I have a LED controller that has several temperature sensors in different places of the system. I want to implement an overtemperature protection for the system.
Now this would be theoretically a simple excercise but the thing is that the system needs to keep on operating at a reduced output power when overheated. The ambient temperature load can vary greatly (sun/no sun etc). So the feedback needs to be proportional, simple hysteretic control will not do. In essence if the ambient thermal load is large enough to trip overheat protection, the system starts operating as an PI controlled unit with the limit acting as a setpoint.
I'm thinking of doing this with a trusty PI control sans the delta function. Is there any proven method of implementing this type of control which in normal operation remains permanently below the setpoint? If I do straight PI control the I portion will grow excessive and will prevent reasonable response to overheat condition.
I'm thinking of imposing a hard cap on "below setpoint" integral portion. For example it cannot exceed whatever 32 minutes at 1 degree below setpoint works out to. This would allow the integral to "reset" relatively quickly at overtemperature condition.
Is this a good solution?