Talking About the Role of Electrolytic Capacitors In Circuit Design

1, filtering, in the power circuit, the rectifier circuit turns the alternating current into a pulsating direct current, and after the rectifier circuit is connected to a larger capacity electrolytic capacitor, using its charge and discharge characteristics (storage energy) to make the rectified The pulsating DC voltage becomes a relatively stable DC voltage. In practice, in order to prevent the power supply voltage of each part of the circuit from changing due to load changes, there are typically tens to hundreds of microfarads of electrolytic capacitors at the output of the power supply and the power input of the load. Since the large-capacity electrolytic capacitor generally has a certain inductance, the high-frequency and pulse-interference signals cannot be effectively filtered out, so a capacitor with a capacity of 0.001--0.lpF is connected in parallel at both ends to filter out the high-frequency. And pulse interference.

2, coupling effect: In the process of transmission and amplification of low-frequency signals, in order to prevent the static working points of the two-stage circuit from interacting with each other, capacitor coupling is often used. In order to prevent the loss of the low frequency component of the signal in the signal, the electrolytic capacitor with a large capacity is generally used.

Method for judging electrolytic capacitor

Common faults of electrolytic capacitors include capacity reduction, capacity loss, breakdown short circuit and leakage. The change in capacity is caused by the internal drying of the electrolytic capacitor during use or placement, and the breakdown and leakage are generally added. The voltage is too high or caused by poor quality. Judging whether the power supply capacitor is good or bad is generally measured by the multimeter's resistance file. The specific method is as follows: short circuit the two pins of the capacitor to discharge, and connect the positive electrode of the electrolytic capacitor with the black meter of the multimeter. The red pen is connected to the negative pole (for the pointer type multimeter, when the digital multimeter is used to measure the intermodulation)

Normally, the hands should first swing in the direction of low resistance and then gradually return to infinity. The larger the swing amplitude of the hands or the slower the return speed, the larger the capacity of the capacitor, and the smaller the capacity of the capacitor. If the pointer does not change somewhere in the middle, it indicates that the capacitor is leaking. If the resistance indicator is small or zero, it indicates that the capacitor has broken through. Since the battery voltage used by the multimeter is generally low, it is more accurate when measuring the low withstand voltage capacitor, and when the withstand voltage of the capacitor is high, although the measurement is normal, when the high voltage is applied, there is a possibility of electric leakage or blow. Wear phenomenon.