LM2596-adj converter simulation

Thread Starter

Fervi

Joined Jul 18, 2019
11
Hey guys i need to simulate the LM2596 on pspice or any simulation program. I have downloaded the models on TI (they doesnt work to me, i dont know why) but they are model for 3V, 5V and 12 V output and i dont need them, I need a 24 V output so that's the reason i need the kind -adj.
I saw in this forum a zip for the adj kind but i dont know how to insert it in my circuit becouse in that zip i found files .asc, .plt or .txt and dont know what to do with them. I attach that zip
Well, anyone could explain me how to import that zip models into pspice or supply me another file with a LM2596-adj??
Thanks in advance and karma!!
 

Attachments

ericgibbs

Joined Jan 29, 2010
18,841
hi,
I have tried to those asc files, but I get an error message 'the LM2596 requires 5 parameters, only 4 are specified ' I have tried to debug without success.
E
 

Thread Starter

Fervi

Joined Jul 18, 2019
11
:D:D:D
I think i have a hard problem here, i have been for a week trying to simulate it and i couldnt yet.
Btw what did u exactly tried when the program gave u that error??
Fervi
 

ericgibbs

Joined Jan 29, 2010
18,841
hi,
Just tried to run the asc file in LTSpice, it will not run, but puts out that error msg.
Looked thru the txt files to try to identify the missing parameter, no luck.
E
 

eetech00

Joined Jun 8, 2013
3,934
hi,
I have tried to those asc files, but I get an error message 'the LM2596 requires 5 parameters, only 4 are specified ' I have tried to debug without success.
E
Hello,

The LTspice developer (Mike E.) recently made a change to the required parameters for a voltage source. It has caused many complaints from various LTspice users. I'll have to take a look at the LM2596 spice code and fix the errors. Check back here in a day or two.

eT
 

eetech00

Joined Jun 8, 2013
3,934
Hello,

The LTspice developer (Mike E.) recently made a change to the required parameters for a voltage source. It has caused many complaints from various LTspice users. I'll have to take a look at the LM2596 spice code and fix the errors. Check back here in a day or two.

eT
Here is the corrected LM2596 model file.

eT

.
 

Attachments

Thread Starter

Fervi

Joined Jul 18, 2019
11
Here is the corrected LM2596 model file.

eT

.
Hi eT, i downloaded and unzip that, what do i have to do now? They are files .asc and i dont know what to do with them.
I opened the adj version (the one i need) and i attach what happens to my program.

Fervi
 

eetech00

Joined Jun 8, 2013
3,934
Hi eT, i downloaded and unzip that, what do i have to do now? They are files .asc and i dont know what to do with them.
I opened the adj version (the one i need) and i attach what happens to my program.

Fervi
The schematic and model is designed for LTspice. You have to use LTspice.
 

Thread Starter

Fervi

Joined Jul 18, 2019
11
The schematic and model is designed for LTspice. You have to use LTspice.
Okay i downloaded and simulated and it works with 5V output ;)
It just doesnt to a 24V output.
I am using the expression given in some datasheets to calculate the resistors:

R2=R1*(Vout/Vref-1)

Does this LM2596 responds to that expression?
I'm using input voltages between 40-60V. Actually, in real, the LM2596 doesnt work to that large input voltages and i use LM2596HV(High Voltage) i assume this is a question that we can skip in simulation or may u put the limit?

Fervi
 

eetech00

Joined Jun 8, 2013
3,934
Okay i downloaded and simulated and it works with 5V output ;)
It just doesnt to a 24V output.
I am using the expression given in some datasheets to calculate the resistors:

R2=R1*(Vout/Vref-1)

Does this LM2596 responds to that expression?
Yes.
You can use any recommended expression from the datasheet.
Make sure to use the adjustable model

I'm using input voltages between 40-60V. Actually, in real, the LM2596 doesnt work to that large input voltages and i use LM2596HV(High Voltage) i assume this is a question that we can skip in simulation or may u put the limit?

Fervi
The model doesn't support that. You, the designer, need to honor the max input specifications from the datasheet or the device will burn up.

Here is a quick example below (input=30V Output = 24V):

upload_2019-7-30_6-10-43.png

eT
 

Thread Starter

Fervi

Joined Jul 18, 2019
11
Yes.
You can use any recommended expression from the datasheet.
Make sure to use the adjustable model



The model doesn't support that. You, the designer, need to honor the max input specifications from the datasheet or the device will burn up.

Here is a quick example below (input=30V Output = 24V):

View attachment 182812

eT
Yeah, due to that reason i'll use the HV version in real (that component version let it have a high voltage)
I was just asking if u created the component with the input limit specification.

Ok, but in ur squematic there are some things i couldnt understand.
Why did u only changed the Vin once and u dint on the *.step param section??Same with Iout, why dint u changed it on .step param too?
how did u changed Iout in the no .step param section? which calculation did u?
thank so much for ur help btw.
Greetings, Fervi.
 

eetech00

Joined Jun 8, 2013
3,934
Ok, but in ur squematic there are some things i couldnt understand.
Why did u only changed the Vin once and u dint on the *.step param section??Same with Iout, why dint u changed it on .step param too?
Because it wasn’t necessary for the 24 v demo.

how did u changed Iout in the no .step param section? which calculation did u?
thank so much for ur help btw.
Greetings, Fervi.
The params show the calculation.

eT
 

Thread Starter

Fervi

Joined Jul 18, 2019
11
Could change that 45V max input limitation or tell me how i could change it?
Thanks for ur help and karma
Fervi
 

Yffig

Joined Aug 25, 2019
29
Hi eetech00,
Thanks for your work and the correcction you made to it.
I now have a working model for the LM2596_ADJ to work with in a linear power supply pre-regulator project i'm working on.
But the model you made seems to have a switching frequency far too low: around 14KHz instead of the 150KHz claimed by the datasheet.
Is there any reason for that ?
Regards
Yffig
 
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