• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1473 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Parallel DC-DC Converters

Kevin Christie
Prodigy 240 points
Other Parts Discussed in Thread: TIDA-00476, TIDA-00120, UCC28880

I am trying to figure out if I can have a MPPT charge controller in parallel with a DC-DC converter (sharing a solar array). I realize the MPPT charge controller is a DC-DC converter and I am also aware that two MPPTs in parallel will cause a possible conflict.

I would rather not get into the "why do this" since that can divert the topic. I am just curious, from a technical point of view, if a DC-DC converter under a constant load, can be placed in parallel with a MPPT charger without causing the MPPT to fail.

I am not sure about the type of isolation that would exist between the devices, but would expect at a minimum, diodes to prevent one devices input from feeding the other devices input. The outputs would be isolated (possible transformer) from each other.  

The two devices would NOT be synchronized so I am worrying about them stepping on each other during switching times, but maybe that is not a valid concern if the two devices have the correct input capacitance to handle transients.

Thanks for your help.

  • 0
    TI__Expert 3860 points

    Hi Kevin,

    Yes, there is no problem in having another DC/DC converter in parallel to the MPPT controller. In effect, it will be like a resistor connected across the panel. You can see that many MPPT reference designs already have this in the form of an auxiliary power supply running off the panel.

    Regards,

    Salil

  • 0 in reply to Salil
    Prodigy 240 points

    Hi Salil,

    Thanks for the info.  If the dc-dc converter running in parallel with a MPPT charger is like a resistor, it must be one noisy resistor!

    I have looked a lot online and have never seen an application where there auxiliary power running off the panels.  Can you point me in the direction of one?  It would be a huge help!

    I have seen a lot of deiversion load controllers, but that is auxiliary power off the output of charge controllers and/or battery bank.

    Kevin

  • 0 in reply to Kevin Christie
    TI__Expert 3860 points

    Hi Kevin,

    Please see the designs TIDA-00120 & TIDA-00476 to see auxiliary power supplies powered from panel. Typically, the auxiliary power supply input will be OR'ed between the battery voltage and the panel voltage. Since the panel voltage is higher than the battery voltage, it will be powered from panel during day time.

    Regards,

    Salil

  • 0 in reply to Salil
    Prodigy 240 points

    Hi Salil,

    Thanks for the reference designs.  TIDA-00476 may prove to be useful in my application.  However, what I am interested in is a device that can simultaneously allow part of a solar arrays power to be delivered to a DC load and the rest of the power diverted to a charge controller.  TIDA-00476 acts as a buck charge controller OR a boost CC-CV power source using the batteries as the input source.  If you imagine this reference design being able to do both functions simultaneously, then you would have the device I am looking for.

    Does that make sense?  Maybe it is one device that handles this or maybe it is two parallel devices that handle this while maintaining stability with each other.

    Thanks again,

    Kevin

  • 0 in reply to Kevin Christie
    TI__Expert 3860 points

    Kevin,

    Sorry to have missed out on this thread. If you look at the schematic closely, you can see that the auxiliary power supply is a DC/Dc converter based on  UCC28880> This is running in parallel to the main MPPT power stage. Of course, the power that can be taken through this path is limited; but I think you can safely increase this power draw to at least about 20% of total power from the panel without seriously impacting MPPT tracking.

    Regards,

    Salil