/diy/ - Do It Yourself

>>1506666
VIPer06 definitely is capable of 5V and less output at around 200mA.
Other in this series as well, VIPer26, VIPer115 etc. They might support higher continous output power.
Output voltage depends on feedback resistor values

Though I would probably go for low frequency ones (30kHz) and limit output current to about 100mA (enough to run ESP8266 without many issues provided sufficient bulk capacitance for wifi communications) as at 4V or 5V output efficiency of ac/dc buck converters isn't exactly spectacular. But for 1-2W designs I'd say just go for it and test (though use of isolation transformer on first iterations is always a good practice to keep).
Still more useful than 20mA current of capacitive supplies.

ST provides a rather good tool for initial design for buck converters to get you started on design.
But for >100mA outputs I'd watch thermal performance of SMPS ICs, maybe use bigger copper plane for pcb layout or some heatsinking.