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LED Driver Analystic
LED Driver Analystic
LED light with many advantages because it is environmentally friendly, long life, high photoelectric efficiency (luminous efficiency more than 130LM / W), seismic and other applications in various industries in recent years rapid development, theoretically, LED service life of 100,000 hours, but in the practical application of the process, some LED lighting designers of LED drive power a lack of knowledge or improper selection or the blind pursuit of low-cost, results greatly shorten product life LED lamps poor LED lamp life of less than 2,000 hours, and some even more low, the result that the advantages of LED lamps are not a very good play. Because of the particularity of LED manufacturing, leading to different manufacturers and even with a production factory in the same batch of products produced by the LED current-voltage characteristics are individual differences. Now a high-power 1W white LED typical specifications, for example, the LED current, the voltage variation to do a brief description of the general 1W white light application forward voltage of 3.0-3.6V, that is, when the nominal 1W LED flowing through the 350 mA current, the voltage across it may 3.1V, may also be in the 3.2V or 3.5V may be other values, to guarantee 1W LED the life, the general LED lighting manufacturer recommends factory with 350mA current drive through across the LED forward current of 350 mA, the forward voltage of the LED at both ends of a small increase in the LED forward current substantial rise in the LED temperature into a straight up, thus speeding up the LED light failure shortened life expectancy, the LED, serious and even burn out LED. Due to the particularity of the LED voltage and current changes, and therefore the power of the LED drive strict requirements. LED drive power LED lamps, it is like a person’s heart, to the manufacture of high quality, LED lamps for lighting must give up the constant voltage drive LEDs. Now many of the high-power LED packaging factory many pieces of a single LED through parallel and series are sealed together to produce a single 20W, 30W or 50W or 100W or higher power LEDs, despite the package before the single LED are strictly selected and paired the internal quantity ranging from dozens of stars, more than a few hundred monomers LED, high power LED products packaged in voltage and current, still there is a big difference, and phase than a single LED (usually a single white, green, blue, operating voltage in the 2.7-4V, single red, yellow, orange voltage of 1.7-2.5V) parameter bigger difference! Many manufacturers of LED light products (such as guardrails, lamp cup, projection lamps, garden lights, etc.), resistance, Yung Buck, and then add a Zener diode voltage regulator to the LED power supply, drive LED there is a great defect, The first is the low efficiency, consume large amounts of power in the dropping resistor, there may even exceed the power consumed by the LED, and can not provide a large current drive, because the greater the current, the electrical energy consumed at the Buck resistor greater, can not be guaranteed by the LED current does not exceed their normal work requirements, design products will be lower across the LED voltage supply drive, so at the expense of price LED brightness. Using resistance, Yung Buck driving the LED, the brightness of the LED can not be stable, when the supply voltage is low, the LED brightness dimmed, the power supply voltage is high, the brightness of the LED brighter. Of course, resistance, Yung Buck drive LED biggest advantage is low cost, is still part of the LED lighting business in this way. Some manufacturers, in order to reduce the cost of the product, constant voltage drive LED also brought mass production LED brightness uneven LED does not work in the best state of a series of Q Constant current source driver is the best LED driver, constant current source driver, without limiting resistor in series in the output circuit LEDs flowing through the current is not subject to changes in the external power supply voltage, ambient temperature changes, as well as the discrete nature of the LED parameters effects, thereby maintaining a constant current, and fully play a variety of excellent characteristics of the LED. LED constant current power supply to the LED lamps will automatically detect and control the flow of power during the LED current, therefore, do not have to worry about excessive current flows through the LED in the power of the moment, do not have to worry about the load short burn out the power. Constant current drive, it can avoid the LED forward voltage change due to the current changes in the constant current LED brightness stability, easy LED lamp factory implementation of mass production, to ensure product consistency, so many manufacturers have fully aware of the importance of the drive power, many LED lamp manufacturers have abandoned a constant voltage mode, choose a slightly higher cost constant current to drive the LED lamps. Some manufacturers fear the power driver board selected the electrolytic capacitor will affect the life of the power, in fact, is a misunderstanding, such as: If I choose to 105 degrees, and the life expectancy of 8000 hours of high-temperature electrolytic capacitors, electrolytic capacitor life estimation method prevailing “Every 10 degrees lower doubling of life expectancy, it is the working life of 16,000 hours, in an environment of 95 degrees in the working life of 32,000 hours in 85-degree environment, the working life of 64,000 hours in 75-degree environment, if the actual work at lower temperatures, life will be longer! Seen in this light, as long as the selection of high-quality electrolytic capacitor drive power of life is not what effect! It is also worth LED lighting business Note: Because the LED will release a lot of heat in the course of their work, so that the junction temperature of the die to the rapid rise in the LED higher the power, the greater the heating effect. LED chip temperature rise will lead to a light-emitting device performance attenuation changes in electro-optical conversion efficiency, even when serious failure, according to the experimental test: LED temperature increase of 5 degrees Celsius, the luminous flux decreased by 3%, so LED lamps must pay attention to the heat of the LED light source, in the case of possible Operating Temperature increase the cooling area of the LED light source as much as possible, try to reduce the operating temperature of the LED itself, if conditions permit, it is best to be able to power part of the light source partially separated, blindly pursue small volume and neglect lamps and power is undesirable ‘s.