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LM5161: improve efficiency performance

Kay Chen53
Expert 2225 points

Part Number: LM5161

Hi There:

Greeting! I'm helping my customer who using the LM5161 and found the efficiency was lower than expected

could you help to advice the solution to improve that? 

a. eff (max)= 80% < 90% (spec) condition: Vin: 30~100V Pout: 5V/1A & 6V/1A

LM5161(HWTCO).pptx

  • 0
    TI__Mastermind 40410 points

    Hello Kay,

    The most effective way to increase efficiency is to reduce the Switching frequency.  Bear in mind, that you may choose to adjust the buck inductor value, while doing so, try to keep the DCR low.

    Also you may be abe to get more efficiency by supplying an external VCC to the LM5161?

    Looking at your results your Efficiency results they appear to be low in comparison, have you confirmed that the Switch node is stable and the converter is working correctly?

    Also where are you measuring Vin and Vout?  Please verify your input and output current measurements are accurate too?

    Hope this helps?

    David.

  • 0
    TI__Mastermind 25590 points
    Kay,

    It looks like the specs are closest to "Figure 2. Efficiency at 300 kHz" on page 8 of the LM5161 datasheet. These expected efficiency values are lower than 90% but still higher than your results. I'd like to take a look at your layout to see if there are any issues there.

    Please share the layout file.

    Thanks,
    -Sam
  • 0 in reply to Samuel Jaffe
    Expert 2225 points

    Hi Sam:

    Thanks again, sorry for late, our customer has feedback us the schematic and layout file as attached

    perhaps you could provide more idea to us for improve the efficiency.

    5265.LM5161(HWTCO).pptx

  • 0 in reply to Kay Chen53
    TI__Mastermind 25590 points
    Kay,

    Thank you for the extra slides. The layout looks fine so I'm going to refer you to David Baba's comment above. Those would be the next steps.

    -Sam
  • 0 in reply to Samuel Jaffe
    TI__Mastermind 40410 points
    There appears to be some questions that were not answered from my previous post?

    1. Looking at your results your Efficiency results they appear to be low in comparison, have you confirmed that the Switch node is stable and the converter is working correctly?
    2. Also where are you measuring Vin and Vout? Please verify your input and output current measurements are accurate too?"

    Also, as mentioned the two largest components to increasing efficiency are the following.

    1. Decrease Switching Frequency.
    2. Supply an External Bias supply turning off the internal VCC regulator.

    Hope this helps?

    David.