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TIDA-00961: RMS current over GaN switches in a bridgeless totem pole non-interleaved design

Lukas Jani
Prodigy 180 points

Part Number: TIDA-00961

Hello all,

in the Whitepaper given for the TIDA-00961 the formula for the RMS-current over the GaN switches is given. I'm trying to figure out the RMS-current over the GaNs in my PFC-design, which is NOT interleaved.

Therefore im taking the equation given, using my peak current over the inductor (16A*sqrt(2)), the equation yields 4,62Arms.

Yet, my Spice calculation results in a ~7A rms over the GaNs.

Attached: my LTspice Modell.

Any help here?

Best regards,

Lukas

  • 0
    TI__Expert 3860 points

    Hi Lukas,

    The problem seems to be that the equations for interleaved topology is applied with non-interleaved topology. With a non-interleaved design, entire input current is handled by a single inductor. So the equation 6 in the design guide has to be multiplied by 2 to get the peak current.

    We are considering the worst case in the design equation. So the current in simulation can be lower than the calculated value.

    Regards,

    Salil

  • 0 in reply to Salil
    Prodigy 180 points

    Hi Salil,

    thank you for the answer. Lucky this issue is solved now, the equations used are:

    Fast Switch:

    I_rms= sqrt(D)*I_L_rms/sqrt(2)

    I_avg= sqrt(D)*I_L_rms/pi

    Diode

    I_rms= sqrt(1-D)*I_L_rms/sqrt(2)

    I_avg= sqrt(1-D)*I_L_rms/pi

    where D ist the duty cycle given by D=(U_DCL-U_in_rms)/U_in

    thank you for your help!

    Best regards, Lukas