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LED lights in the end is high PF important or flicker important?

May 22, 2017

First, the origin of the problem:

There are now two kinds of light engine on the market, one is a high PF but the flicker of the electrolytic capacitor light engine, the other is flicker-free and low PF electrolytic capacitor light engine. So what kind of light engine is better in the end?


Second, the cause:

In order to improve the power factor PF, not only took out the electrolytic capacitor, but also in order to make the current waveform and voltage waveform exactly match, the use of the LED string is divided into several groups and turn on The The result of this must be caused by the intermittent LED light and produce a serious flicker.

Third, the degree of scintillation:

LED is the need to have a certain starting voltage (2V or more) to turn on, and now have to wait for the input voltage to a certain height after the conduction, this will inevitably make in the middle of the two half sine wave has a large Dark area (see the arrow area below), making it flicker much more than other lamps (like incandescent, fluorescent).

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Four, flicker caused by the consequences and problems


1. The impact on the human body:

· Will produce strain fatigue, blurred vision, and traditional headaches;

Will lead to the onset of photosensitive epilepsy;

Increased repetition among autistic children.


2. Impact on production workers

Workers who require vision and vision will lead to a decline in performance;

Workers who use or touch rotating machinery will have the effect of slowing down, stalling, or even reversing, which can lead to work accidents.


3. the impact on the athletes

On the table tennis badminton and other high-speed sports athletes, because every 1/100 seconds there will be 2ms dark, this light flash often lead to the direction of the ball to determine the mistakes and other issues.


4. The impact of literary photography

Will leave a fringe on the photo;

Long exposure lens shot when shooting will produce strange face.

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5. The impact of video, television, film production

The flickering of the light has a bad effect on the quality of the film and television drama, with ghosting and interference fringes that can not be played.


6. The impact of security, security system

Because the camera's camera moment may be just in the dark light when this time it is possible to shoot all black images, that is, lose a complete frame. If this frame happens to be the moment of the mob's attack, then it lost an important evidence.

Five, how to eliminate flicker

The most thorough way is to eliminate the source of this brightness flicker. That is after the rectification of the use of electrolytic capacitor filter, thoroughly filter out this exchange ripple.

After electrolytic capacitor filtering, the rectified sine wave is basically smoothed into a near-dc waveform with only a small ripple, and the larger the capacitance of the electrolytic capacitor, the smaller the ripple. That is, the flicker is basically completely eliminated.


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

Why is this "defect" to bring the quotation marks? Because the test results are measured with the market power factor measured! And these power factor test results are very questionable.


For example, we use the same electrolytic capacitor 102W LED light engine system, using different test instrument test results are as follows: the market commonly used digital power factor tester tester power factor of 0.6590.

However, if we use the national CHNT recognized Cosφ meter to test the same system, but can get PF = 0.9 results. It can be seen that this digital power factor meter test results are very problematic.


So what is the power factor in the end? 

The power factor is inherently cosφ in the linear AC electrical system, which is the cosine of the angle between the voltage sine wave and the current sine wave. It represents the current sine wave that is different from the voltage and is projected into the direction of the voltage vector. Or the current vector to neutralize the voltage vector in phase with the component value. The multiplication of this phase value and voltage is the active power. Two by one component and voltage vector multiplication is reactive power. If cosφ = 1, that is, PF = 1, then there is no reactive power. In the linear AC system to define a cosφ as a power factor, that is, in order to be able to use another phase of the opposite device to compensate, so that the reactive power is zero.

However, in the use of rectifiers in the nonlinear system, the current wave is not a sine wave, so do not know its cosφ is equal to how much. That is, do not know how PF should be defined. There are four completely different definitions in the world. But it is strange that there is now on the market can measure the power factor of non-linear system to sell. Only all of these digital power factor can not give the power factor positive and negative, because they are using active power and reactive power ratio as the power factor, the power is no negative, of course, the ratio of the two power The sign is right. This definition is clearly problematic, and now this topic is the master's thesis of American universities and the doctoral thesis of the University of Sweden. It is easy to explain this problem: one of the most important features of the power factor is the positive and negative sign. Because the power factor is divided into two kinds of inductive load and capacitive load, the sensibility is positive; the capacitive is negative, the two can compensate each other. Usually the home of the refrigerator, air conditioners, televisions are all emotional load. So the electricity bureau often in the transformer secondary parallel to a large capacitor to compensate. And LED power supply with electrolytic capacitor is obviously a capacitive load, it should be for the appliance power factor compensation is also good! But the market of digital power factor meter is not to give a sign!

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As can be seen from the above description, for the electrolytic capacitor light engine of the so-called low power factor "shortcomings" is a fundamental problem is not clear, if you take this problem is not ulterior motives are at least this one stroke.

Seven, low-power LED lighting should not have the power factor limit:

Originally the country's power factor for low-power electrical appliances have a very clear requirement, that is, 75W following low-power electrical appliances without power factor requirements and restrictions. And for the lamp in the past did not put any power factor requirements, such as the domestic commonly used 36W fluorescent lamps are used in most of the ballast inductance plus starter, its power factor is very low, only 0.51 or so. The country has never spoken to it. Later, high-power metal halide lamp, and even the power of up to 1000 watts, also used inductors as a ballast, power factor is only 0.51, but also inductive load, and no one has put it on the power factor requirements. Later, for energy-saving lamps seem to put the following 15W no restrictions (because almost all commonly used energy-saving lamps are less than 15W, so this request does not make sense!)

Just to the LED lights but made a very demanding requirements, 5W below does not require power factor. We all know that the EU is usually the most demanding, and the EU proposed only 25W or more to require power factor, our country's requirements are actually higher than the EU 5 times as much as it is intended to make things difficult to make LED lights like.


Eight, no electrolytic capacitor light engine is not just flashing there are many more serious problems:


The biggest problem is that it uses a very low efficiency linear power supply, its efficiency is only 85%. 15% of the power has become a heat. If this inefficient linear power supply into the aluminum plate made of light engine, then there must be 15% of the heat added to the LED above. Take the 10W light engine as an example. Remove the 1.5W power consumption, only 8.5W supply LED, actually LED electric - light efficiency of 40%, that is 8.5x0.6 = 5.1W of heat, and now an increase of 1.5W of heat, is increased 1.5 / 5.1 = 0.3, equivalent to an increase of 30% of the heat. Which is to make the LED junction temperature increased by 30%. In general, the design of the radiator should make the junction temperature of 85 degrees, now increased to 110 degrees, it will make its thermal efficiency reduced by 25%, life expectancy from 30,000 hours to 10,000 hours.


Effair has invented a linear constant current source with electrolytic capacitors up to 99% efficient, using this constant current source as a light engine that not only does not flicker, but also does not add heat to the LED light source because it's High efficiency, itself almost does not consume power, that is, does not produce heat. So it will not reduce the thermal efficiency of the LED, it will not shorten the life of the light engine! It can be said that only this highly efficient constant current source can be integrated into the LED light source of the aluminum plate to become high-performance light engine. All other so-called high-PF AC light engines actually only reduce the thermal efficiency, shorten the life and flashing serious products.

It should now be clear that the advantage of the flicker-free high-performance light engine is much higher than the so-called high-flickering light engine!

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120cm 300W LED Linear High Bay

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