DC-DC converters: differences between a resistive load vs a CPL, and the "unknown load" case

Conceptual question here: let's assume a simple DC-DC boost converter, with an inner current control loop, and an outer voltage control loop. The question is about the outer voltage loop (which generates the "I_desired" current command for the inner current loop).

In general, IF we have a resistive load, then our outer voltage loop can be a simple PI loop:

I_desired = PI(Vout_actual - Vout_desired) <--- We can tune the proportional and integral gains as needed

IF we have a CPL (constant power load), then the current command is something like:

I_desired = "Power_CPL" / Vin <--- This is a simple appoximation, which assumes that we KNOW the power that the CPL load demands

What if we have an "unknown" load? Our load could be:

• Resistive
• CPL (where we DON'T know the power demanded by the CPL)
• Resistive in parallel with a CPL (I.E. "both")
• Resistive, then a CPL (I.E. the end user switches OUT a resistive load, and then switches IN a CPL [with unknown power demand])

There are many more combinations of the above loads, but I hope I've made the point clear.

--> Are there control approaches for generating "I_desired" that can cover these unknown combinations of loads?

Answer 1

[Joel Van Sickel]

There is no converter/controller than can handle any load, but in general, you can use current mode control for constant power applications and voltage regulaiton applications.