Many thanks. I then understand your question as how feasible is the use of a CPLD in forming the control circuit for an SMPS?
I have only very basic knowledge of PLDs. I believe you can form an SMPS control circuit with a CPLD but a priori I see no real economical or technical advantage of doing it. SMPS ICs with almost any functionality included, apart from capacitive and inductive elements, have been optimized for decades. That means you can form a powerful SMPS with a single IC and a minimum of external components for an unbeatably low price.
A CPLD is a complex logical circuit that will need you to add almost any power component including capacitive and inductive elements to the CPLD before you have an SMPS circuit. I can only imagine this to be more expensive than using a single dedicated SMPS IC.
The CPLD solution will allow you to implement weird and non-linear regulation characteristics but I see little benefit from that. An ATTiny13A micro-controller can do many such tricks, though perhaps at lower speed.
You are clever when you ask yourself what new elements you learn about can be used for also outside of the obvious use. You know much more about CPLDs than I so try to relate the advantages of a CPLD with the features needed for an SMPS control circuit. My immediate impression is that the overlap is limited, in particular when you take the vast number of SMPS ICs into account as alternatives.
