Issues about drive IC for LED lighting

Recently, LED lighting developed rapidly, and LED is widely recognized as a clean and green light source. Working under low voltage, the light intensity is depended on the current flowing through the LED. 

Strong current will cause light attenuation, but weak current will affect the luminous intensity, thus, led the

 drive required to provide constant current and ensure the safety using of LED, at the same time achieve the desired luminous intensity. In the LED light industry, to realize the characteristics of energy saving and long life, choosing a good led driver IC is essential, without good IC, the advantages of LED lamp can not be reflected. LED lighting design requires the following technical details for driver IC:

1) Driver chip input voltage range should be DC8-40V, so that can cover the application requires, if greater than 45V will be better; When in AC 12V or 24 V input, a simple bridge rectifier output voltage will fluctuate with the grid voltage, especially at high grid voltage, DC output voltage will be also high. If driver IC can not meet the wide range voltage, it will be damaged easily when in high grid voltage, and therefore the LED also be destroyed.

2) Driver chips output current is required higher than 1.2-1.5A, as the illumination LED source, 1W power LED is working on standard current of 350mA, and 3W power LED is 700mA, the higher power LED need higher current, thus led driver IC must have enough current output for LED lighting, the best work current for driver IC is at the 70-90% of peak output. If driver IC using the full load current output, the cooling spaces is small, and will cause easily damaged and early failure of LED lamp.

3) Driver chip is required constant current for long-term, so that LED can emit stable and not flicker light; when use the same batch driver chips under the same conditions, the output current should be as consistent as possible, so that automated production lines can produce effective and orderly; for the drive chips with discrete output current should be picked out before ex-work or in use. Then adjust the resistor values (Rs) of the PCB on the picked IC, so that the same light source have the same brightness, also the final product with good consistency.

4) The packaging of driver IC should take die cooling into account, such as the die binding on the copper directly, and extend Pin out of the package, so that it's easy to solder the pin directly to copper foil on PCB board and result rapid thermal. Take a  silicon die (about 4X4mm) as example, the chip must have power coNsume and heating when working on 300-1000mA current for long-term, so the physical structure for thermal is also essential.

5) The anti-EMI, noise and high voltage of driver chip are also related to pass CE, UL and other certification, so the design of driver chip should use the top and excellent high pressure production process at the beginning.

6) the power of drive IC required less than 0.5W, switching frequency is required greater than 120Hz, so as to avoid working frequency interference and caused visible flicker. LED lighting promote development of driver chip to innovative design, led lighting is inseparable from the driver IC, so it's demand for multiple functions driver IC for LED light source. LED lamps using voltage under AC 36V input can be considered the non-isolated power supply, and if use 220V or 100V AC input should be considered isolated power supply. If use AC100-220V driver chips directly, because the demanding of volume, there is greater difficulty technically. Currently, many countries are taking efforts to develop this IC

sources:http://www.articlesbase.com/electronics-articles/issues-about-drive-ic-for-led-lighting-3504057.html