I am working on a 3 phase energy metering project using ADE7752 IC. I am stuck into getting the power supply part in a smaller form factor.
Since energy measurement is being done for all 3 phases, the IC must be able to measure energy even if two phases go down and hence VDD supply must come from all three phases.
After some searching, I came to this schematic:
This involves 3 transformers which will be too bulky in size and hence becoming an issue for me.
Is there some alternative compact circuit which can do the job? I don't need isolated power supply here.
I was thinking about using diodes to rectify all phases and combine them at a capacitor but I think that will end up in smoke if not fire and shock.
Best Answer
You can use a three phase rectifier but the problem is that your DC cap will have to be rated for ~500V. Since your output power is just 250mW this will be overkill.
If isolation is not an issue you could add lots of capacitance in series to drop a large part of the voltage before rectifying it. C1, C2 and C5 are AC caps, values to be decided based on load current, with resistors in parallel to drain residual charge in the caps. C6 is the DC cap and R6 provides the minimum load to ensure that voltage across C6 is always limited. You will also need a fuse in all three phases just in case.
simulate this circuit – Schematic created using CircuitLab