A friend of mine told me about simple rectifier configuration that’s usually deployed in white goods (iron, washing machine, vacuum cleaner, etc). You can view the explanation here and here. It’s very interesting to know that you actually don’t need a big transformer or even switching PSU to supply your MCU from AC source.
Here’s my schematic for my own board:
It will generate 5.1VDC at 21.12mA. Or at least that’s what I hope =)