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Controlling the Charging and discharging of the super capacitor

Lakshminarayana
Genius 3790 points
Other Parts Discussed in Thread: BQ24640, BQ33100

Hi,

I have few queries on Controlling  Charging and Discharging and Monitoring the Super Caps(24V).

Application: Input will be 24V,20A from the power supply and when in power outage it should power(24V,3A) the controller for 3 seconds.

Are there any reference example for this application?.

I found BQ24640 but as i noticed this IC is charger which is like Buck If input is 24V then Super capacitor must rated slightly lesser the voltage of input. Is my understanding correct? But in my case Supercaps has to charge up-to 24V.

  • 0
    TI__Mastermind 24075 points

    Hi Lakshminarayana,

        I am not sure of any reference designs for this specific example, but a common application of super-capacitor is for temporary backup systems. Yes BQ24640 is a buck charger and requires input voltage higher than battery voltage to charge, so some headroom needs to be there between your input voltage and desired supercap voltage.Section 9 Power Supply Recommendations of the BQ24640 datasheet describes input voltage requirements based off of output voltage.

  • 0 in reply to Kedar Manishankar
    Genius 3790 points

    Thank you.

    How about monitoring Discharging of SCaps?

    In my case Input Voltage is 24V and super caps should charge up-to 24V (Either as 4 series caps ( 8.3V)  Or single 27V Super caps). Which SCaps charger IC do you recommend?

    For parallel SCaps Should i have to use individual BQ33100 to monitor? 

  • 0 in reply to Lakshminarayana
    TI__Mastermind 24075 points

    Hi Lakshminarayana,

       From your input voltage specification of 24V and output voltage of 27V you will not be able to use a buck charger as buck charger steps down the input voltage to the output voltage, and requires some headroom between the 2 values as mentioned above. For this application you will need a buck-boost charger as battery voltage can be less than or greater than input voltage. From TI parametric search tool for Battery Charger IC, you can select Control Topology -> Switch-Mode Buck-Boost, Cell Chemistry -> SuperCap, and see if the charger options fulfill the requirements for your application.

      For BQ33100 and battery fuel-gauging/monitoring I would ask another E2E question with the title of the post containing the part number and the Battery Gauge forum, and the expert regarding those parts will be able to answer your question.

  • 0 in reply to Kedar Manishankar
    Genius 3790 points

    How about placing an boost regulator (of 27V) before BQ24640 and then output to 24V?(Capacitor will be charged up-to 24V).

    And what about discharge control?

    I don't see any forum related to  Battery gauge forum?

  • 0 in reply to Lakshminarayana
    TI__Mastermind 24075 points

    Hi Lakshminarayana,

       Yes if you can boost the input power supply voltage from 24V to 27V, and then use 27V as input to BQ24640, you can use this to charge the 24V output supercaps. Sorry, please post the BQ33100 to the power management forum on E2E with the part number in the title and the expert on that part will answer your question.