How to yield more power from salvaged EE33/EI33 pc cores

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Jay B

New member
Hi all.
This is my first post in this forum. After some study and a lot of disassembled smps I decided to make one to power 4 lm3886 amplifiers. The problem is that I have only salvaged EI33 cores from cheap atx psus. Bigger cores are unavailable in local market.
The first question is: can I bind side by side two of these cores to double the output power like we do with linear psu transformers?
The second question: since Im a newbie and I still don't have access to a oscilloscope, what's the rate of success, considering that I want to make everything, including the transformer and pcb (at least) visually perfect?
 
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wally7856

New member
Hard to say if you can do this without a scope you might need a liter of luck. Yes you can stack cores, 2 cores double the power.
 
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norazmi

diysmps Senior Member
you can use double EI or EE from old psu and the winding section for primary is defferent, to be successful build smps for first time is take from already made and test schema & pcb which u can found within diysmps. At least u have basic electronic and have experience make pcb for amp etc...

But for first try better do with single stack EI33 after u learn something and successful build one then u can go far. When u prepare to build u must know that u also need prepare to learn something new :D .
 
J

Jay B

New member
Thanks everybody.
Every place I go i find this project, and I'm being seduced because it looks simple to build.

I want just to change that 4 big primary filter caps with 2 smaller ones, the opto zeners and obviously the transformer core.
The rest I want follow strictly the diagram to minimize the failure possibilities.
Once I get more confident, and learn some more, I'll try to suppress the auxiliary transformer and add a pfc circuit. But just after some serious study.
I think the hardest part for me is to have gut and plug it at the mains.
 
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norazmi

diysmps Senior Member
ok, so with 50Khz u cannot expect more than 200-250 wrms from EI33. The circuit is good, i already done it worked but with no protection. U can use others design here using IR2110 with short circuit protection :D .
 
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Jay B

New member
After your comments I feel more confident to build the psu. I'll study the diagram, when it's done I want to show you my pcb layout for one EI33 core. Thanks again.
 
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norazmi

diysmps Senior Member
no problem, take ur time to study and understand. If u design the pcb, u can post here so i can check it for ya :D
 
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lovesakhi

New member
you can try ir2453, it is two X 1r 2151/2153, it is push pull
so you get double the power of what you would get normally.
best of luck
dr.rao
 
T

T - X - D

New member
Hi, everyone. I'm new in here. I like the smps very much, because smps is the foundation of any power amplifier. When a power amplifier perfroms good, I bet that the power supply is the TOP quality. he he he.....

@lovesakhi
I think you meant IRS2453 not IR2453. And the topology is full bridge. And yes, you'll get double power from the half bridge topology.
 
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norazmi

diysmps Senior Member
Great, anyone who have experience with electronic and build their own amp pcb and others etc, might try out with smps psu, simple one can go with ir2153 and more high power can drive it with ir2110. Lots of success people here with smps project, anything regarding problem, measure, calculation we can discuss in here diysmps. You can choose from here already made and tested smps complete with schema and pcb, or u can make ur own pcb and if success you may look at another project such as class D pwm :D .
 
J

Jay B

New member
This my scratch of the psu. From that diagram i added a second line filter, decreased the filter caps. The varistor and the fuse holder will be placed in the back panel. Since most of the board has direct contact with the mains, I still not confident with this layout, and probably will have a lot to improve. Some components weren't labeled because I haven't decide the output voltage.
Yes, I'll need a better tool than ExpressPCB :D.
 
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rikkitikki

New member
pc powers upplies have a typical turn ratio of 4:7:40 and primary voltage of 160V (half bridge) , giving 5 and 12 V at a Duty cylce of about 45% @ 30-40 kHz. You can increase frequency, and increase duty cycle without risking saturation. This will of course give a higher secondary voltage, but depending on the wiring on primary and secondary you have to reduce output current. Atleast you can assume constant power, so that fex increaseing duty cycle to 90% will give you 10 and 24 V, but at half current. With the higher frequency core loss will increase ( about ^2 ) but the reduced current will reduce secondary I^2 R (factor four due to halv current but doubling due to doube duty cycle as above) but hte primary losses will increase with duty cycle. In the end you have to try to balance all losses and it depends a lot on the winding resistance wether it is possible to squezze more Watts out the the transformer.
 
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Jay B

New member
I wasn't concerned about things like duty cycle and core saturation, util I realize the fact I want to use smaller core with smaller core section. Seems I'll need change the primary winding to something different from that of the diagram. And I just don't know how to do it. Do you guys know some good program to calculate it? I feel safer to do the winding on my own since I see a lot of different atx windings here. Class D? I'm still fashioned by AB but maybe I can change my mind and build class D amps in a near future.
Thanks again
 
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