恒流驱动LED有闪烁,因为总有纹波,LED闪烁造成很多研究机构的担忧,看看下面文章对你会有帮助

来源: 硅谷雄风 2015-03-28 13:31:39 [] [博客] [旧帖] [给我悄悄话] 本文已被阅读: 次 (2085 bytes)
http://www.mondoarc.com/technology/LED/1079132/led_flicker_safety_issues.html
Unfortunately the majority of LED drivers used today have very poor flicker characteristics and a typical constant current LED driver ripple current may be seen in figure 7. Here a nominal 700mA LED driver actually provides 652mA current out with a peak to peak ripple current of 142mA or 21.8% with a ripple frequency of 100Hz (2x Mains frequency). They key aspect for designing or specifying LED products is to ensure that the LED drivers are not overdriving the required maximum forward current specified by the LED manufacturer. Typical measurements of LED ripple current have been seen up to about 85% of nominal current so this could be a major cause of stress on the LED and wire bonds for some manufacturers so make sure you check!

Of course if your LED driver uses Pulse Width Modulation technology then your ripple current is actually 100% as the current through the LED varies between 0 and full current at a specific PWM frequency. If you require high resolution current control then unfortunately a major disadvantage with PWM is that the flicker frequency drops to only a few hundred Hertz at best.

A recent flicker study by the Lighting Research Center in New York State tested how 10 humans detected and more importantly accepted flicker using both the flicker frequency and also the degree of percentage flicker with very interesting results as shown in figures 8 and 9.

In figure 8, the lower the flicker frequency enabled the subjects to detect stroboscopic effects of the light source especially if the flicker percentage is high. For example, the majority (80-100%) of the subjects would be able to see stroboscopic effects of a PWM (100% flicker) driven LED system with a PWM frequency of up to 1KHz whereas an LED light source with a flicker frequency from 1KHz and only 5% flicker would not be seen by observers. For clarity an LED light source with 5% flicker is essentially a DC light source with 5% ripple current.

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