AL17050 is a universal (85-265Vac) universal off-line buck converter with an integrated 500V 30Ω mosfet. Static consumption is 100μA, which my calculator tels me is 24mW at 240V.
“The device automatically adjusts to low loads, so it delivers excellent overall efficiency,” claimed the firm. “The AL17050 delivers a constant 3.3V/5V at up to 60mA, making it ideal for devices based on low power MCUs that integrated IoT connectivity such as Bluetooth LE or Zigbee.”
That said, efficiency of >50% is claimed rather than anything higher is claimed on this document, as is an an operating range of -40 to +105°C, a 3% accurate reference and switching at 70kHz – the latter of which will vary depending on operating conditions.
Also integrated is protection against over-temperature, over-load, output-short, and open-loop conditions. It comes in a SOT25 package.
The chips own Vcc is maintained between 5.3 and 5.6V by switching on and off an internal high-voltage regulator to charge the Vcc capacitor and the output voltage is sampled onto C5 via D4 and is set using the formula: