This zener rectifier bridge rectifies an AC Mains voltage to 5v for powering a mobile phone or Raspberry Pi .
Please do not build this circuit as a real circuit, as mains voltages can kill.
A zener diode works by conducting in both the normal ('forward') direction like a normal diode, but also in the reverse direction at its breakdown voltage (5.45v in this case). The resistor on the mains side reduces the current drop.
