Harm of lighting flicker

Since lighting entered the era of fluorescent lamps, flicker accompanied lights have been flooding our light environment. Subject to the luminous principle of fluorescent lamps, the problem of flicker has not been well solved. Today, we have entered the era of LED lighting, but the problem of light flicker still exists.

What is flicker

Flicker is the change of light intensity or brightness in a certain time period. Lighting flicker occurs in many lighting applications, including slow motion shooting on TV, road lighting, various fields of general lighting and workplaces using fast rotating machinery. Flicker will affect human health, and the degree of impact depends on the frequency of flicker and personal sensitivity to flicker. High frequency flicker will not have a significant impact on the human body, but low frequency flicker below 120 Hz is easy to affect human health.

Weighting function of human eye sensitivity to flicker

Harm of lighting flicker

Light source flicker is closely related to migraine, headache, autism, eye fatigue, blurred vision and other neurological diseases. Studies have shown that low-frequency, range of 3-70Hz scintillation light source may cause photosensitive epilepsy for some sensitive people; 100Hz flicker frequency was identified to cause headache and migraine; 120Hz flickering light source may affect people's mood, such as boredom and anxiety. Visual illusion caused by flicker effect and related mechanical motion is very dangerous in industrial places. Therefore, accurately measuring and evaluating the flicker characteristics of lighting products is directly related to people's health, which is an urgent problem to be solved.

Causes of flicker

The reasons for the flicker of LED lamps include not only the factors of power supply, but also the factors of technical performance of light source and unreasonable lighting design. Ripple current is one of the important causes of flicker in the power supply of many lighting lamps. Ripple current is the AC component that still exists after rectification and filtering. Ripple current is superimposed on DC and has different frequencies and curves. This AC component makes the power of the LED module fluctuate, which in turn will change the brightness. The quantity and frequency of superimposed AC are the decisive factors of flicker.

IEEE Std 1789-2015

Diagram for definition of flicker index and percent flicker

How to eliminate flicker

In addition to the function of eliminating darkness and illuminating the environment, lighting must take into account the health performance of products. Harmlessness to people is a part of the performance of lamps that must not be ignored.

Affected by the rectification of power supply voltage (50Hz in European standard), the frequency of ripple current in a large part of LED drive is twice that of power supply, which is about 100Hz. Moreover, compared with traditional light sources, LEDs can immediately convert the working current into light. In order to achieve the light output effect without flicker as much as possible, high-quality LED driver and the compatibility among driver, dimmer and LED module are indispensable. The following picture is a common method to evaluate the control device through "output current ripple" or "superimposed AC". Typically, the indicated value is 100Hz. The lower the value, the lower the risk of flicker.

IEEE Std 1789-2015

IEEE Recommended Pictures for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers

Wellway's LED lamps and lghtings, whether wet-proof lamps, bracket lamps, panles and dust-proof lamps, including basic models and emergency sensing models, all realize the function without flicker. The high-quality power supply used by the lamp can minimize the output ripple and realize the perfect matching with the lamp components.

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