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Q: Electronic DC / AC Voltage for Infrared or General Surveillance Cameras ( Answered,   0 Comments )
Subject: Electronic DC / AC Voltage for Infrared or General Surveillance Cameras
Category: Reference, Education and News > Teaching and Research
Asked by: hugh007-ga
List Price: $50.00
Posted: 27 Jun 2006 22:18 PDT
Expires: 27 Jul 2006 22:18 PDT
Question ID: 741650
What is 12 Volt Switched Mode Power Supply (SMPS)?  I know that many
cameras (to include specialized infrared cameras like the Clover
CL-501SNH) advertise as having a 12V SMPS.  Does this mean it has an
onboard battery like my personal video camera does and needs AC (wall
receptacle) current to charge the on-board battery?  Or is it
switching between AC to DC to power the 12 volt DC powered Clover
CL-501SNH camera (no on-board battery)?
Subject: Re: Electronic DC / AC Voltage for Infrared or General Surveillance Cameras
Answered By: webadept-ga on 27 Jun 2006 23:15 PDT

--" A switched-mode power supply, switch mode power supply, or SMPS,
is an electronic power supply unit (PSU) that incorporates a switching
regulator ? an internal control circuit that switches the load current
rapidly on and off in order to stabilise the output voltage. Switching
regulators are used as replacements for the linear regulators when
higher efficiency, smaller size or lighter weight is required. They
are, however, more complicated and more expensive, their switching
currents can cause noise problems if not carefully suppressed, and
simple designs may have a poor power factor."--

That paragraph was from Wikipedia on their Switch-Mode Power supply
reference page. That was just the beginning; the page has much more

--" Switch Mode Power Supplies are the current state of the art in
high efficiency power supplies. Conventional series-regulated linear
power supplies maintain a constant voltage by varying their resistance
to cope with input voltage changes or load current demand changes. The
linear regulator can, therefore, tend to be very inefficient. The
switch mode power supply, however, uses a high frequency switch (in
practice a transistor) with varying duty cycle to maintain the output
voltage. The output voltage variations caused by the switching are
filtered out by an LC filter.

SMPSs can be used to step-down a supply voltage, just as linear
supplies do. Unlike a linear regulator, however, an SMPS can also
provide a step-up function and an inverted output function. Typical
applications are given below."--

Those two paragraphs were from a page that gets down into the details
a bit further.

What both of these are getting at, is the Switched Mode Power supply
has really nothing to do with whether the camera is running off a
battery or from the wall, the SMPS deals with how the power is
processed from one of these two sources of power to the circuits of
the camera.

Whether the power is coming in from the wall, or from a battery, the
power level still has to be transformed into the wattage the camera
was designed to work with. Apparently the old system (Conventional
series-regulated linear power supplies) where less efficient than the
SMPS types, and therefore probably ran hotter, and used more
electricity than the more efficient SMPS do (though I did see a
mention about some noise factors).

I couldn't find a Spec Sheet on the camera you mentioned as an
example, but I did find this product page (which seems to be the same
no matter which site you are looking at it on).

From the description here, and what I read about the SMPS, the "power
supply" it is referring to is something like the power supply you get
with a lap top.

Only this one has 60' of cord, instead of 4' or 5' feet. The advantage
of the SMPS for this particular camera would be that it runs cooler
than the older power supply types. I would guess that a camera working
on IR, whose power supply (which would have to be close) was radiating
a great deal of heat, would not be a good thing.

Hope that clears things up for you, but if you have further questions
on this matter, just let me know using the Clarification button.


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