Power supply topology question ...

[[email protected]]

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.

 

[Jasen Betts]

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 :

a 9-0-9 2A transformer is probably sufficienctly
oversized

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.

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

 

[mike]

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.

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

 

[[email protected]]

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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

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

 

[[email protected]]

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

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

 

[Spehro Pefhany]

Who are you and what have you done with John?

 

[[email protected]]

Who are you and what have you done with John?

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

 

[mike]

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

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.

 

[Spehro Pefhany]

<doffs hat> May the rest of the day be better.


Best regards,
Spehro Pefhany

 

[[email protected]]

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.

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.

 

[josephkk]

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






---

If you have a 2A transformer and 1A loads and you need to isolate

the loads, a more sensible arrangement would be to run a separate

FWB supply off of each secondary since 1A transformers will overheat

if you're using capacitor input filters.

---



Version 4

SHEET 1 880 920
[snip]

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

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

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

+3

?-)