DEC H744 +5 supply

Noel Chiappa jnc at
Fri Sep 21 15:03:11 CDT 2018

Oh, one thing I forgot to include:

    > a lot of the incoming power in that 30V AC has to be thrown away, in
    > producing +5V.

So, if my understanding is correct, the 'switching' H744 really isn't much
better than a classic linear supply. It still wastes a very large amount of
the input power, and it still has a massively heavy transformer in it. Yes?

So I wonder what exactly the advantage was in going to the switching approach?
Yes, it keeps the output voltage steadier then a pure linear supply could -
but I'll bet there are analog approaches that can do the same. (They'd need
something that can produce a steady reference voltage, but the switching
approach needs, and has, the same thing.) Maybe the main output transistors
are happier being full-on or full-off, or something like that?


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