• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 317 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS40210: Duty cycle max.

Jose Paza1
Prodigy 220 points
Part Number: TPS40210

Hi,

I am operating the controller TPS40210 @ 110watts 32V In and 355V output using 18uSec period. I having overcurrent issues due to the max duty being generated by the TPS40210 is 99.5%. The off time at this duty is small recording <100nSec.. this created issues with turning off a high gatecharge mosfets.. Figure 2(right side) of the datasheet indicated that duty can be reduced if the frequency is increased. this will increase my loss as well which I prefer avoiding as I am running off batteries.

My question is, is their another way to reduce this duty cycle(200-500nSec off time would be OK)? BTW, the overcurrent engage when my DCDC fly back start after one second of TPS reaching 355V.

Rgds,

Jose

  • 0
    TI__Guru 61335 points

    Hello Jose,

    At the moment I do not have a solution how we could limit the duty cycle on the controller. Why does your controller get to such high duty cycles? Can we have a more detailed look on the requirements, maybe the duty cycle could be kept under control, e.g. by adding a softstart to the output or changing the transformer ratio?

  • 0 in reply to Brigitte
    Prodigy 220 points

    the issue only show at -40degC at the lowest input voltage of 32V. I believe I was able to do a work around by reducing the DCDC(Lt3751) consumption by 10W as at this extreme temp the downstream isolated DCDC is consuming more. I have the choice of changing the boost inductor and bulk caps to increase power of the boost controller but this will difficult to do at this stage.

    thanks.

    Jose

  • 0 in reply to Jose Paza1
    TI__Guru 61335 points

    Hello Jose,

    Does this workaround work for you? If yes, I think this is the best solution.

  • 0 in reply to Brigitte
    Prodigy 220 points

    I was able to resolve the issue by increasing the minimum off time from 200nsec to 800~1000nsec. the implementation is done by putting some sort of miller clamp with delay turn "on" on the input of the driver. I did put a driver between the controller and the boost mosfet. this did the trick and it is working now reliably at -40degC.

    thanks,

    Jose

  • 0 in reply to Jose Paza1
    TI__Guru 61335 points

    Hello Jose,

    Very good, thank you for the information.