Electronics > Projects, Designs, and Technical Stuff
I want to built a Power Supply
H713:
First question is to really look at what the requirements are for the projects you like to work on.
Do you really need all of those requirements? Building a 1.2-30V @1.5A PSU is quite easy. Doubling that to 3A makes it a bit harder. Making it go down to 0 is harder still.
I would forego the SMPS for your first go. In a bench application, the main advantage is cost, size and weight. You don't care that much about efficiency on the bench. Bear in mind however, that the transformer is going to be the most expensive part of this project. Antek will probably be the most economical supplier. The AS-2228 will be fine so long as you don't try to pull 3A on both your power rails for hours on end. Remember that when rectified and filtered a 28V RMS winding will give about 39V DC. You will also see a corresponding decrease in current capacity of about 40%. So while they list a 3.6A current rating on the site, that actually gets reduced to closer to 2A when rectified and filtered. That said, their transformers are quite tough. If, however, you plan to run this at high power continuously, then I would suggest you step up to the AS-3428. One nice thing about the Antek is that it actually has two separate secondary windings, rather than a center-tapped winding. It's easy to turn this into a center tap by wiring them in series, but having two separate windings gives you more flexibility. You can create two completely separate, electrically-isolated power supplies (in one chassis) that can be put together to make a +/- power supply. Lots of advantages of this.
Digital controls add considerable complication, and aside from the "cool" factor, I see minimal advantage.
A scope is highly recommended for this. With just a bone-stock LM317 you will probably be fine so long as you have a reasonable layout and have your .1uF caps on the inputs and outputs. If you're going to do more than that, oscillation is a very real problem.
Another thread you might consider reading through- it's for a high-voltage bench supply, but I think there are some interesting schematics that have been posted that you may consider looking at. A lot of the concepts can be scaled down to lower output voltages.
https://www.eevblog.com/forum/projects/high-voltage-bench-power-supply-design-165562/25/
One other suggestion- I highly recommend playing around with LTspice if you haven't already. It's very helpful when you are learning to be able to quickly simulate ideas. It's not perfect, and a lot of things that are stable in spice will be great oscillators when you actually build them, but it's an excellent tool.
It's easy to say you want all the features, but it is very easy for your "little power supply project" to balloon into something not-so-little.
austfox:
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Hi Phil.
The plug pack will have a 12V out. What would be the current output of the plug pack?
thanks
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Huh? You are replying to a thread you started more than 5 years ago. This power supply you are building is certainly going at a snails pace... :)
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