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Original question:

TIDA-00779: Placement of temperature sensor

TIDA-00779: Changing Design constraints

Nidheesh BR
Expert 1295 points
Part Number: TIDA-00779


Suppose I want to operate this at 90KHz, that I can do by changing the frequency setting resistor.

So for this frequency, calculation saying that we can use a half size inductor core than actual.

So the reduction in size and value of inductance will create any issue in this design?

The initial inductance of the main inductor is actually 790uH, Is this a mandatory condition to satisfy?

If I am making this initial inductance nearer to 350uH but full load inductance is as required 180uH, Is this create any issues(for higher frequency operation 90KHz)?

Thanks.

  • 0
    TI__Intellectual 950 points

    Hi Nidheesh,

    No, please recalculate the PFC choke following the design guide, increasing the frequency will reduce the efficiency and I would not suggest you use sendust at 90kHz.

    BR

    Jason

  • 0 in reply to Yuan Tao
    Expert 1295 points
    Hi Jason,
    Yep. I tried with 90KHz and 210KHz as well.
    with 90KHz it self I can reduce the inductor core to half of that of original with less number of turns and it is working well. Then with same half size inductor I tried with 210KHz then it is noticed that inductor heating got further reduced. Even I can reduce the core size further according to the calculations.
    I have tried both the core material sendust and mega flux. both are well and good.
    Both are not producing any audiable noice.
    Now I have to evalute the efficiency in switching loss point of view.anyway I have to use a forced cooling, so i think it wont that much matters for me.

    thanks.
  • 0 in reply to Yuan Tao
    Expert 1295 points

    Hi Jason, It is found that PFC is catching the output voltage of 390v. But input current waveform seems to be distorted a little while I am changing inductor core size and frequency.

    Current waveforms images for different conditions are given as follows.

    image1: actual design, 45KHz

    image2: actual inductor but frequency 90KHz and load 3KW above this load waveform getting distorted which is in image 3.

    image4: Half the core size 90KHz full 3.6KW

    image5: Half the core size 210KHz full load of 3.6KW

    I am not getting the advantage of increasing the frequency(current is getting distorted while decreasing core size by increasing frequency). So it this means that 45KHz and actual suggested inductor core size is the optimum and proper value for this design?

  • 0 in reply to Nidheesh BR
    TI__Intellectual 950 points

    Hi Nidheesh,

    Of course, the design is be optimized for PFC choke with the frequency, if you want to increase the working frequency, you have to recalculate the choke, otherwise it could not work normal.

    BR

    Jason

  • 0 in reply to Yuan Tao
    Expert 1295 points

    OK Jason

    Let me try with recalculating the inductor design. Currently, I used Mega flux at higher frequencies. This also not giving the result.

    Do you have any core material suggestion for higher frequencies?

    Thanks.

  • 0 in reply to Nidheesh BR
    TI__Intellectual 950 points
    You can try ferrite or amorphous.
  • 0 in reply to Yuan Tao
    Expert 1295 points

    OK. Thanks Jason.