• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 553 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.

Original question:

lm5170-q1: How will Buck and Boost mode operation with unidirectional function of LM5170

LM5170-Q1: How will Buck and Boost mode operation with unidirectional function of LM5170

John Morrow
Prodigy 60 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: LM5170

I note the reply from Youhao Xi which suggests that the LM5170 can be used in buck mode to produce a 28V DC output.

Can you please explain how the output voltage of this device can de changed from the nominal 12 / 48V.

Thanking you in anticipation of a reply.

  • 0
    TI__Guru* 78400 points
    Can you tell me what do you really want? 48Vin to 28Vout, or 12Vin to 28Vout, or something else?
  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Youhao Xi,

    Firstly, many thanks for your prompt reply.

    My application calls for variable input range nominally 42 to 56 V DC and providing a 48 V DC output at approximately 42 Amps (~ 2 kW).  However there is also the possibility of the input exceeding 56 V in abnormal conditions.

    Based on previous posts my thoughts were that we could possible use a back-to-back devices with a buck-boost topology with 42~56V to say 38V to 48V.

    Could a prototype system be constructed using cascaded LM5170EVMs?

    Would one buck & one boost be sufficient for the power level or would parallel devices be required?

    I should be very grateful for your assistance.

    Thanking you in anticipation.

  • 0 in reply to John Morrow
    TI__Guru* 78400 points
    You are right at the point: you can cascase two LM5170 EVMs. For your applications, you need at least four phases to share the power. So, basically 4 LM5170s. Two for 4phase in one stage, and the rest in the other stage. The architecture will look like the followign:

    Input --> LM5170 in buck down --> 36V --> LM5170 in boost up-->48V.

    Hope this clarifies.
  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Thanks again for your prompt reply.

    Can I ask if you would parallel the output of the first stage (i.e. at the 36V bus) or only parallel at the 48V output?

    Thanking you in anticipation.

  • 0 in reply to John Morrow
    TI__Guru* 78400 points
    You should parallel for both stages: the stage from Input to 36V, and the stage from 36V to 48V, in order to evenly share power among the phases in each stage.