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

#### Henrique Orlandini

Joined Dec 23, 2015
5
Hello,

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:

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

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.

#### MikeML

Joined Oct 2, 2009
5,444
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

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#### Alec_t

Joined Sep 17, 2013
10,728
This bit is the diode model:-
.Model DIODE_HEM125PA D(IS=52.4058u N=1.1374k RS=300.5273m IKF=0)

#### eetech00

Joined Jun 8, 2013
1,787
Hi

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.

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#### Henrique Orlandini

Joined Dec 23, 2015
5
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.

Thanks.

#### MikeML

Joined Oct 2, 2009
5,444
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.

Thanks.
Have you read the LTSpice help file for the capital D (diode) component?