But in good model, an overload would "jump out", prompting the designer that something is wrong.



Not necessarily true. Depends how good the model is.

I meant that the 7812 is a 1Amp regulator, but it doesn't current limit until at least 1.5A.
So the circuit could be quite happily running at 1.25A without alerting anyone, but it is outside the design spec.

 

I meant that the 7812 is a 1Amp regulator, but it doesn't current limit until at least 1.5A.
So the circuit could be quite happily running at 1.25A without alerting anyone, but it is outside the design spec.

Again, when a designer designs a model, they should have a good idea of what will be tested. What you describe can certainly be accounted for in the models design. For example, its behavior can be designed to adjust for any current limit you want, for experimentation purposes.

 

I meant that the 7812 is a 1Amp regulator, but it doesn't current limit until at least 1.5A.
So the circuit could be quite happily running at 1.25A without alerting anyone, but it is outside the design spec.

No, it's running within the current limit design spec.

You can say the same for most semiconductor models in a simulation, as they typically and happily run outside their current, voltage, power limits in the sim.
That doesn't mean you shouldn't use the model in your sim.

 

Hi Guys,
Please keep to the TS's topic.
Does anyone have an LTSpice component model/symbol combo for the LM7812 and LM7912
Moderation

 

@DerekP , when you have installed the regulator models, I should be interested to know if they tell you anything about your circuit that you wouldn’t have known from using a SPICE voltage source. Obviously, you have a particular circuit in mind, and the discussions so far have been general.