Quote Originally Posted by batee
A capacitor pump of +12V referenced to the center of the bridge allows the top FET to turn on. I tried it at +170V top, 0V bottom and it works great, but agree the 700V would exceed its ratings.

Why generate a split source to power the inverter? I've not seen that done before. It seems like the cost of the copper and the extra DC link capacitor outweighs the cost of a couple of extra transistors.

If you're custom-winding a transformer to achieve this, can't you just add a tap at +/- 350V and another at +/- 360V to allow a simple level shifter transistor to turn on top FET?
Problem is U haven't caught the thread! We are discussing eliminating
bulky 50Hz transformer for Inverter/UPS. Now there are upteen circuits with psudo sinewave output which are not upto mark in many situations like
running fans. What I have been proposing that instead of using PWM for
sinewave generation from battery there should be high frequency DC to DC
converter and the PWM drive the Half Bridge ckt. Now the load can be connected to output of inverter or normal mains supply just by switching
with relay and referenced to Neutral. Also if U don't want to switch then
U just arrange for proper battery charger and keep inverter always on making
online UPS.
I have found that the transformer costs whopping Rs.1200/- and weighs
more than 7kgs for 500VA output. On the other hand whole inverter costs as
much that amount as we use Ferrite txr of small size operating at 40KHz.
Instead of costly driver ICs one should use Pulse transformer as they cost
just Rs.12 and have 2 windings also. I just checked cost of 800V mosfet which is 6-7 times costly than 600V type 6N60. So what I think that in this
case 2 Mosfets in serries in one leg of HalfBridge would work well with pulse
transformer having 2 secondary windings.