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Topic: Combining the Ampere of two voltage regulator? (Read 4 times) previous topic - next topic

dhenry

Quote
Here's a circuit


The 0.15ohm ressitor needs to be 100x of its current value.

You can buffer that pnp with a power npn / n-ch mosfet so you can use a smaller pnp device instead.

dhenry



thank god we don't live in a simulator.


You don't really know that. (Sorry, off topic, but couldn't resist.  ;))


The latest on that is that they have proposed tests to see if we are real or not.

LarryD

As long as there is a ground connection between the power supplies you don't have to connect the Positive outputs together. Therefore you can have 1,2,3,4,5... regulators connected together (as long as there is a common ground)!
The way you have it in your schematic isn't the same as how you have it wired up!

eloso


I'm using linear regulator because it is easy to make and it is only a school project. So i will only use it once. I already have a big heatsink and thermal paste so generating heat is not a problem.


I think you under-estimate how hot a regulator will get passing 1.5A of current.  I'm too lazy to do the math, but if it's dropping any voltage whatsoever, it may be impractical to keep the die temperature cool enough to survive.  I built a 28v-to-15v regulator to supply 100mA or so of current, and the little 1"x2"x0.5" heatsinks got hot enough that I couldn't touch them comfortably.  You're asking for a lot more current than that.  Trust me -- that "1.5A" spec on the regulator is nothing short of wishful thinking.  There's no way you'll keep the case cool enough that the die won't damage itself at that kind of load.

That is unless the 1.5A spec is for a very brief, worst-case, transient load... and average current is really *significantly* less.


I see, but based on the replies in my topic i can draw a lot of current from pnp transistor not the regulator. My heatsink is 80mmx41mmx15mm. Thank you for the warning. Now i will focus on adding a pnp transistor.

eloso

I tried this circuit a while ago in a breadboard and it is not a working. I tried to draw 1 ampere by using a load of 10 ohm 5 watt resistor and the regulator gets very hot the pnp transistor is very cold and it seems it is not the one supplying it. I'm sure my connections are correct.

http://www.zen22142.zen.co.uk/Circuits/Power/boosti.htm

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