• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 345 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UC28025: Request the recommended part?

David Kim2
Genius 3305 points
Part Number: UC28025
Other Parts Discussed in Thread: UCC28C44

Hi

I'm looking for a part to apply to the following specifications. 

-spec-

Input: DC 380V

Output: DC 7KV / 10W

Topology: hard Switching Half-Bridge

Please recommend me the most appropriate IC.

It's even better if evm is provided.

Thanks

  • 0
    TI__Expert 7395 points

    David,

    thanks for the interest in TI here. Let me ask an applications engineer to comment here.

    Regards,

    John

  • 0
    TI__Expert 7395 points

    David,

    Looking at this again, is this really only 10W output power? If so, i think you could get away with a boost or flyback(if you need isolation). It's pretty low power for a 1/2 bridge. 

    I would suggest using UCC28C44 as either boost or flyback. I don't have a reference design or EVM that meets this requirement closely.

    Regards,

    John

  • 0 in reply to John Stevens
    Genius 3305 points

    It's 10W, but it's 10KV.
    How does that sound?

  • 0 in reply to David Kim2
    TI__Mastermind 32775 points

    David,

    For non-isolated boost, the conversion ratio is 26 and the duty cycle, D~96%, 1-D=4%. The boost is most efficient at lower D (this design is high D) and the stress on VDS of the MOSFET is VDS=VOUT=10 kV! No to the non-isolated boost.

    For the flyback approach you need to consider the turns ratio and what the reflected output voltage will be from the high voltage secondary back to the primary. To get a good answer, you need to work through the flyback transformer design including core selection, Ae, Bmax, Lm and Ipk to get Np (primary required turns) and then work through Ns (secondary required turns) to get the reflected voltage seen by the primary MOSFET. The max VDS seen by the primary MOSFET will be VIN+Vr+Vspike and you may be surprised at how high the VDS stress is for 10 kV output. Maybe a HV SiC MOSFET can be used but otherwise this HV VDS may preclude the flyback.

    If the HV of the flyback is unmanageable, the two-switch flyback might be a good option. The voltage stress for each switch would be half that of a single-switch flyback. The two-switch flyback requires a level shifted high-side drive but the switching is synchronous (timing is less critical, dead-time is not required) as opposed to the half-bridge which is asynchronous (timing and dead-time are critical).

    Maybe a two-stage, cascaded approach using a non-isolated SiC or IGBT boost front end to get the voltage as high as the SiC or IGBT can handle and then followed by a flyback with lower turns ratio, lower Vr?

    The half-bridge gives full transformer utilization, which is not really necessary at this power level and limits the max VDS on the primary switches to VIN. Hard-switching at HV could introduce large HV spike on VDS which may need to be dissipated in RC snubber.

    HV flybacks were used in CRT monitors/televisions and flash tube generators - something you might Google for guidance?

    Regards,

    Steve M