The light I just bought is very bright when used. After using for a long time, the brightness of the lamp will gradually decrease until it finally goes out.
We all know that this is because the life of the lamp is gradually shortening, and when it is completely off one day, it will die. Many people can't help but wonder why there is such a process in lamps and lanterns, and what causes it?
In fact, in the final analysis, this is the problem of light decay of lamps. To put it simply, lamps are the same as the human body. With the increase of service life, the functional mechanism of lamps is constantly decreasing. No matter it is incandescent lamp, fluorescent lamp, or LED lamp, the problem of light decay cannot be avoided.
The light decay of the lamp means that after a period of time, the light intensity of the lamp will be lower than the original light intensity, and the lower part is the light decay of the lamp. Different types of lamps have different causes of light decay.
Ordinary incandescent Light decay
For ordinary incandescent lamps, the larger the bulb of the lamp, the smaller the light decay, which is proportional to the evaporation of tungsten that blocks the light output. In the gas-filled bulb, because part of the gas prevents the tungsten filament from evaporating, the light decay will be relatively small.
If it is an incandescent lamp with the same filament, made in different sizes of bulbs, the light decay at the same time point is indeed smaller than that of the small bulb.
In addition, it is also filled with bubbles. The bulb with a large glass bulb has a large internal space, and the gas convection to the glass bulb has a relatively large heat dissipation area. The temperature of the relatively small glass bulb lamp is much lower, so the temperature of the filament is relatively low and the luminous efficiency is low. The evaporation rate of silk is also low, so the light decay is small.
Fluorescent Light decay
Incandescent lamps will cause light decay due to the size of the bulb and the evaporation of tungsten filaments, while fluorescent lamps’ light decay causes are relatively complicated, generally caused by the following reasons:
◆ Phosphor powder is degraded. In the working process of fluorescent lamp, ultraviolet rays will cause phosphor to produce color center, resulting in a new absorption band in the lamp, thereby attenuating the brightness of phosphor.
◆ Formation of light-absorbing film. After the fluorescent lamp has been discharged for a long time, a black light-absorbing film will be formed on the surface of the phosphor. The existence of this light-absorbing film will reduce the light output.
◆ The lamp tube is blackened. When the fluorescent lamp is working, there will be a large amount of mercury ions or mercury atoms on the surface of the glass tube. The mercury ions will exchange with other ions in the glass tube. Over the years, the glass tube will be blackened. The luminous decay of fluorescent lamps affects the luminous efficiency.
LED Light decay
Although LED lamps are better than incandescent lamps and fluorescent lamps, they cannot completely overcome the problem of light decay. The light decay of LED mainly has the following two factors:
The quality of LED products
◆ The quality of the LED chip used is not good and the brightness decays quickly.
◆ There are defects in the production process, and the heat dissipation of the LED chip cannot be well derived from the PIN pin, which causes the high temperature of the LED chip to increase the chip attenuation.
Conditions of use
◆ The LED is driven by constant current, and some LED lights are driven by voltage, which makes the LED decay too fast.
◆ The driving current is greater than the rated driving conditions.
In fact, there are many reasons for the light decay of LED products, but the most critical one is heat dissipation. The better the heat dissipation performance, the lower the operating temperature of the LED, the smaller the light decay, and the longer the life of the LED.
Luminous decay is a necessary process for the work of lamps. When selecting lamps, we should try our best to choose lamps with better quality and heat dissipation performance. During use, we should also minimize the workload of the lamps to delay the speed of light decay and extend the lamps life.