source and hot source, we can not only from the definition to distinguish. Cold light does not mean that actually what we call the luminous process does not produce heat, but to shine the way not by the heat energy is converted to light energy. Incandescent lamp is typical by electrical energy into heat energy, and then convert thermal energy into light energy of the process. The heat loss is higher, low luminous efficiency. So we can consider LED cold light source.
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【 power supply Term 】
First from the security, the current general LED lights with built-in power design, so the isolation power supply, there is no need for now.
Secondly considering the efficiency, power efficiency mainly depends on the structure of the circuit and the device, in theory, the smaller the output voltage, the higher current efficiency is higher, the lower its power consumption is more efficient.
Now commonly used several kinds of schemes are:
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1. [resistance capacitance step-down LED lamp power supply]
Resistance capacity of the step-down method efficiency is not low cost may be high, will consume electricity and heat resistance itself, and the reliability is low.
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2. [MOS LED lamp power supply]
Do with MOSFET switch tube, and eventually LED fluorescent lamp power factor can reach 0.9, because the MOSFET's own consumption minimum 0.5 W. Using MOSFET is much lower than the triode switch loss.
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3. [RCC LED lamp power supply]
RCC (Ringing Choke converter) is a kind of using blocking oscillator composed of self-excited oscillation pulse converter, commonly used in small power led power supply, low cost is usually a high failure rate.
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4. [current-limiting LED lamp power supply ] (quasi constant current LED power supply)
Is working in the power of the original circuit, set a threshold current, when the original side MOSFET turn-on, the inductor current is linear increased, when up to a certain value, reach this threshold, will shut off the current, the next cycle again conduction is triggered by the trigger circuit, the output is smooth without electrolytic capacitor, output current waveform is trapezoidal, namely current fluctuations type, is a kind of current limiting power, but manufacturers usually call it the constant current power supply.
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5. [type constant current LED power supply switch power supply ]
When the output voltage is a little higher or lower, will produce a voltage, after amplification, to control the PWM signal, so this control mode can be very precise control voltage. This kind of control mode, need a benchmark, very accurate reference signal of the commonly used have a triode, do the benchmark WenPiao is big, and can take 1 v diode conduction value to do benchmark, if feel is not very high, can use operational amplifier with TL431 as benchmark, if the benchmark must enough, operational amplifier magnification is sufficiently large, then it is very accurate, to control the PWM circuit is complex, but the very high precision constant current or constant current power. Additional output must add electrolytic capacitor filter, so the output is a smooth dc, because pulse can't sampling.
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6. [with LED lamp power supply transformer]
Integration of MOSFET switching power supply chip and high frequency transformer, the power factor is high, the cost is moderate, good reliability, is the ideal choice for the LED power supply. And inductance although cost is very low, but not on load capacity, and adjust the volume of feeling is not flexible.
Again considering the heat dissipation, because power is generally on the lamp, and fever are the biggest factors lead to LED light failure, so hot, as far as possible to high efficiency. Because now the power supply can do smaller volume, T8 2 one meter long LED fluorescent lamp can be used two power, one at each end, which is not the heat concentrated in one place.
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【Article is excerpted from: Web Search】
【Reserved Integrate / Just Reference】
【Translation is by The Network】
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