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What the World Needs Now -- Miniature AC to DC Power Supply

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Electronic systems are getting quite efficient these days.  I seldom design a small product that requires more than 100 milliwatts of power.  Often, if the product is not going to be powered by batteries, it requires a wall mounted AC to DC power adapter or a small on-board power module. 

The smallest power module around is made by Bias Power.  As shown below, this thing does not take up much space.  But, if all I need is 100 milliwatts, this 1 watt device is overkill. 

What I would like to see is a smaller 4 pin single inline package (SIP) device, similar in shape to the solid state relay shown below, which contains a universal fully isolated AC to DC power supply. I would not mind if the thing had a low overall efficiency.  It just has to be small and robust.  The DC output might be rated at 3.3v, 5v or 12v.
With a low power requirement, perhaps a different circuit topology could be made to work. One way to do this AC to DC conversion is shown below.  A series capacitor limits the current into a conventional bridge rectifier and filter capacitor front-end circuit.  A 24v zener diode limits the DC input voltage to a miniature isolated DC to DC converter.  The converter output then provides a nice DC output.

January 2011

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Good Idea
done Badly
What the World
needs Now
Wily Widget

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