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Currently I am working on a AC (mains)->DC (split-rails) linear supply project. The intended use is for hobby purposes only.

As I am not used to split supplies and AC/DC sections, I'd like to ask if there are any obvious errors in my schematic.

The AC-input: AC-Input

Goes to the dual-tap rectification (I am absolutely not sure, if the transformer is connected correctly to the diode-briges):

Positive AC/DC Rail

and

Negative AC/DC Rail

to then be regulated with these "building blocks" (multiple devices):

Positive LDO

and

Negative LDO

My questions:

  • I'm somewhat unsure if the transformer is connected correctly. Can this arrangement be used for 240 V/50 Hz? Datasheet

  • Are the diode bridges drawn correctly (correct orientation of diodes in regard to transformer)?

  • Are the MC79XX LDO's connected correctly (it is confusing for me to work with negative voltages)?

  • Are any obvious parts missing or wrongly used?

winny
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ElectronicsStudent
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    I’d suggest putting the low voltage side fuses in the ac from the transformer. It is not uncommon for diodes to fail short circuit. For the 0V rail, use gnd symbols - makes the circuit easier to read. Also the net labels are needlessly long. – Kartman Nov 29 '22 at 05:11
  • @Kartman Thank you! Seems smart - done. – ElectronicsStudent Nov 29 '22 at 05:22
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    You can make positive and negative DC from a center tapped transformer secondary using only 4 diodes, [example schematic](https://3.bp.blogspot.com/-iIFgeCmL0NQ/W96OfWE_l7I/AAAAAAAAAnw/ucvtqa6y4IUJo88cNRXsTYZdWZlnddzXgCLcBGAs/s1600/full%2Bwave%2Bbridge%2Brectifier%2Bwith%2Bcenter%2Btapped%2Btransformer.jpg) – bobflux Nov 29 '22 at 06:33
  • @bobflux Thank you for your response! What would be the advantages besides saving four diodes and a fuse? – ElectronicsStudent Nov 29 '22 at 06:49
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    It saves the power that would be wasted on the extra diode drops. It becomes important in higher power applications (audio amps usually), also high current diodes cost more. Note you still need the same number of fuses. I'd put the fuse on the primary instead of the secondary to protect against a short in the transformer, which can happen if it overheats, or other mishaps like the loose screw in the box shorting stuff – bobflux Nov 29 '22 at 08:40
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    Please don't post repeat questions even if you have changed the diagram colours: [Mains power supply safety](https://electronics.stackexchange.com/questions/644192/mains-power-supply-safety) – Andy aka Nov 29 '22 at 09:57

0 Answers0