Finally a solution to high voltage hi side drive...

[cupoftea]

Hi,
Why is the attached not the de facto method for Offline (post PFC) Two Transistor Forward?
(LTspice sim and jpeg attached)

It shows a heavily damped gate drive, which gains power from a pulse transformer hi side supply. The gate driver used is in fact a 2ED2109…a high voltage Bootstrap driver…..though you can note that its not used in Bootstrap mode. The fact is that the use of active electronics in hi side drive is severely non-recommended, so therefore, a chip that can handle the wildly changing B and E fields is needed…hence the 2ED2109…the best in the business.

Straight Bootstrap drives are just too dodgy for 400V input SMPS converters. This is well documented. Straight pulse transformer hi side drives are dodgy also…because there LC’s ring and can cause trouble…eg if gate drive very suddenly goes to zero duty, the ringing can bring a hi side FET on spuriously and cause shoot-through, or loss of transformer reset in some cases.

So why is the attached not more common…?...why are the semico’s not working on chipsets for this?

 

[dick_freebird]

No doubt there are chipset developments galore, but the meat
of the market probably lies elsewhere.

If this part has particular goodness but (say) wants a SiC MOSFET
or a GaN FET (or GaN/MOS cascode) then that's more like an
opportunity as these lack so many drive alternatives.

I've seen pulse drive + custom IC in a PFM resonant converter
family, big name. Kinda clever, kinda twitchy for my liking though.
And we're not talking kV, more like "aircraft 28". Something that
can ride out a fat ol' MOSFET's high side dV/dt might not at
what GaN vendors like to brag can be done. Maybe no good for
narrow pulse or something. Why not give the datasheet and any
app notes a read and tell -us-?

 

[cupoftea]

Thanks, by the way, the bit in the top post about needing to use the 2ED2109 because its used to that kind of high dv/dt environment, is what it says in an App Note.....but i am sure most would agree that a standard gate drive IC can be used in the hi side. (ie, when its fully located , only in the hi side).