5V 40A Smps - Help

[mashadow]

Hi everyone.
First off thanks for the great information, awesome projects and the skilled members on this site. Especially Microsim, ludo3232, norazmi and stewin. I learned alot from here and built my first successful 1kw smps of mine . I used microsims knowledge, norazmi's schematics of 1kw half bridge self oscillating smps and other members help and built it.

After some modifications for my needs, i can say its good for me and want to share it on here for other people to use and develop further. This project doesnt have an output inductor and lt gives an unregulated outpuf which is ok for a 900 watt ucd style class d module.

I used ETD49 core on that project, EI16 for oscillating at 100khz, 4xirfp460 and 4xmur1560 diodes.

My one turn of secondary winding produces 6.2 volts.


But now for a friend of mine, I should make an smps which can produce only 5v 20amp average and 40amps at peak from 220AC line.

1- Should I go with half bridge self oscillated unregulated output project which I find succesful
2- If yes I would like to use etd39 for the core as etd49 is too much for 5v x 40amps ?
3- I tried to get 5v output from my already built 1kw smps but because of sec. 1 turn is 6.2 volts for 5volt output i should do only 0.5 turn. When load begins to increase, output voltage drops from 5v to 1.5v at 7 amp load of dc brussless motor. Is this because of too short 0.5 turn of sec coil?

4- What is the true way for getting constant 5v even at 35-40 amps ?


Thanks everyone !

 

[MicrosiM]

Best option is fly back SMPS, and a regulated SMPS, you cannot make it unregulated at that current.

Even if you use synchronous rectifiers topology.

Hope that helps

 

[mashadow]

Thank you so much microsim. I will search about flyback topology. I saw someone on the forum saying flybacks arent good above 200 watt needs. Is that true thanks.

 

[wally7856]

Typically the limit for fly-backs is 150W. Personally i would not use a fly back. They are simple on paper but tricky to design and get right.

5V at 40A = 200W this is 2 switch forward or half bridge territory. But because of the 40A requirement, the winding of the transformer will be difficult. Litz wire is hard to buy and copper foil is a little easier to find but tricky to work with. Or you could try multiple output transformers wound with standard magnet wire.

 

[mashadow]

Typically the limit for fly-backs is 150W. Personally i would not use a fly back. They are simple on paper but tricky to design and get right.

5V at 40A = 200W this is 2 switch forward or half bridge territory. But because of the 40A requirement, the winding of the transformer will be difficult. Litz wire is hard to buy and copper foil is a little easier to find but tricky to work with. Or you could try multiple output transformers wound with standard magnet wire.

I am accostumed to half bridge design, have done some projects successfully. But my designs were self-oscillating with a help of EI-16 bobbin. Should I consider using an ic that takes feedbacks and regulates the output? Because in my current half bridge self-osc 1.2kw smps, when load inceareses, 5V output decreases dramatically, even to 1V at 10 amps.

Is that because of 1 turn of 5v sec winding ? Or should i use some different method to regulate output?


Also, I am able to get litz wire in my country, I think there is no problem with getting it.

 

[wally7856]

You definitely need a control chip made for half bridge, and as microsim said you need feedback control. Synchronous rectifiers would be nice but this project will be hard enough without them.

First find out what half bridge drivers you can buy then try to find an ap note to help you. A 5v high current supply should be common but i looked 2x times and did not find a design to follow. Maybe some of the other members know were to find a good schematic for one.

 

[padmanabhan]

Good morning Microsim, and Wally7856,
I am also having a similar project to built for a requirement, would a control chip like sg3525 + tc4427 could be used or sg3525 + Ir2110 with half bridge configuration would be Ok, kindly advice.
regards
padmanabhan.k

 

[MicrosiM]

I would suggest to go for half bridge, current control.

Synchronous rectifier is a robust solution to eliminate serious challenges, but on the other hand this is going to be a challenging project. Specially if you want it commercial.

I saw somewhere on the internet that someone built some project around the UC3842 with 2 IGBTs 2000W for welding machine. I think you can inspire from him, as he will save you lot of time.

And to tell you the truth, whatever your driving circuit is, if you have good control loop, you will just succeed.


Regards

 

[padmanabhan]

Dear Microsim,
can you provide any tested circuit in case you have one.
regards