Technical details determine LED lighting design

LED lighting in the near future by leaps and bounds, LED as a green clean light source has been widely recognized. LED light source, long service life, energy saving, easy to use, low cost, and thus in the home lighting will be massive application, statistical survey of 2008 OSRAM optical semiconductor company, global annual household lighting lamp shipments of approximately 50 billion.

The technology of LED light source is mature day by day, the luminous lumen per watt is increasing rapidly, which makes it decrease year by year. 1WLED light source, for example, the price of the spring of 2008 is the price of 1/3 in the spring of 2006, the spring of 2009 will fall to 2006 of 1/4.

LED green lighting market and the continued growth of a large number of years of steady demand will be integrated circuit industry following the VCD, DVD, mobile phones, MP3 consumer electronics market after the tsunami!

LED lamps of high energy saving, long life, environmental benefits of superior performance has been widely recognized.

LED high energy saving: DC drive, ultra low power (0.03 watts -1 watts) power conversion is close to 100%, the same lighting effect than traditional light source energy saving more than 80%.

LED long life: LED light source is called longevity lamp. Solid-state light, epoxy resin packaging, light body and no loose parts, there is no filament burnability, thermal deposition, fast decay and other shortcomings, the service life of up to 50 thousand to 100 thousand hours, 10 times longer than traditional light source life above.

LED Li environmental protection: LED is a kind of green light source, environmental protection is better. No ultraviolet and infrared spectrum, low heat and no stroboscopic, no radiation, no pollution and waste Recyclable, no mercury, cold light, safe touch, which belongs to the typical green lighting source.

Working characteristics of LED light source

Lighting with LED light source VF voltage are very low, general VF=2.75-3.8V, IF at 15-1400mA; therefore, the output voltage of LED driver IC is VFXN or VFX1, IF constant current in 15-1400mA. LED light LED lamp with low power (IF=15-20mA) and high power (IF>200mA) two), low power LED for LED fluorescent lamp, decorative lamp, grille lamp; high power LED used for family lights, spotlights, underwater lamp, wall lamp, street lamp, tunnel lamp, automobile working lamp etc.. Power LED light source device is low voltage and high current drive, the luminescence intensity is determined by the current flowing through the size of LED, the current is too strong will cause LED light attenuation, weak current will affect the luminescence intensity of LED, therefore, LED driven by the need to provide a constant current power supply, to ensure the safety of large power LED use, and achieve the ideal luminous intensity. In the field of LED lighting, to reflect the characteristics of energy saving and long life, choose a good LED driver IC is essential, there is no good driver IC match, LED lighting can not reflect the advantages of.

Requirements of LED lamps for low voltage drive ic:

1 driver chip nominal input voltage range shall satisfy DC8-40V, to cover the needs of application, such as pressure can better than 45V; AC12V or 24V input simple bridge rectifier output voltage with voltage fluctuation, especially the output DC voltage of high voltage is high, such as IC driver with wide voltage range can not meet, often in the voltage rise will be breakdown, LED light source has therefore been burned.

2 driver chip nominal output current is more than 1.2-1.5A, the LED light source for lighting, LED 1W power source the nominal operating current is 350mA, the LED 3W power source the nominal operating current is 700mA, high power needs more current, so the selection of LED lighting driver IC must have enough current output the design of products need to drive the IC in full load output 70-90% the best working area. The use of full negative output current drive IC narrow space in the lamp poor heat dissipation, easy fatigue and early failure.

The output current required long constant 3 driver chip, LED light source can be stable luminescence brightness will not flicker; the same driver chip used in the same conditions, the size of the output current should be as consistent as possible, which is discrete is smaller, so in mass production of the automatic production line can be effective and orderly; for output current a discrete driver required in the factory or into the production line before stepping on the PCB board, adjust the current setting resistor (Rs) the resistance value of LED lamps to produce constant current drive in the brightness of the similar LED light source, maintain the consistency of the final product.

4 driver chip package should be conducive to the rapid cooling tube driver chip core, such as the tube core (Die) directly binds to copper, and there is a direct extension to the Pin package, can be directly welded heat quickly in the PCB board on the copper foil (Figure 1). Such as in a similar 4X4mm silicon core, to a long time through the 300-1000mA current, there will be power consumption, will inevitably heat, the chip itself is the most important physical heat dissipation structure.

5 driver chip itself anti EMI, noise and high capacity but also to the LED lighting products can pass CE, UL certification, so that the drive chip itself at the beginning of the design to the topological structure of excellent and high production technology.

6 drive chip power consumption is less than 0.5W, the switching frequency is greater than 120Hz, so as to avoid the power frequency interference and produce visible flicker.

LED green lighting to drive the chip to the development of innovative design, LED lighting can not be separated from the driver chip, and therefore requires a variety of functions of the LED light source driver IC. LED lamps and lanterns below 36V AC power supply can be considered non isolated power supply, such as the use of 220V and 100V AC power should be considered