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WEBENCH® Tools/LM5022: No load power consumption is too high

Laszlo Babaly
Prodigy 40 points
Part Number: LM5022

Tool/software: WEBENCH® Design Tools

Hi Everybody,

I have built a boost converter circuit with LM5022 according to the recommended design in Webench.The output voltage is 70V. The boost conversion works perfectly except one thing, the power consumption of this solution is too high, it's around 70 mA with no load condition. Is that normal?

I have built a couple of prototypes with this solution and all of them have the same problem. 

Here is the circuit diagram:

  • 0
    TI__Mastermind 21720 points
    Hi Laszlo,

    Can you please provide the schematic? Shutdown means that there is no switching. Note the the current on the during shutdown (UVLO = 0V) the current is only specified for the VIN pin. This doesn't include the current from the the feedback resistors or the UVLO resistors.

    Thanks,

    Garrett
  • 0 in reply to Garrett Roecker
    Prodigy 40 points

    Hi Garrett,

    Please find attached the schematic. One comment, I mean the current consumption during normal operation with no load and not during shutdown.

    Thank you and Best regards,

    LaszloDCDC_70V.pdf

  • 0 in reply to Laszlo Babaly
    TI__Mastermind 21720 points
    Hi Laszlo,

    Thanks for the clarification. From the schematic it looks like the step up ratio for this application is large. Even at no load there will still be fairly consistent switching. The switching that is needed to maintain the output voltage will consume current to turn on an off the switch as well as supply the current that is pulled to ground to the feedback resistors. For eacmple lets assume VIN is 10V. In this example if the feedback resistors will sink about 3mA when the output is 70V, which translates to about 24mA of input current before accounting for efficiency losses and the internal VCC regulator that will draw current to switch the MOSFET.

    Following this logic 70mA is a reasonable number for a no load input current. This can be reduced by increasing the resistance of the feedback network.

    Please let me know if you have any questions.

    Thanks,

    Garrett