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Power supply topology question ...

Could some electronics guru please shed some light on the following. The standard topology for a linear regulated power supply is basically as follows: isolation step-down transformer | v rectifier(bridge or 2 - diode) | v capacitor ripple filter bank | v voltage regulator | v capacitor ripple filter bank | V Let us suppose that the transformer is a step-down 9 - 0 - 9 1 Amp output device.

Now suppose I want to get two 1 Amp outputs by having a 9 - 0 -9 2 Amp transformer and splitting its output equally with resistors as : isolation step-down transformer | | v v resistor resistor | | V V rectifier etc., rectifier etc., Is this a valid topology ? Or should there be two 9 - 0 - 9 1 Amp isolation transformers connected to the common Ac wall input, and then parallel topology as above, without the resistors. Any thoughts, suggestions would be appreciated. Thanks in advance.

Reply to
dakupoto
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a 9-0-9 2A transformer is probably sufficienctly oversized

use one transofrmer, one rectifier, and one input capacitor bank. double up the regulators and everything downstream.

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Reply to
Jasen Betts

Draw the circuit with the ground/return(s). That, coupled with a clear definition/specification of your objective should give you the answer.

Reply to
mike 

--
No.  

Neglecting the transformer's regulation, whether the transformer is 
rated 9V-0V-9V at 1 or 2 (or 100, for that matter) amperes, the load 
will only take what it needs since the secondary voltages are 
identical and the resistor will drop the voltage into the rectifiers 
depending on the load.
Reply to
John Fields

On Mon, 04 Nov 2013 05:55:27 -0600, John Fields wrote:

Version 4 SHEET 1 880 920 WIRE -2000 -16 -2144 -16 WIRE -1632 -16 -1808 -16 WIRE -1440 -16 -1632 -16 WIRE -1632 16 -1632 -16 WIRE -1440 16 -1440 -16 WIRE -2000 112 -2000 -16 WIRE -1808 112 -1808 -16 WIRE -2144 128 -2144 -16 WIRE -1632 128 -1632 80 WIRE -1568 128 -1632 128 WIRE -1440 128 -1440 80 WIRE -1440 128 -1488 128 WIRE -1632 176 -1632 128 WIRE -1632 176 -1680 176 WIRE -1440 176 -1440 128 WIRE -1392 176 -1440 176 WIRE -1680 208 -1680 176 WIRE -1632 224 -1632 176 WIRE -1568 224 -1632 224 WIRE -1440 224 -1440 176 WIRE -1440 224 -1504 224 WIRE -1632 272 -1632 224 WIRE -1440 272 -1440 224 WIRE -2144 368 -2144 208 WIRE -2000 368 -2000 192 WIRE -2000 368 -2144 368 WIRE -1936 368 -2000 368 WIRE -1808 368 -1808 192 WIRE -1808 368 -1856 368 WIRE -1632 368 -1632 336 WIRE -1632 368 -1808 368 WIRE -1440 368 -1440 336 WIRE -1440 368 -1632 368 WIRE -1632 480 -1808 480 WIRE -1440 480 -1632 480 WIRE -1632 512 -1632 480 WIRE -1440 512 -1440 480 WIRE -1808 608 -1808 480 WIRE -1632 624 -1632 576 WIRE -1568 624 -1632 624 WIRE -1440 624 -1440 576 WIRE -1440 624 -1488 624 WIRE -1632 672 -1632 624 WIRE -1632 672 -1680 672 WIRE -1440 672 -1440 624 WIRE -1392 672 -1440 672 WIRE -1680 704 -1680 672 WIRE -1632 720 -1632 672 WIRE -1568 720 -1632 720 WIRE -1440 720 -1440 672 WIRE -1440 720 -1504 720 WIRE -1632 768 -1632 720 WIRE -1440 768 -1440 720 WIRE -2000 864 -2000 368 WIRE -1936 864 -2000 864 WIRE -1808 864 -1808 688 WIRE -1808 864 -1856 864 WIRE -1632 864 -1632 832 WIRE -1632 864 -1808 864 WIRE -1440 864 -1440 832 WIRE -1440 864 -1632 864 FLAG -1680 208 0 FLAG -1680 704 0 FLAG -1392 176 OUT1 FLAG -1392 672 OUT2 SYMBOL ind2 -2016 96 R0 WINDOW 0 45 47 Left 2 WINDOW 3 45 79 Left 2 SYMATTR InstName L1 SYMATTR Value 50 SYMATTR Type ind SYMATTR SpiceLine Rser=,1 SYMBOL voltage -2144 112 R0 WINDOW 3 24 104 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value SINE(0 170 60) SYMATTR InstName V2 SYMBOL ind2 -1792 208 R180 WINDOW 0 42 73 Left 2 WINDOW 3 48 42 Left 2 SYMATTR InstName L2 SYMATTR Value .5 SYMATTR Type ind SYMBOL res -1472 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName RL1 SYMATTR Value 16 SYMBOL diode -1456 16 R0 WINDOW 0 -38 34 Left 2 WINDOW 3 -98 -1 Left 2 SYMATTR InstName D3 SYMATTR Value MURS320 SYMBOL diode -1648 272 R0 WINDOW 0 -38 34 Left 2 WINDOW 3 -96 72 Left 2 SYMATTR InstName D2 SYMATTR Value MURS320 SYMBOL diode -1616 80 R180 WINDOW 0 42 34 Left 2 WINDOW 3 24 69 Left 2 SYMATTR InstName D1 SYMATTR Value MURS320 SYMBOL diode -1424 336 R180 WINDOW 0 42 32 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D4 SYMATTR Value MURS320 SYMBOL ind2 -1792 704 R180 WINDOW 0 40 67 Left 2 WINDOW 3 45 40 Left 2 SYMATTR InstName L3 SYMATTR Value .5 SYMATTR Type ind SYMBOL res -1472 608 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName RL2 SYMATTR Value 16 SYMBOL diode -1456 512 R0 WINDOW 0 -38 34 Left 2 WINDOW 3 -98 -1 Left 2 SYMATTR InstName D7 SYMATTR Value MURS320 SYMBOL diode -1648 768 R0 WINDOW 0 -38 34 Left 2 WINDOW 3 -96 72 Left 2 SYMATTR InstName D6 SYMATTR Value MURS320 SYMBOL diode -1616 576 R180 WINDOW 0 42 34 Left 2 WINDOW 3 24 69 Left 2 SYMATTR InstName D5 SYMATTR Value MURS320 SYMBOL diode -1424 832 R180 WINDOW 0 42 32 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D8 SYMATTR Value MURS320 SYMBOL res -1840 352 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 1G SYMBOL res -1840 848 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 1G SYMBOL polcap -1504 208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 10000µ SYMBOL polcap -1504 704 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10000µ TEXT -2136 400 Left 2 !.tran 1 TEXT -1984 80 Left 2 !K1 L1 L2 L3 1 TEXT -2160 432 Left 2 ;JOHN FIELDS TEXT -2160 464 Left 2 ;04 OCT 2013

Reply to
John Fields

The resistors are unnecessary.

If you don't need it to be isolated, just make a 2A supply and hook the loads up in parallel.

I think you fail to understand the distinction between the current _rating_ on a supply and the current drawn by a load at a particular voltage, but I'm not sure.

--
Tim Wescott 
Control system and signal processing consulting 
www.wescottdesign.com
Reply to
Tim Wescott

Thanks for the LTSpice file, but I use Ngspice, which like HSpice, uses text file input.

Reply to
dakupoto

Thanks. I am aware of the power rating, versus the actual current drawn by the load. Thanks to each of you for your feedback.

Reply to
dakupoto 

--
Sorry to have disturbed your turpor.
Reply to
John Fields

[snip]

Suggestions:

(1) Lose google and the added white-space (2) Get LTspice, it's free (3) If you must use NGspice, export the netlist from LTspice into NGspice. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Who are you and what have you done with John?

Reply to
Spehro Pefhany

Could you please explain your question a bit ? I personally do not know who John Fields is, so I have no clue why he states that he has disturbed my torpor. Ngspice is freely-downloadable, compiles and can be installed very easily on any platform, especially Linux. I find it very convenient to use it especially when importing the sub-micron MOS files BSIM3, BSIM4 etc., that I often use in my work - for example I recently used it to analyze a 32 64-bit shift register structure with 15 nanometer MOSFET gate length. I am sure it would have taken me a lot longer, and would have made lot more mistakes, if I had set it up with a GUI based version of SPICE. taken me

Reply to
dakupoto

I gotta ask... If you can do this, how come you need to ask such a simple power supply question? Something seems horribly disconnected here.

Reply to
mike 

--
A ray of sunshine on an otherwise bleak day.  Thanks! :-)
Reply to
John Fields 

--
Strange, since you replied to my posts related to alleviating your 
misconceptions and power supply problems.
Reply to
John Fields

May the rest of the day be better.

Best regards, Spehro Pefhany

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"it's the network..."                          "The Journey is the reward" 
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Reply to
Spehro Pefhany

Here is the answer Sir. I was just bouncing off ideas. May I point out that the first power supply, the one with 9 - 0 - 9

2 A rated output transformer has already built and works fine. I was just thinking of alternatives.
Reply to
dakupoto 

--
Did you have to add the current-limiting resistors?
Reply to
John Fields

+3

?-)

Reply to
josephkk

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