Hi,
Just a quick note here...
When you parallel diodes you dont always get half the current flowing
through each diode. This is because both diodes are not always
exactly the same as they are in circuit simulator programs.
For example, say we have two 5 amp diodes and we connect them in
parallel. Can we then pass 10 amps through the two diodes? The
answer to this is a resounding, "No", simply because the two diodes
can not be assumed to be exactly the same and so one diode will
pass a higher current than the other. For that example, one diode
might draw 7 amps and the other only 3, and that would burn up
one of the diodes.
We could probably assume a 1 to 2 ratio, where worst case one
diode will pass two times the current of the other. So for those
two diodes rated at 5 amps each, we might get away with
passing a TOTAL of 7.5 amps (one diode carries 5 while the other
carries 2.5), but certainly not 10 amps total.
The rule of thumb then would be:
Itotal=1.5*Id
where
Id is the current rating of one diode (in parallel with another diode of the same part
number).
For three diodes in parallel we could probably assume another 1/2 diode rating
added to the total current, or
Itotal=2*Id
but remember this is for THREE diodes in parallel.
I prefer to use one diode though with the proper rating instead of doing these
parallel connections, which just adds unneeded complexity.
As to the bridge rectifier question, i think you might have wanted to connect
a full wave bridge rectifier up as a half wave rectifier, but this doesnt work
at all unless you dont mind two diode drops in your half wave circuit, in which
case you can connect the AC to the (-) terminal and take the DC from the (+)
terminal. Again, note that there will be two diode drops instead of one so
more voltage lost then when using a single diode.