I have a power supply design that makes use of a half-wave rectifier and a non-isolated buck Swtich Mode Power Supply IC to step down 120V 60Hz AC power to 12V DC.
I then use a Linear Voltage Regulator (78L05) to step the 12V down to 5V. The 5V will be used to control a micro-controller in a prototype, so there is a risk of people touching the pins.
In this design the Neutral line of the AC supply is connected to the 12V DC after the buck converter.
I realize that this could be dangerous since the 5V supply to the micro-controller is not isolated from the AC supply, so my question is:
Will the use of an isolation transformer just after the AC supply isolate the rest of the circuit from the supply. Will this make the design safer and/or less efficient?