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

Thread Starter

Henrique Orlandini

Joined 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
+ 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.


Joined 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



Joined 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.


Thread Starter

Henrique Orlandini

Joined 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.