A series regulated power supply

Hi Power-U,

Its taken me a while to see the sense in this design.
And for those who still dont follow it,
i will try to say how i see it.

And those who can see clearly how it works,
you should have explained it by now.

So here goes,
The 220 MFD on the base of the output Tr would seem
to me to be there to provide a 'rise time' of about
two seconds from zero to output.

Now the regulation.
Not a method i would have chosen, but it looks workable,
the emitter of the driver or secondary transistor has
the stabilised voltage of 5.8 volts from the zener
diode which also has a 1.2k to supply, probably to
maintain a minimum current through it.
The output voltage has a 'divider' across it, the 820
ohms and the 1k which should put about 6.5 volts on to
the base of the driver transistor, it is this voltage
which is the stabilising sensitive part.
Any attempted change here, would be reflected in the
driver transistor altering its current, until the
voltage on its base assumes a balance with its emitter.

Now that i can see the action of the circuit,
it seems quite reasonable.

If your first smoothing caps are getting burst,
then you are either applying too much voltage,
or the polarity is not clearly marked on them.
And check the voltage,
it might be higher than you think.
As Sebi says, the AC measurement is lower than the
peak, which is what your caps will charge to, add a
little for spikes, and double is about right for the
working voltage you want here.

One advantage of this arrangement comes to mind,
that the zener is run from the stabilised side.
When working properly this arrangement should
give a very tight voltage control, IMO.

Any control is of course shot away by having
that variable in the supply line,
i guess that is temporary.

You could also double check your bridge, error
here could put ac to your first smoothing cap.

Best of luck with this,
i would like to know how stable it is
from none to full load when its working.

Regards, John

The secondary voltage = 28.5v.
THanks again again John 1, but could you or anyone else reading this please tell me where I put the ammeter for the load current, as my teacher sya that I put it after the O/P of the circuit, and a good electronics book to read about regulation for a series power supply.

Hi,

Yes you could put it in one of the output leads,
but then its in the way of the regulating.

Could you do me a little favour, could you press
enter with slightly shorter lengths, panning left and
right is tiresome. Thanks.

Regards, John

how about putting the amp meter before the regulator transistor?

Hi,

That would work just as well of course,
but the quiescent current would still be there,
and the same would apply, to remove it by
adjusting to zero at no load, if it can.

Some people like meters to have one connection
on the ground/chassis.

Cheers, John

still dont get something....what is the 0.09K=90r veriable resistor for...because there will be lots of power lost on it....

0.09K is the set value of the pot. and not its max. value. I think he has used a 1K pot.

That is temporary,
(well i expect it is)
he has a problem with the main supply capacitor(s)

He was asked the secondary AC voltage,
he has said its 28.5 volts, but he did not say
if thats a DC reading or an AC reading.

If its an AC reading, then i would expect the caps
to be around 100 volt DC working, If its a DC
reading i would use 50 volt capacitors.

I might be a touch high in my approximation here,
but i am used to using older second hand rubbish.

I would be interested to read what others think.

Regards, John

The Vr is temporary, the 28.5v is ac.
As i have to writ about the regulation module in my
project, could anyone give me some bullet points about
the regulation to write about. I have some allready like
measurements, and that it shoul stay the same even
if the current changes.