Many manufacturers doing switching power supplies, most of them choose high frequency electrolytic capacitors when purchasing capacitors, do you know the principle? In the power supply circuit, capacitors are often used to pass through the AC isolation DC, or used to store and release charge to act as a filter, smooth the output pulsating signal. Small capacity capacitors are generally used in high frequency circuits, while large capacity capacitors are often used for filtering and storing charge.
    Electrolytic capacitors have good low frequency characteristics, while ceramic capacitors have good high frequency characteristics. For the smoothing filter capacitor at the output of switching power supply, ceramic capacitor capacity is definitely not enough. The output capacitor of power supply module is generally of high frequency and low resistance, because the rectified output of switching power supply is high frequency DC pulse signal, it must be filtered by high frequency and low resistance capacitor, so as to reduce the loss of capacitor itself, otherwise the capacitor will burst and leak after long time working. It should be noted that the electrolytic capacitor has an aluminum case, which is filled with electrolyte and leads to two electrodes, and their polarity in the circuit cannot be reversed.
    High frequency and low impedance means that the capacitor has strong ripple current resistance and its own internal resistance is small, so it is not easy to heat up in the circuit and lead to early failure. Especially for the switching power supply module, because of its miniaturization, light weight and high efficiency, the corresponding electrolytic capacitors are required to be small and large capacity, ripple current resistance, high frequency and low resistance, high temperature and long life and more adaptable to high density.
    The filter capacitor used in the output of switching power supply is different from the one used in the industrial frequency circuit. The pulsation voltage frequency of the common electrolytic capacitor used as filter in the industrial frequency circuit is only 100Hz, and the charging and discharging time is in the order of milliseconds, so the capacitance needed to obtain a small pulsation factor is up to hundreds of thousands of microfarads.
     The electrolytic capacitor used as output filter in switching power supply, because most of the switching power supply works in square wave or rectangular wave state, contains its rich high harmonic voltage and current. The frequency of the sawtooth voltage is up to tens of kHz or even tens of MHz, it requires different from the low frequency application, the capacity is not the main index, but the impedance frequency characteristic is the measure of its goodness.
     The electrolytic capacitor of switching power supply output rectifier requires its impedance frequency characteristics not to show a rising trend at 300kHz or even 500kHz. Electrolytic capacitor ESR is low, which can effectively filter out high frequency ripple and spike voltage in switching power supply. In contrast, ordinary electrolytic capacitors start to show a rising trend after 100kHz and are relatively ineffective in filtering the output rectifier of switching power supplies.
     Guangdong Wangxing has cooperated with many famous capacitor manufacturers and has rich experience. ShiCaXon high frequency low resistance capacitors have strong ripple resistance and can also be customized according to manufacturers' needs for high temperature resistance and long life capacitors.
     Contact: carol@shicaxon.com WeChat: 18822885775