The lights are getting dimmer and dimmer. Where are the […]
The lights are getting dimmer and dimmer. Where are the lights going?
The light just bought is very bright when used. When the lamp is used for a long time, the brightness of the lamp slowly decreases until it is finally extinguished. We all know that this is the life of lamps and lanterns is slowly shortening, until one day it completely does not light, it will die. Many people are unavoidable to 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. Simply speaking, the function mechanism of lamps and lanterns is declining with the increase of their service life, just like the human body. Either incandescent lamp, energy-saving lamp or LED lamp can not avoid the problem of light decay.
The light decay of lamps means that after a period of lighting, the light intensity of lamps will be lower than the original light intensity, and the lower part is the light decay of lamps. Different types of lamps and lanterns have different causes of light decay.
Decay of incandescent lamp
For ordinary incandescent lamps, the larger the bulb shell, the smaller the light decay, that is, the deposition of tungsten evaporation to block the light output is proportional. The light decay of the inflatable bulb is relatively small because part of the gas prevents the evaporation of tungsten filament.
If an incandescent lamp uses the same filament and is made in different size bulb shells, the light decay of the large bulb shell at the same time point is smaller than that of the small bulb shell.
In addition, the same is the inflatable bulb, the large glass shell bulb has a large internal space, gas convection to the glass shell has a relatively large heat dissipation area, relative to the small glass shell lamp temperature is much lower, the filament temperature is relatively low, the luminous efficiency is low, the evaporation rate of tungsten filament is also low, so the light decay is small.
Energy-saving lamp decay
Incandescent lamp will cause light decay because of the size of the bulb and the evaporation of tungsten filament. The reasons for light decay of energy-saving lamp are relatively complex, which are generally caused by the following reasons:
_Phosphor deterioration, in the process of energy-saving lamp work, ultraviolet light will make the phosphor produce color center, resulting in a new absorption band in the lamp, so that the brightness of the phosphor appears attenuation.
The formation of absorption film, energy-saving lamp after a long time of discharge work, will form a black absorption film on the surface of phosphor, the existence of this layer of absorption film will cause the reduction of light output.
When the lamp is blackened, there will be a large number of mercury ions or mercury atoms on the surface of the glass tube when the energy-saving lamp works. Mercury ions will exchange with other ions in the glass tube. Over the years, the glass tube will be blackened, which leads to the light decay of the energy-saving lamp and affects the luminous efficiency.
LED light decay
Although LED lamps are better than incandescent lamps and fluorescent lamps, they can not completely overcome the problem of light decay. There are two main factors for the light fading of LED:
1. Quality of LED products
The quality of the LED chip used is not good, and the brightness decay is fast.
Production process has defects, and the heat dissipation of LED chips can not be well derived from PIN foot, resulting in the high temperature of LED chips, which intensifies the chip attenuation.
2. Conditions of Use
LED is driven by constant current. Some LED lamps are driven by voltage, which makes the LED decay too fast.
_Driving current is greater than rated driving condition.
In fact, there are many reasons leading to the light decay of LED products, but the most critical problem is heat dissipation. The better the heat dissipation performance, the lower the working temperature of the LED and the smaller the light decay, the longer the lifetime of the LED.
Lighting decay is a necessary process of lamp work. When we select lamps, we should try to select lamps with better quality and heat dissipation performance. In the use process, we should also try to reduce the workload of lamps, in order to delay the speed of light decay and prolong the life of lamps.