Discussion on the function of electrolytic capacitor in circuit design

- Oct 27, 2017-

1, the function of filtering in the power circuit, the rectifier circuit into a pulse of AC DC rectifier circuit in, after access to a large capacity electrolytic capacitor, the charge and discharge characteristics (storage), so that the rectified pulsating DC voltage into a relatively stable DC voltage. In practice, in order to prevent the power supply voltage of each part of the circuit to change due to the change of load, the tens of thousands of micro electrolytic capacitors are usually connected at the output end of the power supply and the power input of the load.

2, the coupling effect: in the low frequency signal transmission and amplification process, for the static working point two prevent the circuit before and after the interaction, often using capacitive coupling. In order to prevent signal in rhyme low-frequency loss is too large, generally the larger capacity of electrolytic capacitors.

Electrolytic capacitor common fault, reduced capacity, capacity loss, short circuit breakdown and leakage, which is caused by the volume change of electrolyte of electrolytic capacitor in its internal use or placed in the process of gradually dried up, which caused by breakdown and leakage for the applied voltage is too high or the poor quality of itself. Judging the quality of power supply, the resistance meter of multimeter is usually used for measurement.

The needle should first apply to small resistance to swing, then gradually returned to infinity. Hands swinging larger amplitude or return more slowly, that the capacity of the capacitor is larger, otherwise, the capacity of the capacitor is smaller. As something somewhere in the middle of no change, the capacitor leakage resistance, such as the indicator values are very small or zero, it indicates that the capacitor has short circuit breakdown. Because million use the table using the battery voltage is low, so the measurement of low voltage capacitor is more accurate, and when the capacitor voltage is high, although measurements of the normal play, but with high pressure is possible leakage or breakdown.

More attention should be paid to the use of electrolytic capacitor matters needing attention:

Because of the positive and negative polarity of electrolytic capacitor, the connection can not be reversed when used in the circuit. In the power circuit, the output voltage is at the cathode of the electrolytic capacitor is connected to the power output end, negative ground, negative output voltage when the cathode is connected with the output end electrode. When the power supply circuit of the filter capacitor polarity, because the capacitor filtering effect is greatly reduced, on the one hand, the power supply output voltage on the other hand, due to fluctuations in reverse power make it the equivalent of an electrolytic capacitor heating resistance. When the reverse voltage exceeds a certain value, the capacitor leakage resistance will become very small, so the electric work soon, can make the capacitance due to overheating and explosion damage.

The voltage at both ends of the electrolytic capacitor can not exceed its allowable operating voltage. In the design of the actual circuit, there should be a certain margin according to the specific circumstances, in the design of regulated power supply.

The electrolytic capacitor should not be close to the high power heating element in the circuit, so as to prevent the electrolyte from accelerating drying up due to heating.

The positive and negative polarity signal filtering, can adopt the homopolar series method two electrolytic capacitors, as a non polar capacitor.

The capacitor housing, the auxiliary extraction terminal and the positive, negative and circuit boards must be completely isolated.

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