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TPS92511: Equation of power dissipation

Satoshi
Guru 19645 points
Part Number: TPS92511

Please let me know about equation of power dissipation for TPS92511.

By the way;

I found "estimated from the efficiency curves of Figure 13)" on datasheet P22, 

but I didn't understand and figure 13 is not mean efficiency curve (P10).

Best regards,

Satoshi

  • 0
    TI__Mastermind 28655 points
    Hello Satoshi,

    I don't understand your question. Figure 13 is not efficiency and it's not on page 22.

    "7.3 Feature Description
    7.3.1 Pulse Level Modulation (PLM) Control
    A proprietary Pulse-Level-Modulation (PLM) control method is used in the TPS92511. It can regulate the
    average LED current by sensing only the inductor current at the on-period (Figure 13). The integrated MOSFET
    and the sensing and control circuits in the TPS92511 implement the whole PLM control internally so the control
    does not suffer from tolerance and noise issues that may be coming from external components. As compared
    with the conventional method which regulates average LED current by sensing the current over the entire
    switching cycle, the power dissipation on the sensing circuit in PLM is much lower. For example, consider a duty
    cycle of 0.5, the power dissipation on current sensing in PLM can be reduced by half. PLM requires no external
    loop compensation circuit. Besides, the accuracy of the regulated LED current is high (typically ±3.5% in the
    TPS92511)."

    The statement above about power dissipation has to do with the current sense only needing to measure for part of the switching waveform, not the entire switching period. I only senses during the on-time.

    Figure 13 is showing the inductor current for PLM mode, page 22 is layout guidelines.

    Regards,