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TPS62150 efficiency difference from FSW high to low

Paul S
Prodigy 50 points
Other Parts Discussed in Thread: TPS62150

Hello,

We are using the TPS62150 as a 500ma. battery powered CC WLED driver. Input voltage range is 3.0V-12.0V.  An external voltage is summed with the SS/TR pin for dimming (250ma.-500ma.). In one app note, sorry I cannot the  remember number it states to reduce switching losses reduce the operating frequency. This is done by tying pins FSW & PG together through a pull up resistor to the VOUT pin. A lower inductor value will be needed and 3.3uH is recommended.

Question... We are looking the longest operating time per charge. How much more efficient will the TPS62150 be in this configuration?


Thanks

  • 0
    TI__Guru**** 150650 points

    You can refer to the curves in the datasheet to see the efficiency difference between the two frequencies.  Your LED's forward voltage + the drop on the FB pin is the output voltage in the curves.  The 3.3Vout ones should give you a pretty good idea.

  • 0
    Prodigy 50 points

    Hi,


    We see that the efficiency is better when running at the lower switching speed. Question... If we use a 3.3uH inductor instead of the 2.2uH value will this further improve the efficiency?


    Thanks

  • 0 in reply to Paul S
    TI__Guru**** 150650 points

    Assuming it is the same physical size, a larger inductance would likely improve the light load efficiency but decrease the high load efficiency due to its larger DCR.  A physically larger inductor offers some improvement in efficiency due to larger inductance and lower DCR.