How can AC be converted to DC?

 This is the waveform of 220V AC.

First, connect a diode in series.

At this point, the positive half cycle can pass through, while the negative half cycle is cut off, and the waveform is reduced by half.

This rectification method is called half-wave rectification, but only half of the desired waveform is obtained. We can combine 4 diodes in this way, forming a bridge rectifier.

Then let the AC pass through it. When the positive half cycle of the current flows, the current follows this path, and the output waveform looks like this.

When the negative half cycle flows, the current follows this path, and this is the output waveform. This rectification method is called full-wave rectification, and we obtain the complete desired waveform.

This can be further optimized by adding a capacitor. A capacitor is like a reservoir, where water can be stored little by little, then slowly released, acting as a filter.

In this way, AC can be converted to DC.