No. You simply wouldn't. Because there is going to be potenial difference between the outputs.Hi All,
Wondering if two lm317's can be paralleled to get a max 3A regulated supply?
What other projects have you done Mark?We just had a nice discussion on this topic.
http://forum.allaboutcircuits.com/showthread.php?t=16198&highlight=lm317
But you wouldn't though right? Bonkerz.The scheme in Figure 13 pointed to by KMoffet works because a resistor is added in series with each output, which tends to equalize the current out of each device. A small difference in output voltage between devices now yields a small difference in output currents, so the devices all tend to share near equally instead of one device hogging all the current it can.
The regulator outputting 5 volts would see all of the load. The regulator set at 4 volts would effectively see zero current.If one regulator is producing 5V and the other is say 4.
5V, then the potential difference is 500mV. Would this load down the regulator that is producing 5V?
The "4V regulator" would shut down because it's sensing 5V from the "5V regulator" output and will do what it needs to do to in an attempt to bring its sensed output down to 4V. It can't, so it shuts off its pass element. All the current then comes from the "5V regulator".If one regulator is producing 5V and the other is say 4.
5V, then the potential difference is 500mV. Would this load down the regulator that is producing 5V?
How about unloaded -- there would be 5V not 4?The regulator outputting 5 volts would see all of the load. The regulator set at 4 volts would effectively see zero current.
???? Say that again.I'm thinking of two seperate power sources for an short.
Guranteed short in this case yeah?
Well the potential difference between the two or more regulators.???? Say that again.
Two batteries, different voltages..."short"...yes.I'm thinking of two seperate power sources for an short.
Guranteed short in this case yeah?
Got it.Well the potential difference between the two or more regulators.
If one is putting out 5V and the other 4V, then there is 1V of potential difference. Now if the two regs were operating off different power sources, then there wpuld be an short between the regs. The reg putting out 4V would become an load.
Right?
I do a lot of battery projects so this explains it!Two batteries, different voltages..."short"...yes.
Two voltage regulated power supplies...no.
Same process...the lower voltage one will shut down trying to bring its shared output down to its set reference voltage.
Ken
Thanks Mark for the top answer.Got it.
Generally the answer is no. In order for this to happen the 4 volt regulator would have to sink current as well as source current. That is not how they are built. Every simple linear regulator I know of can only source current. They can not act like a load unless some other parameter has been exceeded and they are in a "failure" mode.
No. The two power supplies will behave exactly like the two LM317s.I do a lot of battery projects so this explains it!
So if I have two mains powered lab power supplies operating off seperate isolation transformers, connect them together and set one at 5v and the other at 4v -- there will be an short though right?
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