# Laptop power supply's capacitor burnout

#### w00bler

Jul 20, 2023
8
Hello all,
Charger's capacitor got burned and as a consequence it did not work and no power reached to the laptop.
One of the capacitor's duties is to store electrical energy and gives it to the circuit when ever it needs.
Why when capacitor gone , power supply not working ?
Instead storing in capacitor, directly giving power to the whole circuit ?

thanks

#### Externet

Aug 24, 2009
900
Welcome.
Replace the bad capacitor and try if works. Storing energy is not the only effect of a capacitor in a circuit.

#### w00bler

Jul 20, 2023
8
Welcome.
Replace the bad capacitor and try if works. Storing energy is not the only effect of a capacitor in a circuit.
It has already been replaced. My question was why capacitor is needed for working charger properly and without that it doesn't work.
Please little bit explain from technical point of view that why charger does not work without capacitor ? How circuit designed ?
In many example I've seen that in either parallel or series, capacitor acts and in case of absence of this electronic part , power supply can provides energy to the rest of the circuit.
If you could show me an example to clarify , I am more than grateful .
Thank you

#### Delta Prime

Jul 29, 2020
2,206
If you could show me an example to clarify , I am more than grateful .
Thank you
An example would only lead to more questions and that is not the scope or breath of my abilities to teach you in a single thread..
Current is the flow of charge over time.You'll find that statement in almost every textbook.... It is incorrect.
Current does not flow! But it paints a picture in the mind!
So I will continue painting.
You wish a technical point of view unfortunately because of your questions you are not there yet.
I only provides you a simple explanation to which you can comprehend about the function of capacitors.
It takes current to change your voltage across the capacitor.
The faster you try to change the voltage the more current you need.
Capacitors will prevent the voltage that appears across them from charging rapidly. Capacitors look like voltage sources for a short period of time.
When a voltage across a capacitor can't change rapidly. There is no constraints on how fast The current can change.
Current through the capacitor can change from 0 to a large value instantly.
Another way of seeing it is current can change abruptly.
If you can think of current as a fluid then you could think of the capacitor as a large tank. The height of water in the tank represents the voltage in the capacitor. Well we can instantly turn the flow of water off and on(meaning we are changing the current) we cannot instantly change the water level inside the tank.(Meaning we cannot change the voltage across the capacitor instantaneously).
It's value changes as a result of integration of the current being added to the capacitor (the tank).
The value of the capacitance
is related to the area of the tank.
This is as far as I can take you.
Provide me a link to the source of your information so I may correct it. Or break it down in a manner in which to understand.

#### kellys_eye

Jun 25, 2010
6,514
In the case of a switched mode power supply, which is presumably what we're referring to(?) the likely dud capacitor could be on the secondary side and the lack of smoothing ability makes the feedback signal (for output regulation) impossible for the switching controller to 'see' properly therefore it adopts a 'there's a fault, close it down' position (very simply speaking).

If it's on the primary then it messes with the main switching device (MOSFET) which requires a relatively steady DC supply and dud capacitors make this more 'ac' than dc.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,799

Feb 19, 2021
824
Output C considerations :

Output and Input considerations :

Regards, Dana.

#### w00bler

Jul 20, 2023
8
Hi
Capacitors will prevent the voltage that appears across them from charging rapidly. Capacitors look like voltage sources for a short period of time.
Yes, I know that
If you can think of current as a fluid then you could think of the capacitor as a large tank
Yes, in the most reference this one has been mentioned as an example for capacitor's functionality
Well we can instantly turn the flow of water off and on(meaning we are changing the current) we cannot instantly change the water level inside the tank.(Meaning we cannot change the voltage across the capacitor instantaneously)
It means that we can not charge the capacitor while we are using it. [ capacitor should be first discharge then start to charging again]. In your example water tank must be empty then start to pour water into it.
I'll ask in related forum , but mostly these types of questions appear because I do not have enough knowledge in making/understanding electronic circuit(PCB) .

#### w00bler

Jul 20, 2023
8
In the case of a switched mode power supply, which is presumably what we're referring to(?)
Yes you're correct AC source to DC .
likely dud capacitor could be on the secondary side and the lack of smoothing ability makes the feedback signal (for output regulation) impossible for the switching controller to 'see' properly therefore it adopts a 'there's a fault, close it down' position (very simply speaking).
Could you please give me an image or a link to demonstrate an electronic schematic (circuit diagram) which I could see that "
... it adopts a 'there's a fault, close it down' position....

Thank

#### w00bler

Jul 20, 2023
8

As an schematic I meant st like this which @danadak.67138 shared already

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,799
It means that we can not charge the capacitor while we are using it. [ capacitor should be first discharge then start to charging again]. In your example water tank must be empty then start to pour water into it.
Not completely so: No full discharge is required. As soon as the capacitor has been discharged only partially, it can be charged ("filled up") again.
THis is what is happening when you use a capacitor to smooth out the voltage variations in a power supply: The load discharges the capacitor, the source re-charges the capacitor as soon as the voltage on the source side is higher than the voltage across the capacitor. See the reference in post #6 for a detailed explanation.

Note that this is only one use of a capacitor. Other uses include e.g.
- blocking of DC (a capacitor in a series circuit will only pass the AC content)
- being part of the resonant circuit in an oscillator
- being part of filters to selectively suppress or enhance specific frequency componnets in an AC signal
and many more.

@Delta Prime : What better question than "why is a capacitor required"? It may seem obvious to you, but obviously it is not obvious to the TS.

#### w00bler

Jul 20, 2023
8
Hi
Thanks
Just for last query .
[url=https://freeimage.host/i/HZJCYzX] [/URL]

In this circuit if we pull out/remove the capacitor , it still working fine ? AM I right ? My doubt is how removing the capacitor leads to malfunctioning of circuit ?Is it related to the circuit's design ? If yes, could you please show me a sample.

#### w00bler

Jul 20, 2023
8
No full discharge is required. As soon as the capacitor has been discharged only partially, it can be charged ("filled up") again.
Yes , I concur , first discharge will be done , then again filled up.
@Delta Prime : What better question than "why is a capacitor required"? It may seem obvious to you, but obviously it is not obvious to the TS.
To be honest , It was also obvious to me . Issue has been arisen when I've seen many circuit diagram that could be working without capacitor(circuit has capacitors in its circuit) my question was , why without capacitor , circuit will not working longer more.
I feel that the design of the circuit should somehow ensure that capacitor is working[otherwise it won't be working]

#### Delta Prime

Jul 29, 2020
2,206
my question was , why without capacitor , circuit will not working longer more.
I feel that the design of the circuit should somehow ensure that capacitor is working[otherwise it won't be working]
Apologies. Thank you for the clarification you have a thorough understanding of the design principles involved.
Your definition has helped me to see circuit analysis entirely different way.
Also... Thank you both for "dumbing" it up for me.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,799
it still working fine ? AM I right ?
No. Without capacitor the output voltage will follow the dotted lines. This is not suitable for operating a circuit.

#### kellys_eye

Jun 25, 2010
6,514
No. Without capacitor the output voltage will follow the dotted lines. This is not suitable for operating a circuit.
Put simply, the circuitry will 'see' the supply as switching on (when the voltage rises to the correct level for proper operation) and then off (as it falls back below the correct operating level) at the speed of your AC supply frequency. Circuitry needs a STEADY and CONSTANT voltage to work.

#### w00bler

Jul 20, 2023
8
Apologies. Thank you for the clarification you have a thorough understanding of the design principles involved.
Your definition has helped me to see circuit analysis entirely different way.
Also... Thank you both for "dumbing" it up for me.
Hello
greatly honored and feel proud about that.

#### Delta Prime

Jul 29, 2020
2,206
Hello
greatly honored and feel proud about that.
As you should.
It was my intent to make you feel something .
I was being facetious, self-deprecating puts people at ease.
If you're wound too tight... it doesn't work .

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