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UCC28600: About valley detection

Ryoma Ohashi
Expert 5085 points
Part Number: UCC28600

Tool/software:

Hi team,

From the QR block diagram, I guess this IC detects the bottom of the valley by comparing the OVP voltage with 0.1V, and also monitor the slope of the OVP pin voltage and detects the valley if slope is -0.1V~0.1V.

But since there is op amp that will source I_LINE, I thought that the OVP pin is clamped to 0V if the valley is smaller than 0V. Like below waveform.

In this case, how will the IC detects the valley? Where is the timing that the slope is -0.1V~0.1V?

Regards
Ohashi

  • +1
    TI__Genius 12795 points

    The slope block convert the voltage slope to another signal which is compared against +/- 0.1V threshold. At the valley, the slope is near zero and the OVP pin is <0.1V. So three AND gates output logic high and valley is detected. 

    The timing of slope detection is an internal parameter but it is small enough that can be ignored.

    The waveform you showed is not operated in QR mode but in DCM mode.