1.5 KW switching regulator

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thanks ,
I corrected the output of TL494 and current sence resistors . and working to find a proper feedback circuit . I attached the circuit . is it ok?
 

thanks ,
I corrected the output of TL494 and current sence resistors . and working to find a proper feedback circuit . . is my correction ok?
 

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Typically, an optocoupled feedback loop would use TL431 or some other kind of secondary voltage sense circuit.

Generally, I suggest to refer to known working DC/DC converters in the intended power range, e.g. manufacturer reference designs. You are just at the very beginning of designing a switched mode converter. Copying circuit snippets (hopefully correctly) is the easiest part, however.
 
Hi again
As FvM said , you should use a variable zener such as TL431 ( it will conduct at voltages above 2.5 volts) and it will be in series with an opto coupler , and at primary of your opto coupler you can get a feed back voltage from emitter ( with two resistor , first one in collector and the other in emitter ) .
Best Wishes
Goldsmith
 
thanks all ,
I am beginer in switching power supply designing. but with your guidance I will finish this project Successfully .
I found a feedback with opto and tl431 .the TL494 with the feedback is in the picture . is this proper for my circuit? when you confirm my circuit I will begin to draw the PCB and work on it .
 

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The feedback polarity isn't right in the present circuit. I noticed, that the TL494 datasheet doesn't give much application details. Some more are here.
http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slva001e&fileType=pdf

I should also mention this TI comment about TL494. I agree, that newer controllers, particularly utilizing phase shifting mode are better suited for H-bridge operation.
http://e2e.ti.com/support/power_management/isolated_controllers/f/188/t/48691.aspx
 
thanks but the first link doesn't work !
 

Hi again , try below circuit :
the voltage across your feed back resistor should be about the internal reference ( 2.5 volt i think ) ( if moc be saturated )

Best Wishes
Goldsmith
 
thanks goldsmith ,
FvM Plz correct the first link .I can't open it .
 

thanks ,
I want to simulate this circuit . what program is suitable for my application ?
 

Dear meysaminter
Hi
I don't think simulation for SMPS is ok , because in practice you'll see some erratic events ! try to test it in practice .
Best Wishes
Goldsmith
 
All available SPICE variants are able to simulate the aspects of circuit behaviour that you are able to model. LTSpice e.g. isn't bad.

I guess, you understand that I'm describing a limitation.
- You won't find models for all circuit components
- Models are simplified and not describing the component behaviour completely
- Some properties of your circuit, e.g. parasitic inductances are either unknown or typically ignored in a simulation setup
- "Multiphysics" aspects like thermal behaviour of power electronic components aren't considered by standard models

In addition, a full simulation may be too time consuming. But it should be basically possible for simple circuits like the present one.
 
thank ,
I downloaded LTspice but I could not find my needed part numbers such as tl494 ir2125 irf740 .... .
 

but I could not find my needed part numbers such as tl494 ir2125 irf740
Click to expand...
Yes, see my previous post.

For some components models can be get from manufacturers, but e.g. not for IR2125 as far as I'm aware of. You can use a basic bootstrap gate driver like IR2110 instead. You'll need to learn how to use vendor models with LTSpice, but there are tutorials on the net.

As another point, you don't necessarily need to perform a full simulation. Some circuit parts can be represented by simplified behavioral models.
 
I am designing the transformer .
I used the eqation in the "practical switching power supply design" by Marty Brown .
the equations are in the "forward transformer design" section .
I don't know are they suitable for my application or not .
and I don't know what is Eff . is ID and Iav same?
 

Usually the meaning of used terms in a book becomes obvious when reading a few pages for and back. In this case Id is said to designate current density, a different parameter than Iav. Eff apparently means efficiency (eta).
 
Thanks FvM ,
with the first equation I calculated Iav . it is 33A!!!!!!
is it correct?
 
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I found tl494, tl431 and ir2110 for LTspice . But I don't know how can I design trance for this program.
 
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