I'm designing my first linear power supply for my project which needs dual rail 12V (the regulation from 15V to 12V is on another board, 7812 and 7912).
The +12V (+15V) rail will draw about 250mA, the -12V (-15V) rail will draw less than 10mA.

My main goal is robustness and reliability. So I put effort to mains filtering and protection.
There is no specific noise I want to protect from. Just noise and spikes that are reasonable in standard household.

I went through many schematics from the internet.
This is what I have created so far:
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(I do not have 3D model for the transformer, so it is not rendered in the middle)

Did I make some obvious mistakes here?
Or are there some reasonable improvements to make (to improve reliability, and safety)?
The X1 and Y1 capacitors have to have specific value? Have to be calculated? Or it just almost doesn't matter?

  • \$\begingroup\$ Total overkill in my opinion, especially if you are not doing any low amplitude audio work,and the current draw is so little. Any noise & spikes will already be attenuated by the 120V to 15V transformer, and further attenuated by the regulators. Make sure the caps are rate for the voltage and 120Hz ripple from the mains, else they will fail. \$\endgroup\$ – CrossRoads Oct 18 '18 at 18:27
  • \$\begingroup\$ @CrossRoads Yes, it could be overkill. But it is not a problem. It's just a hobby project to gain some experience (I am scared by 230V high voltage). I'm going to power my DC load with precision opamps and quite small signals (10s of µV). A good point about those caps and 120Hz ripple. \$\endgroup\$ – Chupacabras Oct 18 '18 at 18:46
  • \$\begingroup\$ You could just put all that stuff After the 15V transformer, except for F1. Then you could work with reasonably rated 50V parts. \$\endgroup\$ – CrossRoads Oct 18 '18 at 18:51
  • \$\begingroup\$ If you want even more robustness, I guess you could protect those electrolytics and bridge from a voltage reversed back-feed (+/-15 volts feeding back the -/+15output, but I'm not sure what you're criteria are on that ("robust" can be a vague thing). If the supply is off, even a small voltage would reverse bias the caps leading to dielectric breakdown and what I refer to as the Pillsbury Doughboy Syndrome, and a large enough current would destroy the bridge diodes. Couple of steering diodes on the outputs would take care of that problem. \$\endgroup\$ – isdi Oct 18 '18 at 19:28
  • \$\begingroup\$ @isdi It's an interesting idea to put backfeed protection diodes. I didn't think about protection from the other side. \$\endgroup\$ – Chupacabras Oct 19 '18 at 6:01

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