Definition of AC vs DC power

[Corranet]

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

 

[Phil Allison]

"Corranet"

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

** DC.

Cos the voltage never changes sign.




...... Phil

 

[John Larkin]

On Mon, 29 Jun 2009 03:52:12 -0700 (PDT), Corranet
<nicgrande@gmail.com> wrote:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

Both. It has AC and DC components.

But the terms AC and DC aren't absolute, so don't take them too
seriously.

John

 

[Tim Wescott]

On Mon, 29 Jun 2009 03:52:12 -0700, Corranet wrote:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

What you call it depends on what you want to do with it.

It's a crappy DC supply, or a _really_ crappy AC supply, or a DC supply
with an impressed AC component, or, or, or.

--
www.wescottdesign.com

 

[Michael Black]

On Mon, 29 Jun 2009, Corranet wrote:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

Why do you want a definition?

The reason for that need may help to define the answer.

The concept is hardly out of the ordinary. Lots of circuits over the
years have that very situation, a tube or transistor fed from a DC
voltage, but amplifying an AC voltage. Nobody fussed over the
definition, it was a natural thing (since the circuit needed the
DC), and you ignored whatever one that wasn't the issue at the time.
Coupling capacitors would strip off the DC component when only the
AC was wanted (such as when feeding the output of one stage into
the other, and each stage was biased separately so you didn't
want the DC voltage from the output of one stage to get into the
input of the next stage) or a big coupling capacitor at the output
of an audio amplifier to keep the DC off the speaker.

Perhaps the concept is less common now since a lot of equipment
does run off dual-polarity power supplies.

Michael

 

[Charles]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:7arnj9F1vbrk1U1@mid.individual.net...

"Corranet"

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

A DC supply with an AC component (used to be called the "ripple" component).

 

[David L. Jones]

Corranet wrote:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

It's effectively a DC supply, as the current no longer "alternates" in
direction.
More commonly it might be clarified as a "DC supply with AC ripple" or some
such.
But what you call it depends on how you want to interpret it for your
application/need.
e.g. It may not be incorrect to say it's an "AC supply with a DC bias"
There are no absolute definitions here.

Dave.
--
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

 

[baron]

Corranet Inscribed thus:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

Its a DC power supply with 20% AC ripple.

--
Best Regards:
Baron.

 

[Jamie]

Corranet wrote:

If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?
A DC supply with a ripple on it.

 

[Rich Grise]

On Tue, 30 Jun 2009 12:42:53 -0400, Jamie wrote:

Corranet wrote:
If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?

A DC supply with a ripple on it.

Or an AC supply with an offset, or bias, of +10V. ;-)

It depends on the application.

Hope This Helps!
Rich

 

[stan]

On Jun 30, 4:58 pm, Rich Grise <richgr...@example.net> wrote:

On Tue, 30 Jun 2009 12:42:53 -0400, Jamie wrote:
Corranet wrote:
If I have an AC power supply alternating between -1V and +1V and I add
to it (in series) a DC supply of 10V, is the resulting power supply
(which varies between 9V and 11V) an AC supply or a DC supply?
A DC supply with a ripple on it.

Or an AC supply with an offset, or bias, of +10V. ;-)

It depends on the application.

Hope This Helps!
Rich

Yup; a +10 volt DC supply with a one volt (Peak) ripple on it.

Or you could consider it a 0.71 volt (RMS) AC supply biased by +10
volts DC.Making an assumption here that the one volt variation is some
sort of typical sine wave. If it is not a typical sine wave variation
(it could be a chopped or square wave variation).

Sounds like a school question to get someone to think about voltages;
not look for a strict black/white definition!