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MOSFET (Si/SiC) Forum Discussions

User19846
Level 1
First question asked
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Hello,Is it difficult to turn off the MOS after it gets hot at work, because its Vgs(th) Max is only 4V
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Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator
Hi,

Yes , at some point if the current is too much it becomes difficult to turn OFF the MOSFET when it is hot enough. IF the Vds times Rdson is sufficiently large enough,
the MOSFET continues to conduct even when the gate to source voltage (Vgs) is turned OFF.

If Vgs low isn't low enough to turn the MOSFET off, it will still be carrying current but probably also dropping some of the supply voltage that should warm up or even get hot.

A proper heat sink must be designed in this condition to avoid this issue.

The following image helps you in understanding leakage currents during increase in MOSFET temperature and maintaining zero gate to source voltage (Vgs=0)

4855.attach


Regards,
Abhilash P

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Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator
Hi,

Yes , at some point if the current is too much it becomes difficult to turn OFF the MOSFET when it is hot enough. IF the Vds times Rdson is sufficiently large enough,
the MOSFET continues to conduct even when the gate to source voltage (Vgs) is turned OFF.

If Vgs low isn't low enough to turn the MOSFET off, it will still be carrying current but probably also dropping some of the supply voltage that should warm up or even get hot.

A proper heat sink must be designed in this condition to avoid this issue.

The following image helps you in understanding leakage currents during increase in MOSFET temperature and maintaining zero gate to source voltage (Vgs=0)

4855.attach


Regards,
Abhilash P
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