Anybody ever used the mosfet body diode as a rectifier?

h_a · 6th December 2010, 06:31 AM

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, 06:48 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, 09:26 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, 09:31 AM

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

krachkiste · 6th December 2010, 11:14 AM

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, 02:10 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, 07:41 PM

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

h_a · 8th December 2010, 09:24 AM

Hi,

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

WuYit · 8th December 2010, 11:58 AM

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).

6th December 2010, 06:31 AM	#1
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	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

6th December 2010, 09:31 AM	#4
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	You have also zero advantages but you could use it as a fun way of using mosfets. __________________ /Per-Anders (my first name) or P-A as my friends call me

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Body diode bypass, elegant way!	fredos	Class D	13	6th December 2010 09:19 AM
Test for blown body-diode in mosfet?	h_a	Solid State	2	29th June 2009 07:47 AM
Disabling MOSFET body diode...	RiskCord	Class D	49	30th May 2008 10:13 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

6th December 2010, 06:48 AM	#2
davidsrsb diyAudio Member Join Date: Dec 2005 Location: Kuala Lumpur	The parasitic "body" diode is nothing special on switching speed, in high speed switchers it can be a nuisance.

6th December 2010, 09:26 AM	#3
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Well, question is, does it last? Nothing worse than a blown bridge. If no crude problems are known, I guess I'll try it.

6th December 2010, 11:14 AM	#5
krachkiste diyAudio Member Join Date: May 2009	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.

6th December 2010, 07:41 PM	#7
WuYit Banned Join Date: Oct 2010	Hannes, it´s a very good idea. http://www.google.se/url?sa=t&source...6c8Eraq17YZ2PQ

8th December 2010, 09:24 AM	#8
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Hi, now that's fun stuff! Thanks for the link!

8th December 2010, 11:58 AM	#9
WuYit Banned Join Date: Oct 2010	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).

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)