In data Tue, 04 May 2004 15:54:21 GMT, David ha scritto:

"Michele Ancis" wrote in message ...
Hi,

[CUT]
can think of is the voltage on the diode bridge...or across the "chopping"
transistor...

Any suggestions are welcome


Michele, Many switching supplies use a doubler for 110 operation in the
line rectifier circuit. There is usually one wire to disconnect which
turns the rectifier into a non doubling full wave bridge. If you can
power it up on 110 and measure the DC feeding the switching transformer
primary, and it measures about 300 volts, than you have a doubler and it
can be rewired easily for 220 operation.

David

Thanks David! I had my friend to describe the rectifier and...yes, there is
a jumper connecting a common node for two series caps to one output of the
bridge..

+---------+
| |
| / \
| / \
(~) +- -------+------+
| | \ / |
| | \ / --- L
| | | --- C1 O
| | | | A
+---------+---/J\----+ D
| |
| ---
| --- C2
| |
+---------------+------+


I've done a simple simulation and this arrangement allows to have either a
doubled DC voltage (jumper ON) or a "normal" voltage (jumper OFF).

That was of great help guys thanks a lot!

M
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