LED light-emitting diodes, because it has the environmental protection, long life, high photoelectric efficiency earthquake, and many other advantages, rapidly developed in recent years application in various fields, in theory, the service life of the LED in the 100000 hours, but in the process of practical application, some LED lamps and lanterns design staff awareness LED drive power supply is insufficient or improper selection or the pursuit of low cost, As a result, the life span of LED lamps is greatly shortened. The life span of poor LED lamps is less than 2000 hours, and some are even lower. As a result, the advantages of LED lamps can not be played well.
Due to the particularity of LED processing and manufacturing, the current and voltage characteristics of LED produced by different manufacturers or even the same manufacturer in the same batch of products have great individual differences. Now take the typical specifications of high-power 1W white LED as an example, according to the current and voltage change rules of LED to do a brief explanation, generally 1W white light application forward voltage is about 3.0-3.6V, that is to say, when the nominal 1W LED flows through 350 mA current, the voltage at both ends of it may be 3.1V, It may also be in 3.2V or 3.5V May be other values. In order to ensure the life of 1WLED, LED manufacturers generally suggest that lamps and lanterns be driven by 350mA current. When the positive current at both ends of the LED reaches 350mA, the positive voltage at both ends of the LED increases very little, which will greatly increase the positive current of the LED. The LED temperature rises straight, which accelerates the LED light decline, shortens the life of the LED, and even burns out the LED in serious cases. Due to the particularity of voltage and current variation of LED, strict requirements are put forward for the power supply driving LED.
Constant current source driving as common drive way of LED drive mode, driven by constant current source, not in the output circuit in series current limiting resistor, LED on the flow of current is not affected by the outside power supply voltage, temperature changes, and the influence of LED parameter discreteness, thus to keep the current constant, give full play to all kinds of the good qualities of the LED.
The LED constant current power supply is used to power the LED lamps. Because the current flowing through the LED will be automatically detected and controlled during the working period of the power supply, there is no need to worry about the excessive current flowing through the LED at the moment of power on, and there is no need to worry about the load short circuit burning out the power supply.
Some manufacturers are concerned that the use of electrolytic capacitors in the power drive plate will affect the life of the power supply, which is actually a misunderstanding, such as: If the high-temperature electrolytic capacitor with a life of 105 degrees and a life of 8000 hours is selected, according to the prevailing electrolytic capacitor life estimation method of "every 10 degrees reduced, the life is doubled", then its working life is 16000 hours in 95 degrees environment and 32,000 hours in 85 degrees environment. The service life is 64,000 hours at 75 degrees, longer if the actual operating temperature is lower! From this point of view, as long as the selection of high quality electrolytic capacitor on the life of the driving power supply is not what impact.
Another point is worth the attention of LED lighting enterprises: due to the LED in the process of work will release a lot of heat, so that the core junction temperature rises rapidly, the higher the power of LED, the greater the heating effect. The increase of LED chip temperature will lead to the change of the performance of light-emitting devices and the attenuation of electro-optic conversion efficiency, and even failure in serious cases. According to the experimental tests, : LED own temperature rise of 5 degrees Celsius, light flux will drop 3%, so LED lamps must pay attention to the LED light source itself heat dissipation work, in the possible case as far as possible to increase the LED light source itself heat dissipation area, as far as possible to reduce the working temperature of LED itself, if conditions permit, it is best to separate the power supply part and the light source part, It is not desirable to blindly pursue small volume and ignore the working temperature of lamps and lanterns and power supply.