LED lights in the end is the importance of high PF or flicker is not important?

Now there are two kinds of light engine on the market, one is a high PF but serious flicker of the electrolytic capacitor light engine, and the other is no flicker and low PF electrolytic capacitor light engine. So what kind of engine is better?

First, the origin of the problem

Now there are two kinds of light engine on the market, one is a high PF but serious flicker of the electrolytic capacitor light engine, and the other is no flicker and low PF electrolytic capacitor light engine. So what kind of engine is better?

Two, cause

A Silicon Valley ExClara company invented a LED system, in order to improve the power factor of PF, not only removed the electrolytic capacitor, and in order to make the current and voltage waveforms match, the LED string is divided into several groups and successively conducted. The result of this is that it causes the LED intermittent light to produce a serious flicker.

Three, the degree of flicker

LED is the need to have a certain starting voltage (more than 2V) can be conducted, now have to wait until the input voltage is increased to a certain height before conducting, this will certainly make a big dark area in the middle of 2.5 sine wave (see below the arrows), thus making it far more than other lamps flicker (like the incandescent lamp, fluorescent lamp) is much more serious.

Four, flashing consequences and problems

1 impact on the human body:

Strain fatigue, blurred vision, and traditional headaches;

Will cause photosensitive epilepsy patients;

Increasing repetitive behavior in autistic children.

2 impact on production workers

For workers who require vision and vision to cause a decline in performance;

For workers who use or contact rotating machinery will produce a slow rotation, stop, or even reverse the effect of serious injury will lead to accidents.

3 impact on Athletes

For high speed sports such as table tennis players, because every 1/100 seconds, there will be 2ms of the dark, the flashing of this kind of light will often lead to the direction of the ball to determine errors and other issues,

4 the influence of literary photography

Will leave a stripe in the photo;

Long time exposure camera shooting will produce strange faces.

5 the impact of video, television, film production

The flicker of the light plays a bad effect on the quality of the production of the film and TV series

6 impact on security and security system

Because the camera's camera is likely to happen in the dark light, this time it is possible to shoot a black image, that is, the loss of a complete frame. If the frame is just the moment of the mob, it loses an important piece of evidence

Five, how to eliminate flicker

The most thorough way is to eliminate the root cause of this brightness flicker. That is, after the rectification using electrolytic capacitor filter, filter out the AC ripple.

After the electrolytic capacitor filter, the rectified sine wave is basically smooth to be close to the DC waveform, only a small ripple, and the greater the capacity of the electrolytic capacitor, the smaller the ripple. In other words, the flicker is basically eliminated.

Six, the use of electrolytic capacitors, "disadvantage" -PF low

Why should this "defect" be put in quotation marks because the test results are measured by the power factor on the market, and the test results of these power factor meters are questionable.

For example, we use LED light engine system with a 102W electrolytic capacitor, using different test instrument test results are as follows: the market commonly used digital power factor test instrument for power factor of 0.6590. But if we use the national CHNT identified Cos Phi to test the same system, we can get the results of PF=0.9. It can be seen that the test result of the digital power factor meter is a problem.

So what is the power factor?

The power factor is linear AC system in COS, is the angle between the voltage and current of sine wave sine cosine value, it represents a different voltage and phase current to voltage sine wave vector in the direction of projection. Or the current vector and the voltage vector in the same component value. Multiplying the in-phase value with the voltage is the active power. The 22 part of a component and voltage vector multiplication is reactive power. If cos phi =1, which is PF=1, then there is no reactive power. The reason why the cos system is defined as a power factor in the linear AC system is that it can be used to compensate the other phase of the device, so that the reactive power is zero.

However, in the nonlinear system with a rectifier, the current wave is not a sine wave at all, so it is not known how much it is equal to cos. That is, I do not know how to define PF. There are 4 different definitions in the world. But the strange thing is that there are now available on the market to measure nonlinear system power factor meter. But all of these digital power factor meter can give positive and negative power factor, because they are using active power and reactive power as the ratio of the power factor, the power is not negative, of course, the two power ratio did not sign. This definition is clearly a problem, and now the subject is the master's thesis of the American University and the doctoral thesis of the Swedish University