Filtering out clutter or interference waves is the most basic and prominent function of capacitors.

1 After the AC input voltage ui passes through the transformer T, it is rectified by the diode VD to output the pulsating DC voltage uo.

2 Because there is no capacitor in the power supply circuit, the output voltage is unstable and fluctuates greatly.

3 Add capacitor C, the output voltage is relatively stable and smooth.

4. Adding capacitor C to the output circuit can make the unstable and fluctuating output voltage more stable and smooth due to the charging and discharging of the capacitor.