Electrolytic Capacitors is the Main Reason for the Short Life of LED Lamps
It is often heard that the short life of LED lamps is mainly due to the short life of the power supply, and the short life of the power supply is due to the short life of the electrolytic capacitor. These claims also make some sense. Because the market is flooded with a large number of short-lived and inferior electrolytic capacitors, coupled with the fact that they are now fighting the price, some manufacturers use these inferior short-lived electrolytic capacitors regardless of quality.
First, the life of an electrolytic capacitor depends on the ambient temperature.
How is the life of an electrolytic capacitor defined? Of course, it is defined in hours. However, if the life index of an electrolytic capacitor is 1,000 hours, it does not mean that the electrolytic capacitor is broken after one thousand hours, no, but only that the capacity of the electrolytic capacitor is reduced by half after 1,000 hours, which was originally 20uF. It is now only 10uF.
In addition, the life index of electrolytic capacitors also has a characteristic that it must be stated in how many degrees of working environment temperature life. And it is usually specified as the life at 105 ° C ambient temperature.
This is because the electrolytic capacitors we commonly use today are electrolytic capacitors using liquid electrolyte. Of course, if the electrolyte is dry, the capacitance will certainly be gone. The higher the temperature, the more easily the electrolyte evaporates. Therefore, the life index of the electrolytic capacitor must indicate the life under what ambient temperature.
So all electrolytic capacitors are currently marked at 105 ° C. For example, the most common electrolytic capacitor has a lifespan of only 1,000 hours at 105 ° C. But if you think that the life of all electrolytic capacitors is only 1,000 hours. That would be very wrong.
Simply put, if the ambient temperature is higher than 105 ° C, its life will be less than 1,000 hours, and if the ambient temperature is lower than 105 ° C, its life will be longer than 1,000 hours. So is there a rough quantitative relationship between life and temperature? Yes!
One of the simplest and easy-to-calculate relationships is that for every 10 degree increase in ambient temperature, the life span is reduced by half; conversely, for every 10 degree decrease in ambient temperature, the lifetime is doubled. Of course this is just a simple estimate, but it is also quite accurate.
Because the electrolytic capacitors used for LED driving power are definitely placed inside the LED lamp housing, we only need to know the temperature inside the LED lamp to know the working life of the electrolytic capacitor.
Because in many lamps the LED and electrolytic capacitors are placed in the same casing, the environmental temperature of the two is simply the same. And this ambient temperature is mainly determined by the heating and cooling balance of the LED and the power supply. And the heating and cooling conditions of each LED lamp are different.
Method for extending electrolytic capacitor life
① Prolong its life by design
In fact, the method to extend the life of electrolytic capacitors is very simple, because its end of life is mainly due to the evaporation of the liquid electrolyte. If its seal is improved and it is not allowed to evaporate, its life will naturally be extended.
In addition, by adopting a phenolic plastic cover with an electrode around it as a whole, and a double special gasket tightly engaged with the aluminum shell, the loss of the electrolyte can also be greatly reduced.
② Prolong its life from use
Reducing its ripple current can also extend its service life. If the ripple current is too large, it can be reduced by using two capacitors in parallel.
Protecting electrolytic capacitors
Sometimes even if a long-life electrolytic capacitor is used, it is often found that the electrolytic capacitor is broken. What is the reason for this? In fact, it is wrong to think that the quality of the electrolytic capacitor is not enough.
Because we know that on the AC power grid of the city power, there are often instant high voltage surges due to lightning strikes. Although many lightning protection measures have been implemented for lightning strikes on large power grids, it is still inevitable that there will be net leakage to residents At home.
For LED luminaires, if they are powered by the mains, you must add anti-surge measures to the mains input terminals in the power supply of the luminaire, including fuses and overvoltage protection resistors, commonly called varistors. Protect the following components, otherwise the long-life electrolytic capacitors will be punctured by the surge voltage.