Hello,
I recently purchased the STEVAL-DPSLLCK1 evaluation board and have been analyzing its design for research purposes.
During my analysis, I noticed what appears to be a discrepancy between the design parameters described in UM2348 and those used in UM2720. Therefore, I would appreciate your clarification on the following points.
Based on the schematic and resonant tank parameters provided in UM2348, I calculated the resonant frequency to be approximately 152 kHz, and the transformer turns ratio appears to be approximately 9:1.
With these parameters, at an input voltage of 400 V, the output voltage at the resonant frequency would be approximately 44.4 V.
However, according to the control strategy described in UM2720, the converter regulates the output voltage to 48 V while operating at a switching frequency higher than the resonant frequency under a 400 V input condition.
As far as I understand, in a typical LLC resonant converter, the voltage gain is generally less than 1 when operating above the resonant frequency. Based on the parameters described in the documentation, achieving 48 V output under these conditions appears to require a gain greater than 1, which seems inconsistent with the expected LLC operating characteristics.
Could you please confirm the following information?
- The actual transformer turns ratio (Primary : Secondary) used in the STEVAL-DPSLLCK1.
- The actual values of Lr, Lm, and Cr used in the resonant tank.
- The actual resonant frequency (fr) of the design.
- Whether UM2348 and UM2720 are based on the same hardware design parameters.
Based on my calculations, the parameters described in UM2348 and UM2720 do not appear to be fully consistent. Therefore, I would greatly appreciate clarification regarding the correct design parameters used in the STEVAL-DPSLLCK1.
Thank you for your time and support.
