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Whats the reason for the diodes on those two mosfets in the inverter?enter image description here

Link: http://inductionheatertutorial.com/inductionheater/inductionschematic.gif

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    \$\begingroup\$ Are you talking about D3 and D4? There's a lot of diodes here. \$\endgroup\$ – KingDuken Jul 26 '18 at 14:23
  • \$\begingroup\$ You should include the circuit image directly in the post in case the link breaks \$\endgroup\$ – Jim Jul 26 '18 at 14:23
  • \$\begingroup\$ only D3 they are marked the same. \$\endgroup\$ – Eric B Ahapaid Jul 26 '18 at 14:23
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    \$\begingroup\$ Please refer them by their designators. If you add parallel diodes which are faster, you may need to block out the body diodes with external (normally schottky) diodes. It’s unusual but not unheard of. I used that on my SSTC. \$\endgroup\$ – winny Jul 26 '18 at 14:38
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    \$\begingroup\$ @winny Huh... Interesting... I was expecting lossy behavior if you zoomed it. \$\endgroup\$ – KingDuken Jul 26 '18 at 14:58
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enter image description here

The MOSFETs have very slow (circa 1 us reverse recovery) bulk diodes so putting a schottky diode (65PQ015) in series with the drain stops the slow reverse recovery playing a role but, you do need diodes so the MUR1560s do this job and they have a reverse recovery of 60 ns. It's probably all about getting a few percent more efficiency from the half bridge when it drives the load induction coil.

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    \$\begingroup\$ That’s what I said! :-) \$\endgroup\$ – winny Jul 26 '18 at 14:45
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    \$\begingroup\$ @winny so you did. No plagiarism intended dear chap. Honest I was looking at data sheets and not comments! \$\endgroup\$ – Andy aka Jul 26 '18 at 14:49
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    \$\begingroup\$ No worries mate :-) \$\endgroup\$ – winny Jul 26 '18 at 14:51

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