# Isolated, regulated, toroidal step down transformer AC power supply design. - Page 2

#### Do you have a question? Post it now! No Registration Necessary

•  Subject
• Author
• Posted on
Re: Isolated, regulated, toroidal step down transformer AC power supply design.

You are assuming that I had a perfect 9 VAC sine wave input to my
application. If I'd had what I wanted, I wouldn't need to ask the question.

What I DO have is an very imperfect NOMINAL 240 VAC, domestic supply, like
everybody else. (actually more imperfect than most, as we live in remote
rural area with many idiosyncrasies in the supply).

I can step down the domestic supply to (nominally) 9 VAC,  but it suffers
exactly the same problems as the domestic supply. i.e. the output of the
transformer isn't 9 VAC and isn't a perfect sine wave.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

On Wed, 28 Mar 2007 13:17:18 +1000, "Mark"
composed:

You are missing the point. There is no way that you can get 15VDC from
a 9.00 VAC rms sine wave using only rectification, filtering and
regulation, even under ideal circumstances. Hint: 15 is greater than 9
x sqrt(2) for all possible values of 2.

- Franc Zabkar
--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Oh, dear me. Yes there is.

It's called a voltage doubling rectifier. It is a variant of the half wave
rectifier.

P.S. How many 'possible' values of '2' are there?

Let's count them togeather, shall we:

One
.
.

...well, I've run out of ideas. Anyone else?

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

On Thu, 29 Mar 2007 17:56:23 +1000, "Mark"
composed:

Is this what you mean?

D1
o-----|--|>|-----|-----o +V
|         _|_ +
9VAC   |         --- C1
rms   |          |
o----- )---------+-----o 0V
|         _|_ +
|         --- C2
|   D2     |
|--|<|-----|-----o -V

- Franc Zabkar
--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

I am no expert, Franc, but I don't think so.

Doesn't look like the one I am looking at (but yours is very difficult to

Anyway, I know that the one I am looking at takes in 9 VAC and outputs +/-
15VDC (after regulation) and looks like two half wave rectifiers with diodes
pointing in opposite directions.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

On Sat, 31 Mar 2007 03:21:09 +1000, "Mark"
composed:

ASCII art needs to be viewed with a fixed width font, eg Courier. Is

This was the original format:

h

- Franc Zabkar
--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Ok, thanks for that link. No, it isn't like mine.

Mine has two extra diodes in the bridge, (four diodes in all) but it ISN'T a
full wave rectifier.

Instead of converting the whole of the input waveform to ONE waveform of
constant polarity, I produces two bi-polar waveforms (+/-) and doubles the
voltage of each of them.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

That's right Mark. Keep pretending you can't see my questions
asking if this fault happened after you fiddled with the electronics.
Just keep babbling on about half-wave rectifiers and voltage doublers as
though this is some mysterious problem unrelated to you tearing out all
those naughty horrible-sounding ordinary capacitors and installing the
Backgates you got from Hawaii.
Half-wit.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

On Sat, 31 Mar 2007 22:12:49 +1000, Bob Parker

In my first post to this thread I tried to diplomatically steer the OP
toward first principles in the hope that the penny would drop, but he
clearly has no understanding of the basics. It would have been far
better for him to have acknowledged his ignorance at the outset.
Instead he has chosen to engage in damage control and in so doing has
only dug himself into a deeper hole.

- Franc Zabkar
--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

You said (in what I think was your second post on this thread).

"You are missing the point. There is no way that you can get 15VDC from
a 9.00 VAC rms sine wave using only rectification, filtering and
regulation "

Well, you were 100% wrong about that, Franc.  I can even produce the
schematic diagram which proves your statement incorrect.

BUT I DIDN'T RESPOND BY INSULTING YOU, as many others would have done.

And now, it is you who "engage[s] in damage control" by trying to draw
attention away from your error and towards my alleged arrogance.

Unfortunately for you, I have acknowledged my ignorance about electronics
the allegation doesn't come through the wash.

I don't blame you particularly for engaging in damage control, but it is a
very weak position for you to take. You must be in that second class of
'Phil-o-phile', one who fears him.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

9.00 VAC RMS * 1.414 (VPeak) = 12.726 Volts, minus the diode drop.
Either the transformer is more than 9.00 VAC, or you aren't getting 15
volts.  That is, unless the laws of physics don't apply on your world.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
We've slightly trimmed the long signature. Click to see the full one.
Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Wrong. The laws of physics do apply in OUR world and it certainly is
possible under those laws.

I believe (because I am no expert) that the design I am looking at is
rightly described as a Voltage Multiplier. (read below)

In any case, I wouldn't be quite so adamant about it, if I were you.

Abyway, whilst you are here, why don't we talk about US laws that aren't
applied in Cuba.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

I can see your questions Bob.

The problem wasn't caused by the recapping, it pre-existed.

It was one of the motivations for recapping the applications power supply.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Finally - a little bit of clarity in an ocean of half-truths,
paranoid secrecy and babble about 'Philophiles'. :-(
I suppose it would be hoping for a miracle to get an answer to the
next question a technician would ask:

Did it have this problem from the very beginning?

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

That would be the meaning of 'pre-existing', Bob.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

No it wouldn't. You are a twit and I give up. I'll just watch from
now on, or maybe killfile you and this absurd thread.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

LOL, that is insane.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

You, Mark, are a mere simple troll. You fit the definition
perfectly. From http://brawl-hall.com/pages/trolls.php ....

"The most basic form of trolling is to submit a post that will
attract the most possible amount of responses, negative or argumentative
replies usually preferred, and then to sit back and bask in the chaos
that has been created.
This troll is simply out for immediate scoreboard and a quick win is
enough to satisfy him. The tactic is basic, relatively uncreative, and
only touches the surface of what a troll can really do; yet it's
effective in accomplishing its singular task--to attract attention and
garner as many responses as possible.
The content delivered by this type of troll generally falls into
several areas; It may consist of an obviously foolish opposition of
common knowledge, many intentional offensive insults or flames directed
to the readers of a community, or a blanket generation on a specific
category which is sure to attract a large number of argumentative replies."

I'm not going to play your silly game.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Have you measured any voltages within the powers supply yet, as advised by
many people here? This is something you should have done before starting to
arbitrarily replacing capacitors.

Oh, and thanks for the term "recapping" I hadn't heard it used in such a
manner before.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.

Whatever, Poxy. It's a term I use. You are welcome to make whatever of it
you will.

No I haven't measured it yet. I haven't even had the lid off, YET!

I think I can do it but I am always cautious about poking around inside
electrical equipment when it is LIVE.