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Old 15th September 2010, 08:22 PM   #11
Did it Himself
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DC is more dangerous, once you get DC on you there is no heart rhythm just a stuck muscle.
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Old 15th September 2010, 09:26 PM   #12
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The heart is much more likely to recover from a stopped condition than from ventricular fibrillation.

See for example

Extra-low voltage - Wikipedia, the free encyclopedia

where 50V AC and 120V DC are classified at the same danger level.
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Old 15th September 2010, 11:01 PM   #13
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What is your desired end result? Why do you want to start with 220VDC?

You won't rectify a 220 volt utility line and directly filter it and get 220VDC. You'll get 1.414 times that. See Root Mean Square.

If you must get 220VDC for some reason from 220VAC you can use higher than the critical inductance (for whatever your load current is) after the bridge rectifier and before the filter capacitor. Unfortunately it's not necessarily useful for doing what you've described so far because you need an isolation transformer anyway to avoid killing yourself by accidentally coming in contact with the primary circuitry, it may as well be wound so you can hit the voltage you want with just a bridge and not have to hold a certain minimum current on the output to keep it from floating up to the peak voltage. Unless for some really strange reason you need a few kilowatt flyback converter, which is just wrong, it's easy enough to use lower voltages on the primary.

Last edited by Andrew Eckhardt; 15th September 2010 at 11:16 PM.
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Old 18th September 2010, 09:09 PM   #14
BrianVG is offline BrianVG  Belgium
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Don't start a war about AC or DC. I think we all know voltages above 42V can easily run through your body and cause damage, not to mention the currents that are flowing.

I hope that coolfox knows what he's doing.
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Old 29th September 2010, 01:03 PM   #15
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1. Always use an isolation transformer when doing things like this. It can save your life. It is for a reason that it is FORBIDDEN on this site to post schematics of, or encourage the use of, "live" power supplies.

2. If the voltage is too great, you might saturate the flyback transformer. As a stopgap measure, you can take it apart and enlarge the air gap.

3. Make sure you don't blow up the MOSFET, it will see voltages much higher than the 300VDC you feed it.

4. Open the windows, if you smell ozone, the concentration is already way beyond the healthy limit! (Yeah, it does smell kinda good )
Never send a human to do a machine's job. --Agent Smith

Last edited by kavermei; 29th September 2010 at 01:06 PM.
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Old 29th September 2010, 02:49 PM   #16
star882 is offline star882  United States
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It is common for electronic air filters to use a flyback transformer driven from rectified mains to create the several kV needed for operation. I have actually done a high voltage flyback design (ion generator) that consisted of a mains based "current source" (series capacitor ahead of rectification) powering a self-oscillating flyback circuit.
"Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!
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Old 29th September 2010, 04:45 PM   #17
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you can't convert 220 ac to 220 dc,because appear lost voltage
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Old 29th September 2010, 11:13 PM   #18
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Danger! These voltages can kill. You have been warned.

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Old 30th September 2010, 01:42 AM   #19
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Originally Posted by BrianVG View Post
Don't start a war about AC or DC. I think we all know voltages above 42V can easily run through your body and cause damage, not to mention the currents that are flowing.

I hope that coolfox knows what he's doing.
Ashes to ashes, dust to dust, if one doesn't get you, the other one must!

AC/DC, both can kill ya, no worries mate!

Doesn't make a difference in da afterlife!
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Old 30th September 2010, 02:09 AM   #20
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Using more input voltage with a flyback circuit does not give more output voltage, it merely reduces the time to charge the flyback inductor. Output voltage is mainly dependent on rate of fall of the primary current as per v = LdI/dT Output voltage is limited by the blocking voltage of the primary current switch not to mention transformer insulation. If you want DC voltage ring around the scrap yards for an Xray power supply beware these kill from a distance, 60Kv + at over an amp, they are the size of a bar fridge, for AC a pole transformer is an option, on a more compact scale a 15Kv neon sign transformer can handle 30mA and make a nice jacobs ladder.
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