2 in parallel

Dec 22, 2003 4 Replies

Hi



Any pro could help. I have an adjustable volt and current Power supply (0-6V and 0-8Amp)



I need 10-12Amp so would it be ok to parallel it with a smaller transformer such (110 to 6V and current of 5Amp).



I can't read the installed diode # but what should be a good one to use with both transformers.



Do I need to change anything else



Thanks



jif


It's not that simple.

If you had two unregulated transformers and could connect them up out of phase so they pump into the same capacitor. That would allow you to take more current out of that capacitor before the ripple becomes too great for any subsequent load/regulator . BUT you said one source is a regulated voltage source....

Think about what would happen if you try to connect two ideal voltage sources together and one was actually 6.1V and the other 5.9V. A current would flow from the 6.1V supply to the 5.9V supply. That current would be given by the equation.... I= (6.1-5.9)/R where R is the resistance of the wire you used to connect them together. If R is small I is very large. For this reason you should never connect ideal voltage sources in parallel (or current sources in series) or something interesting will happen.

If you use two diodes to connect two ideal voltage sources together that would stop the current flow described above but it would also stop your circuit working as intended. This is because the output will be 6.1-0.7=5.4V which means the diode in the 5.9V supply will have 0.5V accross it and won't be conducting (at least not enough). The 6.1V supply will supply all the current and the 5.9V will supply none (or next to none).

Colin

many thanks. I have learned and enjoyed reading your post

I am just starting electronics (some forgiveness) would a volt regulator (ie 78xx or LM3xx) would help overcoming this is so how?

tia

jif

No sorry, you can't do it using the "adjustable volt and current Power supply (0-6V and 0-8Amp)".

The reason is that this power supply can only provide a max power of 6V*8A =

48Watts and you say you need 10-12Amp at 6V which is 60 to 72Watts.

Sure you can make circuits that convert a surplus of volts to amps or a surplus of amps to volts BUT no electronic circuit has a "power conversion efficiency" of more than 100% . eg No circuit can produce more power out than it takes in.

If you do ever manage to invent one that does never connect the output back to the input!

Colin

In article , snipped-for-privacy@pandoraBOX.be mentioned...

Hey, just connec the output to the input with the household power lines. FREE!

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