When viewing the electronics of a Wattmeter, I came across a remarkable Chinese DC-DC converter chip that I had never seen before: the FT8430. The remarkable thing is that it has only 3 pins, whereby the chip has no electrical connection to the GND:

• FT8430 Fremont Micro Devices (FMD)
• Switching frequency 50kHz

The maximum input voltage is 300V, so you can supply directly a from the rectified mains voltage:

This design is remarkably clever because the IC can only indirectly measure the output voltage. This shows that the days of the Chinese copying everything are over. Why isn’t the FT8430 for sale at Mouser or Digikey?