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LTspice AC/DC convertor

Discussion in 'Circuit Simulation & PCB Design' started by mading2018, Feb 28, 2018.

  1. mading2018

    mading2018 Member

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    Yes I did, tried the circuit with LT8312 from #17. It seems to work there.

    1. Ok, I reduce the capacitor to 1uF
    2. So what I understand, I need to have another LT8312 connected? I mean, one PFC controller to Q1 and an another PFC controller to Q2? You want "interleave". Or is it possible to have only one, and having interleave = .A.B.A.B.A?
    3. I forgot to add K2 L3 L4 1 , my misstake.
    4. I added R3 because I want to make sure I have an input current of 16 A. D11, D12 is there because the circuit on configuration looks like that according to the scientist paper. But maybe they are not needed? See the attached files.

    Thank you,
     

    Attached Files:

  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    The diodes are internal to the MOSFET.
    Yes but the LT8312 needs a way to make two work 180 out of phase. I do not see a way.
     
  3. mading2018

    mading2018 Member

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    Aha, I see.

    Hmm, it is possible to change some of the voltage sources with AC phase (180 degree) to the LT8312?
    Cause I do not think there is an interleaved PFC controller for LTspice. I guess there is one for Pspice tough.
     
  4. dave miyares

    Dave New Member

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  5. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I think you can copy form PSpice. I have not done that. You will need to make a symbol for the schematic.
     
  6. mading2018

    mading2018 Member

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    Okay, I will try that. But first, I felt I needed to go back some steps. So I now I focusing on 1-phase PFC (so no interleaved). I think I succeeded to implement a LT1249, and it seems to work.
    I will try with the LT8312 as well and see how it goes.

    But for the DC/DC converter stage, do you how to increase the voltage to around 30o V at the output? I got only around 200 V.
    I need a voltage range between 320-380 V in order to charger the battery in vehicle. I tried to change many parameters in the circuit, but it seems not to increase.

    If you have time, you can please have a look on that. I am so thankful for your help.
     

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  7. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    It is very common for people to think that if you put a voltage on the Gate of a MOSFET the transistor will turn on. The signal must be from Gate to Source. See the changes to M1 and M3 and how they connect to V1 and V3.
    upload_2018-3-6_17-8-45.png
    Next your transformer had problems. I changed to 1:1 transformer and increased the inductance.
    Try this.
     

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  8. dave miyares

    Dave New Member

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  9. mading2018

    mading2018 Member

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    Ah, I see. But doesnt M2 and M4 also need to have the same connection as M1 and M3, regarding a signal from gate to source as well?
    Okay, so the transformer should have 1:1 ratio. But I notice that, I could reach about 320 V output from the converter if the inductance been reduced, maybe that's what you meant.

    Do you think the output voltage is DC enough in order to charge a battery? (I am however not sure about the battery model is correct, need to find one that is corresponding to a lithium battery for a PHEV).
     

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  10. mading2018

    mading2018 Member

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    Hmm, I don't understand why the circuits behave differently when I am just putting in the same file.
    The AC/DC converter do not give the same output voltage, and likewise with the DC/DC converter.
    Have I missed something?
    Because, if these both converters operates properly, I was thinking to connect them together. But maybe that was too early I guess.
     

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  11. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    You had the bottom two MOSFETs correct. (either way you drew them will work)

    Your top two MOSFETs were wrong. Then the Gate goes to 10V the MOSFET turns on and pulls it Source up to about 5V and then stops. The output of the bridge is; pull down good but pull up to only 5 volts).

    Because you could only get 5V (in the old circuit) you changed the transformer to a very large turn ratio trying to amplify the 5V to get 200V.

    "DC enough" I think some ripple on the output is OK. A car battery charger often does not have capacitors on the output. (very large ripple)

    I have seen good batteries model. I often use a voltage source and a resistor (some times add a diode so it only charges).
    Example: 12V battery like a car battery. I know at heavy charging current it will measure 14.5V. I often use a 12V voltage source and a 0.1 ohm resistor. At 0 to 12V the current is zero. At 10A charging current the voltage is 13. At 20A the voltage is 14V.
     
  12. mading2018

    mading2018 Member

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    Okay, I see. Thank you for your great answers. I really appreciate it. I will try to fix a high voltage battery model that is corresponding to a PHEV.

    Sorry, if I am being annoying, but the post in #28, why do you think the circuits do not match with each other?
    Could you please maybe analyze what could be the problem?
     

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    Last edited: Mar 8, 2018
  13. mading2018

    mading2018 Member

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    I going back some steps, which parameters should I changed in order to get increase the speed and avoid transients into the system? I tried to read the data sheet for this PFC IC, but not sure what I should change.
    http://cds.linear.com/docs/en/datasheet/8312fa.pdf
     
  14. mading2018

    mading2018 Member

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    Hello again ronsimpson, I need some advice what to do now. I have tried to simulate the PFC interleaved, but it seems not to working.
    I have decided to separate the AC/DC circuit and DC/DC circuit from each other, and simulate them one by one.

    Do you think it is possible to use only voltage sources as pulses, instead to implement a IC circuit of the PFC (since it is complexed), to simulate an interleaved PFC? Is it possible? Do you have an idea how to do it? I would really thankful if you could help me once more.

    I have attached my attempt to do it. However, I am trying to add EMI-filter after the input, is it consisting of 2 inductors, and 2 capacitors? I am not sure. Some sources says it is including more than that.
     

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  15. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    If you really have to do interleaved in SPICE, and there are no ICs in SPICE, then use a Linear.com part and:
    1) connect MOSFET like normal.
    2) IC output ---(5uS delay)---Gate of second MOSFET.
    This is not perfect but almost does interleaved.

    http://www.ti.com/product/ucc28070
     
  16. mading2018

    mading2018 Member

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    Okay, I see. But what linear.com part do we talking about? Sorry, that I do not follow.

    But do I really need to use ICs circuit necessarily, in order to simulate interleaved. It is not possible only to use voltage sources (since the current and voltage are already in phase with each other) connected to the MOSFETs?
     
  17. mading2018

    mading2018 Member

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    I made my AC/DC converter stage only using voltage sources that are sending PWM (corresponding to PFC circuit as the voltage and current is in phase).
    Do you think the current can be so low from the output from the converter? its only about 500 mA, and I know from design spec it can be maximum 12 A.
    Is it reasonable with 500 mA?
     

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  18. mading2018

    mading2018 Member

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    Could you maybe show me how to use a Linear.com part? I am not sure what to use there?
    I need to save some time, so I would be thankful if you could help me. If this is the best way to simulate interleaved, I am happy to have that.
     
  19. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Look at the datasheet for the LT1249. It includes a typical application circuit.
     
  20. mading2018

    mading2018 Member

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    I have checked that model, it should look something like this I imagine.
    But can you check for errors please? I do not think it works properly, the output looks strange.

    And about the input current? Do you know other ways to change the current? Cause my task is to make sure to that I have
    230 V (rms) with an input current of 4 A, 6 A and 8 A. I must try for all of these currents. Thank you.
     

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  21. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Change the load on the output if you want to change the input current draw.
     
  22. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Your full wave bridge is not working. Remove the ground with the red X.
    I do not know why R1.
    upload_2018-4-3_7-28-12.png
    It is not working right. It looks like the frequency response of the error amp is not right. C2,4, R3.
    I don't have time to fix it today.
     

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