• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 836 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.

BQ24650EVM-639: BQ24650EVM-639 EVM: Using MPPT for SOLAR Input

Daniel Fernandez
Prodigy 30 points
Part Number: BQ24650EVM-639
Other Parts Discussed in Thread: BQ24650, BQ25895

I have recently ordered the BQ24650EVM-639 module and have been trying to use it for mttp. When connecting a solar panel as Vin and the resistive load as Vsys and a 12V battery as Vout, the voltage is not regulating the input voltage to 17.8 V. The input voltage is approximately 22 V, is more needed to get the voltage to regulate at the input? I went through the test summary, so I know the module is working fine.

  • 0
    TI__Mastermind 24075 points

    Hi Daniel,

       To see if BQ24650 is regulating at MPPT, you need to measure voltage on MPPSET pin to see if it is 1.2V. A key point of MPPT tracking is that it doesn't regulate by stepping-down your voltage to the MPPT regulation you set. Please refer to section 8.3.2 for a description on how the MPPT constant voltage loop operates. In this situation, the solar panel power is enough to supply your system so BQ24650 is not in its MPPT voltage regulation loop. If you were to increase the system load till which the solar panel cannot supply, then the MPPT loop will regulate charge current to keep solar panel at its MPP.

  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Kedar Manishankar,

    Thank you for the quick response. I now understand what the system is doing, I did not have that section in the datasheet that I was using. Now my question is, does TI sell a product that does true MPPT (i.e. a boost converter with perturb and observe) not just regulation when the load is too great. To where the max power is regulated at every instance.

    Thank you 

  • 0 in reply to Daniel Fernandez
    TI__Mastermind 24075 points

    Hi Daniel,

       You can also take a look at this reference design using BQ25895 to implement hill-climbing method of finding MPPT, as this IC can set the input voltage regulation point in fine 100mV steps with the use of I2C. This technique is slightly different from the perturb and observe method but the design goes into detail on why it implements the hill-climbing method. Note that this solution does require software implementation Here is the link: http://www.ti.com/lit/ug/tidudj2/tidudj2.pdf

  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Kedar Manishankar,

    Unfortunately, this is not a viable option as the input range has an upper limit of 14V. Most commercial solar panels have an open circuit voltage of 21V-22V with the Vmp around 18V. Does TI have a higher voltage module that is a complete circuit. I am attaching solar panels in parallel, so the highest voltage will be 22V and the current at 2A-3A.

    Thank you.

  • 0 in reply to Daniel Fernandez
    TI__Mastermind 24075 points

    Hi Daniel,

        BQ24650 is a good choice for standalone charger, however to implement perturb and observe, or hill climbing method you would need external software implementation, and a charger IC capable of communication. In our portfolio VINDPM feature is similar to MPPT where VINDPM is our input voltage control loop, and you can use the paramteric search to find an IC with the required control interface, VINDPM feature, and required input voltage. You would still need to implement MPPT according to the reference design, but modify it for the IC you choose.