Why are the lifetimes of LED bulbs getting shorter and shorter?

by rawpixel.com

In the early days when the LED bulb appeared in the world, it was said that the packaging box had "a long life of 50,000 hours", "100,000 hours usable" and so on. However, most of the LEDs sold at the time of article creation has a lifetime of about 7,500 to 25,000 hours. Engineer Ted Yapo explains about the question "Why is the lifetime of LED bulbs less than the initial?"

What Happened to the 100,000-Hour LED Bulbs? | Hackaday
https://hackaday.com/2019/02/05/what-happened-to-the-100000-hour-led-bulbs/

According to Yapo, when talking about the lifespan of a light bulb, I can not avoid avoiding the international cartel " Poibos Cartel" which was once tied to control the production and sales of incandescent light bulbs. Poibos cartel tied in 1924 after the First World War is tied by companies in several countries such as USA, France, Hungary, UK, Germany, so that the life of the incandescent lamp will not exceed 1000 hours We have established the regulation.

There were also incandescent light bulbs with a lifetime of 1,500 hours to more than 2,500 hours before the poibos cartel was joined, but the cartel said that "long-life incandescent light bulbs lower efficiency and problems in light intensity" We have signed an agreement not to sell light bulbs with lifetime exceeding 1000 hours. The cartel seems to be able to achieve the previous double sales by just halving the life of an incandescent bulb and just increasing the brightness by about 11 to 16%.

Light bulbs sold by member companies were inspected at all times, and it was a system that could be fined if life expectancy was markedly shorter than 1000 hours or remarkably long. Regarding this fine contract, it was not publicly disclosed, and the fact that the lifetime of the light bulb is uniform and about 1000 hours was said to have been rationalized in terms of efficiency and the like. Although cartels became dysfunctional during the Second World War, Yapo said that they have continued to hinder the development of incandescent bulbs for nearly two decades.

by Nova

In the case where "life is 1000 hours" is written in the bulb package, this "life span" means the average rated life . This is the average lifespan value when tested under the prescribed conditions and "When 50% of the initial sample of the light bulb reaches the end of life", it seems that the average rated life will be obtained. In other words, only half of all bulbs can achieve the lifetime written in the package, the other half will continue to shine beyond the package's lifetime.

In order to think about the lifetime of the LED light bulb, it is necessary to think about the actual structure of the LED light bulb. Although Mr. Yapo is the same A19 type LED bulb, he purchased three types of light bulbs with a lifespan of "7500 hours", "15,000 hours", "25,000 hours", and checked the contents.

The three types of LED bulbs in the following images have a lifetime of "7500 hours", "15,000 hours" and "25,000 hours" from the left. The LED bulb is composed of not only the LED chip that emits light but also parts such as LED driver and electrolytic capacitor that convert the alternating current sent from the power supply into the direct current. An LED bulb with a lifespan of 7500 hours has an LED chip and an LED driver on the same board, while an LED bulb having a lifetime of 15,000 hours or 25,000 hours is thermally separated from the LED chip and the LED driver It is understood that it is.

It is thought that not only the LED chip which can be said to be the most important for the LED light bulb, but also other parts, because the LED light bulb has various parts but has the parts. The Department of Energy of the United States of America (DOE) supports the research and development of LED technology, it also collects data on the lifetime of LED lamps and causes of failure.

The following image shows the breakdown cause of the LED lamp installed in the outdoor of 5400 pieces collected by DOE as a pie chart. Interestingly, the percentage of failures caused by the LED chips themselves was only 10% of the total, and 59% found that the LED lamps were out of order due to LED driver failure. Housing problems accounting for 31% of the cause of failure are not necessary when considering LED bulbs for indoor use. This data shows that it is not an LED chip but an LED driver that is important for the lifetime of the LED bulb.

The lifetime of an LED light bulb does not exceed the lifetime of any one of its components. Mr. Yapo insists that it is the semiconductor and the electrolytic capacitor that limits the life to the longest among the components that make up the LED bulb. Both of these increase the probability of failure due to high temperature, and the lifetime doubles when the surrounding temperature decreases by about 10 degrees.

Of the three types of LED light bulbs purchased by Mr. Yapo, the LED chip and the LED driver are on the same board with the shortest life, and the heat of the LED chip was very easy to transmit. With this structure, Yapo says that the lifetime of the LED bulb is shortened. The remaining two types are said to be resistant to malfunction due to heat because the LED chip and the LED driver are installed separately.

Also, with LED bulbs with a lifespan of 15,000 hours and LED bulbs with a lifetime of 25,000 hours, there is a difference in the upper limit temperature of electrolytic capacitors, 105,000 hours for 105,000 hours, 25,000 hours for It is 130 degrees in the direction. This difference affects the life span of each LED bulb.

by Klaus Hausmann

The incandescent light bulb also slowly diminishes its brightness before it gets disappeared with a lapse of time, and as of the end of life the brightness is decreasing by 10 to 15% from the beginning. Likewise, as the LED bulb also gets older, it loses its brightness and it will not be able to provide sufficient brightness, but there is no such thing as "light goes out."

Therefore, when considering the life span of the LED bulb in the industry, in addition to the time point "it breaks down and does not come to light", the time point when "the brightness has decreased to 70% of the initial brightness" It is said that she has decided to have a lifetime. " As brightness declines to 70% of the initial level, everyone seems to notice the difference, but as the light bulb slowly reduces its brightness, most people have reduced brightness I do not notice that I am.

In addition, most of white LEDs express white by combining blue LEDs and phosphors, but the phosphor deteriorates over time due to exposure to high temperatures, and the color may change gradually. The mechanism by which this color changes is not fully understood, and it seems that it is difficult to predict color stability and deterioration. However, the reduction in brightness and the change in color have little effect on the LED light bulb. The fact that various factors affecting the lifetime of such LEDs have been found over time is the reason why the life span of LED bulbs in recent years has been shorter than in the early stages of appearance.

by Shawn Harquail

Mr. Yapo changed home light bulbs to LED light bulbs in 2010, so we have been using the same LED bulbs for over 8 years in fact as of 2019. Therefore, I tried to remove the LED bulbs in the kitchen where the LED bulbs are used most frequently and the LED bulbs in the other rooms with the lowest frequency of use, and see how the brightness of each is different. Because each LED bulb is a similar installation method and it is hard to think that the temperature inside of the LED bulb is higher than only one, aging deterioration according to the use frequency is advanced, according to Mr. Yapo Thing.

The images which compared the actual LED bulbs actually are as follows. The LED bulb on the left was used in the kitchen, the right was what was used in the other room, the kitchen LED bulb emitted a rather weak light, the color is also yellowish I understand. Mr. Yapo also noticed that the LED bulb in the kitchen is quite tired, but he said he did not think he was getting worse like this.