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TPS54160: The efficiency of PMLKBUCKEVM

Jerry Zhao
Intellectual 1070 points
Part Number: TPS54160
Other Parts Discussed in Thread: PMLKBUCKEVM

Hi team,

I'm testing the efficiency of PMLKBUCKEVM with vin=24V, Vout=3.3V, Cout=220µF, fs=250kHz. The result is shown in the following picture. I wondering why the trend of the efficiency curve is different form that in datasheet(shown in the following picture), especially in the light load condition. Could please help me to resolve this problem. Thanks a lot.

  • 0
    TI__Mastermind 34790 points

    Hello Jerry,

    I would double check your setup and the accuracy of your output and input current measurement, as well, confirm the device is in regulation at light load.

    The switching frequency of the devices at light load in eco mode might be different with different output inductor selected, assuming you changed that as well.

  • 0 in reply to Marshall_Beck
    TI__Intellectual 1070 points

    Hi Marshall,

    The output inductor is fixed whether in the high load and low load whose value is 18µH. And I wondering how the switching frequency change with the output inductor in Eco mode, and why it may influence the light load efficiency .

  • 0 in reply to Jerry Zhao
    TI__Mastermind 34790 points

    Hello Jerry, the output inductor can impact the switching frequency as the peak current in the inductor is fixed and the frequency is modulated for the required average output power.

    With the additional information you provided, my recommendation to confirm: your setup and the accuracy of your output and input current measurement, as well, confirm the device is in regulation at light load.

  • 0 in reply to Marshall_Beck
    TI__Intellectual 1070 points

    Hi Marshall,

    I have tested the efficiency of switching power as vin=6v in the same setup, and the  efficiency curve is basically the same as one in datasheet. The efficiency curve is shown bellow. So I wondering whether the input voltage will affect the light load efficiency. Moreover, the device is in Eco mode with vin=24V when the load current is 0.2A and below. And device is in DCM mode when load current is above 0.2A and below 1A.

  • 0 in reply to Jerry Zhao
    TI__Mastermind 34790 points

    Hello Jerry,

    You bring up good points.

    Inductor ripple current does impact DCM range, as well, it can impact the transition point in and out of eco mode, as the transition point is impacted by peak inductor current.

    If doing A-B comparison, I would consider analyzing the Vsw waveform where you can see if the device is going discontinuous and what the effective switching frequency is.