What Makes LED Lights Flicker? How to Stop LED Bulb Flickering

Flickering of LED lights could be very annoying. LED bulbs and headlights can flicker in many situations. Sometimes a dimmer switch is involved, other times the flickering happens due to other technical reasons. In this article you will learn the root causes of LED flickering and how you can fix this effect.

Flickering LED lights

After switching to LEDs or when replacing a faulty LED lamp in some cases the LED light will start flickering. The intensity of the flicker effect may vary depending on the situation. However, in most cases it is very annoying and disturbing. To stop the flickering, the root cause must be found first. The most common error sources are in connection with dimmers, transformers and defective lamps.

LED bulb on transformer flickers

In addition to the standard LED lights for the 120V power grid, there are also low-voltage LED lamps. These are often used as replacements for low-voltage halogen lamps. Most low-voltage lamps work with an operating voltage of 12V. This voltage is generated from the power grid by a transformer.

Quality of output voltage

Low voltage LED lamps require a stable and clean input voltage. The old halogen lamps did not have such high demands on the quality of transformer output. An unclean and fluctuating output voltage on the transformer can cause the LED lights to flicker.

What to do?

Old halogen transformers with fluctuating output voltage are inappropriate for LED lamps and must be replaced by an LED power supply.

Check out this power supply from Armacost

Minimum load

Many electronic transformers require a minimum load on the output side. If you want to replace five 20W halogen spots with LEDs, according to the Lumens to Watts calculator, five LED illuminants with 3W each are sufficient. With the old halogen lights, the entire installation had an electrical power of 100W.

With the new LED lights, the entire installation only requires a total power of 15W. But chances are good, a 50 – 150W transformer is in use from the past installation. This requires at least 50W to work correctly. Otherwise the connected lamps will not illuminate or flicker.

What to do?

If the LED lights on the transformer flicker, the minimum load is significantly lower. You could now replace one or two LED lamps with the old ones.

Then the minimum load would be reached, but this mixed operation is not a nice solution. The best solution is to replace the old transformer with a new LED transformer. Check out this power supply from Armacost

LED lights flicker on dimmer

Technically speaking, LED lights are more complex than old light sources. This is particularly important when you want to dim the brightness. To do this, the LED lamp and dimmer must play together properly.

Many LED lamps cannot be dimmed. You have to ensure that the LED light is marked as dimmable at the time of purchase. The dimmer specifications must also fit. Older dimmers often require a high minimum load to function correctly. This is mostly not reached by economical LED lamps.

LED lights sometimes flicker

If the flickering of the LED lamp occurs only sometimes, troubleshooting is the most difficult. The following causes can be responsible for the occasional flickering:

The first two points have already been described in the previous sections. A small power supply is built into all 110V LED lamps. This is a frequent source of errors, especially with no-name lamps. Voltage fluctuations in the mains supply can also be responsible for LED lamps flickering only sometimes.

What to do?

The easiest way for troubleshooting is if you have several identical LED lamps installed in your household. You can simply swap each other and see if the occasional flickering now occurs with the other lamp. In this case, the lamp is likely to die soon.

Voltage fluctuations in the power grid can vary. However, only an electrician can help to find and correct the exact cause.

LED lights flicker when switched on

If the LED lamp flickers for a short time after switching on, the lamp is either of poor quality or is about to become faulty at the end of it’s lifespan. With many no-name lamps the integrated power supply is built with cheap components. Some of these need a certain operating temperature before the flickering stops. If the flickering lasts longer from day to day after switching on, a defect of the LED lamp is slowly indicated.

What to do?

With some cheap LED lamps, flickering is unfortunately normal after switching on. This is due to inferior electronics, which leads to the thermal error mentioned.

However, if the lamp has worked perfectly for a long time, a capacitor inside the electronics will probably lose its capacity. To examine a loose contact, you should try the flickering LED bulb in another luminaire.

To get rid of the flickering after switching on, only the replacement with a new LED lamp will help.

LED lights flickering when switched off

In some cases, an LED lamp may flicker even though the light switch is turned off. The reason for this can usually be found in the electrical wiring. An incorrectly connected light switch or a switch with a night light can be responsible for flickering.

What to do?

The exact backgrounds are identical to the case where LED lamps glow after switching off.

LED lights flicker on motion detector

Some motion detectors can be the reason for a connected LED lamp to flicker. It is mainly caused by motion detectors with an electronic switch (triac, thyristor). These require a certain minimum load so the electrical switch works without leakage currents. Single-wire motion detectors that are simply inserted into the phase-line to the lamp are also problematic.

What to do?

To prevent the LED lamp on a motion detector from flickering, a variant with low minimum load or a switching relay must be used.


As you have seen, LED flickering can have many reasons and could occur in different situations. In most cases it is caused in connection with a dimmer, a transformer or due to electrical wiring. Only in rare cases a faulty LED light itself could be blamed for the flicker issue. With the guidance of this article you should be able to find the exact reason and fix your flickering lights.