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Please help me pick a diode

Y

Yzordderex

Jan 1, 1970
0
I'm putting together a zvs phase shift full bridge circuit to be used
as a modulator to drive a Class E RF Deck for AM radio. I think this
would then be a one of a kind. It's basically a power supply with the
reference voltage driven by a microphone. 115vac input.

This is not a pie-in-sky design - controller boards are stuffed and
tested, magnetics are wound, and mosfets on heatsink. Just a few
steps before I begin smoke testing.

I need some advice for rectifier diodes. Transformer is center tapped
secondary. Output filter will of course be continuous mode. I am
worried about reverse recovery probs. The maximum output voltage
should be around 50v-60v at near 300w. RF deck looks like a 12ohm
load. Rectifier I have picked for this iteration is 150v dual
schottky. I realize that this is pushing the voltage limit on part,
but heatsink is gigantic, and duty cycle at full output is low. There
is no freewheel diode. I figure the current will freewheel through
the rectifiers. I might need a snubbers across rectifiers.

Oh yea, switching frequency needs to be over 100kHz (probably near
200) in order to be able to keep modulator bandwidth high and provide
the necessary filtering to keep switching components out of AM
sidebands.

Problem is my next iteration. I expect to do full 1.5kw pep which
equates to near 150v. Can't easily use schottkys at 150v. Can I use
ultrafast diodes for the rectifiers, and use a big 150v schottky as a
freewheel diode?

Beyond the diode question any comments welcome.

www.monkeypuppet.com

73
Bob
N9NEO
 
Y

Yzordderex

Jan 1, 1970
0
[email protected] (R.Legg) wrote in message
Thank you.

Looks like fairly new design - I'm not familiar with the technology.
Seems a rather strange species, but should work out nicely. At first
glance looks like a large Vth, and slope resistance. Ifsm and I^2t
rather low, but often times with these new parts data sheet doesn't
really reflect part. Not going to be stressing I^2t, so not a
concern. Also, large spread in leakage current with reverse voltage
applied.

I'll try some out and let you know.

best regards,
Bob
N9NEO
 
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