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LEDs are high PF important or flicker-free

Source:M2 Light Stop    Author:Admin    Visit:1986    Pubtime:2016-06-15 00:34:55

1The origin of the problem

Now in the market there are two kinds of light engine, one is a kind of high PF but serious flickering off without electrolysis electric engine, the other is a flicker-free and low PF with electrolysis electric engine. So what is what kind of light engine is better?

2The origin

Silicon Valley company ExClara invented a LED system, in order to improve the power factor PF, not only removed the electrolytic capacitor, and in order to make current and voltage waveforms exact match, using the LED string will be divided into several groups and are sequentially turned on . It cause a LED illuminated intermittently resulting in serious flicker.

3Flashing degree

LED is needs to have certain starting voltage (above 2 v) to conduction,and then have to wait for the input voltage rises beyond a certain height was turned on, this is bound to do so in two and a half sine wave in the middle there is a big dark area (see image below arrow area), so that it flashes than other lamps (such as incandescent lamp, fluorescent lamp) is much more serious.

4Flashing consequences and problems

1. Influence of human body:

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

· Can cause photosensitive epileptic seizures in patients;

· An increase in repetitive behaviors among children with autism.

2. Influence of production workers

· Workers and visual acuity requirements related jobs will lead to a decline in performance;

· The use of or contact with rotating machinery workers will have to rotate slower, stop or even reverse the effects, can cause serious accidents.

3. Influence of athlete

Table tennis and badminton athletes high speed movement, because every 1/100 of a second will be 2ms darkness, this light flashes often causes the ball to the direction of misjudgment and other issues.

4. Influence of Art photography

· Leave streaks on the photo;

· Long exposure shots will produce strange face when moving shooting.

5. Influence of  video, television, film production

Lights flashing have a bad effect to the film and television drama production, it will appear ghosting and interference fringes lead to can not be played.

6. Influence of  security, alert system

Because in the imaging time, the video camera may be in the dark lighting, by this time it is possible to shoot black image, which is the complete loss of one frame. If the frame is exactly the mob attack moment, then it lost an important piece of evidence.

5How to eliminate flicker

The most thorough way is to eliminate the root causes of this kind of brightness flicker. That is after the rectifier electrolytic capacitor filters completely filter out this AC ripple.

After the electrolytic capacitor filter, the rectified sine wave becomes substantially near DC is smoothed waveform, only a small ripple, and the larger capacity electrolytic capacitor, the smaller the ripple. In other words, all the flashes basically eliminated.

6Electrolytic capacitor "shortcoming" - low PF

Why is this "disadvantage" to put quotation marks? Because the results of this test is used on the market there is a problem of power factor meter to measure! And the test results of these power factor meter is very doubtful.

For example, we use the results of an electrolytic capacitor with a 102W LED light engine system, using different test instruments test is as follows: The common market of digital power factor tester measured power factor of 0.6590.

But if we adopt the national CHNT identified Cosφ meter to test the same system, the results is PF = 0.9. The result of this test shows digital power factor meter is very problematic.

7Low-power LED lamps should never have the power factor limits

The country has a very clearly provision for low-power electrical power factor  in originally, is below 75W low-power electrical no power factor requirements and restrictions.For lamps in the past did not offer what the power factor requirements, such as commonly used in the vast majority are used 36W fluorescent lamp ballast inductor plus starter, its power factor is very low, only about 0.51. State said it had never heard. Later, high power metal halide lamps, and even up to 1000 watts of power, it is also inductively as ballast, power factor is only 0.51, but also inductive load, no one has ever made it through the power factor requirements. Later, as if made for the energy-saving lamps 15W or less no restrictions (because almost all common energy-saving lamps are less than 15W, so this requirement does not make sense!)

8No electrolytic capacitors are not just flashing light engine, there are many more serious problems

The biggest problem is that it uses a very inefficient linear power supply, its efficiency is only 85%. 15% of the power is turned into heat. If this inefficient linear power into the aluminum substrate made of a light engine, then it would have 15% of the heat added to the LED above. 10W light engine to be an example. Remove 1.5W power consumption, only 8.5W LED supply, actually LED electro - optical efficiency of 40%, that would have been the heat 8.5x0.6 = 5.1W and 1.5W of heat now added, is to increase the 1.5 / 5.1 = 0.3, representing an increase of 30 percent of calories. Also makes the LED junction temperature is increased by 30%. Under normal circumstances the design of the radiator should make a junction temperature of 85 degrees, and now increased to 110 degrees, so that it will be hot light efficiency reduced by 25%, reduced life from 30,000 hours to 10,000 hours.

Now invented an efficiency up to 99% of the electrolytic capacitor linear constant current source, constant current source made this light engine, not only did not blink, and the LED light source will not increase the heat, because it's high efficiency, power is scarcely consumed in itself, that is, no heat. So it does not reduce the heat from the LED luminous efficiency, light is not shortened engine life! It can be said that only at extremely high efficiency constant current source to be able to integrate it into the aluminum plate LED light source becomes a high-performance optical engine. All other so-called high-PF AC light engine is really just reduces the thermal efficiency, shorten the life of the product and flashes serious.This  is a constant current LED strip, have good quality, adjustable color temperature and dimmable. current LED strip

As the LED lighting industry develops, features like high efficiency and long life alone cannot satisfy the market. People are looking for a better lighting environment, especially when it is related to health. For certain places like offices and living rooms, elimination of strobe flicker is even more important.

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