This is transformerless power supply schematic diagram. Please take a note that this circuit running ONLY for input voltage 110V AC.
I use this power supply for applications that doesn't use too mucho power. It can provide power to circuit that uses less than 100mA without any problem. The disadvantage of this circuit is the danger of an electrical shock, so it cannot be used if the circuit is in contact with the user.
The voltage supplied by this is determined by the zener diode.
The version of the transformerless power supply that uses a bridge rectifier provides more current than the first one because it rectifies both phases of the AC voltage.