Interestingly here is another QX9920 based driver using an op-amp to work with a much lower sense voltage. Apparently the original “3 torroid” SRK drivers worked the same way. The SOT-23-6 chip marked 321 appears to be the op-amp.
@neons97 - look here for some relevant information and links: Skyray King / FandyFire UV s5 resistor mod help needed As I said, these drivers appear very similar, ignoring the fact that the SRK driver is 3-channels instead of one.
@ImA4Wheelr - wow, this is an elaborate mod. I missed this thread earlier. I’ll have to come back and look more closely!