connecting two 12V power supplies together

[z]

Thanks, for the relay idea.... a switch wouldn't work cause it has to
be automatic.... and the power does more than just go to a regulator
so getting the entire 12V passed is a concern, that's why I'm looking
for something other than the Diode-OR.- Hide quoted text -

- Show quoted text -

well, the loss in the diode isn't that much..... you'd have to really
want every milliwatt to go to the complexity of a relay over the
diode, but if you do, then you would.

 

[panfilero]

well, the loss in the diode isn't that much..... you'd have to really
want every milliwatt to go to the complexity of a relay over the
diode, but if you do, then you would.- Hide quoted text -

- Show quoted text -

I'm sorry if this is obvious but I'm just trying to understand why
this is a kind of involved subject... is the problem with switching
between voltage sources and hooking them up in parallel that if they
are not exactly equal sources... something bad could happen? And I'm
thinking bad as in batteries trying to charge eachother or force
eachother towards a certain voltage... but now I just said
batteries... and that's because that's what comes to mind when I think
of these DC Voltages in parallel... so I'm guessing the diode-OR is a
way of keeping current from seeping back in towards a power supply
when two are connected... I'm just tryign to get a good understanding
of the issue and why we need Diode-OR and FETs to connecet power
supplies like this....

thank you

 

[z]

I'm sorry if this is obvious but I'm just trying to understand why
this is a kind of involved subject... is the problem with switching
between voltage sources and hooking them up in parallel that if they
are not exactly equal sources... something bad could happen?  And I'm
thinking bad as in batteries trying to charge eachother or force
eachother towards a certain voltage... but now I just said
batteries... and that's because that's what comes to mind when I think
of these DC Voltages in parallel... so I'm guessing the diode-OR is a
way of keeping current from seeping back in towards a power supply
when two are connected... I'm just tryign to get a good understanding
of the issue and why we need Diode-OR and FETs to connecet power
supplies like this....

thank you- Hide quoted text -

- Show quoted text -

actually, when i think about it, there are most likely diodes in the
power supplies to act as rectifiers, so maybe there isn't anything
external other than just connect them, as you say.

 

[ehsjr]

panfilero wrote:

I'm sorry if this is obvious but I'm just trying to understand why
this is a kind of involved subject... is the problem with switching
between voltage sources and hooking them up in parallel that if they
are not exactly equal sources... something bad could happen? And I'm
thinking bad as in batteries trying to charge eachother or force
eachother towards a certain voltage... but now I just said
batteries... and that's because that's what comes to mind when I think
of these DC Voltages in parallel... so I'm guessing the diode-OR is a
way of keeping current from seeping back in towards a power supply
when two are connected... I'm just tryign to get a good understanding
of the issue and why we need Diode-OR and FETs to connecet power
supplies like this....

thank you

The diodes prevent source A from forcing current
into the output side of source B, or vice-versa.
Pushing current into a source in the wrong direction
can result in burned out parts, wasted power, overcharged
batteries, whatever, depending on the sources involved.
It's _not_ a good thing.

Ed