I am developing a SIC based reference design and used the UCC25800 for gate drive bias power supply. I referred to your EVL board 基于UCC25800-Q1开环LLC驱动器的隔离电源方案设计 - 电源管理 - 技术文章 - E2E 设计支持 (ti.com) and used the same schematic and selected the same components value. but wen I power it on with 13.5V/15V input, it can't start. A very interesting phenomenon, when I put a digital multimeter on the both end Pin 4(OC/DT) and AGND with DC voltage stalls, it starts correctly and when I remove the probe, it still works normally.
it seams that OCP occurs even with soft-start and I tried to add a 33nF capacitor between VREG and RT to increase the soft start timing, no any improvement.
Below is my schematic, could you please help check and if you have suggestions? Looking forward to your feedback with many thanks!