Precautions for electrolytic capacitors
- As electrolytic capacitors have positive and negative polarity, they cannot be connected reversely when used in the circuit. In the power circuit, the positive pole of the electrolytic capacitor is connected to the power output terminal and the negative pole is grounded when the positive voltage is output. When the negative voltage is output, the negative pole is connected to the output terminal and the positive pole is grounded.
When the polarity of the filter capacitor in the power circuit is reversed, the filtering effect of the capacitor is greatly reduced. On the one hand, it causes the output voltage of the power supply to fluctuate; on the other hand, it causes the electrolytic capacitor, which is equivalent to a resistor at this time, to heat up due to reverse energization. When the reverse voltage exceeds a certain value, the reverse leakage resistance of the capacitor will become very small. In this way, the capacitor will be cracked and damaged due to overheating soon after power on.
- The voltage applied to both ends of the electrolytic capacitor shall not exceed its allowable working voltage. When designing the actual circuit, a certain margin shall be reserved according to the specific situation. When designing the filter capacitor of the stabilized voltage power supply, if the rectifier voltage of the transformer secondary can reach 22V when the AC power supply voltage is 220~, the electrolytic capacitor with a withstand voltage of 25V can generally meet the requirements for PCB proofing. However, if the AC power supply voltage fluctuates greatly and may rise to more than 250V, it is better to choose electrolytic capacitors with withstand voltage of more than 30V.
- The electrolytic capacitor shall not be close to the high-power heating element in the circuit to prevent the electrolyte from drying up due to heating.
- For the filtering of signals with positive and negative polarity, two electrolytic capacitors in series with the same polarity can be used as a non-polar capacitor.
- Capacitor shell, auxiliary lead out terminal, positive and negative pole and circuit board must be completely isolated.