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WEN-YUNG
Level 3
Level 3
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Dear IFXer,

Usually, we knew the MOSFET self-turn on caused by commutation switch of half bridge(dV/dt cross-talk), but I also realize my PFC noise couple to gate of LLC MOSFET, may I know the coupling noise can be cause the MOSFET self-turn on?

please ignore the noise coupling level, I just confirm that if the coupling noise higher than Vth_min and the coupling overlay crosstalk both caused self-turn on? 

WENYUNG_0-1704204509657.png

 

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Dipti_Kiran
Moderator
Moderator
Moderator
First question asked 50 solutions authored 100 replies posted

Hi @WEN-YUNG ,

Yes, there is a chance of unwanted turn on due to noise particularly in LLC converter because in LLC converter, high frequency resonant operation makes it susceptible to noise issue.  As you know, in a PFC boost, common mode noise can be generated during switching event. If its not mitigated, then it may couple to MOSFET gate inducing voltage fluctuation in the gate drive circuit which may leads to unwanted turn on.

Can you please share your circuit/schematic and SiC MOSFET you are using in the circuit? What is the gate voltage you are applying for turn off? Can you share the Vgs, Vds, Ig waveform for both HS and LS  switch in half bridge configuration? It will help to understand if there is any unwanted turn on in the circuit.

Regards,

Dipti

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Dipti_Kiran
Moderator
Moderator
Moderator
First question asked 50 solutions authored 100 replies posted

Hi @WEN-YUNG ,

Yes, there is a chance of unwanted turn on due to noise particularly in LLC converter because in LLC converter, high frequency resonant operation makes it susceptible to noise issue.  As you know, in a PFC boost, common mode noise can be generated during switching event. If its not mitigated, then it may couple to MOSFET gate inducing voltage fluctuation in the gate drive circuit which may leads to unwanted turn on.

Can you please share your circuit/schematic and SiC MOSFET you are using in the circuit? What is the gate voltage you are applying for turn off? Can you share the Vgs, Vds, Ig waveform for both HS and LS  switch in half bridge configuration? It will help to understand if there is any unwanted turn on in the circuit.

Regards,

Dipti

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