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Old 24th July 2008, 08:16 AM   #1
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Default Mosfet burn

hi all,

Based on the attached circuit AC - DC circuit, before conecting the PFC ic and the MOSFET and the i have connected my design...but without connecting the PFC ic . MOSFET( IRFP450) and fast recovery diode. I got a pure DC voltage about 320V for a load of 150 ohm's. But what i dont understand here is when i connect the MOSFET ...without giving any signal to the gate it should be functioning as the same, because current don't flow from drain to source when there is no signal to the gate. Here the case is my mosfets keeps burning as if it is shorted. please advise
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Old 24th July 2008, 09:24 AM   #2
Eva is offline Eva  Spain
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There is always some leakage from drain to gate so if you leave the gate open (or in an high impedance state) and apply some voltage to the drain, the MOSFET will tend to turn on by itself.

The gate has to be pulled low to source potential when the MOSFET is intended to be turned off.
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Old 24th July 2008, 05:06 PM   #3
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Heloo eva,

Thank you very much for your tips. It works.
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Old 16th May 2013, 07:12 AM   #4
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Hello Eva,

Could you explain more clearly Why the MOSFET is overheat when the MOSFET tend to turn on by itself?

Thank you.
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Old 20th May 2013, 02:46 AM   #5
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Quote:
Originally Posted by anna2011 View Post
Hello Eva,

Could you explain more clearly Why the MOSFET is overheat when the MOSFET tend to turn on by itself?

Thank you.
Probably because the mosfet is only partly switching on and so is in its none switching mode. This will dissipate a lot of power and burn the mosfet.
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