Why do LED lights flicker?

As modern energy-efficient lighting technologies proliferate in our environment, so does awareness of their impact on biology and even technology. The rapid development and assimilation of LED lighting, often without clear standards, may lead to lighting flickering and adversely affect it. Many organisations and industry professionals across disciplines, including international standards bodies and regulators, are working to measure, understand and appropriately manage flicker.

1. Why does the LED light source flicker?

1. LED light sources are a different story. Based on semiconductors, they respond quickly to power changes, whereas commonly used power systems and drivers can generate excessive flicker.

2. Flicker has been around since the invention of AC (alternating current) powered light sources. A change in the supply power phase produces a correspondingly rapid periodic change in the emitted light radiation and the resulting illumination intensity or brightness. Traditional incandescent lighting systems are affected, but not significantly, because the filament is relatively slow to respond to changes in power. Other light sources, such as fluorescent tubes or other discharge lamps, have a fast response time, so the changes are more noticeable to the observer.

2. How does flicker affect us?

1. Flicker affects workplace safety and productivity, comfortable living spaces, and according to recent research, our overall health and emotional well-being. For example, from a safety point of view, a fast rotating element present in the operator's field of view does not appear to be moving very fast, or stop due to excessive flickering. From a photobiological point of view, prolonged exposure to excessive flicker leads to neurological problems such as headaches, migraines, and even epilepsy.

2. From a technical point of view, flicker can strongly affect the lighting for digital image capture, especially in TV studios and sports venues. Strict broadcast requirements require the use of an appropriate power supply system to avoid camera image artifacts, especially stroboscopic effects during slow playback during high-speed capture.

3. How to limit flicker?

1. In LED light sources, flicker can be reduced by proper design and power supply filtering, for example by using a higher number of capacitors. Alternatively, a high frequency voltage converter can be used. With LED dimmers, light intensity can be adjusted in a number of ways. Changing from pulse width modulation to current regulation, as some LCDs do, also reduces flicker.

2. Manufacturers use several different technical solutions to limit flicker. However, what is technically possible does not always translate into a perfect finished product. Changes in power system design can increase size and cost - not always an option for manufacturers. The result is a product on the market with flicker characteristics that don't match the customer's or designer's expectations. A device defined as having minimal flicker can actually be driven by high frequencies invisible to the human eye, not even a TV camera. Without proper measurements and standards, claims like "flicker free" can be more advertised than quantified properties.

Flicker is an old phenomenon that needs new consideration in the age of LED lighting. The industry has made progress in quantifying flicker and its measurement. Numerous industries and global standards organizations are in urgent need of further understanding and quantification of how flicker affects humans and other biological forms in multiple ways. In the meantime, progressive instrument makers such as GL Optic have developed methods to quantify certain flicker properties precisely and reproducibly. There is no doubt that the light is burning with positive outcomes for all when it comes to the future of addressing flickering.