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A Comprehensive Guide to LED Luminaire Strobe

LED drip strip light

LED luminaires are a popular lighting choice because of their high efficiency and durability. In this article, KingOrnan engineers will tell you what LED lamp strobes are, how they affect human vision, and how LED lamp strobes are formed.

A Comprehensive Guide to LED Luminaire Strobe

What is LED luminaire strobe?

LED luminaire strobe refers to the volatility of the luminous flux output of the luminaire in a switching cycle. The luminous flux, illuminance, or brightness of the LED light source changes periodically with the amplitude of the current under the power supply’s drive. The light source shows rapid, light-dark switching changes over time after the luminaire is powered. Times per unit of time is called frequency. In the case of low output frequency, the greater the depth of fluctuations, the more serious strobe (except for the frequency to reach the exemption class). It can be divided into:

Visible strobe

The human eye is a very complex system, and individual differences are very large, for the vast majority of people can detect the light flicker below 80Hz, when the human eye can perceive changes in light and dark, flicker frequency below 80Hz is also known as a visible strobe (visible flicker). A visible strobe is not acceptable for ordinary lighting or display.
The human eye to the stroboscopic sensitivity weighting function chart:

The human eye to the stroboscopic sensitivity weighting function chart

Strobe effect

For more than 80Hz strobe, the human eye is not easy to detect but has a greater impact on the spatial perception of the human eye. For example, the moving object is seen as a series of still images, that is, the stroboscopic effect (Stroboscopic effect). Because of the stroboscopic effect, people can imagine that some fast-running equipment is slow-running or even stationary is very dangerous. 
Stroboscopic effect diagram:

Stroboscopic effect diagram

Illusion phenomenon

   Similarly, when the flicker frequency of the light source at 80Hz-2kHz, and the object in the environment remains stationary, the human eye in moving position or direction, the stationary light source but will appear to extend the light point of the system, known as the phantom phenomenon, such as car taillights, or sweeping outdoor LED display, etc.

Illusion phenomenon

LED lamps and lanterns strobe what harm

A simple look at strobe refers to the intensity of light over time rapid repeated changes or is the light in a bright and dark flicker. If the flashing speed is relatively slow, the human eye can see, but if it is super fast, the human eye can not see it. Light source strobe on the human visual system has a stimulating effect. It will produce an uncomfortable feeling, usually flicker according to human feelings are divided into visible flicker and invisible flicker. The human eye the light flicker frequency perception is limited, although this varies from person to person; when the light flicker frequency reaches 80Hz human eye basically can not see the flicker, the frequency is greater than 100Hz, the human eye to see the average brightness of the light source, do not feel the flicker phenomenon. However, still cause eye fatigue, headaches, etc., which are the consequences of strobe; it is generally believed that the effect exists within 500Hz. The absolute sense of no strobe is impossible; the Chinese industry standard for qualified products’ strobe requirements is 3125Hz.

Headache, eye fatigue, or vision loss

Many migraine sufferers are very sensitive to light, such as bright light and flicker, which is more likely to cause migraine. A slow flicker is usually more likely to cause migraine than a fast flicker. 100Hz flicker light source is identified to cause headaches and migraine; for 120Hz frequency, flicker light source may affect people’s mood, appear boredom, anxiety, etc.

Photosensitive epilepsy.

People who are photosensitive to visible light modulation in the 3-70 Hz range can have seizures even after short exposure. This affects roughly 1 in 4000 people aged 5-24 years, usually starting around puberty, and 75% of the population will be photosensitive for life.

Distraction

The periphery of the human eye field of vision is more sensitive to strobe; for example, strobe lights or car tail lights produce rapid modulation that will attract drivers to keep staring, which may be dangerous to drivers or people and objects on the driving road. In the speed of the moving object and the light source strobe frequency into a multiplicative relationship, the movement of the object will produce a stationary, inverted, slow motion, and other three states of periodic repetition of the wrong vision, easy to cause work-related accidents.

Autism

Children with autism are especially sensitive to changes in the environment, and strobe in lighting increases the recurrence of this behavior.

LED lighting strobe is how the formation of?

Power supply drive problem

LED lighting products use AC to DC constant voltage or constant current power supply drive; the light source itself does not produce strobe, with or without strobe depends on the LED driver power supply due to the driver varies widely, the strobe performance of each LED product is not the same. In particular, for some manufacturers to save costs, using a simpler driver circuit, there is a larger strobe problem.

The professional version of the power factor > 0.9 power supply, because of the power factor correction circuit, will generate a lot of ripple current; when the ripple current is> 10% or more, there will be a stroboscopic phenomenon.

Solution: Use double base PFC circuit design to control the ripple current within 5%, so there will be no strobe. In addition, low power factor power adapter because there is no power factor correction circuit, so there will be no stroboscopic phenomenon.

LED light source problem

The poor quality light source, a single chip less than 1W, the wattage of the lamps and lanterns false, so that the chip also drive mismatch and not work properly, resulting in strobe.

lighting dimming

For intelligent lighting products, dimming is a necessary function. The strobe often intensifies when the product is loaded with a dimming function. Especially when the dimming is darker, its fluctuation depth is relatively large. Therefore, the dimming function or claim to connect the dimming controller lighting products should be in its brightest dimming and dimming darker when measuring its strobe performance.

LED lighting strobe test method

What are the parameters of strobe judgment?

In the strobe test, there are two very important judgment parameters, strobe percentage, and flicker index.

Strobe percentage

Strobe percentage = the difference between the maximum light output in a switching cycle / to the maximum light output and the minimum light output and the minimum light output and the sum of.

Flicker index.

The Strobe index equals the amount of light output over the average light output in a switching cycle divided by the total light output.
Strobe percentage (fluctuation depth) and the lower the strobe index, the less the light source flicker or cause the strobe effect. We believe that traditional incandescent lamps have no strobe. But the actual incandescent strobe percentage and strobe index are not low. Once considered the most eye-friendly incandescent lamps, once again beyond our knowledge. Incandescent lamps in our country are working under 50HZ by alternating current, positive and negative half-cycle over zero, the heat residue on the filament continues to shine, and 200W incandescent filament is a little thicker, so in positive and negative half-cycle over zero, the filament cools down slower, so the flicker percentage is lower.

Does a Cell phone can judge the light strobe?

Cell phone test strobe is not scientific and reasonable. There are four main reasons.

  1. Some cell phones’ “sampling + display” frequency will be automatically adjusted within a certain range according to the light changes in the camera range. -> Sampling frequency is not high enough and not fixed!
  2. cell phone manufacturers will be through a variety of algorithms, such as hardware and software, to circumvent this problem; the images you shoot have likely been automatically optimized
  3. If the phone’s sampling frequency is the same as the light waveform, then the phone will be tricked into telling you that this light is very good, with no change.
  4. The phone’s shutter will also affect your judgment. ->The shorter the shutter time, the more obvious the “strobe” seen by the phone, but the longer the shutter time, the more likely the “strobe” disappears.

What should be used to measure the LED lighting strobe effectively?

About strobe, there are different definitions and different reference indicators, such as IEEE, Energy Star, IEC, CIE, and so on; there is no unified standard at home and abroad to measure the lamp strobe index, this time you need a professional strobe tester can be applied to multiple countries and regions at the same time. A Strobe tester can measure the important parameters of the strobe, such as “strobe percentage” and “strobe index,” but also has an evaluation function so that users can directly read the quality of light, such as very serious, obvious presence, almost no, high-frequency exemption, etc.

Although the LED light source in energy saving than the traditional light source efficiency, the LED light source can not be like the general light source and can be used directly to the public grid voltage; it must be equipped with special voltage conversion equipment to provide LED to meet the rated voltage and current, to make the LED work properly, that is, the LED driver power supply. But because of the different specifications of the LED power supply, performance, and conversion efficiency varies, so choose a suitable, efficient LED power supply to show the LED light source’s high-performance characteristics. Because the low efficiency of the LED power supply itself requires a lot of power consumption, supplying power to the LED can not highlight the energy-saving characteristics of LED. In short, the LED power supply, in the work of the LED stability, energy efficiency, and life span, has an important role. 

If you want to understand the LED power supply fully, please check: Take you to know the LED power supply

Common standards for strobe at home and abroad

  1. GB/T 31831 -2015 “LED indoor lighting application technical requirements
  2. IEEE Std 1789 – 2015 “IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers
    GB/T 31831-2015 and IEEE Std 1789-2015 strobe coverage band is relatively wide, both in 0 ~ 3000Hz or more.
  3. IEC/TR 61547 – 1: 2015《Equipment for general lighting purposes – EMC immunity requirements – Part 1: An objective light flicker meter and voltage fluctuation immunity test method
    IEC/TR 61547-1: 2015 strobe coverage frequency band is 0.05~80Hz.
  4. CIE TN 006-2016 “Visual Aspects of Time Modulated Lighting Systems-Definitions and Measurement Models
    The strobe coverage band of CIE TN 006-2016 is 80 to 2000 Hz.

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