[LTSpice] - Find/Make a diode similar to HEM125PA

Discussion in 'General Electronics Chat' started by Henrique Orlandini, Dec 26, 2015.

  1. Henrique Orlandini

    Thread Starter New Member

    Dec 23, 2015

    I've been trying to make a single solar cell model (which should be easy), but I'm having a problem with the diode.

    Basically, a solar cell should be composed with a current source, a diode, one shunt resistor, one series resistor and a load. But the diode isn't a simple silicon one, it needs to have some unique properties (so it'll work as a bypass diode and etc).

    I already tried quite a few diodes from LTSpice library with varied breakthrough voltage and forward current, but none of them seems to give the IV curve from a solar cell.

    I googled some schematic and found a model called "HEM125PA", from Honda. I download the files, put in the circuit and it worked. Basically, the only thing that changed from my circuit to Honda's one is the diode, which I can't get any info about it.

    I opened the .sub file and got this:

    *REMARK: Pmax=124.7(W)
    *All Rights Reserved Copyright (c) Bee Technologies Inc. 2009
    .SUBCKT HEM125PA Plus Minus
    R_RS1 N00A Plus 500.3637m
    R_Rsh1 Minus N00A 193.200k
    D_D1 N00A Minus DIODE_HEM125PA
    I_I1 Minus N00A DC 0.66001
    .Model DIODE_HEM125PA D
    + IS=52.4058u
    + N=1.1374k
    + RS=300.5273m
    + IKF=0

    So, it seems that the .sub contain the whole device description to LTSpice. Anyone with a knowlegde of how to read this can tell me what "IS", "RS", "IKF" means? From what I get, RS1 is the series resistor, Rsh1 is the shunt resistor, D1 is the diode (which I can't get any info about it²) and I1 is the current source.

    tl:dr; I need to find a diode that makes a solar cell work. HEM125PA seems to be one, but I don't have its specifications. Could anyone help me with this? Thanks in advance.

    P.S.: I do not know if "General Electronics" is the right place to post a LTSpice related topic. If it isn't, I'm sorry.

    P.S.2: I tried the Yahoo Group of LTSpice, but they were quite... resistant to give me a diode model, instead they gave me whole circuits which again, I couldn't get the diode info. As a beginner in electronics, the basic are the most important aspect of any project I engage. Thanks.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Looks like this panel has a MPP of 125W when loaded with a 367Ω resistor, so that the load voltage is ~215V @ 580mA.


    Try running my .asc
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    This bit is the diode model:-
    .Model DIODE_HEM125PA D(IS=52.4058u N=1.1374k RS=300.5273m IKF=0)
  4. eetech00

    Senior Member

    Jun 8, 2013

    I created an equivalent circuit from the subckt file (attached)
    I didn't test it.

    The diode is D_D1 and uses the .model DIODE_HEM125PA model definition.
  5. Henrique Orlandini

    Thread Starter New Member

    Dec 23, 2015
    I tested both of your suggestions and they worked perfectly.

    And since Alec_t said that IS, N, IKF and RS are part of the diode model, I think I need to know what those mean.

  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Have you read the LTSpice help file for the capital D (diode) component?
  7. Henrique Orlandini

    Thread Starter New Member

    Dec 23, 2015
    No, I haven't, but I'll look up for it and read it right now.