Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Recirculation Current in an Inductor

  1. Dec 6, 2006 #1
    I am trying to derive an equation for a simple inductive circuit which is the serial connection of an inductor (L), a resistor (R) and a Diode (D). The initial condition is a current flowing (Izero). Using Kirchhoff's law, the basic equation is:


    The inductor is L*di/dt, the resistor is i*R and a simple model for a diode is n*VT*ln(i/Is+1) where n, VT and Is are constants. So the differential equation becomes:

    L*di/dt + i*R = n*VT*ln(i/Is+1)

    Putting it in standard form:

    di/dt + [i*R/L - (n*VT/L)*ln((i/Is)+1)] = 0

    I don't know how to deal with the expression in the square brackets.

    Any suggestions?


    PS - the diode function comes from Idiode(v) = Is*(exp(v/(n*VT)-1) as used in spice. Later, I will sum in an additional term for a diodes ohmic resistance.

    Attached Files:

  2. jcsd
  3. Dec 6, 2006 #2


    User Avatar
    Science Advisor
    Gold Member

    Solve numerically the way Spice would. Also check your signs. Shouldn't all terms in your ODE be positive?
  4. Dec 6, 2006 #3
    Inductor is energy source re: Recirculation Current in an Inductor

    You are correct, since the energy is stored in the inductor, it should be (see the updated attachment):

    Vinductor = Vdiode + Vresistor

    It seems like there should be a way to solve it, maybe with a Taylor series or something like that.


    Attached Files:

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Recirculation Current in an Inductor
  1. Current DE Research (Replies: 3)