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BQ25570EVM-206: Can BQ25570 handle harvesting multi sources at the input?

Mohamed Rafat
Prodigy 30 points
Part Number: BQ25570EVM-206
Other Parts Discussed in Thread: BQ25570, BQ25504

Hello,

Maybe its a generic question but I don't have a lot of experience in the power electronics field.

I want to apply multiple harvesters to BQ25570 EVM input in the most efficient way. I have 3 different types of transducers:

-TEG (x3): Provide about 20mv DC per each TEG @the room temperature.

-Small solar panel: Provide about 300mv DC @indoor light.

-Piezoelectric generator: rectified and charging a capacitor. (AC->DC)

My question: Is BQ25570 designed for these types of inputs? and how can I add voltages together in the best practical connection (lowest power loss)?

Thanks

  • 0
    TI__Guru*** 143860 points

    Hi Mohamed,

    Unfortunately, no.  The MPPT feature can only regulate the input voltage to one voltage.  Also, if you connect the outputs of the sources together, one would feedback into the other unless you use connect through a diodes to form a diode OR.  But the losses from a 0.3V drop Schottky are probably too high and most ideal diode OR FET controllers have too high of input power requirements, also.  You can connect the outputs of the boost charger together into one storage element.  So you could use three BQ25570's or one BQ25570 and two BQ25504's.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 30 points

    Hi Jeff

    Thanks a lot for you answer. I did some searching on the internet. I found Adder (summing) circuit using op-Amp.

    So, Do you think  -using MicroPower op amp and supply from the main battery to it (Vs) - will be with benefit here? 

    Thanks in advance.

  • 0 in reply to Mohamed Rafat
    TI__Guru*** 143860 points

    Hi Mohamed,

    I don't actually.  The opamp will likely consume too much current.  Also, having multiple input sources with different maximum power point voltages will be difficult if not impossible to extract maximum power from.

    Regards,

    Jeff