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Question about the UCC28950 phase compensation fomula

Go
Genius 4220 points
Other Parts Discussed in Thread: UCC28950

Hi,

I'd like ask about the UCC28950 phase compensation fomula in app note SLUA560C page17 fomula(105).

In this fomula, It seems that no consideration about Inductor(Lout) can be found.

Usually, there is a element of inductor(Lout) in the transfer function, I think.

Is this fomula correct? 

Kindly advice.

Regards,

Go Toguchi

  • 0
    TI__Guru* 86266 points

    The application note is question uses peak current mode control and the inductor is modeled as a current source.  This is why Lout is not part of the control to output transfer function.  This model work quite well for compensating the voltage loop and is correct.  If this was voltage mode control Lout would be part of the control to output transfer function.

  • 0 in reply to Mike O'
    Prodigy 60 points
    Hello Mike,
    We have designed a 2.5kw prototype using UCC28950 and i was wondering if i can i find a derivation/explanation of the voltage loop compensation formula, especially of Gco(f). As i understand Gco(f)*Gc(f) is the open loop transfer function and i understand Gc(f)(Type 2 feedback), but having difficulty understanding different parameters of Gco(f), any help would be very much appreciated.