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TIDA-00443: Inductor Current increases abnormally sometimes when sudden increase in load

Lenin Prakash
Intellectual 660 points
Part Number: TIDA-00443

Hi

  We have done a 900 W PFC based on  TIDA-00443 design. It's working fine in both constant output and boost follower mode.

we use a incandescent lamps as the load of the PFC for testing. However when we increase the load in steps of 100 W, we find no issue..

But whenever we increase the load in steps of 240 W, some times (not every time) the inductor current goes abnormally high and the AC input fuse blows off..

This we observed in the boost follower mode.

I guess the controller is capable of allowing almost 90 % increase in load as given in the design reference document.

We have not made any changes from the schematic or BOM..

Kindly help resolve this issue..

Thanks

Lenin.

  • 0
    TI__Intellectual 1260 points

    Hi Lenin,

    Appreciate your efforts in using the TI design and testing it for your application.

    I will analyzed this situation in detail before giving the feedback and will come back to you soon.

    I understand that, you are using multiple incandescent lamps  as load and switch them together for creating load steps of 240W, right?

    Thanks,

    Manu

  • 0 in reply to Manu Balakrishnan
    Intellectual 660 points

    Hi Manu

     Thanks for the response. We have a load set up like this. 

    5 strings of lamp connected in parallel at the output of the PFC.

    String 1 - 2 x 200 W lamp connected in series ( Consumes 240 W when switched ON)

    String 2 - 2 x 200 W lamp connected in series ( Consumes 240 W when switched ON)

    String 3 - 2 x 100 W lamp connected in series ( Consumes 140 W when switched ON)

    String 3 - 2 x 100 W lamp connected in series ( Consumes 140 W when switched ON)

    String 3 - 2 x 100 W lamp connected in series ( Consumes 140 W when switched ON)

    Hope this clarifies our load arrangement.

    Thanks

    Lenin.

  • 0 in reply to Lenin Prakash
    TI__Intellectual 1260 points
    Hi Lenin,

    The said behavior is due to the type of load you have used. The incandescent lamps has a very low cold resistance. This means at start up the incandescent lamps acts as huge load as high as 10 times the rated load. For example, in this case you are making a step of 240W, but at start up the with lamp in cold condition, the equivalent steps the PFC seeing could be high as 2.4 kW. You can validate it by measuring the cold resistance and hot resistance of lamp. Due to this heavy start up load, the there could be uncontrolled behavior and the current can increase and the fuse can get blown. Try to use a constant resistive load or electronic load. Hope this clarifies. Let me know if there is any questions.

    Thanks,
    Manu
  • 0 in reply to Manu Balakrishnan
    Intellectual 660 points
    Hi Manu

    Thanks, I suspected the same.

    Thanks
    Lenin.