1. Filter effect
In the power supply circuit, the rectifier circuit converts the alternating current into a pulsating direct current, and after the rectifier circuit, a larger capacity electrolytic capacitor is connected, and the pulsating direct-current voltage after the rectification is changed to the charge-discharge characteristic Relatively stable DC voltage.
In practice, in order to prevent the various parts of the PCB manufacturing circuit supply voltage changes due to load changes, the power output and the load power input generally receive electrolytic capacitors tens to hundreds of micro-law. As large-capacity electrolytic capacitors generally have a certain inductance, the high-frequency and pulse interference signals can not be effectively filtered, so at both ends in parallel with a capacity of 0.001--0.lpF capacitor to filter out high-frequency And pulse interference.
2. The coupling effect
In the process of transmission and amplification of low frequency signals, capacitive coupling is often used to prevent the static operating points of the two stages of circuits from interfering with each other. In order to prevent the signal rhyme low frequency component loss is too large, the general use of larger capacity electrolytic capacitors.
To determine the electrolytic capacitor fault method
Electrolytic capacitor common fault, capacity reduction, capacity loss, breakdown short circuit and leakage, of which capacity change is due to the use of electrolytic capacitors or placed in the process of its internal electrolyte gradually dried up, and the breakdown and leakage are generally added the voltage is too high or caused by poor quality.
To determine the quality of PCB proofing power capacitors
Generally use the resistance of the multimeter to measure.
The specific method is:
The two short-circuit capacitor to discharge, with a black meter pen multimeter positive electrolytic capacitor. Red pen then negative (on the pointer multimeter, with a digital multimeter test pen intermodulation), the normal needle should first swing to the direction of small resistance, and then gradually returned until the infinity department. The greater the swing amplitude of the hands or the slower the speed of return, indicating that the greater the capacity of the capacitor, the other hand, the smaller the capacity of the capacitor.
If the index finger in the middle no longer change, indicating that the capacitance leakage, such as resistance indication is small or zero, it indicates that this capacitor has been breakdown short circuit. Because the voltage of the battery used by the multimeter is generally very low, it is more accurate when measuring the capacitor with lower withstand voltage. When the capacitor with higher withstand voltage, although the measurement is normal at the time of the blowout, leakage or blowout may occur with high voltage Wear phenomenon.