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Thread: LED fixture with AC LED module from the flicker hell and energy standard loophole

  1. #1
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    LED fixture with AC LED module from the flicker hell and energy standard loophole

    I am one of the many who hates flicker with a passion. You've probably seen tail lamps on newer cars look like flying tiny dots when your eyes scan across even though they look steadily lit when there is no relative motion.

    I just came across an LED fixture that has an AC LED module from the flicker hell. It flickers so much that I'm pretty sure this type of LED driver ballast makes the record for the most flickery general service lighting apparatus in the history of electric lighting. Incandescent bulbs have very little flicker and has been regarded as the gold standard of lighting quality. The filament's thermal capacity keeps it glowing through the zero crossing. Fluorescent lamps have after-glow. Glowing hot arc tube of MH does the same thing. LED or its phosphor coating have almost no after glow to buffer flicker. This particular LED flickers at 100% flicker percentage (shuts off all the way each zero cycle) and ~0.45 flicker index. There's really nothing in Energy Star that clamps down on this. Until standards become established and pressure the LED industry to disclose poor performance or stop pushing out extremely flickery products, it is important to bench test a fixture before installing the lot so you do accidentally install a lighting downgrade. A fixture with this much flicker would produce multiple image effect on anything in motion and it will be obvious.

    Just for your reference:


    LED industry is putting effort into finding ways to lower build quality and compromise on performance parameters. The compromises are carefully crafted to leave widely published specs or those that matters for regulations and incentives alone while slicing away at unpublished specs that sometimes have dramatic impacts on the functionality of the product and encourage snap-back (putting old fixture back in).

    Product tested

    Commercial Electric 696 626 11 in Ceiling Light, Model HUI8011L-3
    1055 lumen, 17.1 lm, 82 CRI , 2764K
    Rated life: 35,000 hours

    Verified:
    shocking amounts of flicker.
    Dims over a wide range without rumbling or shimmer and I can't hear any buzzing.
    Power factor and THD are good.
    Seoul Semiconductor SMJD2V16W2P light engine.
    It's not a ballast bypass. It uses a monolithic LED ballast chip that can switch the length of LED strings rapidly in four steps to fit around the contour of each half cycle. these are the possible chain links 2, 4, 5 and 6.

    Conveniently, they don't talk about flicker performance.
    There six strings of 7 23v LEDs in parallel.
    Strings are arranged as 2+2+1+1. Transformerless LED ballast rapidly switches extends and shortens the string length to fit the contour of sinewave, but completely extinguishes at zero crossing. There's no smoothing capacitor at all, but full extent of line frequency flicker gets spat out by LEDs. When LEDs are operated like this, it is detrimental to their efficiency compared to running all of them on a steady current. So, even if ballasting loss is reduced, it may not result in an overall efficacy gain. For the record, the efficacy of this fixture is quite poor at 60 something



    Terrible power regulation and do not handle voltage variations very well. See how much the input power shifts between 114 and 126v.


    The Korean light engine attaches to a thin gauge metal base that looks like the thing you put under a house plant with 3 screws and cheap feeling hardware and cover completes the rest of the fixture. The build quality feels skimpier than the average builder's grade mushroom fixture.

    When I had a look inside a Lithonia Versilite in 2014, I came across the same type of low cost LED ballast that was just as terribly flickery. I was hoping something like this have long been phased out, but now I know it isn't. This is one of the deficiencies in Energy Star. It doesn't put restrictions on flicker beyond requiring the flicker to be equal to or greater than 120Hz and rectified AC power fed to LEDs without any smoothing produces flicker at exactly 120 Hz so it falls under "equal to 120 Hz", so something like this, which I think is utter junk ends up on shelves.

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    Interesting post so in the graph up there light output is flickering because the LED is not running on smooth DC? What kinds of LED's do you find have the least flicker?

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    Quote Originally Posted by tortuga View Post
    Interesting post so in the graph up there light output is flickering because the LED is not running on smooth DC? What kinds of LED's do you find have the least flicker?
    Kind that use a ballast with very low ripple current. The problem is that it's usually not part of the published specs making it difficult to choose.
    You have to obtain a sample and test it but the sample test finding could become invalid with cost cutting engineering changes to products.

    http://www.ecmag.com/section/lighting/fighting-flicker

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    Most flickery??? I think you meant highest flickerisity....

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    Quote Originally Posted by Electric-Light View Post
    Kind that use a ballast with very low ripple current.
    Dont LED's just need smooth DC? Would a quality rectifier/switching power supply that supplies constant DC current eliminate all flicker ? Like a computer power supply?

    The concept of a "ballast" "driving" an LED I dont quite get can you explain further?
    When I think of a ballast I think of a lamp that needs "starting". A old fashioned ballast would be a transformer that can send a hi voltage spike along with a starting cap to spark or ignite an arc lamp. Also it would include a running cap. Like HID lighting, and fluorescent.
    I suppose the newer electronic "ballasts" are like VFD's changing the frequency, but they still have to "start" the lamp and the lamp is still AC.
    An LED seems to me like a DC lamp that does not need "starting", thus no ballast.

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    Quote Originally Posted by tortuga View Post
    Dont LED's just need smooth DC? Would a quality rectifier/switching power supply that supplies constant DC current eliminate all flicker ? Like a computer power supply? The concept of a "ballast" "driving" an LED I dont quite get can you explain further?
    When I think of a ballast I think of a lamp that needs "starting". A old fashioned ballast would be a transformer that can send a hi voltage spike along with a starting cap to spark or ignite an arc lamp. Also it would include a running cap. Like HID lighting, and fluorescent.
    I suppose the newer electronic "ballasts" are like VFD's changing the frequency, but they still have to "start" the lamp and the lamp is still AC.
    An LED seems to me like a DC lamp that does not need "starting", thus no ballast.

    An LED needs a ballast even if operated from a battery and it is provided somewhere in the system even if concealed. An LED connected directly to a power supply that sets a constant voltage will go from hardly powered to letting out the smoke over a very small voltage change and this voltage varies from each sample of LED. When ballasted almost the same electrically, LEDs still flicker more than anything else, because they have almost no after glow that rides through the zero crossing unlike fluorescent.

    Ballast vs driver is a word game, partly driven by the LED industry's desire of not wanting LEDs associated with the word "ballast". A fluorescent or some HPS needs a push to start rolling down the hill, but it still needs ballasting to keep rolling down at a steady speed and it's the latter part that is needed by LEDs as well. A commonly used LED ballast is a plain resistor which is fine for indicators. The ballast quite often consumes just as much or even several folds more power than the LED. This is not an issue for indicators, but it wastes a lot of power for lighting applications. You could ballast a fluorescent as well as HID from a resistor too. A power supply constantly adjusts voltage to hold a set current is the ideal power supply. 12v rope and tape LEDs usually use a plain resistor as a ballast and it consumes about 25% of the power plus whatever loss in converting utility power to 12v DC.

    Currently regulated, high input power quality, very low ripple output, high efficiency usually means cost

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    Sorry, but I'm a little skeptical that led flicker is any kind of issue in any of the brand name fixtures, and even more skeptical its an issue in any quality fixtures. There is just no reason in the world any manufacturer would pulse the LED's slow enough to make this an issue.

    Sure, manufacturers can pulse the LED's on and off. It even saves energy to do that. Remember the old calculators with the 7 segment LED digits? They never lit up more than one digit at a time. A chip would send a clock signal that would light up one and only one digit at a time. So for a 8 digit calculator, no segment was ever on from more than 1/8th of the time. Turning on all 8 as the same time would have fried the small battery powered electronics. But just like you old TV, they all looked like they were constantly on because the eye responds to the peak level of brightness.

    So lets make some comparisons. Fluorescent lights with magnetic ballasts pulsed the tubes at 60 hz. Some people claimed that could be perceived by sensitive people, and that's quite possible. If you hold your phone camera up to such a light, you can easily see the flicker on the phone display as a series of darker bands that move across the fixture. (The scan frequency of the phone camera combined with the 60 hz. frequency produce a new frequency at a few hertz that can easily be seen.) We also know TV's scanned at 60 hz, and that is fast enough that is usually fast enough to produce smooth pictures and motion.

    So 60 hz. is iffy, and can be detected with a phone. However, when we get a little higher, say 300 to 600 hz. range or more, there is no way anyone is going to be able to see any flicker. Bump it up a little higher to the 18,000 hz or more of a fluorescent ballast and the flicker can no longer be detected with a phone.

    I just see no reason in the world any manufacturer would use a frequency for a LED light fixture low enough to have flicker. The simplest most basic electronics in the world can easily make an LED driver that works high enough to make flicker not an issue. I can't imagine why any manufacturer would pulse the LED's at anything less than a few KHZ.

    I've looked at a couple of LED lights with my phone since you posted this, and they have detectable flicker with whatsoever. They would basically be equivalent to an fluorescent light with a electronic ballast.

    I think its more likely you have a couple of bad lights.

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    Quote Originally Posted by steve66 View Post
    Sorry, but I'm a little skeptical that led flicker is any kind of issue in any of the brand name fixtures, and even more skeptical its an issue in any quality fixtures. There is just no reason in the world any manufacturer would pulse the LED's slow enough to make this an issue.
    I'm bothered by it and it's enough of an issue that it's become a topic of discussion at performance standards and technical bodies and professional organizations (US Department of Energy, IEEE, EnergyStar, Light Fair) https://energy.gov/sites/prod/files/...htfair2015.pdf

    Single phase 60 Hz power loses power 120 times a second. Incandescent and fluorescent lamps continue making light without any power for a period of time. The heat held by the filament or the afterglow of fluorescent lamp phosphor glides through zero cycle to keep significant amount of light output going through the zero crossing. Mechanical inertia smoothes out torque ripple in anything motorized.

    LEDs have no inertia. This is why they can switch fast enough for communication signaling. LED back lit fluorescent lamps use a phosphor blend with no after glow that light output decays to zero twice per cycle. The only way to get around this is to add an optical buffer by glow-in-the dark components or keep LEDs burning by buffering the input power and this can not be accomplished without enough energy storage (capacitor, battery or large coils) or provide DC power to LED through a rotary rectifier that produce smoother DC through rotor inertia.


    Quote Originally Posted by steve66 View Post
    Sure, manufacturers can pulse the LED's on and off.
    It's not intentional. LEDs MUST drop to zero brightness at 120 Hz (full wave rectifier) or 60 Hz (half wave rectifier) unless there's a capacitor to ride through the zero crossing. The difference in peak max and min output has a big influence on flicker.


    Quote Originally Posted by steve66 View Post
    can not work But just like you old TV, they all looked like they were constantly on because the eye responds to the peak level of brightness.
    And CRT monitors were well known for causing eye strain and headaches when refresh rate was not high enough. The refresh rate of CRT affects its flicker index.

    Quote Originally Posted by steve66 View Post
    So lets make some comparisons. Fluorescent lights with magnetic ballasts pulsed the tubes at 60 hz. Some people claimed that could be perceived by sensitive people, and that's quite possible.
    Correct and it is one of the reasons fluorescent critics dislike fluorescent lighting. The peak vs average ratio is also not as most line frequency LEDs. This is because you needed to keep lamp peak current divided by RMS current less than 1.7 to guarantee proper lamp life. Additionally, the afterglow of the long persistence phosphor provides significant amount of light output through the zero crossing each half cycle.

    We also know TV's scanned at 60 hz, and that is fast enough that is usually fast enough to produce smooth pictures and motion.
    LCD monitors pretty much eliminated flicker due to the difference in the way image is refreshed. CRT redraws everything at at refresh rate. Steady objects are not redrawn every time on LCD. Well, CRT style flicker did come back with the introduction of low cost, PWM dimmed LED back-lit LCD monitors.

    So 60 hz. is iffy, and can be detected with a phone. However, when we get a little higher, say 300 to 600 hz. range or more, there is no way anyone is going to be able to see any flicker. Bump it up a little higher to the 18,000 hz or more of a fluorescent ballast and the flicker can no longer be detected with a phone.
    Keep in mind that there are crappy electronic ballasts out there that operates at 10s of KHz but carries over residual 120 Hz pulsation which is akin to AM radio. The carrier wave maybe at 760 KHz, but audio signal is infused by varying it at audio frequency. So when you run the light output from an LED through a photo diode and an amplifier, the amout of 120 Hz passing through depends on the filtration quality of the LED BALLAST. LED ballast design engineers realized they can satisfy line side power factor requirements as well as allow phase cut dimming by cutting down on flywheel size (use a smaller capacitor) and increase the amount of flicker by raising how much 120 Hz bleeds into light output. As implied in the title of my thread, it is the loophole in the energy standard that permitted this specification compliance through performance reduction by finding a specification parameter that is not made into a requirement but nonetheless has a profound effect on final product performance. So the various bodies are working on rewriting requirements to fill this loophole. It's quite possible that the LED industry left it in place initially in order to use mediocre low cost ballast just to make sure that LED lamp elements that were extremely expensive at the time can remain anything close to cost competitive based on lumen, watts and cri performance.

    Quote Originally Posted by steve66 View Post
    I just see no reason in the world any manufacturer would use a frequency for a LED light fixture low enough to have flicker. The simplest most basic electronics in the world can easily make an LED driver that works high enough to make flicker not an issue. I can't imagine why any manufacturer would pulse the LED's at anything less than a few KHZ.
    Allowing huge amounts of 120 Hz flicker to bleed through to the LED elements is the cheapest way to satisfy line side power quality requirements which was created after realizing the poor power factor performance of commercially available CFLs. LEDs can tolerate the very high lamp current crest factor that would ruin CFLs quick so they were able to get away with it.

    Low flicker, high line side power quality and exceptional output regulation (110-130v makes the same exact output as 120v) generally require a two stage front-end topology which is costly. This is a standard feature for commercial application fluorescent ballasts and high power factor computer power supplies. LED luminaires with comparably performing ballast are usually extremely expensive. Value LED fixtures generally have inferior spec ballasts and high degradation factor LEDs.

    You can get a good flicker performance with a large front-end capacitor as with many CFLs, but the power factor is around 0.6


    I've looked at a couple of LED lights with my phone since you posted this, and they have detectable flicker with whatsoever. They would basically be equivalent to an fluorescent light with a electronic ballast. I think its more likely you have a couple of bad lights.
    Cell phone camera makes automatic exposure adjustments to ISO and electronic shutter speed, so you might not always catch it. A checkered pattern printed on paper and attached to something you can spin, such as a top works good for this. You could try holding it up very close so that ISO is bottomed out to force the camera to make exposure changes by reducing the shutter speed.

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