High-frequency low-impedance refers to the ability of the capacitor to withstand ripple current and its small internal resistance. Compared with ordinary, the product itself is not easy to heat in the circuit and cause premature failure. In particular, because of its miniaturization, light weight and high efficiency, switching power supply modules require small and large electrolytic capacitors, ripple current resistance, high frequency and low resistance, high temperature and long life, and more suitable high density.
Electrolytic capacitors have good low-frequency characteristics, while ceramic capacitors have good high-frequency characteristics. For the smoothing filter capacitor at the output of the switching power supply, the ceramic capacitor capacity is definitely not enough. The output capacitor of the power module is usually high-frequency and low-resistance. Because the rectified output of the switching power supply is a high-frequency DC pulse signal, high-frequency low-resistance capacitors must be used for filtering to reduce the loss of the capacitor itself, otherwise the capacitor will only work after a certain amount of work. long time. Will rupture and leak.
Due to the miniaturization, light weight and high efficiency of switching power supply modules, electrolytic capacitors are required to be small in size and large in capacity, resistant to ripple current, high frequency and low resistance, high temperature and long life, and more suitable for high density.
The electrolytic capacitor used as output filter in the switching power supply, because most of the switching power supply works in the state of square wave or rectangular wave, contains extremely rich harmonic voltage and current. The frequency of the sawtooth voltage on it is as high as tens of kilohertz or even tens of megahertz. Its requirements are different from those in low-frequency applications. The capacitance is not the main indicator. What measures it is its impedance frequency characteristics.
The electrolytic capacitor of the output rectification of the switching power supply requires that its impedance frequency characteristic does not show an upward trend at 300kHz or even 500kHz. The ESR of the electrolytic capacitor is low, which can effectively filter out the high-frequency ripple and spike voltage in the switching power supply.
