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Pure sin wave inverter

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Without knowing further details, I would have to say that the drop is due to switching losses. I'm guessing you didn't use the totem-pole drivers and just attempted to drive the MOSFETs from the SG3525. Try with the totem-pole drivers and then post the results.

Hope this helps.
Tahmid.

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At higher frequency switching losses are higher. You have witnessed this through the voltage drops at higher frequency.

Use the totem-pole drivers and test with 50kHz. You can then adjust as required. 50kHz should be good.
 

tahmid what frequency should i use for etd44 core? as at higher frequency output is also high, but is there any disadvantage of using higher frequency?

in input of my transformer i hve only three turns,, i hve closely wind the three turns and it covered only half the area of the bobbin .so my question is should i closely wound the thee turns or widely wind the three turns so that whole bobbin get covered?
 

At higher frequency switching losses are higher. You have witnessed this through the voltage drops at higher frequency. How can you say that output is high at higher frequency? You showed that output voltage dropped with higher frequency.

Use the totem-pole drivers and test with 50kHz. You can then adjust as required. 50kHz should be good.
 

sorry tahmid,i was talking about power not voltage ,,i mean that power is high at higher frequency
in etd44 at 100khz output power can be 581w and at 50khz ,u hve said that its around 350w..



in input of my transformer i hve only three turns,, i hve closely wind the three turns and it covered only half the area of the bobbin .so my question is should i closely wound the thee turns or widely wind the three turns so that whole bobbin get covered?
 

At higher frequency you have higher switching losses. 50kHz should be okay. You can adjust the frequency and observe the results. Don't go over 100kHz or below 30kHz. You should experiment with this yourself and see the results.

I cannot exactly answer the second question. I've used both methods and obtained proper output. So, I can not tell you which is better. However, usually I try to make sure the entire bobbin gets covered. If required, I use more wires in parallel. So, you have the entire bobbin covered and thicker conductor, so less loss (and thus heat) in the wires.

Hope this helps.
Tahmid.
 
thanx tahmid, now i will implement all the things that i hve learnt today in my dc dc converter stage, after that i will proceed to my second stage i.e dc to ac.
 

Great! I wish you success in your design.

In every stage of the design, proceed with caution. Make sure you always check everything repeatedly. In SMPS, even the slightest mistake can make your circuit go BOOM! 8-O

Remember to use gate-to-source resistors for each MOSFET. They've been the source of headache many a times in my designs.

Also be careful since the circuit will not be isolated (since you're using voltage divider based feedback, low voltage and high voltage grounds must be connected together) and you can get a nasty electric shock even if you touch parts on the low-voltage side.
 

thanx alot tahmid,
i will follow all the rules as u said,
without u it was hardly possible.
thanku n happy new year...:)
 

Hi tahmid
Yesterday I successfully completed my dc dc converter stage .its output is 316vdc constant, but today when I again connected the wire to the battery , a strong spark come when I connected the wire to the battery terminal and my mosfet got damaged, yesterday everything was working fine , I replaced the mosfet , then my bulb glows, then I connect the feedback, my bulb goes very dim, n suddenly my mosfet blown again, please tell me the reason behind that coz today my 10mosfets blown away??
 

Assuming you didn't make any changes at all, check for loose connections, improper contacts and any short circuits.

And by the way, always keep the feedback circuit connected. Don't remove it. It's part of the entire circuit. Let it stay there. Once you've ensured that the feedback circuit is fine, keep it there and don't replace or remove it.

With the feedback circuit placed, check. But use less number of MOSFETs, if needed use 1 + 1 to avoid blowing too many MOSFETs.

Hope this helps.
Tahmid.
 

Tahmid
I hve made only one change today, I replace the wire from battery to the mosfet with a thick one so that it can handle 35 ampere current,
N today there was also a problem in my feedback after changing the wire because without feedback , bulb was glowing very high and again after connecting the feedback .bulb was glowing low , I vary the pot connected to feedback but notging happened.also there was a noise coming from transformer. After 30 to 40 second my mosfet blown and my sg3525 also blown,, what coluld be the reason behind that ?
Is the output of my feedback network circuit was very greater than 3.2volts? What can I do to protect my mosfets from burning, next tym ??
 

--BawA-- said:
Tahmid
I hve made only one change today, I replace the wire from battery to the mosfet with a thick one so that it can handle 35 ampere current,
N today there was also a problem in my feedback after changing the wire because without feedback , bulb was glowing very high and again after connecting the feedback .bulb was glowing low , I vary the pot connected to feedback but notging happened.also there was a noise coming from transformer. After 30 to 40 second my mosfet blown and my sg3525 also blown,, what coluld be the reason behind that ?
Is the output of my feedback network circuit was very greater than 3.2volts? What can I do to protect my mosfets from burning, next tym ??
Click to expand...

well done bawa.
make sure you get full circuit details and components values from everyone and try them all out without ...
 

My feedback is through voltage divider network...

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My feedback is through voltage divider network...
 

Measure the resistances of the divider resistors and ensure that they're okay. Ensure that they have sufficient power rating.
Measure the output voltage of the circuit with feedback connected. Disconnect the circuit quickly to avoid damaging it.
Measure the voltage at pins 1 and 2 of SG3525.
 
Can you upload your circuit diagram please let see what is wrong on with it?
 

I made my circuit again .and now it is working fine, feedback is also working ...only one small problem is there ...
Case 1)
i set the voltage at 330 volts with no load then after i apply a 100 watt bulb , my output voltage was still 330volts..but when I connect 200 watt bulb , my output voltage goes to 270volts

Case 2)
I set the voltage at 220volts using feedback with no load then after I connected a 100 watt bulb and measure the output , the output was still 220volts as expected , but when I apply 200watt load and measure the output .the output was still 220volts ...

So where should I change ,, so that my output will be 330volts constant at 200 watts or greater,; should I increase the no. Of output turns of the transformer...or should I increase the value of inductor that was used in the filter stage ...because when I remove the inductor my output voltage goes too low with feedback..n I hve wound the inductor myself and the value of inductor is around 1mh ,,
So please suggeat me what should I do??
 

Increase the value of the output inductor, ie increase the output inductance. Then adjust the feedback to obtain constant output. Adjust the feedback with the 200W load. I assume that the drive section is proper and the transformer turns ratio is sufficient (since you had mentioned this in an earlier post). Uploading your schematic will make it easier to detect the cause of the problems.
 
Tahmid, is it possible to generate modified sine wave using sg3525? If yes then how to proceed?
 

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