Hi there
I'm looking for a schematics to build 240V AC to 120V AC step-down converter. I need to power up 350 Watts battery charger designed to run of the US 120V AC mains from 240V. I don't want to use a huge transformer and I'm not sure if a simple triac light dimmer type circuit would do the job.
Any suggestions?
Thanks
Yes, buy a new charger
I dont usually take that above advice either ha ha but many people would
want to do that because it is the simplest, easiest, and most of all
the safest.
I do see that the charger looks like a good one, so you may try to sell
the old one.
I also see that the conversion in the link shows simply changing the
MOSFET and the cap with a cap of higher voltage rating, and that might work,
but another thing to think about is
the ripple current in the filter capacitor. If it is too high for the cap
rating the cap will get hot and burn up. It may survive just the same,
but it would be a good idea to keep an eye on the temperature of
that component just to make sure. What i would do is stick a thermometer
on there for at least the first 12 hours run time and watch it to see
if it goes up high. 70 degrees C might not be too much but i wouldnt like
that either, but many caps are rated for 105 deg C so maybe it will be
ok if the charger isnt used all day and all night for many days.
For higher voltage like that using the SAME coil there is also the chance
that the coil will saturate. That will screw things up badly, but again
it may get by. A good idea would be to measure the current with a
scope to check for inductor saturation.
In any case, i wish you the very best of luck with it.
ADDED LATER:
I just noticed that they post that that mod is not recommended by Makita.
I also noticed, more importantly, that the charger can be used with Li-ion cells.
You should know that Li-ion cells have issues of their own and any problem with the
charger (such as higher output ripple voltage due to a higher input voltage)
can cause the cells to burn up or explode violently. I would think twice about
doing this, or at least check over the design more thoroughly. If you have a
schematic or can make one by tracing out the circuit board we can take a look
and help to ensure nothing blows up in the end.