The withstand voltage of surface mount aluminum electrolytic capacitors refers to the working voltage they can withstand continuously under certain conditions. If the operating voltage on the circuit exceeds the rated voltage of the surface mount aluminum electrolytic capacitor, the insulation medium inside the capacitor may be broken down, which may slightly affect the short circuit or leakage of electronic products, and in severe cases, it may directly burn out the entire circuit board. So, the working voltage of surface mount aluminum electrolytic capacitors cannot exceed their rated voltage, which not only extends their lifespan but also ensures the reliable operation of the circuit.

When purchasing or using surface mount aluminum electrolytic capacitors, it is necessary to conduct this withstand voltage test on them. The performance of surface mount aluminum electrolytic capacitors needs to be tested for leakage current, which is an important indicator of their performance. The leakage current of surface mount aluminum electrolytic capacitors is closely related to voltage. The leakage current increases with the increase of operating voltage. When the working voltage approaches the enabling voltage of the aluminum foil on the anode, the leakage current will sharply increase. By testing the leakage current of aluminum surface mount aluminum electrolytic capacitors, we can calculate their ultimate withstand voltage and rated voltage. This relationship has direct reference significance for us to determine the withstand voltage of surface mount aluminum electrolytic capacitors in circuits.

Based on this principle, we can simply design an experiment.

Two transformers, TI,T2。 Same model. Back to back docking, providing two sets of high and low voltage power supplies for isolation purposes. After rectification and filtering, the low-voltage power supply is composed of RI, DW1, Q1, RaL~RaL to form a constant current source with adjustable current. After rectification and filtering, the high-voltage power supply is divided into Rb1~Rb10 and DW2, and Q2 outputs an adjustable DC voltage. When using, select the appropriate voltage Uc and current Jc, and connect the tested surface mounted aluminum electrolytic capacitor to the points Cxa and Cxb. At this time, you will see the pointer of the voltmeter slowly deflect and stop after reaching a certain position. The voltage pointed by the pointer is the withstand voltage that the surface mounted aluminum electrolytic capacitor can withstand when the leakage current is 1c.

The band switches K3 and K4 (each with 11 positions) are respectively the selection switches for testing voltage and current (i.e. leakage current).

After testing, you will find that the larger the capacity of the surface mounted aluminum electrolytic capacitor, the higher the leakage current obtained from the test.