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Sonsivri > Electronics > General Electronics (Moderators: o2, pickit2) > Help needed
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Bacra2k
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« on: March 03, 2006, 10:55:44 22:55 »
Hi
I need a circuit that can convert 220VAC to 90 VDC 500mA without transformer
any help are welcome
 
 
Salu2
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Parmin
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« Reply #1 on: March 04, 2006, 03:47:37 03:47 »
Yeah right 45watts and no transformer...
I would like to have one too Smiley

Seriously, at least you would need an inductor,  the result would be a pretty complex circuit but is doable.  I would rather use a small transformer..
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Fred Murn
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« Reply #2 on: March 05, 2006, 04:31:57 16:31 »
Not a good idea. Even if you resort to a voltage divider technique like they used back in the days of vacuum tubes (remember those ??) the heat generated would be intolerable,not to mention the risk because of the lack of isolation from the mains. Use any step up/down transformer then appropriate division or multiplication after rectification.
 
Fred Murn
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Parmin
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« Reply #3 on: March 05, 2006, 10:10:46 22:10 »
GAH!!!  90V 500mA voltage divider !!!  Strewth!!!  

***  D A N G E R ! ! !  *****

Dont do that !  it'll either kill you or burn down your house!!
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Bacra2k
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« Reply #4 on: March 07, 2006, 06:13:47 06:13 »
Thanks to all for his answers

 
I have solved the problem with a simple dimmer circuit


This does not generate heat and it is stable for the required purposes
About of the risk because of the lack of isolation from the mains is to take in mind, may be need a insulating transformer.

 
Salu2
 
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max
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« Reply #5 on: March 07, 2006, 06:44:20 18:44 »
You can also use an ac capacitor to drop the voltage
xc = 1/(2fc * pi)
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Parmin
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« Reply #6 on: March 07, 2006, 10:11:54 22:11 »
Quote from: Bacra2k
Thanks to all for his answers

HIS?   Oh  you've broken my heart you chauvinist you!!!  Smiley
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