As an instructor can I use previous work history as examples? I teach computer science (USA - graduate level).  I am teaching a software design course, and for a lecture I am to give on software anti-patterns I would like to use a real world example from an institution I was previously employed with.  To share the example I would create some abstract UML class diagrams showing the pattern that was used, I would explain the general purpose of the application and share where we got it wrong and how the students could learn from the anti-pattern.  I don't have to reveal any code (not that I have any) or share any trade secrets, and I don't even have to use the name of organization.  However if someone was to read my C.V. they could probably ascertain what organization I was speaking in reference to. 

Is it considered 'ethical' behavior to share this example? Or should I seek authorization from the previous institution? Are there certain things I should do to protect myself or further obfuscate this example?

As far as I know I never signed any sort of NDA or non-compete covenant.
Yes, students always like “real” examples. You seem to have “anonymized” it sufficiently.

Those examples that start “You have 3 widgets produced by a widget company...” are SO boring, using relevant material is always good.

Could you re-write it as a case study if that is relevant.