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Triac SCR pre regulator
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Lee McLaren
Mon, 11 Sep 06 07:09:26 +0000
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
12 replies folowing
Tom Sefranek
Mon, 11 Sep 06 12:58:34 +0000
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
>
>


*
| __O Thomas C. Sefranek WA1RHP@ARRL.net
|_-\<,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

dicsEE
Mon, 11 Sep 06 13:52:58 +0000
 
Russell McMahon
Mon, 11 Sep 06 13:52:58 +0000
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?


Russell McMahon
Mon, 11 Sep 06 14:00:05 +0000
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
Steve Smith
Mon, 11 Sep 06 19:58:05 +0000
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: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 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
David VanHorn
Mon, 11 Sep 06 20:12:46 +0000
On 9/11/06, 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.



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.
Dwayne Reid
Mon, 11 Sep 06 21:25:44 +0000
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 .

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

Dwayne Reid
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax

Celebrating 22 years of Engineering Innovation (1984 - 2006)
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Vasile Surducan
Tue, 12 Sep 06 08:04:05 +0000
On 9/11/06, David VanHorn wrote:
> On 9/11/06, 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.
>
>
> 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
Lee McLaren
Tue, 12 Sep 06 11:15:26 +0000
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 wrote:
>
>> On 9/11/06, 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.
>>>
>> 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
>
Mark Rages
Tue, 12 Sep 06 11:33:06 +0000
On 9/11/06, 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?
>


The diagram for an HP power supply?

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

Regards,
Mark
markrages@gmail
You think that it is a secret, but it never has been one.
- fortune cookie
Steve Smith
Tue, 12 Sep 06 18:31:32 +0000
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: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 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 wrote:

> On 9/11/06, 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.
>
>
> 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
David VanHorn
Tue, 12 Sep 06 20:17:40 +0000
>
>
> > 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.
Steve Smith
Tue, 12 Sep 06 20:23:41 +0000
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: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 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.