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UCC28070

catalin dimitriu
Prodigy 10 points
Other Parts Discussed in Thread: UCC28061, UCC28070

Hi,

I have some problems with the two-Phase Interleaved CCM PFC Controller    -UCC28070-

 1 Observation : in the starting phase, during the soft start, the impulses start 

    on both channelssimultaneously, and at a certain moment a double impuse

    is applied to one channel and saturates the coil, by producing a short-circuit.


Questions :

1. Why the impulses do not start in antiphase?

   ( after the soft-start phase, the impulses are shifted correctly)

 2.What shall be done, so that the impulses shall remain in antiphase during the soft-start?

Tks,

 

 

  • 0
    TI__Guru* 85676 points

    I know the UCC28061/2/3 devices start up in this fashion and it is documented in the data sheet.  This is because this a transition mode converter that uses a phase lock loop for synchronizing.

    I talked to one of the internal systems engineers at TI and he said that the UCC28070 comes up phase A first then phase B 180 degrees out of phase.  I would expect this to be the case since this is continues conduction mode and has a fixed frequency.