Hello all, I’m new here.
Background
I’ve been doing electronics as a hobby for quite a while now, and for power supply I’ve been using cheap buck converters hooked up to an old laptop power supply I got from a friend that would trow it away, however I’ve been more and more in need of something with more control, not just voltage but current, I dabbled with the idea of designing my own, from scratch. I did manage to build something that many engineers would call an abomination, but it works, a buck topology using 555 and irf 9540 and works ok, however, I don’t feel it is up to spec, specially when I need more than 3 amps at voltages higher than 5 volts. if anyone manifest interest, I will post the schematics(just know that 1st – it is not pretty and 2nd – it is a collection of schematics I gathered on the web over the years, so I do not have any sources, though it has my own touch of madness all over).
Objectives
With this post, my objective is simple, I’m not even asking for schematics or ready done work. after all, my end goal is designing and building my own handmade stuff, I could shell some bucks and buy a decent bench PSU with current control and voltage regulation, but I feel it takes away from the hobby, I like when I can make and use my own tools, it feels right to me. With that said, I want advice and answers to some questions that will help guide me in this journey, when answering these questions, please keep in mind what I’m asking here is a bit of experience, I did read some documents from Texas Instruments(TI) and since I’m not a professional some stuff went over my head and some of what I wanted to know was left blank.
Questions
1 – Linear or Switched(buck/boost/buck-boost)? what should I choose and why? I’ve read a TI pdf comparing smps with linear, however I was still in the dark for my choice, I want a bench power supply capable of supplying the maximum at least 15v @ 3.5-4 amps with current and voltage control, all of it is gonna come from the wall outlet, should I be concerned about efficiency? if I go linear, will the heat be so much as to melt everything? and what would you do if you could compromise in max current but needed get the absolute maximum precision possible?
2 – Precision, is there a difference in precision from buck converters to linear regulators? how much? which one is more precise and why? also, how much should I worry in regards to noise?
3 – Complexity, I am not afraid of complexity, but I do prefer the KASAP concept as in Keep As Simple As Possible, sure, I could go for some specialty IC to do buck-bost but I wanted all to be the most diy thing you can do, down to the minimal components. so, I have no problems using lm317, OpAmps or the 555, however beyond that, for me is a no go. I know I am limiting the potential for my build, but that is what I want, to see what is possible, and the absurd factor is kinda fun to me. so, here it goes, smps is more complex, but compared with the simplicity of linear route is it worth it? or can it at least be done properly without specialty ICs?
4 – Opinion, if at all possible, please, tell me, what would you do under these circumstances and requirements? which would you choose and why?
I know it became quite lengthily and I am sorry for it, but I wanted to lay down all the cards so I can get the most information I actually need.
You would like to have at least a cheapo PS unit with voltage and current control at minimum, in my opinion. TEMU has them starting at $13.00 Amazon has a decent one for about $300.00 (or by old and repair or both). Better than computer power supply are printer bricks (I have a 32-volt power supply brick, I added regulator, 10 turn pot and meter to make a fine voltage control, though the current is fixed, I us it to power my capacitor leakage tester.)
Welcome,
First off, I have not personally build anything from scratch to date. However, I agree you have to start from somewhere. Buying a simple supply to get you off the ground is the best in my opinion. There is always time to build and it is easier when you have all the equipment to play with. I started my bench with a triple output supply, a 3 amp single output supply, and a function generator. They were free but you can find the same or cheap deals anywhere.
Second, it all depends on what you are using it for. Space is a premium? Go switch mode. Need clean quiet power? Linear is the go to. They both have differences as you know. Linear you will need a much larger transformer as the frequency is lower than a SMPS. Low freq=more core, high freq=smaller core. Linear is much simpler to manage, build, and diagnose. SMPS will be compact and higher current for the size but will naturally be more noisy.
Precision will all depend on the circuitry and how accurate you want it.
I did build a supply from “scratch” pretty early on. The cabinet and stuff I hand made from sheet metal (that was fun and something I want to get back into instead of buying). The supply itself was a computer power supply, new that I bought for one I thought died but turned out to have a mainboard issue (I never revisited it) so I figured I would make it into something useful. SM of course but it had a good current supply and I used the 12v and 5v rails, not adjustable but I didn’t need that. The goal was just to have a fixed supply to flip on and power stuff.
At the end of the post, it all depends on what you want. Anything can be done, every project is different. Determine your needs and take a direction from that. If you need something new, build it. That is the beauty of electronics.
Radios + Tubes + Scopes + Cars= Nothing better!
Get a decent dubble linear, then you only need to buy a psu once. It’s one off the most vital gear you have.
When in doubt use a microcontroller.
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