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-   -   Anybody ever used the mosfet body diode as a rectifier? (http://www.diyaudio.com/forums/solid-state/178588-anybody-ever-used-mosfet-body-diode-rectifier.html)

h_a 6th December 2010 07:31 AM

Anybody ever used the mosfet body diode as a rectifier?
 
Hi,

I was tinkering with the idea to build a bridge rectifier from mosfets, or more exactly from their internal body diodes.

Datasheets suggest these are pretty sturdy, though not terribly effective due to large forward voltage. Should do well for low power stuff at least.

Anything I'm missing here?

Have fun, Hannes

EDIT: I just remembered these diodes are commonly used in switching stuff, but if I'm not mistaken only for short pulses. Rectifying 50Hz is eternity in comparison ;)

davidsrsb 6th December 2010 07:48 AM

The parasitic "body" diode is nothing special on switching speed, in high speed switchers it can be a nuisance.

h_a 6th December 2010 10:26 AM

Well, question is, does it last?

Nothing worse than a blown bridge.

If no crude problems are known, I guess I'll try it.

peranders 6th December 2010 10:31 AM

You have also zero advantages but you could use it as a fun way of using mosfets.

krachkiste 6th December 2010 12:14 PM

I would concider it, if mosfets were significantly cheaper, than the dedicated integrated bridge rectifiers that I normally use.

The question is, how "big" must the mosfet be, that its body-diode can handle the startup burst currents in standard powersupply setups with capacitor loaded rectifiers.
Thats one thing rectifier diodes are specifically suited for - handling the large peak currents with low rms in these circuits.

If there are already mosfets involved one could start thinking about a way to controll their gates to minimize conduction losses in a standard 50/60Hz rectifier application.

h_a 6th December 2010 03:10 PM

Hi P-A!

Long time no see ;)

Quote:

You have also zero advantages
Well, you know...my advantage is I don't have to buy them, I already have 'em.

The big package is a nice bonus, too.

Problem is, the body diode is usually not well documented. For your average IRFP240 max continous diode current is 20A, but no peak/surge values given.

As I said, I guess it would work well for lower power stuff.

@krachkiste:

Sure one could do a more clever way of rectifying. I think something like this was already tried, but probably efforts were limited.

WuYit 6th December 2010 08:41 PM

Hannes,
its a very good idea.
http://www.google.se/url?sa=t&source...6c8Eraq17YZ2PQ

h_a 8th December 2010 10:24 AM

Hi,

now that's fun stuff! Thanks for the link!

WuYit 8th December 2010 12:58 PM

Hannes,
it is my firm conviction that using MOSFETs as a diode is well worth the effort, a noticeably cleaner high frequency performance is to be expected due to smoother switching characteristics (much less nasty spikes).


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