Other Parts Discussed in Thread: UCC24612, UCC2897A
Good day my fellow engineer,
Background:
1. My goal is to get an isolated 2V 30A converter working on the bench relatively quickly, and so I purchased five pieces of the UCC2897AEVM (active forward clamp evaluation module), which outputs 3.3V@30A. My intention was to modify these five 3.3V converters to function at 2V.
2. I then realized that I hadn't considered the gate drive requirements of the synchronous rectifier MOSFETs. (At 2V, there might be insufficient gate drive for these SR's, since this design features self-driven SR's.)
3. My first thought was to swap out the SR MOSFETs for Low-Gate Threshold devices, and I implemented the change. None of the converters worked after swapping out the fets, and i then realized that there was probably a conflict with turn-on and turn-off timing that created a simultaneous conduction situation (short circuit) on the output. (Apparently it was not as easy as swapping in the LGT fets!)
Question(s):
My thoughts are to design a direct drive circuit on a piggyback board as proof of concept before proceeding to an all-new design.
Do you think it is possible to build a small piggyback circuit to modify my 2897a EVM's for (direct-drive) operation down to 2V??? (I see that T.I. has chips that are designed for direct drive SR circuits, like the UCC24612, and so I was hoping for a simple solution like this.)
Can I use the existing secondary-side voltages to drive a chip that can then my SR's, or do I need to use pulse transformer(s) to achieve isolated gate drive signals from the UCC2897 outputs? (Either way, it's fine.)
Lastly, do you see any other problems with operating the 3.3V EVM's at 2 volts? (I can derate the output current to 20 or 25A if peak mosfet currents become an issue.)
Please tell me how you would proceed with my goal. If you feel that the ucc2897a EVM's were not the right choice from the beginning and that I should just scrap the converters and start over, could you kindly suggest what to do or what to buy?
Thank you, I eagerly await your feedback.
Best,
Henry Frankowski / AEB Sapphire Corporation
