Searching \ for '[EE]: Shunt Regulator' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=shunt+regulator
Search entire site for: 'Shunt Regulator'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Shunt Regulator'
2001\01\25@173005 by Thomas McGahee

flavicon
face
part 1 338 bytes content-type:text/plain; (decoded 7bit)

For those that like to make their own circuits instead of
buying them pre-packaged, I offer the attached GIF of a simple
shunt regulator circuit that I use as a zener replacement.

If you use a power transistor and adequate heat sink, you will
have the equivalent of a power zener.

Fr. Thomas McGahee


part 2 29510 bytes content-type:image/GIF; (decode)


part 3 136 bytes
--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email spam_OUTlistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body


2001\01\25@183149 by Olin Lathrop

face picon face
> For those that like to make their own circuits instead of
> buying them pre-packaged, I offer the attached GIF of a simple
> shunt regulator circuit that I use as a zener replacement.
>
> If you use a power transistor and adequate heat sink, you will
> have the equivalent of a power zener.

A possible improvement to your circuits would be to use a real zener as the
voltage reference.  You are implicitly using the base-emitter voltage of the
first transistor as a voltage reference.  This will provide regulation, but
is very dependent on temperature and current.  An easy way to add the zener
is to put it in series with the emitter of the first transistor.  The B-E
junction is still in there, but will be a lower fraction of the overall
voltage reference.  The down side is that the overall clamping voltage can
not be lower than the zener plus the B-E junction voltage.  Other topologies
can use just the zener as the reference, but those are significantly
different from what you showed.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, .....olinKILLspamspam@spam@embedinc.com, http://www.embedinc.com

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamKILLspammitvma.mit.edu with SET PICList DIGEST in the body


2001\01\25@213535 by rottosen

flavicon
face
See comments below.


Olin Lathrop wrote:
{Quote hidden}

The B-E diode has a temperature coefficient of about -2.1mv/deg C.  If
we assume that the forward voltage is 0.7v then that works out to be
about 0.3%/deg C.

The equivalent dynamic impedance should be about 25mv/ma. This would be
about 250 ohms at 0.1ma of base current. Not real good.



>  An easy way to add the zener
> is to put it in series with the emitter of the first transistor.  The B-E
> junction is still in there, but will be a lower fraction of the overall
> voltage reference.  The down side is that the overall clamping voltage can
> not be lower than the zener plus the B-E junction voltage.


Trivia time. I seem to remember that the best reference zener diodes
(either 6.2 volt or 8.2 volt, I think) are actually a zener diode in
series with a signal diode. This is done so that the temperature
coefficients of the 2 diodes cancel out. Does anyone else remember the
same thing?


-- Rich


{Quote hidden}

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body


2001\01\26@045117 by Alan B. Pearce

face picon face
>Trivia time. I seem to remember that the best reference zener diodes
>(either 6.2 volt or 8.2 volt, I think) are actually a zener diode in
>series with a signal diode. This is done so that the temperature
>coefficients of the 2 diodes cancel out. Does anyone else remember the
>same thing?

Nearly correct. The 6V point is the nominally 0 temp coefficient, but it is not
done by putting a diode in series with it. It has more to do with the zener
mechanism inside the diode. Below 6V there is a different process in the way the
majority carriers move in the silicon to the way they move above 6V. I guess it
is related to the processing to achieve the zener action.

Anyway the important thing is that one process has a positive temp coeff, and
the other has a neg coeff. You will find all zeners below 6V will have one temp
coeff and above 6V they have the opposite, but by happy circumstance the
manufacturing process uses both processes to achieve the 6V breakdown and hence
the temp coeff cancel.

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestKILLspamspammitvma.mit.edu


2001\01\26@130605 by Harold M Hallikainen

picon face
On Thu, 25 Jan 2001 19:34:19 -0700 Richard Ottosen <KILLspamrottosenKILLspamspamIDCOMM.COM>
writes:
>
> Trivia time. I seem to remember that the best reference zener diodes
> (either 6.2 volt or 8.2 volt, I think) are actually a zener diode in
> series with a signal diode. This is done so that the temperature
> coefficients of the 2 diodes cancel out. Does anyone else remember
> the
> same thing?
>

       I STILL like the LM399H. http://www.national.com/pf/LM/LM399.html
Looking at my old drawings, I first designed it into a circuit in 1978.
It's tempco is .0002%/degree C (2ppm/degree C). I then spent a couple
bucks each for resistors with a 5ppm/degree C tempco to divide the 6.95V
reference down to what my A/D needed. I'd always thought National
should've made the chip with voltage divider resistors on the chip where
they'd be in a constant temperature environment...

Harold


FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
dl.http://www.juno.com/get/tagj.

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu


2001\01\26@132350 by Scott Dattalo

face
flavicon
face
On Fri, 26 Jan 2001, Harold M Hallikainen wrote:

> On Thu, 25 Jan 2001 19:34:19 -0700 Richard Ottosen <spamBeGonerottosenspamBeGonespamIDCOMM.COM>
> writes:
> >
> > Trivia time. I seem to remember that the best reference zener diodes
> > (either 6.2 volt or 8.2 volt, I think) are actually a zener diode in
> > series with a signal diode. This is done so that the temperature
> > coefficients of the 2 diodes cancel out. Does anyone else remember
> > the
> > same thing?
> >
>
>         I STILL like the LM399H. http://www.national.com/pf/LM/LM399.html
> Looking at my old drawings, I first designed it into a circuit in 1978.
> It's tempco is .0002%/degree C (2ppm/degree C). I then spent a couple
> bucks each for resistors with a 5ppm/degree C tempco to divide the 6.95V
> reference down to what my A/D needed. I'd always thought National
> should've made the chip with voltage divider resistors on the chip where
> they'd be in a constant temperature environment...


I concur. However, to obtain that very stable tempco, the LM399 has a heater to
keep the silicon junction at a relatively constant temperature. Keep this in
mind for those low power applications.

Scott

--
http://www.piclist.com hint: To leave the PICList
TakeThisOuTpiclist-unsubscribe-requestEraseMEspamspam_OUTmitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...