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UCC28056: What is Gplant0?

Motoyasu Hattori
Genius 10975 points
Part Number: UCC28056

Hi,

We can find Gplant0 on UCC28056 datasheet [SLUSD37E] P.42 Equation101.   What is "Gplant0"?   What value is used for Gplant0?

Please advise us.

Thanks and best regards,

M.HATTORI.

  • 0
    TI__Mastermind 40520 points

    Hello Motoyasu-san,

    Thank you for your interest in the UCC28056 PFC controller.

    Gplant0  is the constant term of Gplant(jw) as shown in Equation 83 on page 40 of the datasheet.
    The value of Gplant0 used in Eqn 101 = ~622 and the factors in Gplant0 consist of Poutmax = 165W, Vcomax = 5V, Voutreg = 390V, and Cout = 136uF. 

    Voutreg comes from Eqns 70 through 81, Cout from Eqns 41, 42,  Poutmax is a design specification as in Table 1 (page 29).
    Vcomax is not specifically defined anywhere, but taken as 5V which represents the linear range of the error voltage for the control.  It is clamped at Vcoclmp of ~5.6V (near top of Spec table page 8), but voltages >5V have not additional control effect.   

    (Vcomax can be approximately derived using the information in the paragraph just above Figure 25 (page 25), by back-calculating the 11% and 16% of the average boost rise and fall thresholds.  The result is approximately 5V.)  

    Regards,
    Ulrich