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Thread: 1000w smps based on LUDO3232

  1. #401
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    Hi mituadas, the waves look ok to me it is only the little oscillation you have on the switch off at the bottom of the wave form. This can be corrected by putting a 4.7k resistor from gate to source. The resistor will help the mosfet to stay off between each cycle and any stray inductance and capacitance will not false trigger them. A snubber across the primary will also tame down the spikes. Do not be fooled as the more load you add to the output the spikes will get larger. you will correct this when the smps is stable.

    I see you have an owon scope and this can work on battery. It is important that during the test you work on battery power so that it will be galvanically isolated from the mains. If your scope can handle 300v in the input you can directly connect the probe across the transformer primary with these set to X10. If not you can make a resistive divider across the primary of the transformer to limit the voltage for the scope. The resistive divider can be made with a 100k and 10k resistors in series. These will divide the voltage seen by the scope by 10.
    Important that your scope probes will be put across the 10k resistor. Use only one probe and ground

    Now you can measure the wave form across the primary of the transformer and see the real result,

    It is important that you put a 100w lamp in series with the mains supply as a current limiter. Do not try to operate directly from the mains without a current limiter lamp. if something is not right you will blow the mosfets again.

    You will only remove the 100w lamp if the smps is stable after 5 minutes of operation and nothing gets hot.

    See how it goes from here and we talk later on your findings

    Silvio

  2. #402
    Hi Silvio

    Thanks for your good advice.

    Today I have tested my SMPS using 100W bulb in series. It was OK. I got 46-0-46 v output without any load. I have tested it for 1 minute. MOSFETs are without heatsink but no such heat observed in any components. Can I switch on without series ?? How much voltage i should get at output?My transformer is as per your design mean primary 11+11 and secondary 7+7 in ETD 49. Frequency is 62Khz.

    Thanks once again

    S Das

  3. #403
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    Quote Originally Posted by mituadas View Post
    Hi Silvio

    Thanks for your good advice.

    Today I have tested my SMPS using 100W bulb in series. It was OK. I got 46-0-46 v output without any load. I have tested it for 1 minute. MOSFETs are without heatsink but no such heat observed in any components. Can I switch on without series ?? How much voltage i should get at output?My transformer is as per your design mean primary 11+11 and secondary 7+7 in ETD 49. Frequency is 62Khz.

    Thanks once again

    S Das
    Hi Das well it looks ok till now. Did you observed the waves across the transformer? They should be nice and square. Use the resistive divider I told you and take a look. It will be noticed that when loading the smps if there are any kind of spikes they will show more with load.

    do not forget to put heatsink before loading the smps as the mosfets will heat up.

    Regarding the output voltage you can calculate like this:- The half bridge voltage is around 155v at 230vac input.

    So 155v / 22turns in primary = 7.05 volts per turn. Round off for 7 volts per turn.

    for 7 turns secondary then multiply 7v X 7 turns = 49v.

    The Peak no load output will vary according to the input voltage and you have to make a little allowance for the voltage drop in the output diodes etc.

    The output voltage will drop with load to around 10% to 15% depending how good is the coupling in the transformer winding and also the mains input and flux density. Your output at full load of 300w or so will be more or less 46v/ 1.15 (15%) 40v. Do not worry much about this as when fitted with the amplifier it will not drop that much as the amplifier will not have a constant load and the voltage drop will be much less.

  4. #404
    HI Silivio

    I forgot to ask you one think that when i was testing my SMPS in series, 100W bulb was glowing till i switched off. Any mistake or it is normal? My scope model is PC based VDS1022 which can take maximum 40v input.

    Thanks

    S Das
    Last edited by mituadas; 05-08-2019 at 04:49 AM.

  5. #405
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    IF the lamp is glowing its not good it should stay off after start up with no load. Check that you are running a good frequency at least 65Khz or more. The lamp should glow at start up and then it should come off, Try to increase the frequency until the lamp will not glow.
    If you are in excess of 85 or 90khz and the lamp still glows it means that you have something wrong in the transformer winding or somewhere else

  6. #406
    Hi Silivo

    For testing I have detached Transformer from PCB after that i tested with series again bulb is glowing. After that i remove PWM board then also bulb is glowing ,at last i remove mosfets then bulb turn off. I have tested mosfets using it is ok. Can you please analyse and let me know what to do next?

    Thanks

    S Das

  7. #407
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    Quote Originally Posted by mituadas View Post
    Hi Silivo

    For testing I have detached Transformer from PCB after that i tested with series again bulb is glowing. After that i remove PWM board then also bulb is glowing ,at last i remove mosfets then bulb turn off. I have tested mosfets using it is ok. Can you please analyse and let me know what to do next?

    Thanks

    S Das
    Can you post a picture of your pcb. I would like to see it. See that it is large enough so that I can follow the traces.

  8. #408
    Today I add 10K register at Source to Gate of Mosfet. after that i connect mosfet and it was ok without PWM board and Transformer. Then i connect PWM board and bulb glow continuously. Then i connect Transformer and found output put voltage +44 and -44.

    I took this wave form at Transformer.Which is not proper as per me.Please guide me how to improve.
    Wave at Trafo.JPG

  9. #409
    Today I have tested my SMPS . Wave form taken from Mosfet attached. Please guide me what is the issue.

    Wave at Trafo-1.JPG

  10. #410
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    Quote Originally Posted by mituadas View Post
    Today I have tested my SMPS . Wave form taken from Mosfet attached. Please guide me what is the issue.

    Wave at Trafo-1.JPG
    That is not a proper wave form it must show a square wave. Power up only auxiliary supply and check wave form. If it is not square then either sg3525 or IR2110 is not good. Try changing SG3525 first.

    Buy genuine parts otherwise you will be disappointed.

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