The relationship between the working temperature and temperature rise of LED lamps and the light decay and lifespan
The ambient temperature at which the LED lamps can work normally is the working temperature of the LED lamps. The general LED lamps are designed at -20℃--40℃, which can meet the requirements of most areas in my country. In some areas, the temperature in winter may reach -40°C. The working temperature of the lamp must be designed at -40°C-40°C to meet the use requirements, while the summer temperature in the equatorial area may reach 50°C or higher. The lamp design must It can work normally in the working environment of 0℃-50℃.
The process requirements and component selection of LED products are different for different operating temperatures. Components in cold and low areas must choose low-temperature-resistant electronic components, and in high-temperature areas, high-temperature-resistant electronic components must be selected. Different temperatures The production process and aging conditions of LED lamps working in the area are different. This is especially important for technicians with little design experience.
What is temperature rise?
The allowable increase in temperature when the lamp is working is also a marking method to measure the heat dissipation capacity of the radiator, and it is also an issue we need to focus on.
We know that incandescent lamps, gas discharge lamps (including fluorescent lamps, high-pressure sodium lamps, metal halide lamps) generally do not require special heat sinks to dissipate heat, but only LED solid-state lighting lamps need special heat sinks to dissipate heat, which is also LED semiconductor The special feature of lighting.
LED semiconductor lighting chip emits light when it is working, and its light does not contain ultraviolet and infrared, so its light cannot take away heat; therefore, the temperature of the chip will rise when it is working. In order to ensure that the temperature does not rise too high when the chip is working, it is necessary to install a heat sink for the LED.
The light decay of LED is related to its junction temperature. The so-called junction temperature is the temperature of the semiconductor PN junction. The higher the junction temperature, the earlier the light decay occurs, that is, the shorter the lifetime.
If the junction temperature is 105 degrees, the lifetime when the brightness is reduced to 70% is only more than 10,000 hours, 95 degrees is 20,000 hours, and the junction temperature is reduced to 75 degrees, the lifetime is 50,000 hours, and it can be extended to 65 degrees. 90,000 hours. So the key to prolonging life is to reduce junction temperature.
Different LED chips have different light decay curves, and their thermal resistance and heat dissipation are also very different.
According to our investigation and analysis, the temperature rise of an LED lamp can be preliminarily summarized according to the grade of the lamp: high-end LED lamp temperature rise≦15℃, mid-range LED lamp temperature rise≦25℃, low-end LED lamp temperature rise ≦35℃.
The temperature on the radiator of the LED lamp = ambient temperature + the temperature rise of the lamp.
For example: a high-end LED lamp manual shows that its temperature rise is ≦15℃, when the ambient temperature is 37℃, what is the temperature of the aluminum alloy radiator of the LED lamp? How many hours can the lamp's life span?
Ambient temperature 37℃+heat sink temperature rise 15℃=lamp radiator temperature 52℃
That is to say, when the ambient temperature is 37℃, the temperature on the LED aluminum radiator should be ≦52℃, otherwise the lamp will not meet the factory requirements.
How many hours is the life of this lamp? The life of the lamp is closely related to the junction temperature of the chip. To know the junction temperature, you must know the integrated thermal resistance from the chip to the radiator. Generally, there are four thermal resistances from the chip to the aluminum radiator. Therefore, if the thermal resistance of the chip is 4℃/W, the total of the 4 thermal resistances is 16℃/W, and the junction temperature of the chip is 52℃+16℃=68℃. The temperature and life curve shows that the lamp has a life span of nearly 90,000 hours.
Similarly, the lifespan of mid-range lamps is about 50,000 hours, while that of low-end LED lamps is about 25,000 hours.
Therefore, the temperature rise of the radiator is a very important indicator. At present, there has not been a manufacturer in the country that has marked the temperature rise of the radiator in the manual. Only the operating temperature range is marked. This kind of indication makes it impossible for consumers to determine the LED lamp radiator. What is the normal temperature, it is impossible to calculate the life of LED lamps.
Of course, the temperature is too high will affect the life of the lamp, but also pose a threat to personal safety, there is a risk of skin burns. As a consumer, the lamp that consumers want to buy is of good quality, long life, low failure rate, and durability. As a vapor proof light fixture factory, he hopes to reduce costs and strive for greater benefits. It is hoped that the life of the lamps will not be too long, and users will update quickly before buying products. This is an inherent contradiction between consumers and manufacturers.
From the above description, we can see the importance of temperature rise, LED lamps should fully consider LED heat dissipation from the chip and structural design. At the same time, we recommend that consumers fully understand the temperature rise of the lamps when buying LED lamps. Before buying, test the actual working temperature of the LED lamps as a reference standard for choosing LED lamps.
