Lamps also have a lifespan
Each of us has a lifespan, and the same is true for lamps. As time goes by, the function mechanism of lamps will continue to decline. Whether it is incandescent lamps, fluorescent lamps, energy-saving lamps or LED lamps, they cannot avoid "end of life", and this is the problem of light decay of lamps.
As for what is light decay? Generally speaking, the light decay means that after a period of time, the light intensity of the LED lamp will decrease compared with the initial light intensity, and it cannot be recovered, that is, the reduced part is called the light decay of the LED lamp (different types of lamps, resulting in light The reasons for the decline are different)
Cause of light decay
There are still many controversies about the cause of light decay, and the microscopic mechanism of the light decay is still inconclusive. However, generally speaking, the light decay of LEDs is mainly caused by heat dissipation.
It is well known in the industry that LEDs are afraid of heat. The ideal working temperature of LEDs is between -5 and 0°, but this is basically impossible. Heat will affect the light decay and life of LED lamps. When LEDs are working, they will About 80% of the electrical energy is converted into heat energy, and 20% of the electrical energy is converted into light energy. The LED radiator is used to dissipate heat for the LED, because when the LED chip is working, its own ambient temperature is inversely proportional to the light output rate. , the higher the temperature, the lower the light output rate. When the temperature reaches the maximum operating temperature of the LED chip, the lamp will be broken
In addition, the thermal resistance of the LED chip itself, the influence of the silver glue, the heat dissipation effect of the substrate, as well as the glue and gold wire also have a certain relationship with the light decay.
How to solve the light decay of lamps?
In fact, strictly speaking, LED lamps cannot avoid light decay. It is a technical problem that the industry is concerned about and urgently needs to be solved.
But before talking about the heat dissipation of LED lamps, we must first understand it: junction temperature
What is Junction Temperature? The so-called junction temperature is the operating temperature of the PN junction of the semiconductor chip (wafer, bare chip). The higher the junction temperature, the earlier the light decay will appear.
If the junction temperature is 105 degrees, the lifespan is only more than 10,000 hours when the brightness drops to 70%, 20,000 hours at 95 degrees, and 50,000 hours when the junction temperature is reduced to 75 degrees, and can be extended to 65 degrees. 90,000 hours. Therefore, the key to prolonging the life is to reduce the junction temperature, and the key to reducing the junction temperature is to have a good heat sink, so how to systematically identify the heat dissipation of LED lamps?
Generally, as the LED junction temperature rises, the luminous flux will decrease. Then, as long as we measure the illuminance change of the lamp at the same position, we can reverse the change of the junction temperature. The specific method is:
1. Choose a place that is not disturbed by external light, preferably at night, and turn off other lights.
2. Turn on the light in a cold state, measure the illuminance of a position immediately, and write down the reading at this time as "cold state illuminance".
3. Keep the position of the lamp and illuminance meter unchanged, and the lamp continues to work.
4. After half an hour, read the illuminance value here again, and write down the reading as "thermal illuminance".
5. If the two values are similar (10~15%), the heat dissipation system of the lamp is basically good.
6. If the difference between the two values is far (greater than 20%), the heat dissipation system of the lamp is doubtful.
Luminous decay is an inevitable process of lamp work. When we buy lamps, we must choose lamps with better quality and heat dissipation performance. During use, we should also reduce the workload of lamps as much as possible, so as to delay the speed of light decay and prolong the life of lamps. life.
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