Author Topic: A simple low drop linear power supply by MIC29752  (Read 1719 times)

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Offline Md Mubdiul Hasan

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A simple low drop linear power supply by MIC29752
« on: December 19, 2016, 09:00:53 am »
Hello,

Kindly take a look this attachment.
I am trying to make a low drop/ current control regulator circuit.
Online circuit is available.
Need to be analyze more.

LM358 is using for  a buffer may be.
Kindly explain more, what bottom IC is used in this design.
Is it a low drop high current application?



« Last Edit: December 19, 2016, 09:02:52 am by Md Mubdiul Hasan »
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Offline mariush

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Re: A simple low drop linear power supply by MIC29752
« Reply #1 on: December 19, 2016, 09:18:45 am »
The opamp ( LM358) is there to help both linear regulators (MIC29752) output the same voltage and work together so that in total they can deliver more current.

Each one can do up to 7.5A , together as you can see from the picture they can do up to 15A.

The 0.01 ohm resistors on the output of each regulator are also important components in making sure both regulators work and it's not just one of them doing most of the work.

REad the datasheet for that regulator if you want to learn more: http://ww1.microchip.com/downloads/en/DeviceDoc/mic29150.pdf
 
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Online Kleinstein

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Re: A simple low drop linear power supply by MIC29752
« Reply #2 on: December 19, 2016, 10:59:48 am »
There is a small mistake in the circuit: there should be no direct connection of the two outputs. So R3 should only go to the upper regulator.
 
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Offline jeroen79

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Re: A simple low drop linear power supply by MIC29752
« Reply #3 on: December 19, 2016, 03:41:17 pm »
Yes, remove the link between R3 and the output of the lower regulator.
Then the opamp will keep the voltage over R4 and R5 the same so that each regulator will supply the same amount of current.
 
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Offline Md Mubdiul Hasan

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Re: A simple low drop linear power supply by MIC29752
« Reply #4 on: December 20, 2016, 12:47:27 am »
Hello Sir  Mariush,

Thank you to keep your eyes in this post.

Quote
help both linear regulators (MIC29752) output the same voltage and work together so that in total they can deliver more current

Yes it makes sense, did you see both output are connected its non-inverting point with R3?


Quote
both regulators work and it's not just one of them doing most of the work.


Definitely first one, because its adj point controls the output voltage measuring the ratio of R1 and R2 with a constant.(according to datasheet)

How about the feedback capacitor on LM358, does it work for frequency dependent impedance ?
It seems like , LM358 is using for just keeping the bottom ICs output at constant.

« Last Edit: December 21, 2016, 04:40:32 am by Md Mubdiul Hasan »
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Offline Md Mubdiul Hasan

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Re: A simple low drop linear power supply by MIC29752
« Reply #5 on: December 20, 2016, 01:01:44 am »
Hello sir Kleinstein,

Thank you to your suggestion.

I think, if you look the opamps inverting and non-inverting inputs, it should have some differences.
If we remove lower portion of R3's wire, that means the input difference will be more, that will cause unbalance situation on bottom IC's output.

R3 can make a difference(connected with both output)  and taking another reference from same bottom output.
« Last Edit: December 21, 2016, 04:41:50 am by Md Mubdiul Hasan »
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Offline Md Mubdiul Hasan

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Re: A simple low drop linear power supply by MIC29752
« Reply #6 on: December 20, 2016, 01:05:08 am »
Dear Sir Jeroen79,


Quote
then the opamp will keep the voltage over R4 and R5 the same so that each regulator will supply the same amount of current.

Kindly explain it more. :)
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