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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24 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.

      • ScottLJanuary 8, 2018 at 6:43 am #

        Can you explain how the socket could be the problem? If it’s solid copper between the socket and breaker, I don’t see how this could be a valid possibility. But, I’m all ears in case there is something to the equation I’m missing. I have flickering LEDs in table lamps plugged directly into the wall. No dimmer switches. No funny business. Just the LED bulb, truly basic lamp with an On/Off switch, and the wall socket that is a straight copper run to the breaker. I have tried multiple lamps, three brands of LED bulbs, and multiple wall sockets. They all flicker. What gets me is that it is the newer LED bulbs that are flickering. My older LED bulbs do not flicker.

        • MarcusJanuary 18, 2018 at 6:18 pm #

          You need to realize that the wire from a receptacle does not go directly to a breaker. There can be anywhere from 2 – 50 different splices or connection points where the circuit feeds in then out of other devices (switches or receptacles). If any one of these splices is not made correctly or a connection has weakened over time, you will have resistance and variables in voltage. I have been a service repair electrician for over 25 years. Poorly made splices and crappy workmanship are too blame for a vast majority of all service calls.

  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?

    • MarcusJanuary 18, 2018 at 6:20 pm #

      There’s no such thing as 2 phase. it is either 3 phase or single phase.

  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.

  12. Hugh LambertJanuary 6, 2018 at 2:56 pm #

    I have LED bulbs that flicker only when the motion sensor goes off. Is there a motion sensor that will cut them completely off when the sensor shuts down?

  13. MikeJanuary 7, 2018 at 7:22 am #

    I put led in all of my light fixtures with 2 or 3 bulbs each fixture. I have one in my bathroom where 2 of 3 will flicker on and off. I have a light fixture in my kitchen where 1 of thev2 flicker. All the others in my home don’t have this problem. I can replace them with non led bulbs and the flickering goes away. What causes this to work in most and not in these. They are all the same fixtures for the most part.

  14. R. NapierJanuary 8, 2018 at 9:05 pm #

    It is a shame that no industry standards are in place for LED components….fixtures, lamps, devices (both switches and controllers). It is ridiculous for US consumers to be expected to know that certain LED lamps work best with certain LED devices….if that’s really true. We are used to buying almost any incandescent lamp brand and coupling that with any device brand and the result is perfect operation. I have recently install thousands of dollars worth of Insteon switches, dimmers, keypads and outlets. I have also purchased LED lamps and light tape with two criteria: dimmable, 2,700 K. About 70% of my applications work well. The rest flicker, flash or strobe. We have reached out to Insteon support and have been put off repeatedly. Finally I got an email with only a lamp list of products they claim woeks best. Where is standardization????? Where is a UL lab? Where are solutions? We installed Aspect wafers in several areas….these flash in sequential pattern, like engine pistons. Aspect says its the device. Who knows? Sadly, the Insteon concept is truly smart. So is the variety thst Aspect offers. Too bad there’s poor support, few solutions, no standards.

    The country is more focused on DC politics, Hollywood “stars” and media talking heads than pressing for LED solutions and standards.

  15. TombilliodeauxJanuary 9, 2018 at 6:07 am #

    I have 2 installed in a light fixture…..DC power in a camper. One flickers and the other does not. i wiggled the flickering one and it stopped but started again at high frequency flickering. I belief it is the contacts that has different resistance. Also temperature as i removed the plastic cover when it started flickering again and it stopped. you may not have that option, but cooling seemed to help it.

  16. TombilliodeauxJanuary 9, 2018 at 6:11 am #

    Correction to above: The flickering DC powered bulb has one row of LED’s that is out. Other 2 rows are lighted. The bulb is defective.
    This is the only one flickering out of 12 installed.

  17. Tom GwozdekJanuary 14, 2018 at 12:26 pm #

    I don’t exactly have a flicker problem I have a flash problem. I have a light fixture about 5 years old. It came with 8 halogen G4 base 20W bulbs. I started replacing the halogen bulbs with LED G4 base 1.5W bulbs. The LED’s worked fine till I got to the last bulb. With 8 LED’s when the switch was turned on the lights flashed and would go out. As long as 1 halogen bulb was in the fixture, didn’t matter which socket, the 7 LED’s would stay on. I know little about electronics but would this problem have something to do with a minimum current draw on the fixture ( and transformer in the fixture 12V.)

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