[AMPS] Bridge vs. Doubler

[David A. Pruett]

Regarding the question of the preferred HV P/s design, a full wave bridge
vs. a doubler, I think the nod goes to the brdige for several reasons.

First, I think the G3RZP comment about higher peak currents refutes AG6K's
comment about wire size. If the currents were equal, Rich would be correct
- however the transformer currents are not equal for a given output load
current.  Conservation of energy applies, so if the rectifier circuitry
raises the output voltage, the input current must increase.  The analogy is
somewhat equivalent to an impedance matching transformer.

Second, the voltage doubler circuits typical to ham amplifiers are in
reality two half-wave circuits with the outputs stacked.  The percent
voltage regulation for a full wave bridge is significantly superior to a
half-wave circuit.  Two half-wave rectifiers are not going to be superior
to a full wave bridge if regulation is the criteria.

IMHO, either circuit will work fine with the appropriate transformer. 
There may be other factors too - for example, if your filter cap is a
single oil-filled unit, I don't see how you can use a doubler without
buying another, identical cap.  On the other hand, the rectifiers in a
doubler only carry half the current so this might allow some flexibility in
component sizing.

Hmmm...with regards to my posting a week ago about 2A diodes to run two
amps off one supply, has anyone tried running two rectifiers off one
transformer to power two amps?  My engineering intuition tells me that
there might be a problem with a FWB, because if you look real close certain
diodes will wind up in parallel.  However, if the two rectifiers were half
wave this would not occur.  The idea of using half-wave vs. full wave might
sound like heresy, but if it works OK in doublers why would it not be
suitable in a single rectifier?  Negative lead metering of plate current
would be still be possible too.

Comments?

73,

Dave/K8CC


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