Obtainign Bode plots for SMPS feedback loop?

[grigson]

Hello,

Is there any company, anywhere in the world, that can provide us with Bode Plots for the SMPS Feedback loop if we send them our SMPS schematic and the specification to which the SMPS is intended.?

We would pay for this.

 

[Skogsgurra]

You can do it yourself. Linear Technology's LTSpice does that. And it's free.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[grigson]

Hi,

As far as i see, LTSpice doesnt have voltage mode full-bridge pwm controllers, so i wouldnt be able to put many of our schematics in there.

I have previously used LTSpice to get individual points on the Gain and phase plots......but it would be very time consuming to get enough points for a whole plot.

I have the book by Basso that gives transfer functions for certain standard TL431/Opto feedback circuits, but many of our schematics dont use those standard types, because of eg high output voltages such as +/-50V.

 

[Comcokid]

There is a good size LTSpice users group on Yahoo where people have created many non-Linear Tech part models for use in LTSpice. Additionally, many PSpice component models will run or only need minor modifications to run in LTSpice. You may be able to find the model for the voltage-mode chip you're using.

The drawback to doing the SMPS loop in LTSpice, or any other spice program is that those little minor layout parasitics tend to make your loop response a bit different. Not only that, the typical spice transformer (& inductor) is not much like a real-world transformer and no one seems to have come up with a usuable general-purpose model.

I know what you mean about the TL431 - The SMPS world is in love with it, but it's not ideal for all feedback needs. I've used the LT4430 for SMPS feedback where the output was around 200Volts.