Doug revealed that the PI in 2010, according to the LED driver shipments to calculate its market share for the world\\ s first! The large number of customers the use of PI can be a deep understanding of the LED application trend and continue to in troduce new products to meet customer needs. Looking ahead, he said the 2011 indoor LED lighting, LED fluorescent and LED lights will have a good application.
The 2011, Australia has been the first to ban the use of incandescent lamps, the prelude for the large-scale adoption of LED lamps, with the EU, Japan, Canada and other countries in 2012 to prohibit the use of incandescent lamps, LED lamps, lighting will further enhance the penetration, which makes the Nuggets green lighting revolution thousands of LED lighting manufacturers rejoiced - because a huge market will open, but this time played the leading role that the Chinese manufacturers. It should be noted, however, the LED lamps to be universal, not only need to reduce costs, but also need to address the problem of energy efficiency and reliability, how to solve these problems, Doug Bailey, Power Integrations\\ marketing vice president, shared the efficient and highly reliable LED lighting design Five advice.
One, do not use the bipolar power devices
Doug Bailey pointed out that the bipolar power devices are cheaper than the MOSFET, usually about 2 cents, some designers in order to reduce the cost of LED driver using bipolar power devices, this will seriously affect the reliability of the circuit, because as enhancement of the LED driver circuit board temperature, the effective operating range of the bipolar devices will rapidly diminishing, this will cause the failure of the device temperature rise thus affecting the reliability of the LED lamps, the correct approach is to opt for the use of MOSFET devices, MOSFET devices life is much longer than bipolar devices.
Second, do not use pressure to 600V MOSFET
Withstand voltage 600V MOSFET is relatively cheap, a lot of LED lamp input voltage is usually 220V, pressure 600V enough, in the surge, but many times the circuit voltage to 340V, and 600V MOSFET is easy to be breakdown , thus affecting the life of the LED lamps actually selection of 600V MOSFETs may save some costs, but pay the cost of the entire board, therefore, do not use 600V withstand voltage of the MOSFETs, and the best selection of voltage exceeding 700V MOSFET , \"he stressed.
Third, try not to use electrolytic capacitors
LED driver circuit in the end to the use of electrolytic capacitors? There are supporters and opponents, supporters believe that If the circuit board temperature control, in order to achieve the purpose to extend the life of the electrolytic capacitor, for example, use 105 degrees life of 8000 hours of high-temperature electrolytic capacitor, electrolytic capacitor according to the prevailing life estimation formula reduce a temperature of 10 degrees, the doubling of life expectancy, then it is in the working life of 16,000 hours under a 95-degree environment, 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 The lower operating temperature, then life will be longer! Seen in this light, as long as the selection of high quality electrolytic capacitors of the drive power of life is not what effect!
Some supporters that the low-frequency flicker caused by the high ripple current electrolytic capacitors bring will have some of the human eye cause physical discomfort, and a large range of low-frequency ripple will lead to some digital camera equipment poor The frequency of the flashing light and dark grid. Therefore, high-quality light source lamp or electrolytic capacitors. Opponents argue that the natural aging electrolytic capacitors, In addition, the temperature of the LED lamps extremely difficult to control, will inevitably reduce the life of the electrolytic capacitor, thus affecting the life of the LED lamps.
In this regard, Doug Bailey, without electrolytic capacitors in the LED driver circuit input section can be considered, in fact, the LinkSwitch-PH PI eliminates the need for electrolytic capacitors, the PI of the single-stage PFC / constant current design allows the designer eliminates the need for large capacity capacitor, the output circuit, high voltage ceramic capacitors instead of electrolytic capacitors to improve reliability, \"Some people in the design of the two circuits when using a 400V electrolytic capacitor in the output, it would seriously affect the reliability of the circuit, it is recommended that single-stage circuit using ceramic capacitors can, \"he stressed. \"Not very concerned about the dimming function, high-temperature environment, and industrial applications that require high reliability, I strongly recommend to not use electrolytic capacitors design.\"
Fourth, to make use of MOSFET devices
If the design of LED lighting power is not very high, Doug recommended using the integrated LED driver product in the MOSFET, because the benefits of doing so is less integrated MOSFET on-resistance, heat generated by less than the separation, the other is the integrated MOSFET controller and FET together, in general, over-temperature shutdown, when the MOSFET will automatically shutdown circuitry to protect the LED lamps, LED lamps is very important, because the LED lamps are generally very small and difficult to carry out air cooling . \"Some will happen when the LED burning due to overheating of wounding, but our program never.\" He said.
Five, try to use a single-stage architecture circuit
Doug said some LED circuit uses two architectures, PFC (Power Factor Correction) + isolated DC / DC converter \"architecture, this design will reduce the efficiency of the circuit. For example, if the PFC efficiency is 95%, while part of the DC / DC efficiency is 88%, the efficiency of the entire circuit will be reduced to 83.6%! PI LinkSwitch-PH device while PFC / CC controller, a 725 V MOSFET and MOSFET driver integrated into a single package, the drive circuit efficiency to 87%! \", Doug pointed out that\" this device can be greatly simplified circuit board layout design, can save up to 25 components used in traditional isolated flyback design eliminates the need for the components include high-voltage large-capacity electrolytic capacitor and optocoupler. Doug LED two-tier structure applies must use a constant The flow of the drive circuit to make the old PFC drive LED c onstant current drive. These design is outdated and no longer cost-effective, in most cases, the best single-stage design.
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