1. Long-life electrolytic capacitors have positive and negative polarity, so th...
1. Long-life electrolytic capacitors
have positive and negative polarity, so they cannot be connected upside down when used in a circuit. In the power supply circuit, when outputting a positive voltage, the positive electrode of the electrolytic capacitor is connected to the output terminal of the power supply and the negative electrode is grounded. When a negative voltage is output, the negative electrode is connected to the output terminal and the positive electrode is grounded. When the polarity of the filter capacitor in the power supply circuit is reversed, the filter effect of the capacitor is greatly reduced. On the one hand, the output voltage of the power supply fluctuates, and on the other hand, the electrolytic capacitor, which is equivalent to a resistor, heats up due to the reverse energization. When the reverse voltage exceeds a certain value, the reverse leakage resistance of the capacitor will become very small, so that the capacitor can burst and damage due to overheating shortly after power-on operation.
2. The voltage applied to both ends of the electrolytic capacitor cannot exceed its allowable working voltage. When designing the actual circuit, a certain margin should be left according to the specific situation. When designing the filter capacitor of the stabilized power supply, if the AC power supply voltage is 220~h The rectified voltage of the transformer secondary can reach 22V. At this time, choosing an electrolytic capacitor with a withstand voltage of 25V can generally meet the requirements. However, if the AC power supply voltage fluctuates greatly and may rise above 250V, choose an electrolytic capacitor with a withstand voltage of 30V or more.
3. The electrolytic capacitor should not be close to the high-power heating element in the circuit to prevent the electrolyte from drying out due to heat.
4. 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.