Would this isolated AC peak voltage detection circuit work?

Question

I have adapted the circuit from Michael's circuit in Efficient method for isolated detection of AC voltage without a stepdown transformer to detect on either side of the positive half-cycle peaks, rather than at zero crossing. I did this for two reasons, one being that I would like to simplyfy the circuit, and secondly, to save some energy - and only drive the opto-coupler on either side of the positive peak.

Does anyone see any disadvantages/dangers with this design, besides having a much shorter time period in which to read the output pulse?

If I recorded the midpoint in time between the falling and rising edge of the output on one half cycle, I am hoping to detect within 1mS of the voltage peak.

Answer 1

Your circuit itself will not detect a peak, it will simple create a voltage range that has some transfer function that converts a half-wave rectified 240vac mains signal to a low-voltage (between 0-3.3v) that another circuit (or device) operating at this voltage range can be used to detect the peak.

Typically. A real peak detector will be a diode or other switching mechanism followed by a capacitor to trap the signal at its peak voltage and then discharged to allow another signal to captured and measured.

I would label you circuit a rectifier and level shifter.