The Stroboscopic Phenomenon of LED Lighting Fixtures

LED lighting products have many excellent lighting characteristics, but there are also many problems to be further studied, among which Stroboscopic Phenomenon is an important aspect.

The Stroboscopic Phenomenon of a lamp or light source refers to the fluctuation characteristics of light output. It refers to the corresponding changes of light flux, illumination or brightness with the periodic change of current amplitude driven by AC or pulsed DC power supply.That is to say, the intensity of light varies with time. Flicker is often used in English.

Stroboscopic Phenomenon reflects the changing characteristics of light intensity with time. There are two main aspects of this change. One is the periodic characteristic of change, which indicates the changing speed; the other is the magnitude of change, that is, the magnitude of amplitude. Frequency and amplitude have different effects on human body.

For example, long working or living under low flicker lights，such as inductive ballast fluorescent lamps， can cause visual fatigue and even headache. According to the report of the IEEE Standard P1789, the human eye can recognize stroboscopic flickers below 70Hz, which may cause headache, blindness, distress or epilepsy in human physiology.The flicker above 70Hz, though not perceptible, but can cause headache, visual fatigue, long-term use can cause visual impairment, even faster heartbeat and other reactions.Research shows that it is harmless to human body only when it is above 160 Hz or even above 200 Hz. The effect of amplitude on human body will lead to different physiological reactions with the frequency of stroboscopic flicker.

Periodic characteristics of flicker, which refers to frequency. As mentioned earlier, although many studies have suggested that it takes more than 160Hz to do no harm to human body, there is no conclusion. Sometimes it is also defined according to the relevant power harmonic characteristics.

Since the LED has a very fast response time, under certain conditions, the Stroboscopic Phenomenon of the LED are mainly determined by the characteristics of the driver.The traditional light source is insensitive to the current  because of its slow response (long rise and fall time) and great delay. Therefore, the stroboscopic problem of LED light source is more prominent and serious than that of traditional light source.