Olin said
> Frankly Russel, this is getting a bit tedius.
etc etc .....

Sorry about LH & RH confusion - I got one wrong at one point.
LH = left hand and RH = right hand - not necessarily obvious to people who
speak English as a second language.

As I said -

> > do note its "thought experiment" status

and

> > The circuit will definitely need work

That said, I believe that it's not as bad as you seem to think.
However, rather than traipsing through a detailed series of counterpoints
and rebuttals, I will build one at some stage and report on the working (or
not :-) ) circuit. A few brief comments only given below.

As I noted - there are various simplifications which may well prove
unjustified in practice.
This circuit is less likely to be useful than my original 3 transistor buck
only circuit.

As discussed repeatedly lately, hysteresis is present but not by normal
static means.
This can be increased (and established more formally) with a capacitor at
the junction of ZBUK1 and RBUK1.
You can certainly defeat the hysteresis mechanism by suitable "design
decisions".

The reason for the varying length but consistent naming scheme is that the
long names come from the original cicruit whereas the short names are more
recent changes.  In any future circuits I will rename all parts with the
same system.

The diagram with D3 added is simplified. I realise that there are back paths
through the zeners which can be corrected with extra diodes. I noted that a
hold-off mechanism would be needed. The point was that D3 provides the
hold-off mechanism need to discharge the inductor fully. Exact
implementation will obviously differ from this.

I'll let you know when / if I have a working version to demonstrate :-)
Not liable to be in the immediate future alas.




regards

            Russell McMahon

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