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TIDA-010025: TIDA-010025 (question about gate driver signals)

Mohammad Rastegar
Prodigy 60 points
Part Number: TIDA-010025
Other Parts Discussed in Thread: UCC23514, SN74ACT244

Hi,

I hope my email finds you well.

I am a UT Dallas student. I read the reference design TIDA-010025 (Three-phase inverter reference design for 200–480 VAC drives with opto-emulated input gate drivers). I have some questions about the gate driver part of inverter.

1. In the Figure 3. in reference design, it stated that x4 (+15V and -8V) isolated power supply have been used. It means three +15V and one -8V have been used or four +15V and four -8V power supply is needed?

2. In Figure 9. in reference design, for high side IGBTs definitions (VCC-U and VEE-U) and for low side IGBTs (VCC and VEE)  have been used. Can you please tell whether their value or sign (+ and -) are different or they are the same? I mean for both high and low side IGBTs these value are the same or should be different?

Many thanks for your consideration and supportive guidance as always.

  • 0
    TI__Intellectual 1070 points

    Hi Rastegar,

    Thank you for reaching to us on the questions about the reference design.

    1. Here it means four pairs of +15V and -8V power supply.

    The three low-side channels share one pair of the power supply because they are all referenced to the VDC-.

    The three high-side channels all have their own pair of the power supply because they are referenced to U, V and W respectively.

    2. Ideally these should be in the same values and signs, although there may be some little differences in reality. 

    The difference matters here is in their references: the high-side ones are referenced to U, V, W; and the low-side one is referenced to VDC-.

    Think about the difference in this case:

    There are two desks of the same type been placed in a 2 floor buildig; and both of the desks are in 1 meter high. One is placed in a room in the first floor, and the other is placed in a room in the 2nd floor. So their heights are same, but their referenced 'grounds' are different.

    Best regards,

    Jerome Shan

  • +1 in reply to Jerome Shan
    Prodigy 60 points

    Many thanks for your fast and perfect support and very nice description as always.

    So, we need 4 pairs of power supply signals (3 for high side) and one for the three low side (since their reference is the same).

    And the all 4 power supply signal pairs (+15V and -8V) are in the same value and signs, but with difference references.

    At first, I thought that for the low side, we need negative polarity of voltage for gate driving.

    Many thanks,

    Mohammad Rastegar.

    The University of Texas at Dallas.

  • +1 in reply to Mohammad Rastegar
    Prodigy 60 points

    Hi and I hope all is well with you.

    I have also another question.

    I am interested to use the buffer that you recommended in this application note.

     

    In this figure, for buffering the PWM signals,  SN74ACT244DWR has been used and I want to use this IC in my design. Just two question:

    1. Vcc of this should be connected to +5 V and OE pins should not be connected to anything for the non-inverting application (I do not want to invert my gate signals)?

    2. Is it better to use 6 separate SN74ACT244DWR for the 6 PWM signals if I want to have 6 separate signals (since all of my 6 PWM signals are being produced separately due to the modulation technique that I am implementing) or I can use one of these for all 6 switches and then use 6 UCC23514S (gate drivers) for all switches.

    Many thanks for your response.

    Mohammad Rastegar.

    Student at The University of Texas at Dallas. 

  • 0 in reply to Mohammad Rastegar
    TI__Intellectual 1070 points

    Hi Rastegar,

    1. Yes, the Vcc should be connected to +5V, but the /OE should be connected to GND or just follow this reference design, becaused it is 'output enable' input, not invert enable. This device does not invert the input signals in this design, and you can follow it directly.

    2. You need to follow this reference deisgn, using 1 piece of SN74ACT244 and 6 pieces of UCC23514.

    Best regards,

    Jerome Shan

  • +1 in reply to Jerome Shan
    Prodigy 60 points

    Thank you for your response and perfect support as always.

    Best regards,

    Mohammad Rastegar.

    The University of Texas at Dallas.