This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TIDM-02008: gain and pashe margin dip between lab2 and lab3

Part Number: TIDM-02008
Other Parts Discussed in Thread: SFRA


We are evaluating TIMD-02008 design and I have run into an issue.

I followed the labs for a system bring up and managed to run software frequency analyzer successfully. When running in PFC mode both in open loop (lab1) and closed current loop (lab2) I get similar frequency response to the one described in reference design document (but with a lower magnitude). See below: 
What could be the cause of this difference in magnitude? Most components match reference design, although the inductors are slightly different with marginal difference in inductance and resistance.

Now that I am trying to perform lab3 I run into another issue, here is a frequency response I get:

What could be the cause of discontinuity of both magnitude and phase curves? (also note that magnitude is still lower than what is expected according to reference design)

Could this be caused by my setup? I am supplying AC through variac and I am using electronic load with 500Ohm constant resistance setting to load the DC side.

Also should be pointed out that I am supplying 5, 12 and 24V from bench power supply which means that all isolated and non isolated power rails are powered from same PSU. (could this cause similar issues?)

Also there is a side effect of weird buzzing noise coming from both the pcb (to the lesser extent) and seems like same noise comes from DC load. (when board comes out from undervoltage in lab 3 and noise increases with current)

I have also checked to see if all legs with gan mosfets are switching, by measuring between Inductor leg and a ground, and I can see 100kHz with varying duty cycle (although I'd probably expect it to be more stable for constant load), there are weird rounded or incomplete periods of a square wave from time to time which shouldn't be there.

What would be the best way to find the source of this issue as to avoid stabbing in the dark?

Best Regards