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Thread: 1000w smps based on LUDO3232

  1. #351
    .... Silvio's Avatar
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    Hi Upik, Please tell me what
    1) IGBTs or Mosfets are you using?
    2) Fast output diodes?
    I need the part numbers to check out your calculations
    3) why are you using such high frequency? getting down a bit say at 65Khz you can do with thicker wire like 0.5 mm this will bring less number of strands for the same current. However IGBTs carry less than the rated current at higher frequencies. Check this out on the data sheets
    4) Do you really need 6Kw of power?
    5) Have you considered that the traces need to carry a lot of current and the copper clad must be at least a 4 ounce and traces have to rather wide.
    6) I think you are going to use a PFC or some kind of boost converter in the input. Have you tried this part alone at 6Kw load? Around 25A at 230v ac.
    7) Input capacitance need to be adequate as the output will suffer a lot of ripple
    8) Usually such high current smps are divided in two power supplies rather than a large one. It will make life easier and they will perform better.

    Regards Silvio
    Last edited by Silvio; 10-26-2018 at 09:09 PM.

  2. #352
    diysmps Senior Member
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    Quote Originally Posted by Silvio View Post
    Hi Upik, Please tell me what
    1) IGBTs or Mosfets are you using?
    2) Fast output diodes?
    I need the part numbers to check out your calculations
    3) why are you using such high frequency? getting down a bit say at 65Khz you can do with thicker wire like 0.5 mm this will bring less number of strands for the same current. However IGBTs carry less than the rated current at higher frequencies. Check this out on the data sheets
    4) Do you really need 6Kw of power?
    5) Have you considered that the traces need to carry a lot of current and the copper clad must be at least a 4 ounce and traces have to rather wide.
    6) I think you are going to use a PFC or some kind of boost converter in the input. Have you tried this part alone at 6Kw load? Around 25A at 230v ac.
    7) Input capacitance need to be adequate as the output will suffer a lot of ripple
    8) Usually such high current smps are divided in two power supplies rather than a large one. It will make life easier and they will perform better.

    Regards Silvio
    1. I use mosfet 47n60 ,, 2. in rurg 5060, 3, I only follow the components on the pcb, 4. at least 5kw, I use pfc ..

  3. #353
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    Quote Originally Posted by Upik View Post
    1. I use mosfet 47n60 ,, 2. in rurg 5060, 3, I only follow the components on the pcb, 4. at least 5kw, I use pfc ..
    1) You must include RDS on for 47n60 in the software 0.07 Ohms (from datasheet) and not U sat in this case

    2) Diode forward voltage drop for RURG5060 according to datasheet at 30 amps is around 1v

    3) if you still want to use 85Khz then correct the copper wire thickness from 0.5 to 0.4mm for the primary as it is too thick for this frequency

    Plug the values and see what you get.
    When you press calculate then move the mouse on the output voltage result and it will be displayed the peak output voltage. If your smps is not regulated this is what you will get in the output as the result shown will give you the result at load with an output inductor included.
    You will get 3 results according to the input voltage (min, Mean and max)

    Some hints

    Make a bundle of wire with the required number of strands and see how they fit in the transformer try to cover one whole layer. you need to sandwich your secondary between the primary for good coupling. try to avoid partial coverage of the bobbin with each winding as this will bring a lot of leakage inductance and asymmetry. You can lessen some strands if this is the case so that you will have a good fit. You can use 2 or more bundles instead of a single bundle for each winding ( Ex. 2 bundles of 20 wires each will bring 40 strands or 3 bundles of 13 each will bring 39 strands etc)
    Use adequate tape (Mylar) to avoid any danger of primary leaking with secondary. 3 layers between pri and sec. 1 layer tape between layers of the same winding. Try to leave some margin space with the windings at the cheeks of the bobbin. 2-3mm on each end.

    Good luck Silvio

  4. #354
    diysmps Senior Member
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    hi mr. silvio, what if I want to measure a mosfet wave, using an oscilloscope ?? where do I connect the GND probe, ?? to the Sourse fet's leg, ??

  5. #355
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    Upik In half bridge you have two fets one is the high side fet and the other is the low side fet.
    You will attach the ground lead to the source of the fet. Measure one fet at a time do not use two probes

    See also that the scope is isolated from ground and if it is attached to a laptop do not use the power adapter during tests.

    Post some pictures upik we like to see your work
    Last edited by Silvio; 11-29-2018 at 06:35 AM.

  6. #356
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    Quote Originally Posted by Silvio View Post
    Upik In half bridge you have two fets one is the high side fet and the other is the low side fet.
    You will attach the ground lead to the source of the fet. Measure one fet at a time do not use two probes

    See also that the scope is isolated from ground and if it is attached to a laptop do not use the power adapter during tests.

    Post some pictures upik we like to see your work
    hi mr.silvio ,, I have not tried it, how about a full bridge, if I want to see the high side and the low side simultaneously, I use GDT for the mosfet driver. give me the correct sample image for the correct probe

  7. #357
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    If you are using a gate drive transformer you will have separate windings feeding the fets. You still cannot see both wave forms at the same time because the ground of the oscilloscope is common on both probes. The high side source and the low side source are not common to each other and if you connect both at the same time BOOM you smps fets will die and also maybe your scope.

    You can see the wave form across the primary of the transformer but be careful as now you have 320 volts across and this maybe too high for the scope. You can put 2 resistors in series one of 100K and the other of 10K. ( use 1 watt resistors) Solder the resistors in series and then solder them across the primary. You will put probe and ground across the 10K resistor. Here you are dividing the voltage across the primary by 10 so now the scope will see 32v and not 320v ( be sure that your scope is isolated from ground).
    If you are using laptop work on battery for the test.

    Note Be careful and do not touch anything during the test as there are lethal voltages on the SMPS.
    Last edited by Silvio; 11-29-2018 at 10:54 PM.

  8. #358
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    yes mr.silvio ,, I only have owon vds 1022 with a max input of 40vpp

  9. #359
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    Hi Upik I think the 100K resistor at that voltage might get a little hot with 320v you can either use 2 X 47K resistors (1 watt each) in series with the 10K resistor thus you will get 2 watts as the power will be divided.
    As for the Owon scope you can also use the X10 probe as well so that the resultant voltage arriving at the oscilloscope will be 3.2v.

    By the way you will see the whole waveform across the primary.

    This is what is should look likeIMG_0575.jpg

    I hope that helps.
    Last edited by Silvio; 11-30-2018 at 04:30 PM.

  10. #360
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    is it just a probe, what about the GND probe, is it also given a resistor of 100k and 10k, ??

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