PSU "plant" gain/phase

Is it possible to use the Cleverscope FRA function to measure the control to output or "plant" transfer function of a power supply?

I would connect the signal generator across a 20 Ohm injection resistor in the voltage feedback path and measure the power supply output voltage on channel B as usual, but I would move channel A to the voltage at the optocoupler LED anode, which is proportional to feedback current in my power supply.

The motivation here is that I got the calculations wrong for tuning the compensator and the supply is not stable. I plan to really slow down the compensator (should stabilize the supply), measure the plant transfer function using the setup above, and then properly tune the loop based on the measured plant transfer function.

Is it possible to use the Cleverscope FRA function to measure the control to output or "plant" transfer function of a power supply? I would connect the signal generator across a 20 Ohm injection resistor in the voltage feedback path and measure the power supply output voltage on channel B as usual, but I would move channel A to the voltage at the optocoupler LED anode, which is proportional to feedback current in my power supply. The motivation here is that I got the calculations wrong for tuning the compensator and the supply is not stable. I plan to really slow down the compensator (should stabilize the supply), measure the plant transfer function using the setup above, and then properly tune the loop based on the measured plant transfer function.

This ended up working great.

This ended up working great.

Sorry about the lack of reply, which should have been yes you can do that. I'm glad you worked it out.
We dod have a new improved FRA module coming along, which is faster, and achieves better SNR. I'll let you know when it is out.

Sorry about the lack of reply, which should have been yes you can do that. I'm glad you worked it out. We dod have a new improved FRA module coming along, which is faster, and achieves better SNR. I'll let you know when it is out.