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[EE] Triac / SCR pre regulator

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[EE] Triac / SCR pre regulator

Lee McLaren-2
I remember once seeing a circuit for a triac or SCR preregulator for a
DC power supply but can no longer find the circuit. It was in the form
of the bridge rectifier and used and error feedback from the output of
the final regulator so that the final regulator had a pre-set voltage
drop to keep power dissipation down.

Anyone seen such a thing?

regards

Lee McLaren
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Re: [EE] Triac / SCR pre regulator

Thomas C. Sefranek
I'll need to dig it up, but I have used this in power supplies before.

Lee McLaren wrote:

>I remember once seeing a circuit for a triac or SCR preregulator for a
>DC power supply but can no longer find the circuit. It was in the form
>of the bridge rectifier and used and error feedback from the output of
>the final regulator so that the final regulator had a pre-set voltage
>drop to keep power dissipation down.
>
>Anyone seen such a thing?
>
>regards
>
>Lee McLaren
>  
>

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Re: [EE] Triac / SCR pre regulator

apptech
Either Electronics Australia or ETI I think.
I'll almost certainly have the mag in my deeper dungeon  (that's the
one before the deepest dungeon) but finding it may be another matter.
If you can find the magazine details I could look.

Gargles.

EA & ETI indexes

    http://www.electronicsaustralia.com.au/cgi-bin/downloads.pl?area=4

EA projects list

        http://www.electronicsaustralia.com.au/files/ea_proj.txt

ETI projects list

    http://www.electronicsaustralia.com.au/files/eti_proj.txt


It could be this one, but it sounds too recent

        2/PC/61   Add-on Regulator for 12V Battery Chargers
HpH       Jul 97


EA projects  1965 on CSV zip

        http://www.electronicsaustralia.com.au/files/projects.zip




>>I remember once seeing a circuit for a triac or SCR preregulator for
>>a
>>DC power supply but can no longer find the circuit. It was in the
>>form
>>of the bridge rectifier and used and error feedback from the output
>>of
>>the final regulator so that the final regulator had a pre-set
>>voltage
>>drop to keep power dissipation down.
>>
>>Anyone seen such a thing?


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Re: [EE] Triac / SCR pre regulator

apptech
In reply to this post by Thomas C. Sefranek
SILICON CHIP PROJECTS & CIRCUITS PUBLISHED NOV 1987 TO AUGUST 2006

        http://us1.webpublications.com.au/static/downloads/articles/104804_Projects.txt

Says:

        SCR Pre-Regulator Circuit                         May 1997

___________________

SILICON CHIP PROJECTS & CIRCUITS PUBLISHED NOV 1987 TO AUGUST 2006

SUBJECT HEADINGS AND PCB PREFIX NUMBERS

AUDIO/HI-FI                       01
TV/VIDEO                          02
SECURITY (BURGLAR ALARMS, ETC)    03
TEST & MEASUREMENT                04
AUTOMOTIVE                        05
RADIO COMMUNICATIONS              06
COMPUTERS                         07
GAMES                             08
MODEL RAILWAYS/RADIO CONTROL      09
MAINS POWER CONTROL               10
BATTERY POWER (INVERTERS, FENCES) 11
TELEPHONES/FACSIMILE  12
PHOTOGRAPHY           13
BATTERY CHARGERS      14
REMOTE CONTROL        15
LASERS & LIGHTING
SAFETY
WOODWORKING
CIRCUIT NOTEBOOK
BACK ISSUES
PROJECT BOOKS

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RE: [EE] Triac / SCR pre regulator

smith steve
In reply to this post by Lee McLaren-2
Build them all the time...
1 phase 3 phase 6 pulse 12 pulse
Fully regulated from about 6v to 600v 150Va to 150Kva

What sort are you looking for ?

Phase angle controlled rectifier (UPS battery charger ect)

I saw a circuit recently that uses the area around the ZCO to charge a large
cap via a  FET / IGBT enabling 5V from 230vac with very small dissipation
also cant remember where???

Steve

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of
Lee McLaren
Sent: 11 September 2006 08:09
To: PIC List
Subject: [EE] Triac / SCR pre regulator

I remember once seeing a circuit for a triac or SCR preregulator for a
DC power supply but can no longer find the circuit. It was in the form
of the bridge rectifier and used and error feedback from the output of
the final regulator so that the final regulator had a pre-set voltage
drop to keep power dissipation down.

Anyone seen such a thing?

regards

Lee McLaren
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Re: [EE] Triac / SCR pre regulator

David VanHorn
In reply to this post by Lee McLaren-2
On 9/11/06, Lee McLaren <[hidden email]> wrote:
>
> I remember once seeing a circuit for a triac or SCR preregulator for a
> DC power supply but can no longer find the circuit. It was in the form
> of the bridge rectifier and used and error feedback from the output of
> the final regulator so that the final regulator had a pre-set voltage
> drop to keep power dissipation down.


I did that in a printer design, wasn't hard.  Basically, take a "light
dimmer" sort of circuit, and apply the output of a voltage comparator, so
that if your voltage is high enough, you skip the next half-cycle.  Bridge
rectifier on the front end, and SCR between that and the filter cap.
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RE: [EE] Triac / SCR pre regulator

Dwayne Reid
In reply to this post by smith steve
At 01:58 PM 9/11/2006, Steve Smith wrote:

>I saw a circuit recently that uses the area around the ZCO to charge a large
>cap via a  FET / IGBT enabling 5V from 230vac with very small dissipation
>also cant remember where???

You may be thinking of the ST (SGS Thomson) VIP family.

I rolled my own version long before I ever saw the ST parts: ** VERY
** low cost and (now) darned reliable.

Had some teething problems with about 1% of the first few hundred
units but got that solved by eliminating a single resistor.  Gotta
love it when simplifying the BOM improves reliability <grin>.

FWIW: my version supplies about -20V at 50 mA, that's further
regulated down to -5V for the PIC.  Circuit topology required that
everything be referenced to Vdd of the PIC - thus the negative rails.

dwayne

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Re: [EE] Triac / SCR pre regulator

Vasile Surducan-2
In reply to this post by David VanHorn
On 9/11/06, David VanHorn <[hidden email]> wrote:

> On 9/11/06, Lee McLaren <[hidden email]> wrote:
> >
> > I remember once seeing a circuit for a triac or SCR preregulator for a
> > DC power supply but can no longer find the circuit. It was in the form
> > of the bridge rectifier and used and error feedback from the output of
> > the final regulator so that the final regulator had a pre-set voltage
> > drop to keep power dissipation down.
>
>
> I did that in a printer design, wasn't hard.  Basically, take a "light
> dimmer" sort of circuit, and apply the output of a voltage comparator, so
> that if your voltage is high enough, you skip the next half-cycle.  Bridge
> rectifier on the front end, and SCR between that and the filter cap.

Maybe the SCR in front of the bridge on the AC path, or two thyristors
as half bridge and two diodes as other half bridge. Else how you fired
off the SCR as long there is no zero cross (or lower than sustaining
current of the SCR) current on the filter capacitor ?

Vasile
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Re: [EE] Triac / SCR pre regulator

Lee McLaren-2
The one I remember had 2 diodes and 2 scr's in the bridge rectifier,
very simple circuit, probably not a very regulated output but suitable
to feed into a series regulator to lower dissipation.

I will try to track down some of the articles  mentioned, I may have
some of the magazines mentioned.

The output from the final reg will be 80v 20-30 amps momentarily  and
15-20 amp average.


regards

Lee McLaren




Vasile Surducan wrote:

> On 9/11/06, David VanHorn <[hidden email]> wrote:
>  
>> On 9/11/06, Lee McLaren <[hidden email]> wrote:
>>    
>>> I remember once seeing a circuit for a triac or SCR preregulator for a
>>> DC power supply but can no longer find the circuit. It was in the form
>>> of the bridge rectifier and used and error feedback from the output of
>>> the final regulator so that the final regulator had a pre-set voltage
>>> drop to keep power dissipation down.
>>>      
>> I did that in a printer design, wasn't hard.  Basically, take a "light
>> dimmer" sort of circuit, and apply the output of a voltage comparator, so
>> that if your voltage is high enough, you skip the next half-cycle.  Bridge
>> rectifier on the front end, and SCR between that and the filter cap.
>>    
>
> Maybe the SCR in front of the bridge on the AC path, or two thyristors
> as half bridge and two diodes as other half bridge. Else how you fired
> off the SCR as long there is no zero cross (or lower than sustaining
> current of the SCR) current on the filter capacitor ?
>
> Vasile
>  
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Re: [EE] Triac / SCR pre regulator

Mark Rages
In reply to this post by Lee McLaren-2
On 9/11/06, Lee McLaren <[hidden email]> wrote:
> I remember once seeing a circuit for a triac or SCR preregulator for a
> DC power supply but can no longer find the circuit. It was in the form
> of the bridge rectifier and used and error feedback from the output of
> the final regulator so that the final regulator had a pre-set voltage
> drop to keep power dissipation down.
>
> Anyone seen such a thing?
>

The diagram for an HP power supply?

http://cp.literature.agilent.com/litweb/pdf/5959-5310.pdf

Regards,
Mark
markrages@gmail
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RE: [EE] Triac / SCR pre regulator

smith steve
In reply to this post by Vasile Surducan-2
Use a pair of diodes and a pair of thyristors... AC to the junction between
the series diodes and the other AC to the A/K junction between the
thyristors you get the flywheel diode for free then L,C filter shouldn't
need any further regulation if the control loop is good (it's a big battery
charger / PSU)

STeve

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of
Vasile Surducan
Sent: 12 September 2006 09:04
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Triac / SCR pre regulator

On 9/11/06, David VanHorn <[hidden email]> wrote:

> On 9/11/06, Lee McLaren <[hidden email]> wrote:
> >
> > I remember once seeing a circuit for a triac or SCR preregulator for a
> > DC power supply but can no longer find the circuit. It was in the form
> > of the bridge rectifier and used and error feedback from the output of
> > the final regulator so that the final regulator had a pre-set voltage
> > drop to keep power dissipation down.
>
>
> I did that in a printer design, wasn't hard.  Basically, take a "light
> dimmer" sort of circuit, and apply the output of a voltage comparator, so
> that if your voltage is high enough, you skip the next half-cycle.  Bridge
> rectifier on the front end, and SCR between that and the filter cap.

Maybe the SCR in front of the bridge on the AC path, or two thyristors
as half bridge and two diodes as other half bridge. Else how you fired
off the SCR as long there is no zero cross (or lower than sustaining
current of the SCR) current on the filter capacitor ?

Vasile
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Re: [EE] Triac / SCR pre regulator

David VanHorn
In reply to this post by Vasile Surducan-2
>
>
> > I did that in a printer design, wasn't hard.  Basically, take a "light
> > dimmer" sort of circuit, and apply the output of a voltage comparator,
> so
> > that if your voltage is high enough, you skip the next
> half-cycle.  Bridge
> > rectifier on the front end, and SCR between that and the filter cap.
>
> Maybe the SCR in front of the bridge on the AC path, or two thyristors
> as half bridge and two diodes as other half bridge. Else how you fired
> off the SCR as long there is no zero cross (or lower than sustaining
> current of the SCR) current on the filter capacitor ?



The SCR turns off when the output of the bridge won't keep enough current
into the filter cap.
There is not a zero-cross on the output of the bridge, but output current
DOES go to zero every half-cycle.
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RE: [EE] Triac / SCR pre regulator

smith steve
If you use inductive smoothing you need to recover the energy from the choke
hence freewheel diode. Make the choke big enough the current goes continious
and you can get to 200mV ripple in 120V with a single stage of L / C

STeve

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of
David VanHorn
Sent: 12 September 2006 21:18
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Triac / SCR pre regulator

>
>
> > I did that in a printer design, wasn't hard.  Basically, take a "light
> > dimmer" sort of circuit, and apply the output of a voltage comparator,
> so
> > that if your voltage is high enough, you skip the next
> half-cycle.  Bridge
> > rectifier on the front end, and SCR between that and the filter cap.
>
> Maybe the SCR in front of the bridge on the AC path, or two thyristors
> as half bridge and two diodes as other half bridge. Else how you fired
> off the SCR as long there is no zero cross (or lower than sustaining
> current of the SCR) current on the filter capacitor ?



The SCR turns off when the output of the bridge won't keep enough current
into the filter cap.
There is not a zero-cross on the output of the bridge, but output current
DOES go to zero every half-cycle.
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