I am trying to bias a linear optocoupler on the AC mains side of a circuit, in order to transfer analog information to the secondary side of the circuit. I have designed the following capacitive power supply to provide the 6mA required and it works.
However, the reviewer at the certification lab is indicating that the voltage specifications for the capacitors after the bridge rectifier must be rated for line voltage (~400V). I am skeptical of this, because this would make the capacitors massive to meet the capacitance needs and transformerless power supplies are typically smaller units limited by the size of the X capacitor used to provide the reactance. It also doesn't make sense, because the zener would burn out long before the capacitors could fail.
Even this application note suggests that the capacitors only need to be 2x the zener voltage:
Does anyone know the specification that would govern this or have appropriate experience in getting a power supply like this certified, to let me know what to look for? Can these power supplies be certified or are they an internet relic?