[Amps] switching power supply for tube amplifier

[David Cutter]

Manfred

My personal problems with stabilising (I have limited experience in this 
design area) are:

adding regulation means putting an inductor in the output and as a 
consequence getting the phasing/feedback correct for all possible 
conditions:  fine for steady no-load up to full load conditions, but for all 
the ssb and cw combinations I would need help.  I would be interested to 
know what the extreme combinations were in your  design.  Did you just make 
the feedback loop longer time constant than the ssb/cw loadings?  After all, 
how much ripple is tolerable to a power amplifier?

at higher voltages, there "seems" to be less need for good regulation for 
fixed mains input voltage, more need for stabilising against mains 
variations, eg using a generator or at the end of a long ac distribution 
network at a farm for instance.

without switching regulation a smaller output capacitance (smaller size and 
weight) is needed as the guard band is very small compared to the triangular 
dip when using an inductor

Your experience would be helpful

On the subject of insulating the rf and control stages rather than the mains 
voltage stages:  I'm very glad to hear someone of your experience suggest 
this; I have been greeted with incredulity and disdain (not on this list). 
In my work on MW power supplies to the mining and steel industries, it's the 
controllers and final output device (motors, furnaces, etc) which are 
insulated, I don't see why suitable insulation systems cannot be designed 
for rf stages.  At the other end of the power scale, this was also an 
approach taken in medical monitoring when I was in that field.

David
G3UNA
>
> In any case, a switching power supply without voltage regulation is
> pretty stupid. Adding voltage regulation costs almost nothing, compared
> to the cost of the power components which need to be there in any case.
> This is very different from a linear supply, in which the addition of
> regulation means adding lots of parts, which are expensive and generate
> lots of heat and thus lots of loss.
> >
> A REALLY advantageous active device
> would be one that can work directly off the line voltage! Insulation
> from the line would then be accomplished in the input and output RF
> transformers, making the whole amplifier MUCH lighter and less expensive.
>