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Thread: diy 500W smps with voltage or current regulation

  1. #51
    Hi Silvio

    Information for material you can look hear : http://www.lasfcy.com/pages/pro-tx-e.html

    On the picture you can see information for core (that is information from producer that core ) .

    core data.jpg

  2. #52
    diysmps Member* res_smps's Avatar
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    you can use formula from this link http://tahmidmc.blogspot.co.id/2013/...lation_22.html
    only Ac parameter is required (Ac or Ae = Effective Cross-Sectional Area in cm2), you can get it from datasheet or measure and calculate manually
    I always use the formula for unknown core manufacturer/material

  3. #53
    diysmps Senior Member Silvio's Avatar
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    Quote Originally Posted by mojalovaa View Post
    Hi Silvio

    Information for material you can look hear : http://www.lasfcy.com/pages/pro-tx-e.html

    On the picture you can see information for core (that is information from producer that core ) .

    core data.jpg
    The chart you sent me the core type EI is not mentioned but only EE cores. What type of core have you got is it EE or EI?

    You can opt to go to Tahmid's Blog as Res suggested and use the normal formula. Again be careful of the Bmax you choose according to the frequency. If you are using 25Khz and the core you chose is in fact EI42 I think is small for your need. In case you have to rise up the frequency to around 60 or 70Khz but still the core may be a bit small, You need thick copper for the current handling needed and this will make it difficult to fit in a small core.

    Regards, Silvio

  4. #54
    Sorry my tape mistake , EE core.
    Frequency will be 80 kHz or more if need but max 100 kHz .

  5. #55
    diysmps Senior Member Silvio's Avatar
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    Quote Originally Posted by mojalovaa View Post
    Sorry my tape mistake , EE core.
    Frequency will be 80 kHz or more if need but max 100 kHz .
    Ok I will try to figure out what the headings mean as I cannot read Chinese

  6. #56
    diysmps Senior Member Silvio's Avatar
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    Quote Originally Posted by mojalovaa View Post
    Sorry my tape mistake , EE core.
    Frequency will be 80 kHz or more if need but max 100 kHz .
    I chose the core material N87 which has an AL value a bit less than zp40 as I could not find an exact match. this will be on the safe side not to let the core saturate. I am sending a file worked with Exellent IT 7300 the frequency used is 80Khz and the current density is 6A/mm^2. See what fits best in the trafo bobbin either wires side by side or bundle of wires twisted together. Do not forget margin clearance and use mylar tape in your construction. Use high temperature PT sleeve for primary winding (at the ends of winding)

    The file is attached

    Calc for trafo Mojolovaa.pdf

  7. #57
    Hi

    I m buck to work today , Silvio thanks for calculation .
    One question for SG3525 dead time , If I'm look correct on the scope my dead time is 3 uS , and with this calculator that mind more winding on transformers , have some sample for see how calculate dead time on SG3525 ?
    My circuit use RT= 2.2 k , CT = 3.3 nF and DT = 100 R .

  8. #58
    diysmps Senior Member Silvio's Avatar
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    Quote Originally Posted by mojalovaa View Post
    Hi

    I m buck to work today , Silvio thanks for calculation .
    One question for SG3525 dead time , If I'm look correct on the scope my dead time is 3 uS , and with this calculator that mind more winding on transformers , have some sample for see how calculate dead time on SG3525 ?
    My circuit use RT= 2.2 k , CT = 3.3 nF and DT = 100 R .
    Hi Mojalovaa, I have seen the data sheet of the SG3525 and according to the graph shown I calculated that with a 3.3nf cap you will be needing around 33k series resistor to get 80Khz however you have to experiment a little with the resistor value as it will never be the exact value. You can always put a small preset potentiometer to get to the exact frequency.

    Regarding the dead time it all depends if you have a resistor (470K) tied from pin 9 to pin 1 of the sg This will limit your dead time to 1uS. however the discharge resistor will be small around 33 to 100 ohms. If the 470K is eliminated the discharge resistor will be according to the graph shown on the datasheet around 100 ohms or more for 1uS dead time

    It will be best to probe with the oscilloscope on both wave forms a put them on each other to calculate the dead time.

    This is a Pic of my 1000w smps checking dead time and frequency

    dead time and frequency.jpg

  9. #59
    Today I'm run my smps and after few second with load is damage , first is burn diode D7 (A1 is short to K ) after that is burn FET , all so short between D and S .
    Have you idea why is happen that , because on secondary side after diode voltage is 29V and diode is for 45V , and load is bee 3R and that is 9.6A , but diode is for 40A ?

  10. #60
    diysmps Senior Member Silvio's Avatar
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    Quote Originally Posted by mojalovaa View Post
    Today I'm run my smps and after few second with load is damage , first is burn diode D7 (A1 is short to K ) after that is burn FET , all so short between D and S .
    Have you idea why is happen that , because on secondary side after diode voltage is 29V and diode is for 45V , and load is bee 3R and that is 9.6A , but diode is for 40A ?
    It looks that your short circuit protection is not set right or it is not working. Did you make a short circuit protection to your PCB? Did you check the wave form at load? Did you work out the snubber value and check it at a partial load to see how it is behaving? You must load gradually and check things out as the more current drawn at the output the more things change regarding stray inductance and also stray coupling to the fet gates. You need to filter out these first otherwise the wave form will be deformed and spikes start emerging everywhere. Load your smps gradually and monitor as you go along. Try to find some heating elements from old heaters and load gradually with them until you go to the final load.

    Regarding the output diode it looks like it has exceeded its operating voltage due to spikes on the output.


    I hope that helps

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