Hi everyone,

I am designing an average-current control boost converter as a learning example. I am at the point where I would like to desing the current compensator for the current loop. To get the converter into the correct operating point, I use a slow voltage loop, which sets the reference current to the current loop. However as soon as I connect this voltage loop, my current loop measurement changes significantly.

Here is a picture of my current loop measurements.


The gain labelled "With voltage loop" is the current loop gain I measure when I connect the voltage loop.
The gain labelled "Manually fixed current reference" is the current loop gain I measure, when i dont have a voltage loop, and I manually set the correct current reference as to achive the desired operating point.

I measure the current loop gain by stimulating the output of the current compensator.

Does anybody have an idea what is going on? I always thougth that I can measure the current loop gain independently from the voltage loop.

Thank you all for your help.

Regards,

Samo

 

The gain of the current loop in a boost is dependent on the pulse width. It is not a fixed value. When your voltage loop is switched on, the operating point, and thus the pulse width changes. This may be why you see a difference.