LED lighting has been rapidly developed in the near future, and LED has been widely recognized as a clean and clean light source. LED light source has the advantages of long service life, energy saving, simple and convenient application, low cost of use, etc., so it will be used in the future in home lighting. At present, the output value of China's LED lighting industry exceeds 150 billion yuan; Guangdong's current LED lighting scale accounts for 70% of the national market. Last year, the LED industry in Guangdong Province achieved a total industrial output value of 85.3 billion yuan. Some professionals predict that the fastest in 2015, LED lighting in the Chinese lighting market will reach 20%, driving the industry scale will reach 500 billion yuan, when China will enter the top three global LED lighting market.
The LED light source used in LED lamps has two types of low power (IF=15-20mA) and high power (IF>200mA). Low-power LEDs are mostly used for led fluorescent lamps, decorative lamps and grille lamps; high-power LEDs are used for Home lighting, spotlights, underwater lights, wall washers, street lights, tunnel lights, car work lights, etc. Among them, the high-power LED light source is a low-voltage, high-current driving device. The intensity of the light is determined by the current flowing through the LED. If the current is too strong, the LED light will be attenuated. If the current is too weak, the LED's luminous intensity will be affected.
In general, the VF voltage of the LED light source for illumination is very low, generally VF = 2.75-3.8V, IF is 15-1400mA; therefore, the output voltage of the LED driver IC is VF XN or VF X 1, IF constant current is 15-15 1400mA.
In summary, the LED driver needs to provide a constant current power supply to ensure the safety of high-power LEDs and achieve the desired luminous intensity. In the field of LED lighting, to reflect the characteristics of energy saving and long life, it is important to choose a good LED driver IC. Without the matching of a good driver IC, the advantages of LED lighting cannot be reflected.
Now, due to the needs of the LED green lighting market, LED lighting power supply driver chips are being developed into innovative designs. The massive demand market for LED lamps has given all IC design companies a chance to make a big impact.
Everyone knows that LED lighting power supply is inseparable from the driver chip, so it needs a variety of functions of LED light source driver IC. LED lamps use AC power below 36V to consider non-isolated power supply. For example, 220V and 100V AC power should be considered for isolated power supply. As for the direct use of the AC100-220V driver chip, due to the demanding application, there are higher technical requirements and greater difficulty in the technology. At present, countries are working hard to develop.
LED lighting fixture power supply requirements for low-voltage driver chips, as follows:
1. The nominal input voltage range of the driver chip should meet DC8-40V to cover the application surface. The withstand voltage should be better than 45V. The simple bridge rectifier output voltage will follow the grid voltage when AC 12V or 24 V input. Fluctuation, especially when the voltage is too high, the output DC voltage will also be high. If the driver IC cannot adapt to the wide voltage range, it will be broken down when the grid voltage rises, and the LED light source will be burnt.
2. The nominal output current requirement of the driver chip is greater than 1.2-1.5A. As the LED light source for illumination, the 1W power LED light source has a nominal working current of 350mA, and the 3W power LED light source has a nominal operating current of 700mA. Larger ones require more current, so the driver ICs used in LED lighting must have sufficient current output. The design of the product must be such that the driver IC operates at 70-90% of the best working area of ​​the full negative output. Driver ICs that use full negative output currents have poor heat dissipation in the narrow space of the luminaire, which is prone to fatigue and early failure.
3. The output current of the driver chip must be constant for a long time, the LED light source can be stably illuminated, and the brightness will not flicker; the same batch of driver chips are used under the same conditions, and the output current should be as uniform as possible, that is, the dispersion is small, so High-volume automated production line production can be effective and orderly; for the output current has a certain discrete drive chip must be selected before the factory or put into the production line, adjust the resistance of the current setting resistor (Rs) on the PCB, so that The constant current driving board of the LED lamp produced by the same has the same brightness of the same kind of LED light source, and maintains the consistency of the final product.
4. The package of the driver chip should facilitate the rapid heat dissipation of the chip die. For example, the die (die) is directly bonded to the copper plate, and a pin extends directly outside the package for direct soldering on the copper foil of the PCB. Rapid thermal conductivity. For example, on a silicon die similar to 4X4mm, it takes a long time to pass 300-1000mA current, which inevitably has power consumption, which will inevitably heat up. The physical heat dissipation structure of the chip itself is also crucial.
5. The ability of the driver chip itself to resist EMI, noise and high voltage is also related to whether the entire LED lamp product can pass CE, UL and other certifications. Therefore, the driver chip itself must use excellent topography and high voltage at the beginning of design. Production Process.
6. The power consumption requirement of the driver chip is less than 0.5W, and the switching operating frequency requirement is greater than 120Hz, so as to avoid visible flicker caused by power frequency interference.
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