Solving Diode Equation for Current?

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Discussion Overview

The discussion revolves around solving the diode equation for current, particularly focusing on the challenges of rearranging the equation due to the presence of the current variable in the exponential term. Participants also explore the diode ideality constant and its implications for modeling in MATLAB.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • Some participants express uncertainty about rearranging the diode equation to isolate the current, noting the complexity introduced by the current appearing both independently and within the exponential function.
  • There is a question regarding the diode ideality constant, with some participants suggesting it typically ranges from 1 to 1.5, while others consider assuming it as 1 due to lack of specific data from manufacturers.
  • One participant mentions using numerical methods, specifically Newton's method in MATLAB, to find the current.
  • Another participant observes that varying the ideality factor between 1 and 2 does not significantly affect the current in their model, leading to speculation about its relevance or potential issues in their code.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to solve for the current in the diode equation, and there are multiple views regarding the significance of the diode ideality factor in modeling.

Contextual Notes

Participants note the limitations of their approaches, including the unresolved nature of the diode ideality factor and the potential inaccuracies in modeling due to assumptions made about its value.

physics_197
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Homework Statement



I need to find the current, but not sure how to rearrange the equation because of the I in the exp.

Homework Equations



wmbeyd.png


The Attempt at a Solution



Thanks, just need to be pointed in the right direction. Seems like I will either be in ln or exp.
 
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Also, just a follow up question, the diode ideality constant... Is there a way to solve for it? My notes just say its between 1 - 1.5, Should I just assume its 1? The manufacturers data sheet does not mention a value for this.
 
physics_197 said:

Homework Statement



I need to find the current, but not sure how to rearrange the equation because of the I in the exp.

Homework Equations



wmbeyd.png


The Attempt at a Solution



Thanks, just need to be pointed in the right direction. Seems like I will either be in ln or exp.
Because I appears on its own and as the argment of the exponential, you can't solve for it using elementary operations.
 
physics_197 said:
Also, just a follow up question, the diode ideality constant... Is there a way to solve for it? My notes just say its between 1 - 1.5, Should I just assume its 1? The manufacturers data sheet does not mention a value for this.
Are you talking about I0? That one you can solve for.
 
No, I'm talking about just I. So how would I go about finding it?
 
physics_197 said:
No, I'm talking about just I. So how would I go about finding it?
Using numerical methods
 
Thank you, I used Newtons method on matlab, I think it should be correct :)

Also, do any of you have an idea about the diode ideality factor? I am trying to model a PV module in Matlab and the data sheet does not mention this. I read online that people tend to assume its just 1... Any ideas?
 
Nevermind! After running through the code using different values (between 1 and 2), There is no difference in terms of the current... well either, it can be neglected or my code is wrong (I tried entering a large number, that affected the current)
 
physics_197 said:
Thank you, I used Newtons method on matlab, I think it should be correct :)

Also, do any of you have an idea about the diode ideality factor? I am trying to model a PV module in Matlab and the data sheet does not mention this. I read online that people tend to assume its just 1... Any ideas?
Which variable is the diode ideality factor? That's what I was asking about in post #4.
 

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