LM317 Pspice

[krispots]

ok, so i'm trying to simulate this circuit. i'm using transient analysis on this one and then when i clicked run, the green circle above the Lm317 appeared. Is there a problem in this circuit? or this anything first i must do before i can use the LM317 here? the voltage readings indicate that there is a problem and i don't know what it is. Anyone can help me?

I'm using Orcad Capture 9.2

View attachment 41047

 

[Hero999]

You haven't said what software you're using so how are we supposed to know what the green circle means?

There are two things wrong with the circuit: R1 should be 120R or less for the LM317 and the output voltage is set for more than 28V so it will be in drop out; maybe the green circle signifies the latter?

 

[krispots]

oh, sorry about that, i'm using orcad capture 9.2.

i'm trying to simulate a typical application based on the circuit described in a national semiconductor datasheet for the Lm317

here's the link
http://www.futurlec.com/Linear/LM317HVT.shtml

i'm new to using orcad, i thought maybe you need to tweak something on the LM317 parameters which i currently don't have any idea of.

thanks for the reply

 

[Hero999]

I've never used Orcad so I can't help you with that.

The only thin I can suggest is addressing the concerns I raised in my previous post then trying again.

 

[krispots]

i tried reducing R1 to 120 ohms, still the problem exists.

i found out now that the green circle signifies a lack of pspice template for the LM317, and maybe the program thought of it as an open circuit.

thanks for the reply.

still, if anyone can help me or anyone can post a link to a tutorial using orcad, that would be much appreciated.

 

[Hero999]

i tried reducing R1 to 120 ohms, still the problem exists.

What output voltage do you need?

The circuit is no good if the values are wrong.

 

[krispots]

i'm experimenting with the simulation software to match the actual LM317 and the part in orcad, so that i can just simulate in the future if i need some output voltage. Unfortunately, i don't know yet how to use the program. 

 

[ardian]

Although LM317 is an adjustable regulator, it is sometimes preferred for high-precision fixed voltage applications instead of the similar LM78xx devices because the LM317 is designed with superior output tolerances