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I want to design my own power supply. I know it can be dangerous for someone whit not much of experience, but at least I want to learn it on the paper!

I am aiming for a 12 V/10 A (120 watts) DC switching power supply.

What I think the system block should look like

1- 220 V AC to some DC value this will be mainly a transformer, plus usual filter caps, etc...

2- A switching IC to convent the secondary side of the transformer to 12 V

3- Some safety ideas:

  • over current -> monitor output current with a shunt resistor
  • over voltage -> ???
  • over temperature -> a microcontroller with some SMD temperature sensors around hot areas (switching FET, etc)

The questions are:

  • I would need to search for a transformer which is rated for 12 A? 12 A being my output, so maybe the transformer must be rated higher because some energy will get lost?

  • Are there any standard schematic (opensource hardware, etc) that I can take as reference?

  • Where I can find any reference?

  • In general what should be careful about, dos and don'ts?

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I am aiming for a 12V/10A (120 Watts) DC switching power supply.

OK

What I think the system block should look like

1- 220V AC to some DC value this will be mainly a transformer, plus usual filter caps, etc...

2- A Switching IC to convert the secondary side of the transformer to 12 V

Here's where you are going wrong. A switching supply or converter powered from the AC mains will: -

  1. Rectify the AC directly
  2. Smooth the rectified mains to produce a fairly ripple-free DC voltage of several hundred volts
  3. Use a switching circuit (including a switching transformer) to convert to a low voltage, high current DC output.

For instance, here is a circuit of a 15 volt, 7.33 amp DC output flyback converter that incorporates what I mentioned above: -

enter image description here

That circuit came from this data sheet by Premier Magnetics and, in turn, that data sheet was found by referring to this general guide on various switching power supplies.

3- Some safety ideas

All the ideas are good but the basic designs you will find won't usually include those features. You have to shoe-horn those features in yourself.

I would need to search for a transformer which is rated for 12A? 12A being my output, so maybe the transformer must be rated higher because some energy will get lost?

You will be searching for a switching transformer and not a regular AC mains transformer so, use the Premier Magnetics link above to get a feel for what they are all about.

Are there any standard schematic (opensource hardware, etc) that I can take as reference?

Premier Magnetics appear to be the most complete that I have come across.

In general what should be careful about, dos and don'ts?

"Off-line" converters might be too big of a hurdle for you at the moment but, going down the route you suggest in your question misses the point about converting AC mains to low voltage DC.

I have no affiliation with Premier Magnetics; I just came across their website several years ago and find it a useful reference at times like this.

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