Other Parts Discussed in Thread: PMP40766, , UCC27517A
Hello TI Team,
I am currently designing an LLC DC-DC converter using the UCC256403. My design is based on the PMP40766 reference circuit.
After several tests in which the MOSFETs were damaged, I restarted the evaluation from the open-loop stage. I initially tested with the FQP8N60C MOSFET and confirmed that the switching waveforms were operating normally, as shown in the attached data.
However, when I tested with the IPA60R170CFD7XKSA1 MOSFET, I was unable to obtain the expected switching behavior. I am attaching the measurement data and schematic for your review.
My design specifications are VIN = 390 VDC and VOUT = 58 V, but for the open-loop test I am operating the system at VIN = 39 V with a target output of 5.8 V.
With the FQP8N60C, I was able to achieve the 5.8 V output even with the feedback circuitry connected.
However, with the IPA60R170CFD7XKSA1, there is no output voltage.
From the waveform observations, it appears that the low-side MOSFET does not turn on when using the IPA60R170CFD7XKSA1. I have checked all wiring and connections, and everything appears to be correct.
I would appreciate your guidance on the possible root cause of this issue, as well as recommendations regarding MOSFET selection criteria for use with the UCC256403.
Previously, I reached out to the TI team regarding the UCC256403 design, but the responses were either delayed or not very helpful. I would greatly appreciate prompt assistance this time.
Best regards,
