Author Topic: Can you help me with a design of a smps  (Read 1601 times)

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Offline K-ExperimentTopic starter

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Can you help me with a design of a smps
« on: March 01, 2019, 10:11:07 am »
input: 220vac  60hz
output: 12vdc   5a
efficiency:80-100%
wattage: 60w
 

Online Zero999

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Re: Can you help me with a design of a smps
« Reply #1 on: March 01, 2019, 10:33:50 am »
The standard advice here is to just buy one. 12V at 5A is a fairly standard requirement so a ready made one will be much cheaper than designing one, even in large volumes.

Examples:
https://ph.rs-online.com/web/p/embedded-switch-mode-power-supplies-smps/1618285/
https://ph.rs-online.com/web/p/desktop-power-supply/0188769/
 
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Offline K-ExperimentTopic starter

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Re: Can you help me with a design of a smps
« Reply #2 on: March 01, 2019, 10:38:16 am »
thanks for your answer but where i am right now thats too expensive so thats why i am asking for help in designing an smps
(i have searched but its all too expensive)
 

Offline coromonadalix

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Re: Can you help me with a design of a smps
« Reply #3 on: March 01, 2019, 10:39:02 am »
yeah  dont loose time and cash, buy one already made

A 60 watts smps wont cost a fortune,  please avoid cheap china made ones. And for the price sometimes they have 85 - 240 vac inputs
 

Offline coromonadalix

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Re: Can you help me with a design of a smps
« Reply #4 on: March 01, 2019, 10:41:22 am »
to build one, you have google as your friend, you have many things to consider  before building one, ovp ocp thermal protection, pfc  etc etc ...

Simply take a linear transformer instead, with basic parts  way simpler   unless space is a problem


Or maybe salvage an power supply ??  5 or 12v is pretty standard nowadays
« Last Edit: March 01, 2019, 10:43:35 am by coromonadalix »
 

Offline Ice-Tea

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Re: Can you help me with a design of a smps
« Reply #5 on: March 01, 2019, 10:55:44 am »
You'll never beat a ready-made PSU on price by cobling something together out of parts. A decent PSU will cost you, what, 20$?

Or else you can dig up an old ATX PSU and use that...
 

Offline nick_d

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Re: Can you help me with a design of a smps
« Reply #6 on: March 01, 2019, 10:59:05 am »
Building your own SMPS will be much more expensive than buying one. I know, I have a reel of expensive double insulated mains wire (probably $80 plus $20 delivery from the UK) and a big box of coil formers and such from Digikey (expect to pay $10 to $20 per transformer plus the delivery etc), have tried several SMPS chips with and without internal FET (another $10 to $20 per chip as you'll need to get at least 10, you will blow up about 5 of them), the FETs, the voltage references, the opto isolators... etc etc. Why did I do this? Because I was willing to spend thousands in cash and time to learn about SMPSs. If you are too, then do it!

A cheaper route is to pull apart broken SMPSs and put together a Frankenstein with the controller from this, the transformer from that, etc. But, this requires MUCH more skill and frankly if you have that skill you should be working at a high salary not making one off PSUs. Also the transformers and other parts are quite fragile and usually get damaged during the disassembly.

Nick
 

Online SiliconWizard

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Re: Can you help me with a design of a smps
« Reply #7 on: March 01, 2019, 03:16:10 pm »
This is just not any SMPS, it's necessarily an isolated one powered from mains. Safety is a real concern, so designing this if you've never done that before is a hazard IMO.
Also, this usually calls for a flyback topology, and it's full of potential traps if again you're new to this.
As for the cost, unless you can find ready-made parts (especially the flyback transformer) that exactly fits your design, you'd have to design the transformer and have it custom-made or try finding an off-the-shelf one (while exactly understanding what you're looking for). Forget about it.

As said above, buying an off-the-shelf supply will be cheaper even from your country. Unless maybe you're going to have tens of thousands of them manufactured. And even so, with those quantities you'd be able to get pretty nice deals with many chinese suppliers, so...
« Last Edit: March 01, 2019, 04:37:13 pm by SiliconWizard »
 

Offline Siwastaja

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Re: Can you help me with a design of a smps
« Reply #8 on: March 01, 2019, 05:35:46 pm »
With your specs and assumed experience (if you knew anything about it, you wouldn't ask like this), assume about 1000 hours build time (about 2 years of calendar time, if you start now, assuming some basic knowledge) + about $2000 in tools and parts.

You'll learn a lot, and I recommend taking massive, difficult projects for learning purposes, but if you just want the power supply, this isn't the way.
 

Offline Bassman59

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Re: Can you help me with a design of a smps
« Reply #9 on: March 01, 2019, 06:03:29 pm »
input: 220vac  60hz
output: 12vdc   5a
efficiency:80-100%
wattage: 60w

This runs off of your AC mains. If this is your first such design, follow the advice of others and just don't even try. Buy something off the shelf so you don't kill yourself.
 

Offline BravoV

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Re: Can you help me with a design of a smps
« Reply #10 on: March 01, 2019, 06:06:56 pm »
thanks for your answer but where i am right now thats too expensive so thats why i am asking for help in designing an smps
(i have searched but its all too expensive)

1st the most important thing, what is your max budget for components ? $1? $10?  $20? and so on ...

As this will help experienced people to give you a clue if its possible or not ?


Offline chris_leyson

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Re: Can you help me with a design of a smps
« Reply #11 on: March 01, 2019, 06:55:15 pm »
You can't build them cheaper than you can buy them and as it's an offline supply then you need to consider safety, things like creepage and clearance distances across isolation barriers especially in the transformer design. If you are thinking about building thousands of power supplies instead of a one off then you can build them cheaper.
 

Online Zero999

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Re: Can you help me with a design of a smps
« Reply #12 on: March 01, 2019, 08:10:32 pm »
thanks for your answer but where i am right now thats too expensive so thats why i am asking for help in designing an smps
(i have searched but its all too expensive)
Then the likes of ebay and Amazon are your friends: look for a second hand one. Indeed, it may even make sense to buy a broken one and repair it!

The only real reason for designing a mains powered SMPS is for educational purposes, but as many people have said: it'll be much more expensive than simply buying one. This is because buying components in small quantities is extremely expensive and the power supply manufacturers can purchase them in huge volumes for a fraction of the price.
 

Offline stmdude

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Re: Can you help me with a design of a smps
« Reply #13 on: March 01, 2019, 08:23:46 pm »
Meanwell RS-75-12 would give you 6A @ 12V.  You can find them on eBay for $22.

Meanwell is a very reputable PSU manufacturer, and will give you much better performance than anything you can build for $22.
 

Offline james_s

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Re: Can you help me with a design of a smps
« Reply #14 on: March 01, 2019, 09:14:46 pm »
please avoid cheap china made ones.

Virtually every commercial power bricks is made in China.

I think you know the sort of "cheap china made ones" he's talking about, obviously some very high quality stuff is made in China but if a power supply costs $5 retail brand new, it's probably a piece of crap.

My advice here would be look for something surplus, there are tons of good used and new surplus power supplies out there available at a fraction of their original cost. I have a 12V 6A power brick style that I got for 99c at a junk store.
 


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