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TPS23754EVM-383: TPS23754EVM-383 power consumption of active rectifyer

Bjoern Harre
Prodigy 105 points
Part Number: TPS23754EVM-383

The gate-driver transistors Q1/Q2 are getting quite hot. I have to adopt the switching frequency to 469kHz due to a transformer with less inductivity. Is there a chance to reduce the power consumption?

  • 0
    TI__Mastermind 21320 points

    Hello Bjoern,

    The equation for the power on gate 2 is as follows:

    So there are some options: lower the switching frequency, change the FET to lower the gate charge / increase the gate drive voltage or lower the VC voltage.

    Or lastly you could try increasing the physical size of the components. 

    Calculating the power dissipation on the gate of Q2 is not as straight forward. The following paper has more information on how to calculate power losses the FET itself. I would say that increasing the size of the components should help as well. 

    http://www.ti.com/lit/an/slua535a/slua535a.pdf

    Unfortunately an inherent problem of increasing the switching frequency is increased power losses and the thermals. That is in part why we choose the transformer as we did. A last resort method could be working with a transformer vendor to define a new transformer that hast the size / inductance requirements to meet your project. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 105 points

    Hi Michael,

    I have got a question concerning the MOSFETS (switched rectifier). Do you think I can reduce the power loss due to the high frequency, if I take this MOSFET NVTFS6H880N?

    It has lower gate capacity but a bit worse RDS(on).

    Br

    Björn

  • 0 in reply to Bjoern Harre
    TI__Mastermind 21320 points

    Hello Bjorn,

    I  get lost in the different naming conventions of the FETs.

    If you are talking about the secondary FETs, you can use the FET you mentioned. I will say it essentially moves the power loss from the gate to the drain-source, but that is the trade off for higher switching frequency.

    That will not work for Q1 since the FET shown is a N channel. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 105 points

    Hello Michael,

    only to avoid missunderstanding...

    Q1 and Q2 won't be changed. My idea is to exchange U3 and U5 to MOSFETS with less gate capacity.

    Br

    Björn

  • 0 in reply to Bjoern Harre
    TI__Mastermind 21320 points

    Bjorn,

    Can you clarify, there is no U5 on the board.

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    TI__Mastermind 21320 points

    If you are talking about the secondary FETs (Q3 and Q5), you can use the FET you mentioned. I will say it essentially moves the power loss from the gate to the drain-source, but that is the trade off for higher switching frequency.

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 105 points

    Here is the schematics: (Q: transistors, U:MOSFETS)