Aluminum electrolytic capacitors are widely used in electronic devices, because they have high capacitance and are inexpensive, but caution is required due to their limited lifetime. The typical lifetime of an aluminum electrolytic capacitor is said to be ten years. This is because the capacitance decreases as the electrolytic solution dries up (capacitance loss). The amount of electrolytic solution lost is related to temperature and closely follows the "Arrhenius equation" of chemical reaction kinetics. If the usage temperature increases by 10°C, then the lifetime will be reduced to half. If the usage temperature decreases by 10°C, then the lifetime will be doubled, so it also called the "10°C double" rule. For this reason, the lifetime is reduced even more when used under conditions with significant self-heating due to ripple currents. The drying up of the electrolytic solution also increases the ESR. Attention should be noted that the peak value of the ripple voltage does not exceed the rated voltage (withstanding voltage) when the ripple voltage is superimposed on the direct current voltage. A capacitor used in a power supply circuit has a rated voltage that is three times that of the input voltage.