Alternate Use of the HV9922 as an Off-line, Non-isolated, 50 to 100 mA Auxiliary Power Supply
The HV9922 was originally designed to be a high voltage switching-converter for driving LEDs at a fixed, regulated, 50mA output current.
It has found use as an off-line, non-isolated, 50mA auxiliary power supply.
It will operate from 80 to 240VAC, is stable with open and short circuit loads, and since there is no feedback loop, it is unconditionally stable.
HV9922, power supply, design note