Due to its low cost characteristics, aluminum electrolytic capacitors have been a common choice for power design for a long time. However, their limited life and sensitivity to extreme high and low temperature environments are their main defects. Aluminum electrolytic capacitors are composed of metal thin slices on both sides of paper sheets immersed in electrolytes. As the use time increases, the electrolyte will gradually evaporate, which will affect the electrical characteristics of the capacitor. The failure of capacitors may cause internal pressure to increase, thereby release flammable, corrosive gases, and may even explode.
The electrolyte evaporation speed of the capacitor is closely related to the working temperature. If the working temperature is reduced by 10 degrees Celsius, the life of the capacitor can double. The rated life of a capacitor is usually calculated at its maximum rated temperature. The typical rated life is 1,000 hours of 105 degrees Celsius. For example, in the case of LED bulbs, such as long life applications, capacitors become a problem of life bottlenecks. In order to meet the 25,000 -hour life requirements, the working temperature of the capacitor should not exceed 65 degrees Celsius, which is particularly challenging in high temperature environments.
In addition, the life temperature dependence of the capacitor also affects the method of reducing the rated voltage. Although it may first consider increasing the rated voltage of the capacitor to reduce the possibility of the media failure, this will increase the equivalent series resistance (ESR) of the capacitor. Because capacitors usually withstand high -patterned wave current stress, higher resistors will bring more internal power consumption and increase the temperature of the capacitor, thereby increasing the failure rate. In fact, aluminum electrolytic capacitors usually use only about 80%of its rated voltage.
In low temperature environments, ESRs of capacitors will increase sharply. For example, under -40 degrees Celsius, the resistance may increase in order, which will significantly affect the performance of the power. If the capacitor is used for the output terminal of the switching power supply, the output ripple voltage may increase significantly. In addition, due to the frequency of zero point of ESR and output capacitors, the width rate may increase the number of magnitude, affect the stability of the control ring, and cause the power to oscillate and instability. Therefore, in order to adapt to strong vibrations, controlling the circuit usually requires major compromises in space and work at a higher temperature.
In summary, although aluminum electrolytic capacitors are a lower cost, it is necessary to fully consider the influence of its shortcomings on product performance. The capacitor needs to be reasonably selected according to the work temperature and the expected life span, and the rated voltage is appropriately reduced to achieve low temperature operation, thereby extending the service life. At the same time, understand and determine the applicable ESR range in order to correctly design the control ring, and meet the design requirements of the design. Through these measures, the common defects of aluminum electrolytic capacitors can be effectively avoided and the stability and reliability of electronic products can be ensured.