MOSFETS keeps exploding i dont now why ...

[billu8660]

hi,
what should be the deadtime in this circuit...as this might saturating the transformer and inturn blowing MOSFETS

 

[Tahmid]

In your construction whether on verroboard or PCB, keep your tracks short and wide. It's okay if you're using verroboard as long as you avoid the long hanging wires and you keep track or connection length at a minimum. One other thing you should keep in mind is gate-to-source resistors. Not using these has been the reason for MOSFETs blowing up many a times in my circuits. Make sure you have 1k resistors between gate and source of each MOSFET. You may also need to connect a snubber across the transformer primary.

 

[wally7856]

I do not remember ever seeing a 1K resistor between gate and source. What does it do.

 

[Tahmid]

It prevents accidental turn on of the MOSFET by external noise usually at startup when the gate is floating. The MOSFET may sometimes turn on with a floating gate because of the internal drain to gate "Miller" capacitance. A gate to source resistor acts as a pull-down to ensure a low level for the MOSFET. I have had MOSFETs blowing up in high voltage circuits, without the resistor in place. In most of the commercial power supplies / inverters I have seen, there is a 1k resistor used.

A similar experience is narrated in Sanajaya Maniktala's "Switching Power Supplies A to Z". This is also talked of in Raymond Mack's "Switching Power Supplies Demystified".

Hope this helps.
Tahmid.

 

[wally7856]

Thank you for your answer. I also see you also talked about it here in your blog.

http://tahmidmc.blogspot.com/2012/10/magic-of-knowledge.html

 

[Acca]

You must have a storage inductor.

 

[tebci]

Problem fixed or no?

I dont like IRFP460, there are much better mosfets for the JOB!