AC-DC Conversion and Efficacy

So I’m trying to find a cheap, easy, yet safe way to turn 110V/220V into 5V with enough current to drive an AVR and a couple LEDs

Here’s a schematic of what I’m thinking:

I know it’s inefficient and such, but it’s cheap and easy.

I’m open to/would prefer to use something like this instead though. However, I can’t find a suitable transformer to make it work. A 1.5mH transformer with unusual windings. If someone could find one, I’d owe you and would seriously appreciate it as it would be exactly what I’d like.

Otherwise, if I could get input on the schematic above, that’d be great.

Is there a way to add a soft start or inrush protection to it?

Thank you!

Can you please comment on the fact that your circuit has no 120VAC line isolation? How exactly are you planning to make it safe?

@dominicluciano, you shouldn't be playing with circuits like this, since you clearly don't know what you're doing.

Go and buy a real mains-powered 5V supply.

If you really must build your own, start with a step-down transformer for full isolation.

Yeah... You REALLY NEED a transformer!

I've built quite a few power supplies with regular 50/60Hz transformers. But, I probably wouldn't try making a 120V o 240V switching supply. If I want a switching supply, I'll buy one. (Low voltage switching regulators aren't too hard with modern chips.)

When you start messing around with high-power active circuits, there's a good chance of blowing a few parts during development & debugging and to me it's just not worth the cost or effort.

You are going to kill yourself.

Just buy a 100/220vac USB 5v 2amp power supply from eBay. ~$3.00

The problem is I need 300V for another part of this circuit. I have yet to find a suitable way to generate 300V from 5V. So I decided to turn 120V into 300V and 5V

Yes, I actually do know what I'm doing. I went to school for this stuff. I just don't work with power supplies very often. So I'm getting a second opinion so I DON'T kill myself, which I'm not going to, so please don't degrade me or make me out to be stupid. I'm not. There's a reason I'm running simulations and asking for second opinions before actually building it.

I don't need to be heckled, degraded, or told I don't know what I'm doing when I do. So if you're not going to help, please don't comment!

If you're willing to help, please do the following: 1. Correct the schematic 2. Offer suggestions on how to improve the schematic 3. Give me a better schematic

OR

  1. Provide a schematic that can turn 5V into 300V

Fair? Fair. Thanks :)

Your 120VAC to 5VDC circuit is dangerous, and you neglected to mention that you also needed 300V elsewhere, so the answers above were correct.

Furthermore, you haven't said how much current you need at 300V, so no one can help with that anyway.

Hi,

The problem is I need 300V for another part of this circuit. I have yet to find a suitable way to generate 300V from 5V. So I decided to turn 120V into 300V and 5V

What is your application?

Tom..... :) Low Cost 220Vac to 5Vdc for avr, USB Plugpack (Wallwart)

Sorry, but the ground symbol on your schematic is a dead giveaway that you DO NOT know what you are doing. With almost all 120V/60 Hz systems, it is possible to insert the plug the wrong way, directly connecting line voltage to whatever is connected to that idiotic ground, incidentally bypassing the worthless fuse.

Use a standard tube transformer with 125VAC (voltage doubler rectification) and 6.3 VAC secondaries to provide both required voltages.

"You are going to kill yourself" was said to you as a concern, and not in any way as an insult. Take it from someone who has seen someone who was electrocuted with 440v, you do not want to fool with this stuff.

You need 100% isolation. Do what others have suggested, or don't, you will feel more than foolish when something goes seriously wrong.

"Cheap, easy, and safe" and now 300 volts is very interesting criteria.

Seriously, good luck.

.

dominicluciano: I'm open to/would prefer to use something like this instead though. However, I can't find a suitable transformer to make it work. A 1.5mH transformer with unusual windings. If someone could find one, I'd owe you and would seriously appreciate it as it would be exactly what I'd like.

Maybe this can be suitable. Other IC similar to the one you linked is the LNK364GN.

Ciao, Ale.

Hi, Please, see post #7, what is your overall application? What is your project?

Tom..... :)

The problem is I need 300V for another part of this circuit.

There is a circuit called a voltage doubler. I haven't studied those for a long time, but I think you can get (approximately) double the peak voltage so you should be able to get 300VDC from 120VAC RMS.

Of course those circuits are not isolated from the power line either because if you are using transformer you can simply use a step-up transformer and there's no need for a doubler. And, 300V isn't "safe" even if it is isolated.

Have you looked at tube amplifier transformers to create the higher AC voltage? http://www.hammondmfg.com/5cindex.htm