Hello. I am trying to understand the stability requirements of the UCC27840.
In the datasheet the open-loop Bode plot is given, but any other information on feedback is conspicuously absent from the datasheet.
1: Does the loopgain zero-cross frequency change with switching frequency or is it internally limited to the frequency shown in the loopgain plot?
2: The opto-feedback component values given in WEBENCH do not make any sense to me based on the loop gain curve given in the datasheet. Ccomp1 is not large enough to not interfere with zero-crossing at 1KHz and even then the circuit gain is too much. Can I assume the loop gain measurement is using the Vfb pin and the primary side transformer voltage? WEBENCH link is below.
https://webench.ti.com/webench5/power/webench5.cgi?origin=ODS__UCC28740&VinMin=90.00&VinMax=265.00&O1V=5.00&O1I=2&base_pn=UCC28740&AppType=AC&Flavor=None&isolated=Y&Topology=Flyback&op_TA=30&source=AC&line_fsw=60&optfactor=3&lang_chosen=en_US
