Voltage drop

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
I have 4 DC supplies of 6V, 3.3V, -5V and 5V. But in my circuit voltages drops like
6V to 5.4V
3.3V to 2.7V
-5V to -5.6V
5V to 4.3V.
Is this problem due to common grounding issues?
I cannot debug this problem.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi Atif,
Welcome to AAC.
What are the loads for the voltages, current ratings etc.?

What type of common 0V/Gnd are you using.
E
 

dl324

Joined Mar 30, 2015
16,846
Welcome to AAC!

You need to give us more information. What is the load on each power supply and what are their current ratings? What are the open circuit power supply voltages?

When discussing circuits, it's best to provide schematics.
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
Welcome to AAC!

You need to give us more information. What is the load on each power supply and what are their current ratings? What are the open circuit power supply voltages?

When discussing circuits, it's best to provide schematics.
Thanks for reply
For 6V, load is 3 Rf amplifiers, they draw 0.24A current.
For 3.3V, load is Pll ic which draws 0.16A current.
For 5V, load is Amplifiers, they draw 1A current.
-5V is used in switching IC and it draws 0.1uA current.
Before connecting load, Voltages are fine and there is no drop but when i connect load, the voltages drop.
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
Thanks for reply
For 6V, load is 3 Rf amplifiers, they draw 0.24A current.
For 3.3V, load is Pll ic which draws 0.16A current.
For 5V, load is Amplifiers, they draw 1A current.
-5V is used in switching IC and it draws 0.1uA current.
Before connecting load, Voltages are fine and there is no drop but when i connect load, the voltages drop.
hi Atif,
Welcome to AAC.
What are the loads for the voltages, current ratings etc.?

What type of common 0V/Gnd are you using.
E
Thanks for reply
My loads are Amplifiers and pll ic.as i replied in comment below.
6V has load of Amplifiers.They draw 0.24A current.
3.3V load is Pll ic which draws 0.16A current.
5V load is Amplifiers which draws 1A current.
-5V is used for switching and it draws 0.1uA current.
I have common all supplies ground.
With out connecting load there is no voltage drop but when i connect load all the voltages drop.
I think common grounding is the issue.
 

MisterBill2

Joined Jan 23, 2018
18,176
I have 4 DC supplies of 6V, 3.3V, -5V and 5V. But in my circuit voltages drops like
6V to 5.4V
3.3V to 2.7V
-5V to -5.6V
5V to 4.3V.
Is this problem due to common grounding issues?
I cannot debug this problem.
This sounds a whole lot like a computer power supply, and the problem sounds like a voltage drop in the black wires connection. That is why the negative voltage increased in magnitude.
 

MisterBill2

Joined Jan 23, 2018
18,176
Because the negative supply voltage reads more negative, that is an indication that the "ground" reference point being measured has moved more positive. So the problem is in the common side of the connections. more specific, it is in the connection located between the point of the negative meter attachment and the power supply common connection to the circuit.
And the drawing that was posted does not provide the information that was requested.
Do you know how much current is being drawn from each supply? and can you tell us what the rated current is for each power supply?
 

ericgibbs

Joined Jan 29, 2010
18,766
hi,
The TS asked this question.
Can the problem be that all dc voltages have not a common ground reference?
also his drawing shows no 0V connections.

So how does my post not answer his question.?
E
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
Because the negative supply voltage reads more negative, that is an indication that the "ground" reference point being measured has moved more positive. So the problem is in the common side of the connections. more specific, it is in the connection located between the point of the negative meter attachment and the power supply common connection to the circuit.
And the drawing that was posted does not provide the information that was requested.
Do you know how much current is being drawn from each supply? and can you tell us what the rated current is for each power supply?
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
By giver proper common ground reference now i have drop has been reduced
Now 6v drops to 5.75V
3.3V to 3.14V
-5V to -5.1V
5v to 4.45V
6V load draws 0.24A current
5V draws 1.2A current
But there is another problem without switching 5V supply, load of 6V draws 0.24A current from its supply which is correct but as soon as i switch on 5V supply, current of 6V supply drops to 0.16A from 0.24A.
I have checked impedence between common ground and board ground
Without turning on 5V supply, impedance is 0ohms which is correct but when i switch on 5v supply impedance changes to 89ohm which is a problem
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
hi,
The TS asked this question.


also his drawing shows no 0V connections.

So how does my post not answer his question.?
E
By giver proper common ground reference now i have drop has been reduced
Now 6v drops to 5.75V
3.3V to 3.14V
-5V to -5.1V
5v to 4.45V
6V load draws 0.24A current
5V draws 1.2A current
But there is another problem without switching 5V supply, load of 6V draws 0.24A current from its supply which is correct but as soon as i switch on 5V supply, current of 6V supply drops to 0.16A from 0.24A.
I have checked impedence between common ground and board ground
Without turning on 5V supply, impedance is 0ohms which is correct but when i switch on 5v supply impedance changes to 89ohm which is a problem
 

Thread Starter

Atif hussain shah

Joined Sep 6, 2020
18
hi Atif,
This is a marked up image, showing the Common 0V/Gnd for each supply, linked back to the central power supply,
E
By giver proper common ground reference now i have drop has been reduced
Now 6v drops to 5.75V
3.3V to 3.14V
-5V to -5.1V
5v to 4.45V
6V load draws 0.24A current
5V draws 1.2A current
But there is another problem without switching 5V supply, load of 6V draws 0.24A current from its supply which is correct but as soon as i switch on 5V supply, current of 6V supply drops to 0.16A from 0.24A.
I have checked impedence between common ground and board ground
Without turning on 5V supply, impedance is 0ohms which is correct but when i switch on 5v supply impedance changes to 89ohm which is a problem
 
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