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-   -   how do i convert 220VAC to 220VDC? (http://www.diyaudio.com/forums/power-supplies/173512-how-do-i-convert-220vac-220vdc.html)

coolfox 13th September 2010 03:13 PM

how do i convert 220VAC to 220VDC?
 
i'm trying to drive my eht transformer with 220Vdc which sounds crazy:D i used bridge rectifier with 1N4007 to regulate network and a filter capacitor about 100uf/400V.. isn't that true?at the end of this line i must get it ? could you please explain me clearly how do i get 220V DC from network[help=?][/help] i'm stuck!

bob91343 13th September 2010 05:45 PM

First, you can't drive a transformer with dc. Second, if you connect a rectifier and capacitor, you will get the peak voltage (without load) and that will be the rms ac voltage times the square root of two, so you get from 220 Vrms over 300 Vdc.

If you attempt to put dc into a transformer winding, the core will saturate and you will get a very high current, and probably burn out something. Or cause a fire.

BrianVG 13th September 2010 06:23 PM

Transform to 157V then recitifie it. You'll get about 220V.
DC is 3 times more dangerous than AC THERE IS NO CHANCHE TO LET THE POWER CORD GO ONCE YOU TOUCHED IT!
I won't recommend to use such DC voltages. For instance you need about 10kVDC to make an arc of 3cm. But only 220VDC to do the same ;)

macboy 13th September 2010 06:31 PM

Quote:

Originally Posted by coolfox (Post 2301658)
i'm trying to drive my eht transformer with 220Vdc which sounds crazy:D

No, that doesn't sound crazy.
It is crazy.
You need to study and learn a lot more before you do something stupid and kill yourself. The questions you asked show how little you know about this stuff, so maybe playing around with high voltages (high DC voltages in fact) is a bad idea.

coolfox 13th September 2010 07:04 PM

i dont drive directly the eht with DC..there is a 555 trigger on the network line driving the ırf830 mosfet's Gate and the primer winding of the eht transformer is to the mosfet's Drain..yes there is about 300Vdc on the drain and i can't drive the mosfet still.. i succeed that when i give about 128Vdc to drain and give the 555 's supply voltage externally..i don't expect to extend the cm too much(may be 6 cm) but though i couldn't make it , this plug/jack structure sounds me practical..

BrianVG 13th September 2010 08:03 PM

I just don't get what you want to do. A 555 is a counter wich only needs 16Vdc? Primary winding of the transformer is 300Vdc? Do you understand how a transformer works? The there is a magnetic flux created between the two windings wich is only possible with alternating currents. This way you are heating your transfo. If you do this for to long the insulation will start to melt and not much later you'll end up with a fire.

coolfox 13th September 2010 09:01 PM

ofcourse i know how a transformer works..my circuit is a simple flyback driver circuit with 555.. i use the 555 as an square wave generator in a eht's desired spec. at low levels. 555 generates ttl and this is connected to mosfet's gate.. mosfet creates an alternate at the eht's primer..then transformer works..
in my first test i used an external supply ;about 12Vdc for 555 and 128Vdc to" mosfet drain" (i said eht before,sorry..).. this works very well..there is an 3-4 cm arc..
then i tried to drive 555 over network . i regulated with bridge rectifiers and reduced the voltage with and power resistors and used filter caps to minimize peaks to 14Vdc ( i think there is a problem) .. this structure works on its own..
lastly i try to get 220Vdc (which is about 300Vdc) after the bridge rectifier and filter capacitor to mosfet drain.. from that point nothing works ...

Th3 uN1Qu3 14th September 2010 09:46 AM

He isn't going to kill himself with a flyback transformer, but he may kill himself when the transformer dies and there's 230v all over the place. Anyway, all it takes is a bridge rectifier and a capacitor. BUT i wouldn't run anywhere close to 300v DC into your typical flyback transformer. You're going to kill it as soon as you plug it in. I'd run 100 volts at the very extreme, it's best that you don't go over 40v if you want that transformer to survive for any reasonable length of time.

Anyway, here's why your circuit does not work. When wiring a bridge rectifier to the mains you will still have phase on one of the leads (depending what orientation you plug it in), meaning everything may be floating 230v above ground, which is NOT a good idea.

You need isolation between the 555 and power MOSFET. For best results drive a smaller mosfet with the 555 and have that output into a drive transformer from an old ATX power supply. At the other side of the transformer you wire your power MOSFET. This should work, but again, i wouldn't run it straight off the mains, you will damage the high voltage transformer.

@ BrianVG: AFAIK 50Hz AC is more dangerous than DC, i'll try to remember where i read that.

DF96 14th September 2010 11:07 AM

AC more dangerous because it disrupts your cardiac rhythm?

DC more dangerous because it makes your muscles contract and force you to hang on to it? I believe there used to be an old technician's trick (DON'T TRY THIS AT HOME) of touching a potentially live DC circuit with the outside of a finger (i.e. the side with the fingernail) so that the resultant muscle twitch (if it was live) would pull the finger away - much safer than touching with other side and grabbing the circuit.

Oh, and RF will give you a nasty deep burn which takes months to heal.

megajocke 15th September 2010 08:19 PM

AFAIK 50Hz AC will also make you unable to let go. That combined with that it is more likely to upset your heart rhythm makes it much more dangerous than an equivalent DC source.


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