how to bootstrap using transistors
Hello,
I am seeking a “Bootstrap” High and Low side gate driver IC for driving the transistors of a (240V mains input) two-transistor-forward-converter.
I have searched many fab houses www sites and find that they have no off-the-shelf offerings for this, -they only do them for half or full-bridge topologies.
I appreciate that I could augment their offerings by adding additional circuitry, -but the amount of additional circuitry is such that it wouldn’t be worth doing,
-and it would be better to just use a pulse transformer high side drive instead.
The IC that I seek (if it exists) would simply receive the single gate drive signal from my PWM controller, and drive the FETs ON/OFF in synchrony, it would also need to provide a third gate drive signal for a Lo side “bootstrap high side capacitor ‘refresh’ transistor”.
-this transistor would simply come ON some 300ns after the two “main” FETs have gone off, -and then go off a settable delay time after it came ON.
I cannot simply use a single bootstrap high side driver…….because…..
The problem with using a single high side driver to just drive the upper transistor, is that during light load times, the low side “demagnetisation” diode would not conduct for long enough to allow the high side bootstrap capacitor to sufficiently re-charge.
Does any reader know of a suitable “bootstrap Hi & Lo side driver IC for a two-transistor-forward-converter?
Its such a common topology that I am amazed none of the fab houses I’ve googled have anything.