Here you can see the simple One-phase AC converted to DC.
This effect is mainly achieved through the four diodes which eliminate the negative voltages around the Lamp.
However the other very important component is the capacitor which smooths the rough DC by filling the gaps between the cycles of the PSU with the power gained from the circuit.
You can see the difference with the green and blue Lamp.
This is just a smiplified version of an AC to DC converter.
