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TPS54160: PMLK Buck Experiment - efficiency

Ian Shin
Prodigy 590 points
Part Number: TPS54160

Hello, I read Experiment Buck and have been doing experiment using it.

While measure efficiency of TPS54160, I found something strange.

I have two questions.

 

First question,

In datasheet of TPS54160, the efficiency curve shouldn’t meet in high load.

But my experiments confirmed that, they meet together about from 1.3A

 

Second question,

in my opinion, due to switching losses, I think efficiency at 500Khz should have lower efficiency than 250Khz.

But also, experiments confirmed that, as you see, efficiency at 500Khz is slightly higher than 250kHz.

Also, you can see humps of 500Khz nearly around 0.3A

 

What factor do you think caused these results?

  • 0
    TI__Genius 12475 points

    Hi Ian, 

    Thank you for your question. Please share your test setup, your measurement method, and your calculation method so we can form a basis of understanding your test results. 

    Thank you,

    Joshua Austria

  • 0 in reply to Joshua Austria
    TI__Prodigy 590 points

    Hello, Joshua

    I just setup my test as book recommended.

    But to reduce voltage drop by jumper, I didn't use input voltage meter. also, didn't use osiliscope.

    Instead, I just used multimeter and electric load to measure output I and V.

    And calculate efficiency by using formula P=Vout/Vin.

    Input V and I value measured from power supply.

    Iout measured from multimeter, and Vout measured from another multimeter.

    Thank you. Ian shin

  • +1 in reply to Ian Shin
    TI__Genius 12475 points

    Hi Ian, 

    Thank you for sharing your setup with us. Taking a look at your setup, it seems as if there are a number of factors that could cause anomalies within your data. Just to name a few, here are the most pressing issues:

    Measuring output voltage and current through an E load is not advisable as this can often inaccurately report output voltage and current. Connecting your sense lines from your power supply directly to the board as opposed to the metal jumpers near the DMMs terminals may help as well, as this will allow your power supply to directly read and compensate for the voltage that the board directly sees at its terminals as opposed to at the power supply terminals. To double check this, a DMM is advised to be placed on the board as well.

    Overall, TI recommends using the setup in the picture you sent to measure efficiency as it produces more consistent results over a sweep of input voltages. Separate DMMs for measuring output voltage and output current will often produce more accurate results than a singular electronic load. Likewise, separate DMMs for measuring input voltage and input current will often produce more accurate results than a singular power supply. 

    Please let me know if you need anymore help with this,

    Joshua Austria