Led lighting has been developed by leaps and bounds in the near future. As a green and environment-friendly clean light source, led has been widely recognized.Led light sources have a long service life, energy saving and power saving, simple and convenient application, and low cost. Therefore, there will be a large number of applications in home lighting. According to the survey of osram optical semiconductor in 2008, about 50 billion household lighting lamp stands are shipped worldwide every year.
The technology of led light source is mature day by day, and the luminous lumen per watt increases rapidly, which makes it decrease year by year.In the spring of 2008, for example, the price of 1W leds was one-third that of the spring of 2006, and will fall to a quarter in the spring of 2009.The mass market of led green lamps and the steady growth demand for several years will be the super tsunami of the consumer electronics market in the integrated circuit industry after VCD, DVD, mobile phone and MP3.Led lighting is widely recognized for its high energy saving, long life and environmental protection.
Led high energy saving: dc drive, ultra-low power consumption (single tube 0.03-1 watt), electric power conversion nearly 100%, the same lighting effect is more than 80% energy saving than the traditional light source.
Led long life: led light source is called longevity lamp.Solid cold light source, encapsulated by epoxy resin, there is no loose part in the lamp body, and there are no defects such as easy burning, hot deposition and fast light decay of the filament. The service life can reach 50,000 to 100,000 hours, which is more than 10 times longer than that of traditional light source.Led is environmentally friendly: led is a kind of green light source, better environmental benefits.There is no ultraviolet and infrared ray in the spectrum, low heat and no stroboscopic, no radiation, and waste can be recycled, no pollution and no mercury, cold light source, which can be safely touched, belonging to the typical green light source.The working characteristics of led light source are very low. Generally, VF = 2.75-3.8v, IF it is 15-1400ma.Therefore, the output voltage of led drive IC is VF X N or VF X 1, IF the constant current is 15-1400ma.The led light source used for led lamps is of low power (IF= 15-20ma) and high power (IF>200mA). Small power led is mainly used for led fluorescent lamp, decorative lamp and grille lamp.High-power led is used for household lamp, spotlight, underwater lamp, wall lamp, street lamp, tunnel lamp, automobile work lamp, etc.Power led light source is driven low voltage, large current device, its luminous intensity is determined by the size of the current through the led, too strong electricity will cause led light attenuation, too weak electricity will affect the led luminous intensity, therefore, the led driver needs to provide constant current power supply, to ensure the safety of high power leds used, at the same time to achieve the ideal of luminous intensity.
In the field of led lighting, to reflect the characteristics of energy saving and long life, it is crucial to select a good led driving IC. Without a good driver IC match, the advantages of led lighting cannot be reflected.Technical details for led lighting design
Led lamp requirements for low-voltage drive chip:
1. The nominal input voltage range of the drive chip shall meet the requirements of dc8-40v to cover the application surface.When AC 12V or 24v input is used, the output voltage of the simple bridge rectifier will fluctuate with the grid voltage, especially when the voltage is high, the output dc voltage will also be high. If the driving IC cannot adapt to the wide voltage range, it will be broken when the grid voltage rises, and the led light source will be burnt.
2. The driver chip nominal output current demand is greater than 1.2 to 1.5 A, as the lighting of led light source, 1 w power led light source, the nominal working current is 350 ma, 3 w power led light source, its nominal working current is 700 ma, the needs of the large power larger current, so the led lighting lamps and lanterns chooses driver IC must have enough output current, make the driver IC work needed to design products in full load output of 70-90% of the best work area.Drive IC with full negative output current is not able to dissipate heat in the small space of the lamp, easy to fatigue and early failure.
3. The output current of the drive chip must be constant for a long time, so that the led light source can shine stably without flickering;When the same batch of drive chips are used under the same conditions, the output current should be as consistent as possible, that is, the dispersion should be small, so that the production can be effective and orderly in the mass automatic production line.For the drive chip with discrete output current, it must be divided before leaving the factory or entering the production line, adjust the resistance value of the current setting resistance (Rs) on the PCB board, so that the constant current drive plate of the led lamp produced is consistent with the luminescence of the same led light source, and maintain the consistency of the final product.
4. The encapsulation of the drive chip shall be conducive to the rapid heat dissipation of the drive chip core. For example, the tube core (Die) is directly tied to the copper plate, and a Pin extends directly to the package, so that it can be directly welded on the copper foil of the PCB plate and conduct heat quickly (figure 1).For example, in a silicon chip core similar to 4X4mm, to pass through a current of 300-1000ma for a long time, there must be power consumption and heating, and the physical heat dissipation structure of the chip itself is also crucial.
5. The ability of the drive chip itself to resist EMI, noise and high pressure is also related to whether the whole led lighting product can pass CE, UL and other certifications. Therefore, the drive chip itself should choose excellent topological structure and high pressure production technology at the beginning of design.
6. The power consumption of the drive chip is required to be less than 0.5w, and the operating frequency of the switch is required to be greater than 120Hz, so as to avoid visible scintillation caused by power frequency interference.Led green lighting promotes the development of drive chip towards innovative design. Led lighting cannot be separated from the drive chip, so it needs led light source driving IC with multiple functions.Non-isolated power supply can be considered when using ac power supply below 36V for led lamps. For example, isolated power supply should be considered for 220V and 100V ac power supply.Direct use of ac100-220v drive chips, due to the demanding application volume, there are higher requirements in technology, more difficult, countries are now working hard to develop.The huge demand market for led lamps gives all integrated circuit design companies the chance to be successful again, to quickly transform, to produce early, and to win.