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TPSF12C1: Constant setting using Excel's calculation tool

Conor
Mastermind 9800 points
Part Number: TPSF12C1

Tool/software:

Hi,

I am using an Excel calculator to determine the constants of IC peripheral components. Please confirm whether my understanding is correct.

Q1. The source impedances estimation is difficult. Are there standard values ​​on the calculator? In reality, I think it is necessary to adjust it based on the characteristics of the system and circuit, but can you give me some advice on the guideline value?

Q2. fLFstability (an index of low frequency stability) is an important factor for the stable operation of the design. TI's design guidelines state that the system may become unstable in the range of 10-100kHz. Is my understanding correct?
Also, if the above understanding is correct, when I entered the constants based on Step 6, fLFstability = 17.5kHz. What settings do I need to review to set fLFstability to 100kHz or more?

Q3.With what frequency should the calculated results of fLFstability, fRD1-CD2, fRD1-CD1, fRD2-CD2, fRD3-CD3, and fRD1A-CD1 be compared? Also, do they affect the AEF-Loop Gain?

Q4. In the waveform below, the high magnitude area shows that the filter is effectively reducing noise. Phase is an index for checking stability. In particular, a phase margin of 45° or more at the crossover frequency (the point where the gain is 0 dB) is a condition for stable operation. Is my understanding correct?

Q5. The frequency band where Magnitude (green line) is increasing is the area where the active filter suppresses noise more effectively than the passive filter. The larger the Delta (gray line), the greater the improvement effect. Is my understanding correct?

Q6. This graph analyzes the impedance characteristics of a common mode choke. The dashed line chart shows the phase characteristics, which indicates the phase change of impedance according to frequency. Also, there is no indication of the Grid-side choke, but it can be displayed by parameter input settings. Is my understanding correct?

Thanks,

Conor

  • 0
    TI__Intellectual 1400 points

    Hi Conor

    thanks for your question. I will get back to you on this

  • +1 in reply to Naresh Adepu
    TI__Intellectual 1400 points

    Hi Conor,

    1. To start with, you can use the values mentioned in the excel calculator. They are the generic standard values for the system - you can take them as guideline. If you need accurate values, you have to ask the customer to evaluate the impedances and share them with you as they are specific to each system. Except CSRC all other values don't have a significant impact on the performance. 

    2. fLF stability is something internal which is used to adjust the damping component values in the step 6. You wouldn't have lot of freedom to adjust it. We recommend using the calculated values in Step6 for the selected column for stable operation. Look at the gain and phase plot for stable operation. It is okay if the fLF stability is less than 100kHz. 

    3.   fLFstability, fRD1-CD2, fRD1-CD1, fRD2-CD2, fRD3-CD3, and fRD1A-CD1 are the values which are used to calculate the damping component values. They do affect the AEF gain but you wouldn't have the freedom to change them independently. Please choose RD1, CD1, CD2, RD2, RD1A, RD3, CD3 component values based on the calculated column and use them in the selected values column. 

    4. Yes Conor, that is correct. As long as you don't have sharp transition in phase and phase doesn't cross -180 or +180 deg then it would be a stable system. 

    5. That is correct.

    6. No, currently in the graph you shared, both grid side and regular side choke profiles are overlapping. That's why you are not able to see the difference. But if you change one of the data, you will see different graphs for both. If you have model data for your choke, use equivalent model parameters and enter them. If you have impedance vs freq data for the chokes, select "impedance vs freq" data and enter that data.

    Thanks and Regards, 

  • 0 in reply to Naresh Adepu
    Mastermind 9800 points

    Naresh,

    Thank you. I appreciate your help!

    Thanks,

    Conor

  • 0 in reply to Conor
    TI__Intellectual 1400 points

    Thanks Conor.