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TINA/Spice/UCC28950: tina/spice/ucc28950

ilia hadzhiev
Prodigy 160 points
Part Number: UCC28950
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

hello

I try to simulate 18kw full bridge with 400V input and 450V output.
Output current 45A to 1mA. I tried to do that with the EVM sim model but with no succeed. I cant make the output voltage up to 450V. Its stays at 18V max.
I want to use it in battery charger. I already made the output current to change but now i want to simulate with 450V output voltage. 

Do you have any suggestions why i can't reach the output voltage.

regards

ilia

  • 0
    TI__Mastermind 25570 points
    Hi Ilia

    There are a number of things you will need to change to get the model to give a 450V output and I'll list the ones that occur to me below.

    First however, it is worth running the model with the original settings - this will give you a 'feeling' for how the system should operate.

    You should download a copy of the excel calculator for this device - it's on the product page under the tools and software tab. This will allow you to calculate the component values that you must change so that the converter gives a 450V output rather than a 12V output.

    You will need to change the transformer turns ratio - BE VERY CAREFUL HERE - the calculator rounds the turns ratio to the nearest integer - this is ok when the ratio is 21:1 for a 12V output but completely wrong where the input is 400V and the output is 450V. The calculator may suggest a turns ratio of 1 - the correct (un-rounded value) is 0.62. You can either cut and paste the value from cell C25 into cell C26 or directly write 0.62 into cell C26 -
    The transformer in TINA should be changed to have 21T on the primary and 34 turns on EACH of the secondaries (0.62 ratio)
    The calculator will also suggest output capacitance and output inductor values - change the TINA model to use these values.
    The output voltage sensing chain (R6/R7) nekeds to be changed. Calculate R6 so that at 450V at the output you have 2.5V at the EAP input.
    You should change to diode rectification - delete Q5 and Q6 and their associated drivers (OUTE and OUTF may be left open circuit.
    You may also have to change the loop compensation - but let's get you started first.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    Prodigy 160 points
    Hi

    i found that i can regulate the voltage from zero to max with Rsum
    i can regulate it from the feedback either but it gonna be easier to regulate it by Rsum

    Do you think i can regulate the voltage from there
    Is there any problem if i do that.

    Regard
    Ilia
  • 0 in reply to ilia hadzhiev
    TI__Mastermind 25570 points

    Hello Ilia

    You can't use RSUM to regulate Vo - it might appear to work in a simulation but this pin is supposed to set the slope compensation and to select either Voltage mode or Current mode control methods.

    The correct way to regulate Vo is to use the feedback network.

    Regards

    Colin