With the advancement of lighting technology, compared with traditional lighting, LED lighting products have quickly won the favor of the market and consumers with their overwhelming advantages of low power consumption and long life. However, the stroboscopic problem of LED lighting products has not been solved "revolutionary". How to face it scientifically? This is still an open question.
In recent years, with the continuous improvement of living standards, people's requirements for the light environment of work and life are getting higher and higher, especially the problem of stroboscopic flashing of indoor lamps, which has attracted more and more attention. Then, what exactly is the strobe of the luminaire, what harm does the strobe have to the human body, and the misunderstanding of the strobe, how to solve the stroboscopic problem of the luminaire? Xiaobian will answer you one by one.
Why did the strobe come from?
Strobe is the depth of fluctuation of the luminous flux of an electric source. The greater the fluctuation of the luminous flux, the more severe the stroboscopic. The depth of the fluctuation of the luminous flux of the electric light source is directly related to the technical quality of the electric light source. Conventional luminaires are powered by alternating current, and their brightness varies with the periodic variation of the alternating current. The strobe of the luminaire is formed by the change of light and darkness of the light. It is usually divided into two types: one is that the frequency of change is below 100 Hz, and the stroboscopic light can be captured by the human eye; the other is that the frequency of change is above 100 Hz. This strobe will not be seen.
What are the potential hazards of strobe to the human body?
There are related biological and medical studies on the possible damage to the human body caused by stroboscopic:
1. May cause brain cell damage. Some researchers say that by observing EEG, even if the stroboscopic light in the environment is so fast that it is undetectable, the retina of the organism can still resolve and respond to light with a frequency of 100-160 Hz or even 200 Hz. In the animal experiment represented by cats, 100-120 Hz light has caused cell burns in the brain, and the burnt cells belong to the lateral geniculate tissue, which plays a role in controlling the eyeball.
2, may affect reading and vision. Studies have shown that the stroboscopic strobe of fluorescent lamps and CRT displays can affect the trajectory of eye movement when people read text. In addition, in some health check reports, visual impairment is caused by stroboscopic fluorescent lamps.
3, may induce migraine. Experiments have found that stroboscopic flashes with a frequency of 100 Hz may cause an increase in the incidence of headaches for office workers. Of course, this effect is often considered a special case and is only produced in special populations.
Is it a reliable way to identify the strobe on the phone?
With the gradual development of LED lighting, more and more people will habitually take mobile phones to shoot LED lamps, and observe whether there are stroboscopic lights to determine whether the lamps are harmful to human eyes. This is not complete. correct.
The LED luminaire is powered by DC Power Supply, and the light emitted by the light source will also be in the form of DC. However, the input power supply is still in the form of AC. It is difficult to completely avoid the AC ripple through the LED light source, so there will be a digital LED lamp. There is flicker when the camera is shooting.
Overcoming stroboscopic, is there any good strategy at present?
At present, if LED lighting fixtures are more and more commonly used, if constant DC power supply is used, it is theoretically possible to achieve constant stroboscopic illumination. But in fact, due to the lack of industry standards, the market competition is fierce and disorderly. The market is filled with low-quality LED lamps, especially indoor low-power LED lamps, which also have stroboscopic problems. To get a pure and constant current source to ensure that there is no stroboscopic LED lighting, LED driving power is the biggest key. At present, Led Power Supply can only be achieved by satisfying the requirement of no stroboscopic flash. There are roughly three ways:
1. Increase the output electrolytic capacitor. In theory, this scheme can use electrolytic capacitors to absorb part of the AC ripple, but the actual experience tells us that when the ripple is controlled within a certain range (10%), it is difficult to further reduce it unless the electrolytic capacitor is not cost. Adding more can't be completely eliminated at all.
2. Adopt the valley filling passive PFC scheme. This program is also the most mainstream one. Two large capacitors and three diodes are used for power factor correction. Because there is a large electrolytic capacitor behind the rectifier bridge, the AC ripple is absorbed, and the current through the inductor or transformer to the secondary is DC. However, there are some problems in the valley filling scheme. The output voltage of 40-265V cannot be made into a full voltage input of 40V or more. The valley of the output voltage of the valley filling circuit is only half of the valley value of the electrolytic filter circuit, and the output voltage ratio of the valley-filled rectifier method is rectified. The output voltage after ordinary rectification is much lower. It is possible to use the valley filling type and the low voltage input is insufficient. Furthermore, harmonic testing simply cannot be passed regardless of the isolated or non-isolated valley-filling scheme.
3. Adopt a two-level solution. By adding a DC to DC to the existing isolated power supply, the effect of AC ripple can be completely eliminated. Electrical parameters can also fully meet the certification standards. However, this solution has a certain increase in cost, and it is necessary to add one more power management chip and some peripheral circuits.
In summary, the valley filling scheme can solve the stroboscopic problem of LED lamps, but there is no full voltage input when the output voltage exceeds 40V, but the cost is relatively cheaper than the two-stage scheme, and there is strict requirement for no stroboscopic. This type of stroboscopic power supply solution can be considered when the output voltage exceeds 40V and does not require full voltage input. For customers who do not have stroboscopic and other requirements, you can choose a two-level solution.
Edit: Cedar
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