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Thread: 1kW smps project (based on MicrosiM design)

  1. #1341
    diysmps Member CDJKuznec's Avatar
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    Silvio, very big thank you.

  2. #1342
    hi silvio,



    my current protection not working...im using 24mm yellow toroid found in pc atx supply....

    100:1 turns ratio....without protection smps works fine ,i loaded smps with 1000 watts halogen (+ 90-0-90).....when protection connected smps does not start
    led stays on pin 3 of ne555 . i changed it with lm358 smps works ok but ocp not working i want to set it on 1kw...

    iam using 4 mur160 and 100 ohm as burden resistor before the bridge getting 6 volts across diodes when loaded with halogen... can vary vollage with preset how many volts needed on pin 6 of lm358 to trigger ne555....i have changed multiple lm393 and 358 all showing same behaviour...iaam attaching the schematic

    thanks in advance...
    Attached Images Attached Images

  3. #1343
    .... Silvio's Avatar
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    Hi Ravs, I see no detail in schematic for the current transformer however in my version I used a ratio of 22:1. I suggest you select a green core instead and the diameter of this core may also be 15mm.
    Wind the current transformer with 0.4mm ecw and change the resistor R113 to 10 ohms. You can also use 2x22R in parallel of 0.5W each instead as a burden resistor. The 1uF capacitor is to be left in circuit and changed to a non polarized low ESR one. I also suggest that the burden resistor be on the AC side before the diode. The diode will preferably be after the burden resistor.

    Please understand that there are spikes generated by the current transformer and these are triggering you overload protection. These have to be looked at by making a 2 turn coupling loop on the core and seen on an oscilloscope These spikes must be clamped with a capacitor and resistor (snubber) or capacitor across the burden resistor otherwise you get a lot of false triggering.

    It could also be the case that the cold filament of the lamp is drawing a lot of current until it heats up and overloading your smps, this current surge may be triggering your protection circuit.

    This part of overload setting your smps is important and must be conducted by inserting loads gradually until you get to the wanted tripping current. Keep in mind that with the transformer and mosfets used settle out for no more than 1200W at the output do this by calculation the V X I= W. Be informed that IRFP460 could not handle more than 13A at the halfbridge this current will give you around 1500w but you have to consider also the efficiency of about 80% and at the output the wattage will be somewhat less due to switching losses and diodes, transformer, volt drop at the input capacitors etc.

    If a mosfet is rated at 20A it does not mean you run at that current we rate for 0.25 for continuous use and maybe a little more than 0.5 for audio purpose. So at the peak watts of 1200W do not leave the load for more than 5 seconds at a time.

    One last note. See that you have adequate supply de-coupling near the op amp as these have very sensitive inputs and may false trigger. Be sure to fit the heatsink to the mosfets and output diodes, these heat up very quickly with load.

    Good luck Regards, Silvio

  4. #1344
    .... Silvio's Avatar
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    Quote Originally Posted by ravs View Post
    hi silvio,



    my current protection not working...im using 24mm yellow toroid found in pc atx supply....

    100:1 turns ratio....without protection smps works fine ,i loaded smps with 1000 watts halogen (+ 90-0-90).....when protection connected smps does not start
    led stays on pin 3 of ne555 . i changed it with lm358 smps works ok but ocp not working i want to set it on 1kw...

    iam using 4 mur160 and 100 ohm as burden resistor before the bridge getting 6 volts across diodes when loaded with halogen... can vary vollage with preset how many volts needed on pin 6 of lm358 to trigger ne555....i have changed multiple lm393 and 358 all showing same behaviour...iaam attaching the schematic

    thanks in advance...
    Regarding the threshold voltage which the over current protection triggers is around 2.5v. As you can see the rail voltage to the opamp is 5v, this is divided by 2 with R123 and R118. (22K) creating a voltage reference of 2.5v.
    To sum up all 2.5v should show up on pin 6 (LM393)at a current of around 6 to 8 amps on the output depending on how regulation holds the voltage at the output.( I am assuming you are loading both rails in series creating 180vdc)
    I also do not see an output inductor and looks very odd to me as the smps is a regulated one. You will need inductors of around 20uH on each rail.

    Regards Silvio
    Last edited by Silvio; 05-29-2020 at 10:11 AM. Reason: Forgot a few tips

  5. #1345
    hi microsim sir
    i need winding detial off (etd 39) frequency is 70 khz
    my supply volt is 50 volt ,6 amp, topology is half bridge
    circuit is 1kv based on microsim

  6. #1346
    please give me winding detial off primary and secondary

  7. #1347
    smps v2.1 sch.pdf here is the schematic

  8. #1348
    .... Silvio's Avatar
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    Primary winding 30 turns. (15T +15T) ECW 4 wires 0.5mm twisted together. Leave 4mm margin space at bobbin cheeks on each side.

    Secondary 10 turns. for single winding if you want double winding then wind two bundles together starting from center tap.
    ECW secondary 5 wires 0.5mm twisted together.

    Winding sequence
    1) first 15 turns
    2) 3 laps maylar tape
    3) wind secondary windings taking two bundles of 5 twisted wires each. Start from center tap and wind together until you wind 10 turns. connect the ends on the pins of the transformer and solder.
    4) 3 laps maylar tape.
    5) Wind the remaining 15 turns of the primary and connect with transformer pins.
    6) 3 laps maylar tape.
    7) if you have any auxiliary windings then calculate at 5v per turn. wind auxiliary winding last.

    Note that ETD39 cannot go to 1000w but maximum of 750w at 70Khz.

    If you want you can take a look at the video so that you understand more about winding transformers for smps.

    Link https://www.youtube.com/watch?v=_K3ixhcTYFg&t=1s

    Regards Silvio

  9. #1349
    hi sir silvio
    thanks for your kind reply i will try this winding ,one more thing i want to tell is that the core material i am using is
    cf (139 cosmo ferrouse )is the above winding detial is ok for this core material .
    thanking you
    p.s.raju

  10. #1350
    .... Silvio's Avatar
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    CF139 is a little bit better core material than N87 TDK.

    Your primary winding can be 28 turns instead of 30 turns. (input 230vac)
    Using this formula then 155v/ 28t = 5.53 volts per turn therefore the secondary winding becomes 9 turns for 49.8v.
    if you adopt for 10 turns for each secondary than your output voltage be around 55-56v. For a primary of 28turns.

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