There is one point that needs to be brought out here ...
The mosfet gates are essentially capacitors ..... activated by a charging and discharging current.
If your control signal switching frequencies are too great, the mosfet might be operating at a point on the performance curve where it could overheat or be otherwise damaged. Also, check the charts given in the data sheet for the specific part that you are using.
There were one or two informative articles regarding this subject in Circuit Cellar Magazine, earlier this year .... maybe Dec. 08, Jan. 09.

 

Yes you are right.Even I have heard sound form MOSFETS while giving PWM to it.But if you consider the general use than there is nothing like that.IRF 840 and IRF 9520 works till 20 kHz.And I think that is too higher.So you can use them with proper isolation like optoisolater,transistor etc.

Another problem while dealing with MOSFETS is Floating.That is when you dont give any signal and supply is connected with D and S than sometimes they get heated and excess of heat burns them out.we need some extra protection circuit for that.

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Rikil Shah
B.Tech-2nd year,
Electronics Engineering
Sardar Vallabhbhai National Institute Of Technology,
India.

Currently working on ARM,AVR,PIC

My Official Blog:-www.rikil-svnit.co.nr

 

For setups like this i used simple transistor voltagedoublers
(when i had MCU to provide a clockpulse)
If i cant spare the MCU pin i use the same idea but with 555 as pulse generator .
(i attached both setups)
About your mosfets ,i would use all n-mosfets (and forget about irf540) .
Nowadays you have much better mosfets then irf540 .
I would look at something like irf1407 or something with simular or even lower RDSon .
Just have a look at the IRF website and look for mosfets for synchronous rectification .
This will save you a lot of heat in the mosfets and reduce the amount of heatsinks .
About your gatedriver ,you can either use a gatedriver ic like the ir21xx and keep the bootstrap capacitor charged with a chargepump .
(IRF has application notes on this topic)
http://www.irf.com/technical-info/appnotes/an-978.pdf
Or just build it discrete with a few transistors for levelshifting and gatedriving .
Both methods would do the job reliable and simple.
Good luck .

Attached Thumbnails

   

 

Hi,

I posted this on a different thread but in case you didn't see it perhaps it will be useful.

I found this chip (VNH2SP30) used by robot hobbyists. It's an H-bridge originally used in cars to driver power windows and the like. It's rated at 30A burst and about 14A continuous with no heat sink. Pololu sells carrier boards if you don't want to do surface mount. I bought some from Digikey for about $15 (CAD).

Pololu - VNH2SP30 Motor Driver Carrier MD01B

Dr Iguana