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UCC28070: Replace the current transformer by a hall sensor in series with the inductors

John Doe
Prodigy 10 points
Part Number: UCC28070
Other Parts Discussed in Thread: LMG3522R030-Q1

Tool/software:

Hello,

On my design, I plan to use TI GaN LMG3522R030-Q1 components as switching devices.

These components are extremely fast and I am afraid that the current transformer inductance creates high overshoot.

Are my worries right?

Many thanks

  • +1
    TI__Mastermind 40580 points

    Hello Adrien, 

    The primary inductance of a current-sense transformer (CT) (of the single turn) is the secondary inductance divided by square of the turns-ratio.

    For example, a 100:1 CT with 10mH secondary inductance would have 1uH inductance reflected on the single primary turn.   
    But most of the primary current does not flow through this inductance.  Almost all of it flows through the burden resistor reflected to the primary. 
    Only a little magnetizing current is built up in the primary inductance (due to the volt-seconds impressed across it). 

    Therefore the energy content in the primary inductance is very small and will not raise the Vds of the GaN Fet much, even though the Coss of the GaN FET is much lower than a Si-FET.   You can calculate how much higher Vds goes based on equating the stored inductor energy to transfer to the Coss of the GaN Fet. 

    I don't think that a hall-effect sensor is necessary. 

    Regards,
    Ulrich