My understanding of AC/DC adapters


Old 02-08-14, 07:53 PM
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Join Date: Feb 2014
Location: United States
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My understanding of AC/DC adapters

I was hoping someone could correct me if I'm wrong about how AC-DC converters work:

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The Primary Winding is in blue and receives AC from the outlet. The red wire brings it from the prongs to the Primary Winding. As the current goes around the primary winding, it creates an electromgnetic field around the Iron core (labeled Fe Core). This field creates a much lower AC voltage to form in the Secondary Winding (labeled SW)

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The current from the SW goes through these Diodes, which are called the rectifiers. A diode only allows current to cross one direction.

So am I correct in understanding the current to be AC all the way up until the diodes? The primary winding, secondary winding and iron core are all there to just reduce the voltage and increase the amperage?

Also what do the white illistrations on the printed circuit board mean?

Thank you in advance for your help.

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Old 02-09-14, 04:52 AM
Join Date: Aug 2012
Posts: 231
Your correct. The missing components are probably a capacitor to filter (smooth) the output DC voltage. The four diodes are probably wired in a bridge configuration to produce full wave DC output (both halfs of the sine wave).
Old 02-09-14, 08:02 AM
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Also, the number of windings in both the primary and secondary determines the voltage ratio. Transformers are used both to increase and to decrease voltage. Our power distribution grid depends on them.

Here's a wonderful page with everything you ever wanted to know about xformers in layman's terms: Practical Transformer Winding

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