There are several ways to
convert an AC voltage at a wall receptacle into the DC voltage required by a microcontroller. Traditionally, this has been done with a transformer and rectifier circuit.
in applications that involve providing a DC voltage to only the microcontroller and a few other low-current devices, transformer-based
power supplies may not be cost effective.
They require only three external components to provide a fixed output voltage of 5.0V. CMOS technology ensures ultra low supply current and makes them ideal for battery-operated applications powered from one or more cells. HT7750A consists of an oscillator, a PFM control circuit, a driver transistor, a reference voltage unit, and a high speed comparator.
Circuit 3V to 5V Converter
If you do not have a LCR meter the inductive part (L1) of the circuit is a bit more complicated to make! Capacitors (C1 & C2) also recommended by the manufacturer for this circuit is a bit hard to get, I have used tantalum types recovered from a discarded smps circuit board. Last but not least, say that the diode (D1) has to be a fast, not worth as the 1N400X rectifiers, the 1N5817 is recommended schottky type, characterized by high response time and low internal resistance, which is what ideal for this type of boost-converter circuits.