Capacitor Knowledge Lecture: Introduction electrolytic capacitor - capacitor, capacitor - the electronics industry

Capacitor Knowledge Lecture: Introduction electrolytic capacitor - capacitor

, capacitor - the electronics industry

An electrolytic capacitor in the circuit of the role of

1, filtering role in the power circuit, the rectifier circuit to exchange into a pulsating DC, and in the rectifier circuit after the access of a large-capacity electrolytic capacitors, using its charge-discharge characteristics, so that the rectified pulsating DC voltage into a relatively stable DC voltage. In practice, in order to prevent parts of the circuit supply voltage changed due to load changes, so the output power and load power input generally has had dozens to hundreds of microfarads electrolytic capacitor. As the large-capacity electrolytic capacitors usually have a certain inductance, high frequency and pulse can not effectively filter out interfering signals, it has a parallel in his capacity both ends of 0.001 - 0.lpF capacitor to filter out high frequency and pulse interference.

2, Coupling: In the low frequency signal transmission and amplification process, before and after the two circuits to prevent the static work point of interaction, often using capacitive coupling. Signal in order to prevent excessive loss of the low frequency components rhyme, generally the larger the total capacity of electrolytic capacitors used.

Second, determine methods of electrolytic capacitor

Electrolytic capacitor common faults, capacity reduction, capacity disappeared, short circuit and leakage breakdown, in which capacity change is a result of electrolytic capacitors in use or placed within the electrolyte during the drying up of its cause, and the general breakdown and leakage to the increase of voltage is too high or caused their poor quality. The quality of power supply capacitors to judge the general use multimeter to measure the resistance profile. Specific methods are: to discharge the capacitor short-circuit the two pins with multimeter black table document then the positive electrolytic capacitors. Red Table document connected with negative (for Analog Multimeter with digital multimeter measurement table document interchange), normal resistance of small gauge needles should be the direction of first swing, then gradually return to office until the infinite. Larger the gauge needles swing or return more slowly, indicating the greater capacity of the capacitor, otherwise explain the capacity of the smaller capacitor. If somewhere in the middle of the table needle that does not change, indicating that this capacitor leakage, such as the direction is very small or zero resistance, capacitance, indicates that the breakdown has been short. Multimeter used for battery voltage is generally low, so low voltage of the capacitance measurement is more accurate when the capacitor voltage is high, the playing time despite the measurement of normal, but with high pressure is likely to occur when the leakage or strike wear phenomena.

Third, note the use of electrolytic capacitors

1, due to the polarity of electrolytic capacitors, and therefore can not be reversed when used in the circuit connection. In the power circuit, the output voltage electrolytic capacitor is positive then the power output, negative ground, the output voltage is negative then a negative output, positive ground. When the power circuit of the filter capacitor polarity reverse, due to greatly reduce the capacitance of the filtering effect, while the output voltage caused by power fluctuations, on the other hand because of reverse power to make this point is equivalent to a heat resistance of electrolytic capacitors. When the reverse voltage exceeds a certain value, the capacitance of the reverse leakage resistance will become very small, so that work near energized, the capacitor can overheat and burst damage.

2. Increase in the voltage across the electrolytic capacitor can not exceed its allowable working voltage, the actual circuit design should be based on specific circumstances leave a margin in the design of power supply filter capacitor, if the AC power supply voltage when the transformer 220 times level rectifier voltage up to 22V, then select the voltage to 25V electrolytic capacitor generally meet the requirements. However, if the AC power voltage fluctuations and there is much more likely to rise to 250V, the best choice over voltage 30V electrolytic capacitor.

3, electrolytic capacitor in the circuit should not be near the high-power heating element to prevent the acceleration due to electrolyte dry heat Er Shi.

4, for a positive and negative polarity of the signal filtering, can take two electrolytic capacitors in series with the polarity of the method, as a non-polarized capacitor.

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