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TPS61200 - operating from solar cell

Franck-D
Prodigy 165 points
Other Parts Discussed in Thread: TPS61200, TPS61220, TPS62120

Dear All

in my application i need to work with solar panel used into indoor (like sanyo AM1815).

The operating voltage and current at 200lux are typicaly 3V and 18.5µA.

Is the TPS61200 and his MPPT circuit able to work into thoses conditions in order to recharge a battery

with a low trickle current at 3.3V.

 

thanks for your replies

Franck 

  • 0
    TI__Mastermind 36110 points

    The current capability of your solar cell is very low and may not supply the current required to get the TPS61200 up and running.  The TPS61200 will definitely work with larger solar cells capabable of delivering more current.  You can review the following application note http://focus.ti.com/lit/an/slva345a/slva345a.pdf "suppling TPS61200 with a single solar cell" for a more in depth look at a solar cell application.  You may need to experiment with different size solar cells to determine the minimum size required for your application.  For your current and voltage ranges, the TPS61220 might be a better option.  It has much lower quiescent current.  You will need a very large output capacitor on the solar cell to provide the peak currents required for a switching converter.

  • 0 in reply to Matthew Day
    Prodigy 165 points

    Hello Michael

    Do you think the TPS61220 is able to work as the same maner as the TPS61200 in the application

    note.

    Franck

     

  • 0 in reply to Franck-D
    TI__Guru**** 150880 points

    Possibly, though there are a few key differences.  You can try it and let everyone know if it works.

    The added MPPT circuit in the TPS61200 app note turns on before the TPS61200 starts switching.  This reduces the inrush current which would otherwise sag the solar cell voltage.  This circuit turns on first because it runs off Vaux.  The TPS61220 has no Vaux pin.

    But the above may not be an issue.  The TPS61220 passes Vin to Vout even when off (notice the diode in the block diagram).  So, startup would consist of the solar cell being basically shorted by the output capacitor on the TPS61220 and this short circuit current charging the output caps.  Once they charge up, the load on the cell would relax and normal operation could begin with Vout being already charged up a little.

    What is the open circuit voltage and short circuit current of your panel?  If the MPPT is truly 3V @ 18uA, you will definitely need a bigger panel to get any amount of useable power for this kind of application.  Boosting the input is harder than stepping it down.  2 of these panels in series might work with the TPS62120 or an LDO like the TPS71533.