Greetings. I am designing a linear power supply with CC/CV capability. The output voltage is controlled by a voltage control loop that controls the current control loop. My current control loop has been compensated so that its crossover frequency is approximately 100 kHz. According to the simulation, a reasonable phase margin was achieved using a simple type I compensator.
Now, I want to close the voltage control loop. However, the plant transfer function is now strongly dependent on the load current and output capacitor parameters. My general goal is to create a stable system for any type of output load. I have modeled some cases of an output load and output capacitor value to estimate the best points to close the loop. According to the plant transfer function, the load variation influence starts at approximately 10 kHz. After 10 kHz, major variation in the plant transfer function shape can be observed under full or no load. Therefore, closing the loop at <10 kHz seems reasonable.
However, the capacitor value at the output drastically changes the whole picture.
Plant transfer functions for different configurations:
1 Output capacitor 100 uF 175 mR,
2 Output capacitor 470 uF 50 mR,
3 Output capacitor 2200 uF 20 mR,
What is the optimal strategy for compensator design in my case? Is it possible to lower the influence of capacitors and load parameters on the plant transfer function?