Characteristic due to its low cost, aluminum electrolytic capacitors have been a common choice for power. However, their limited life span, and vulnerable to the effects of high and low temperature extremes. Paper saturated with electrolyte for electrolytic capacitors placed foil on both sides. This electrolyte capacitor evaporates during the life, so as to change its electrical properties. If the capacitor fails, it appears a violent reaction: capacitor forming pressure, forcing it to release flammable and corrosive gases.
Electrolyte evaporation is closely related to the speed and temperature of the capacitor. Working temperature drop 10 degrees Celsius, the capacitor lifetime extension 1 time. Capacitors rated life is usually the result at its maximum rated temperature. Typical rated life for 1000 hours at 105 degrees Celsius. Select these capacitors are used as shown in the figure 1 long-life applications such as LED light bulbs (LED the life of 25,000 hours), the capacitor's life became the problem. To achieve 25,000 hour lifespan, the capacitor requires working temperature does not exceed 65 degrees Celsius. Which the temperature particularly challenging, because in this application, the ambient temperature will exceed 125 degrees Celsius. Some high temperature capacitors on the market, but in most cases, aluminum electrolytic capacitors will become the bottleneck of LED lamp life component.
Temperature dependence on the actual effect of this life you reduce the rated voltage of the capacitor. Your first thought may be to increase the capacitor rated voltage to minimize the risk of media failure. However, doing so will make the capacitor equivalent series resistance (ESR) is higher. As capacitors with high ripple current stress in General, so the high resistance leads to extra internal power consumption and increasing the capacitor temperature. Failure rate increases with temperature. In fact, aluminum electrolytic capacitors usually use only the rated voltage of about 80%.