# 2W Regulated Power Supply

Discussion in 'The Projects Forum' started by washer, Jun 22, 2012.

## What is the easiest/cheapest/fastest 2W supply design with a 277Vrms in and 3V3 out?

Poll closed Jun 29, 2012.

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5. #### None of the above!

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1. ### washer Thread Starter New Member

Nov 25, 2009
10
0
Hi all,

It's been a while since I've posted but I've been lurking around.

I'm working on a 2W power supply with a 277Vrms (line-to-neutral) source and a 3.3Vdc output with a max current draw of around 200mA.

Since our requirements are pretty meager requirements, I've been looking at a resistive or capacitive supply similar to the ones discussed in this <SNIP>. I simulated the rectified resistive supply in LTspice and found out (more from trial and error with load resistors than the equations in the note) that it can't support a load of more than 50mA. I've attached two pictures of my simulation with a 16Ω load failing the ckt, and a 70Ω load showing proper operation.

I can follow the math in the note, but am a little confused as to which equations apply to which topologies and how I can find out what the capacity of the supply is.

Can anyone help explain what is the bottle neck in this supply? Is there a way to pull 200mA from a resistive or capacitive supply? If not, what would be the next easiest/cheapest/fastest design?

I haven't found many step down transformers that I could use for a linear supply, but maybe I haven't been searching well enough. I've also started to look into some Flyback and other SMPS designs, but was getting pretty confused and would really like to get a "good enough" design working while I try to learn about a more efficient SMPS design. If anyone has any advice/references for a SMPS, I'd love to hear that as well!

So is there any way to pull 200mA from this type of cheap supply?

Thanks for any help!

Last edited by a moderator: Jun 22, 2012

Apr 5, 2008
18,596
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Hello,

I am closing this thread as it violates AAC policy and/or safety issues.

Quote:
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• Any kind of over-unity devices and systems
• Automotive modifications
• Devices designed to electrocute or shock another person
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• Phone jammers
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• Transformer-less power supplies
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