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TPS92682-Q1: TPS92682-Q1 Control Question

Part Number: TPS92682-Q1

Tool/software:

Dear TIer,

According to Figure 7.3, the synthesized signal (SLOP & iSW) cannot trigger VCOMP. How can GATEx determine whether it is on or off?

  

  • Hi Kuo,

    I don't understand  your question- "How can GATEx determine whether it is on or off?", what does 'it' refer to?

    your switching frequency is set by your clock and the PWM comp varies the duty cycle when there is an error on the output. If ISP registers 0V then the duty cycle will reach the maximum duty cycle to compensate appropriately.

    Best,
    Daniel

  • Hi Daniel,

    I would like to confirm the conditions for PWM turn-off. With the negative slope of V_slop added to V_isw, it seems unable to trigger VCOMP. Does this result in the PWM staying high (MOSFET always on)?”

  • Hi Kuo,

    PWM will turn off when the sensed switch current, ViSW (added with VSLOPE), exceeds the compensator voltage, VCOMP.

    I understand where your confusion arises- based on the graph you posted above, it appears as if ViSW + VSLOPE will never reach VCOMP if VSLOPE is negative.

    However, when ViSW interesects with VSLOPE:

    ViSW = VSLOPE

    We can also assume that:

    VSLOPE = VCOMP - m*Ts (m being the slope)

    Finally, we can rearrange the equation in terms of VCOMP:

    VCOMP = ViSW + m*Ts

    So if ViSW + m*Ts exceeds VCOMP, PWM will turn off

    Best,
    Daniel