Hi Chris,
A H bridge can handle the 320V DC much easier. It is a question of the
availability of high voltage rated MOSFETs. In a H bridge you can use
normal 500V types, like the cheap IRFP460A. For the design you chose you
will need 1000V FETs. They are available nowadays. So just try it if you
like :-)
I never used gate resistors in front of my FETs. Oh, no, thats wrong. I
used 1 Ohm resistors to flatten the oscillation that appears on the L to
H edge. But this was in the H bridge only where i have to use gate
transformers. For hard switched FETs you don't need them (even if others
tell you to you do!) :-)
73, Stefan
Am 25.11.2016 14:56, schrieb Chris Wilson:
25 November 2016
I have built a 1kW Class D amp for none linear digital transmissions
around 136kHz.
My Dave Pick designed amp uses four MOSFETS, two in parallel each side
driven by a dedicated driver chip. I see the odd LF amp design using
what's described as a H Bridge MOSFET array. The one I most recall
most, by Andy Talbot used rectified 240 volt single phase mains to run
it. My question is why use an H Bridge rather than paralleling more
MOSFETS in what to me is a more conventional format? Does it overcome
voltage or current limitations? Is it due to adding more capacitance
with paralleled devices? Or does it allow a linear amp to be built?
I realize a meaningful reply might be quite lengthy, so I assure you I
have Googled it, but most stuff related to in the articles is
industrial motor control.
Secondly, in a Class D none linear amp, how is the gate resistor value
chosen, and is there ever a case for not using one at all?
Thirdly, am I alone in thinking the terms Drain and Source seem back
to front and the names would intuitively be reversed so a Drain was
called a Source and vice versa? :)
Thanks. 2E0ILY
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