What Makes an LED Bulb Flicker and How to Solve the LED Flicker Effect

Guide to LED Flickering

With fluorescent lighting gradually being displaced in favor of LED, many thought the days of dealing with flickering lights were over. Despite flickering being less present in LED than with fluorescent systems, it is certainly still a factor. What are the causes of this, and are there solutions?

Types of Flickering

There are two types of flickering with lights – visible flicker and invisible flicker. Obviously visible flicker is the one our eyes can see, which is when the light output from a given source changes rapidly. It is considered that anything below a frequency of 100Hz can be seen.

There are health concerns with visible flickering. Short-term exposure to frequencies in the 3Hz to 70Hz range are associated with epileptic seizures, with the highest possibility of occurrence being in the 15Hz to 20Hz range. With 1 in 4000 people suffering photosensitive epilepsy and many more who have not been diagnosed, this has become a public safety issue.

Invisible flicker is just as much of a problem if not more. It is the flicker that is present but we cannot see. The symptoms include dizziness, eyestrain, headaches, migraines, impaired thought, and other general sick-feeling symptoms.

Where does flicker come from?

To better understand flickering in lights, consider the theatrical effect known as strobe lighting. This is a deliberate flicker effect that delivers light at certain frequencies, causing the brain to interpret moving objects as if they were in slow motion. These specified frequencies are generally just a few flashes per second, but they are very close to frequencies that cause epileptic seizures.

Unintentional flickering in lighting equipment can be traced back to our power companies that designed electricity flow to use alternating current (AC) as opposed to direct current (DC). With AC power, the sine wave will peak both positively and negatively. This leaves it susceptible to being in a range that will cause flickering, or sometimes an audible hum.

How to solve LED flickering issues?

LED flickering can be tied back to the driver component within the lamp. The essential purpose of the LED driver design is to rely on a simple circuit to control output current, but without altering the frequency, the LED becomes likely to show visible flicker. However, this can be fixed by using constant current drivers, which remove the peaks of the sine wave.

Power correction components within the driver circuit must also be addressed. Without this, ripple currents in the power flow will cause flickering.

Ultimately if the driver design of the LED bulb meets the requirements of both a stable DC current and ample ripple suppression, there should be no flicker. If flickering is present in your LED lamp (and you are not dimming with it), it was likely created with cheap driver components. The technology in LED lighting has advanced to the point where this should not happen, unfortunately there are companies that care more about their bottom line than the health of their customers.

How Dimming Causes LED Flickering

Another challenging variable for LED lamps to avoid flickering is through dimming. Most standard wall dimmers work by phase cutting, which removes part of the sine wave and reduces the voltage. However, this can have negative affects on an LED circuit and actually result in the flicker effect being amplified to a potentially dangerous level (3-15Hz range).

This is one of the main reasons why it’s hard to trust old dimming systems with new LED bulbs. The only way to be sure no flickering will be present is to get LED-specific dimming solutions for your LED lamps. It all comes back to the fact that LED is a long-term investment. In turn it is worth doing research to ensure you are getting a quality LED bulb, and that if you plan to dim with it you are getting an LED dimming system that has been tested as being compatible to the LED bulbs you intend to use.

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15 Responses to “What Makes an LED Bulb Flicker and How to Solve the LED Flicker Effect”

  1. SteveMay 16, 2017 at 9:43 am #

    I have changed out fluorescent lamps to LED lamps and changed out the ballast, and they still flicker. What would be the problem then.

    • PremierMay 16, 2017 at 9:45 am #

      Did you install a new ballast or used Type B LED T8 lamps that wire direct? If you got a new ballast, it’s possible it’s not compatible with the lamps you have. Direct wire (Type B) LED T8 lamps should not flicker unless you have a power fluctuation issue (either that or the lamp is defective).

    • Jon LaBranchJuly 27, 2017 at 7:32 pm #

      Steve, I replaced four fluorescence tubes in two fixtures. One works perfectly and the other flickers and then dark. Fixtures are identical as are the bulbs. Any thoughts?

  2. Scott DyessMay 18, 2017 at 8:14 am #

    So my problem is that occasionally, one of my Great Value brand, non-dimmable, LED bulbs will flicker for a couple of seconds, or for a few minutes. It doesn’t seem to be consistent with the starting or stopping of appliances in the house. Thus, am I to interpret that you are saying it’s very likely a defective driver components within the bulb?

  3. Jerry ListerJune 5, 2017 at 5:52 am #

    Good article. A very complex subject that I am heavily involved with.
    I would maybe add a category for stobe effects as in car rear lights. Strobe effects become visible when it’s dark and you move your head. This means this type of flicker becomes visible at much higher than 100Hz. With Red LEDs of rear lights having no persistance (no phosphers) this can be visible at quite high PWM frequencies. Some research says 3,000Hz PWM frequency should be used.
    The other remarkable thing I’ve found is the difference in person to person perception. We had a test of 5% flicker at 22Hz, this was immediately intolerable to 3 people and gave eyestrain/headache. 2 people could see it, but another 2 said ‘I don’t what you’re on about, I can’t see anything!’
    The best thing a consumer can do it get the flicker app for iPhone. This will give you some information, but not the full story.
    Problems are very likely if you use a dimmer switch as well…
    The lighting industry is struggling with this issue with no standards really applicable. IEEE1789 is gaining traction, but even that is incomplete + full of holes..good old fashioned tungsten fails to meet this standard !

  4. ChrisJune 10, 2017 at 1:12 pm #

    I replaced an incandescent lightbulb with a new LED light bulb. The LED flickers.

    The incandescent was old and I recently moved in. I did not know that the wattage or voltage of the incandescent bulb. Could this be part of the problem?

    • PremierJune 12, 2017 at 8:33 am #

      Could be a cheap LED bulb, an issue with the socket, or dimmer. If you know the wattage/voltage of the lamps you are replacing (and of the replacements), that would help.

  5. Peter ErwinJune 11, 2017 at 9:08 am #

    On LpS 2016 in Bregenz the CFD (Compact Flicker Degree) has been successfully presented. The CFD is the world’s first sensible measurement method to measure light modulation which, unlike all other methods, takes into account the amplitudes of all occurring frequencies with regard to the influence on humans and expresses them in a single percentage value.
    On the websites of Der Lichtpeter you may read much more about it.

  6. CullenJune 13, 2017 at 12:37 pm #

    I have some LED can light retro fits and they flicker like crazy. They seemed to work fine until I replaced the old dimmer with a new led dimmer from Lutron. I tried replacing the dimmer with another one but that still didn’t solve the problem. I have replaced the lights with new ones and they will work correctly for a little bit and then the flicker starts again. It’s driving me crazy!!!

  7. Jim MakepeaceJuly 5, 2017 at 8:55 am #

    This is an interesting subject – I specify lights for various types of projects, mostly residential with some commercial and mixed use.

    I have replaced 90% of my own incandescent bulbs with Juno and Lithonia LED trim modules, nothing special, just standard residential grade.

    I am mostly happy with the performance, but the strobe/flicker affect at times is annoying and makes me second guess some of the fixtures we’ve specified – even though the developers are asking for low-cost fixtures.

    I have also noticed as one commenter above that older incandescent dimmers seem to work better than newer ELV dimmers specified by the fixture manufacturer as being ‘compatible’ (e.g. dimming range is poor, or fixtures pulsate at bottom of range).

    On another note, I lost several LED modules after a lightning strike very near my house (also took out a cable modem and wireless router) – no other equipment in my house was affected, and the lights in question were not on at the time (I live in SW Florida and have surge protection on my main panel).

    • Peter ErwinAugust 2, 2017 at 12:28 am #

      LED illuminants usually do not contain any means against surge for this takes more space. Incandescents cannot be harmed by surge because they do not contain any sensitive electronics. May be the surge protection of your mains power supply needs to be enhanced. I live in Germany and have not heard of any surge problems with LED illuminants yet.

  8. MarcJuly 21, 2017 at 6:40 pm #

    I installed a high end brand ceiling lamp in my kitchen with good dimmable G15.5 bulbs and changed the dimmer. It all worked perfect until they remodeled my kitchen and the fixture was moved. Now it flickers like crazy unless dimmed to low. Any ideas what may have happened? Thanks

  9. bubledSeptember 4, 2017 at 6:17 pm #

    If we add capacitor parallel to LED driver output, will it remove flickering? My opinion that it would have positive effect on Flickering index.

  10. Alan BartramSeptember 9, 2017 at 10:25 pm #

    The government has just replaced the lights in the house with LCD bulbs. The majority of these have started to flicker at different rates and some not at all. The power to the house is two phase but every other light in the past has worked normally. Is it the bulbs I suppose they would be cheap?

  11. RandyNovember 4, 2017 at 9:00 am #

    working on a Lowe’s fixture with 4 multiple LED lights, on 2 driver boards. problem started about 1 year and 2 weeks, just out of warranty. not replacing a $150 fixture when repair is an option. replaced 1 driver board and it seemed smaller in component size. it was a constant current, when replacing these, what is the main spec I should be looking for? driver boards are cheap, but not lasting very long, replacement start flashing after a few months.

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