I was trying to simulate a 3 phase AC full wave rectifier, and wanted a 5V output.
I connected an LM2596 module to turn the rectified voltage into the desired 5V output and ran the simulation in LTSpice.
To my disappointment, I found that the voltage was not only higher than the expected output (it was about 6.7V at first), but was also constantly decaying (in 210 ms it went from 6.7 to 6 V.)
The rectified voltage was almost totally constant but the output voltage (that is, the voltage produced after being passed through the regulator module) was not, this suggests that there maybe some problem with the module.
Is there anything wrong that I'm doing that you can point out to fix this problem?
At the same time, suggestions are also welcome for building a 3 phase AC full wave rectifier, with 12 V input and 5V regulated output, without this module in a better way as well.
P.S. – Also can someone clear up why my rectified voltage (11.4V) is slightly lower than the input voltage?
Best Answer
Just think about how you have shorted out the diodes in the rectifier stage: -
Consider V1 (red box) for one minute. On one half cycle it will produce a voltage polarity as shown. This will drive current into the ground connection and that current will re-emerge into the main part of the circuit just below U1. Just follow the purple arrows round and you will see that basically V1 voltage is shorted on each half cycle. Ditto V2 and V3.
The problem is that your star point is earthed. Remove it and re-check. Or remove D1, D3 and D5 and live with it being a half wave 3 phase rectifier.
I'm not saying this is the only problem but it's the big glaring problem.