TL494 buck converter, trouble simulating

Thread Starter

Tryingtomakethiswork

Joined Dec 21, 2013
4
Hey all, new here. Sorry if this thread is misplaced.

I've been working on a project using a TL494 PWM chip to drive a buck converter. Problem is my simulation is having convergence errors. Attached is the picture of my schematic. If I replace the TL494 with a function generator I can run the simulation just fine, but when I use the TL494 and try to incorperate a feedback loop I can't seem to get it to work. Would love a solution, thanks in advance to all those that help out!



Sorry if this picture doesn't work, it's been attached as well.
 

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Thread Starter

Tryingtomakethiswork

Joined Dec 21, 2013
4
These supply currents failed to converge:

I(X_U3.xinsttl494.Ev103) = -36.90nA \ -110.41pA
I(V_V2) = 1.967uA \ 95.04nA

These devices failed to converge:
Q_Q3 Q_Q4 X_U3.xinsttl494.X_U3.X1.Q1 X_U3.xinsttl494.X_U3.X2.Q1
 

Thread Starter

Tryingtomakethiswork

Joined Dec 21, 2013
4
Does LTspice just not have a library for it? You're the second person who was sad about not being able to help due to using LTspice. I'm super new to the simulating world, so I don't know much about anything other than Orcad's PSPICE, and even then it's minimal :(
 

Dodgydave

Joined Jun 22, 2012
11,284
Dont understand what you mean by Convergence Errors, also why are you pulsing L2 with 32V and looking to get 16V output across C3, using a N chan mosfet as a follower, when your supplying it with 16V already?
 
Last edited:

Alec_t

Joined Sep 17, 2013
14,280
Why have you got pin 11 of the 494 grounded?

I've now found a sim model on Yahoo for the '494.
With a few changes to your circuit I got the sim to run initially, but got a 'time step too small' error at ~1ms sim time when the ripple on the output voltage across R12 had dropped to a small value.
Here's the amended circuit:
 

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