Transformerless Power Supply Circuit
Warning: There is no isolation between low and high voltage from wall receptacle in this type of DC power supply, so you have to be very careful when experimenting or work with this circuit.
This power supply is suitable when designing for application that requires low power and where cost and size are of great consideration as expensive and bulky transformer is eliminated in this type power supply.
All the components in this circuit are sized so that the circuit can deliver 12 volt and 30mA of current at the output to the load. The ripples in the voltage from the rectifier is filtered by capacitor C2 while zener diode ZD regulates the voltage to produce 12 volt. The output voltage will remain constant as long as the output current is not more than the input current. The input current is determined by AC voltage input, capacitor C1, resistor R1 and R2. R2 also perform an important task of limiting the inrush current .