What causes LED lights flicking

What causes LED lights flicking and how to solve it?

Well, in short, LEDs flicker when their light output fluctuates. This fluctuation occurs because your dimmable light-emitting diode use to turn on and off at a very high rate.
We’ll dig deeper in the following article.

Why do LEDs flicker?

Using plain white LED tape doesn’t flicker – that’s how!
Although you won’t always see it, all mains-powered light sources flicker – whether incandescent, halogen, fluorescent or LED.

In the USA, utility power is alternating current (AC) power, supplied at 50 hertz. It means that the current filling your lamp (any lamp) switches back and forth 50 times per second.

We didn’t notice it before with the old incandescent bulbs because the residual heat from the bulb caused the filament to glow between flickers. It is a side effect of the inefficiency of traditional light bulbs. These old incandescent bulbs usually waste about 90% of the input energy through the heat!

So, let’s start the discussion by debunking a common misconception. Since the power supply causes LED flicking, some people think that as long as the input power (current and voltage) remains constant, you can avoid it altogether.

It is not true. All power-powered light sources flicker all the time.

Since all lights flicker, why do some people think LED flicker is a problem?
LED flicker happened a lot in the past. That’s because – unlike incandescent, halogen, and fluorescent lamps – LEDs are not persistent. When the power to the LED turns off, the light output stops immediately. Therefore, if connected directly to AC power, an LED will turn on/off 50 times per second – enough for the human eye to see.

LED flicker is not a problem with modern LED installations. That’s because we no longer connect LEDs directly to the mains. Instead, we use LED drivers designed for this purpose to power the LEDs.

How High Quality LED Power Supplies Solve LED Flicker Problems

LED lighting requires direct current (DC) rather than AC power. That’s good news because the key to eliminating LED flicker is the type of power supply you use to drive your lights.

While the lighting industry often refers to its power supplies (aka “drivers”) as simply “LED transformers,” they are much more than that. An LED driver does more than reduce (convert) voltage. It can also alter the current from AC to DC. Choose a quality LED power supply, and it will also provide a constant current to your LEDs. So you’ll get light without visible flicker.

However, a low-quality, clean LED driver does not provide constant current. Instead, it simply converts the current from AC to DC. This most basic power conversion produces an oscillating current, although it usually doubles the input voltage frequency. In the USA, it results in a frequency of 100 potential blinks per second.

Lightly loaded

One hundred flickers per second are much better than 50 flickers per second. But that still sounds like a problem. Fortunately, there is nothing to worry about – because the human eye doesn’t have enough perception to see it. Most of us only register light that fluctuates less than 100 flashes per second-usually 50 or slower. (Computer screens typically flicker in the 60 to 70 Hz range, which we barely notice.)

So even though there are indeed very few people who can see faster strobes, this is not a problem for most of us. In many project installations, all you need is a bare, clean LED “transformer.” Even in some applications, LED strobe may be the desired effect: think nightclubs, for example, or oscillating bike lights.

Constant current = constant brightness

However, suppose a simple LED power supply is not enough for your project. In that case, a constant-current power supply is a good alternative.

These higher specification LED drivers can eliminate flicker by varying the voltage across the circuit to produce a constant current. This ensures that the current delivered to the LED does not fluctuate, thus mitigating AC/DC conversion effects.

In some cases, even a constant-current LED driver cannot eliminate flicker. Interference caused by incompatible control circuits is a common cause. Before installing, you should confirm that your LED product is suitable for the control circuit and power supply you are using.

Frequent blinking – attention warning!

If the cause of the LED blinking is interference or incompatibility, the blinking effect will not be uniform. But this may not be the problem you are facing. Suppose your lights produce regular, rhythmic blinking (e.g., every second). In that case, they are probably consuming more power than your LED driver has built-in.

High-quality LED power supplies are designed to do just that, producing a flickering effect as a warning. Regular blinking indicates that your LED needs a more extensive, higher specification power supply (or several smaller ones).

Loose wiring and other misconnections can also cause problems.

Suppose you have multiple electronic devices installed nearby (for example, on the same switchboard). In that case, the combined heat may overload your LED dimmer. It is likely to cause intermittent flickering. The Diginet website in Australia has a great article discussing the best way to derate overloaded dimmers.

When LEDs use cinema applications (e.g., TV studios, theaters, etc.), you will need very high frequency, high-resolution output. It is beyond the scope of standard drivers. Suppose you are involved in such professional projects. Send us a message to discuss the benefits of a constant voltage LED driver for the film industry?

LEDs for motion pictures use high-frequency, high-resolution drivers designed for that task!

The most common cause of visible flicker is the implementation of dimming functions!

Handling dimming

Even in otherwise perfect LED lighting installations, dimming can cause problems. This is because conventional dimmers work by extending each switch flicker cycle’s “off” portion to reduce the total amount of light output.

It is called pulse width modulation (PWM). PWM works very effectively – as long as the switching frequency does not drop to a level that the human eye can perceive.

We are working to solve this by developing LED dimmers with faster blink cycles. A cycle of several kilohertz is the goal. This would mimic the solution used by the electronic ballasts that have been powering fluorescent lamps for years. However, there is a downside: the higher the flicker frequency, the closer your LEDs need to be to the transformer. This isn’t always practical.

Instead of installing these less flexible (and more expensive) dimmers, you can also very easily avoid the visible flicker generated by pulse width modulation. Simply by not dimming the LEDs too low, you can prevent their flicker cycles from becoming visible to the naked eye.

Just a few years ago, this usually meant not dimming below 50% of full brightness. But now. The dimmers in our current lineup all give you more flexibility. You may find that you can cover down without any visible flicker!

Typically, you will find that zero to 10V dimmers are less likely to flicker than mains TRIAC controls.

Warm white 10W LED strip lights create a pool of light in this residential parking lot.

Avoid flickering LED lights under kitchen cabinets.

Summary – How to Stop LEDs from Flickering

Over the past decade, LEDs adopted by the lighting industry as the future of energy-efficient lighting solutions. With all the advantages they offer, this is no surprise.

Avoid the LED flicker. You and your electrician need to have a basic understanding of the issues behind it. Always keep the following points in mind.

1. Always use an LED power supply designed to drive LED products. Do not use any LED strips powered by AC power!
2. Ensure that all your LED products are compatible with the control circuit and power supply you are using.
3. Check loose wiring and other faulty connections. And make sure your LED lights dimmer is not overloaded.
4. Consider using a constant current LED driver.
5. When installing a dimming system, try to see if there is a minimum dimming level that should not be lower.
6.For dimming systems, consider using a zero to 10V or digital voltage dimming system instead of a TRIAC alternative.