Dear Andy, LF group,
To a reasonable approximation, the voltages in the tank circuit, and
the guard circuit, will vary in direct proportion to the supply volts for
a given value of load impedance. This should hold provided the
forward voltage drop of the guard circuit diodes, and the voltage
drop across the "on" Mosfets is much smaller than the supply
voltage. So the guard circuit will operate at a particular impedance
level, rather than a particular power/current/voltage level as with
most overload protection.
So one way to experiment with this type of circuit whilst minimising
explosions would be to run the amp at a much lower supply voltage,
say 34V - reducing the energy and power dissipation everywhere
by a couple of orders of magnitude. Of course, in a circuit full of
non-linear components, waveforms (eg. gate drive) will change a
bit, and adjustments are bound to be needed when the full supply is
restored, but it should be a good starting point. You could use
cheaper low voltage components for the initial experiments, too.
Cheers, Jim Moritz
73 de M0BMU
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