After the alternating current (power frequency or high frequency) is rectified, it needs to be filtered by a capacitor to smooth the output voltage, and the capacitor capacity is required to be large, and aluminum electrolytic capacitors are generally used. The main problem in the application of aluminum electrolytic capacitors is the relationship between temperature and life, which basically follows the 50°C rule. Therefore, in many occasions requiring high temperature and high reliability, electrolytic capacitors with long life (such as more than 5000h, or even 105℃, 5000h) should be selected. Generally small electrolytic capacitors have relatively short lifespans.