Thyristor pre-reg for a Linear adjustable CV-reg

[Hr_Satch]

Hi, forum,
just to ellaborate on an 'older' topic I recently discovered:
a thyristor pre-reg, that limits the charging of a rectifier cap
as to limit the following CV-regulator's power heat dissip.
-- --
So it regulates the THY or SCR on the zero crossings of the ACV.
But isn't it adviced to switch a transformers' primary on the Peak Amplitude ;-?
Dixit Mr. Rod Elliot from Australia.
-- --
Seen a transformer's behaviour in the primary acts on the secondary;
but it also goes up the other way ;-?
-- --
So wouldn't it be better to trig the SCR (in the secondary)
also on the peak/amplitude of the sine voltage ?

Just an idea, Harry.

Moreover, istead of complicating me things: I'd rather rewind the secondary windings
to suit my purpose, to achieve minimum dissipation.
ofcourse this goes more up for fixed voltages.

I'd be pleased to see some older thread responders coming back up again, thanx.
 

[David Hess]

A thyristor pre-regulator implies some type of phase control and not just switching between transformer taps.

[PCB.Wiz]

Hi, forum,
just to ellaborate on an 'older' topic I recently discovered:
a thyristor pre-reg, that limits the charging of a rectifier cap
as to limit the following CV-regulator's power heat dissip.

How many amps & watts are we talking?

A bridge rectifier makes better use of transformer windings, so gives lower loss / more maximum power for a given transformer.

SCR’S are simpler-older tech, but they do drop about 1V, so much more than a mosfet bridge.
A modern design might choose a stky bridge and buck regulator, for lowest pcb heat budgets.

[Benta]

The design that David Hess shows is basically a 120 Hz, PWM controlled buck converter using SCR phase-angle control. Note the 1 mH inductor.
PWM is controlled by the gate firing transformer and the feedback circuit.

Very old school and not really relevant today IMO.

[Konkedout]

I agree that it is not very relevant.

Many years ago I did design a medical grade battery charger which used SCR phase control regulation in the output circuitry.  This output did not need to be filtered.

But if you want to preregulate ahead of a linear regulator, I think it makes a lot more sense to use one of many buck switching regulators that are available.  Those can be implemented with fewer parts and probably lower cost.