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Boost Converter ICs with externally controllable duty cycle.

Parth Kharade
Prodigy 70 points
Other Parts Discussed in Thread: MSP430F5529, TIDA-00120, BQ24650, BQ25713, BQ25882

I am a part of undergraduate student satellite building Team, Team Anant. We are working on building an MPPT plus boost configuration for battery charging. We  wanted to use boost IC whose output is connected to batteries and input is connected across solar panels. The MPPT controller changes duty cycle which due to Vout being constant changes Vin across solar panel hence tracking maximum power point. We wanted to implent all of this with ICs i.e either boost IC with variable duty cycle input or a complete MPPT and boost converter battery charging circuit. We will be using TI's msp430f5529 to implement MPPT code and supply PWM if we only use boost converter IC.

Kindly suggest some appropriate ICs for our usage. Our majority work depends on this design, kindly reply as soon as possible.

  • 0
    Prodigy 5 points
    Hello Parth,
    Thank you for posting.

    Have you seen this design?
    www.ti.com/.../tida-00120
    It uses an MSP430 to control the charging.
    Granted it is in BUCK mode, however this is easier to control the current and voltage to the battery.
    A boost has the boost diode which allows current to flow uncontrolled when the panel voltage is higher than the battery.
    So you have to go to a synchronous boost if you want to continue down that path.

    Solar MPPT Charge Controller Reference Design
    This design is a 20A Maximum Power Point Tracking (MPPT) solar charge controller created for solar panel inputs corresponding to 12V and 24V panels. The design is targeted for small and medium power solar charger solutions and is capable of operating with 12V/24V panels and 12V/24V batteries up to 20A output current. Designed with scalability in mind, it can easily be adapted to a 48V system by changing the MOSFETs to 100V rated parts. The user can also increase the current to 40A by using the TO-220 package version of same MOSFETs used currently. The Solar MPPT Charge Controller was created with real world considerations, including reverse battery protection and software programmable alarms and indications provided in hardware but were left non-configured. The design has an operating efficiency of above 97% at full load in a 24V system. For 12V systems the efficiency is above 96% and includes losses in the reverse battery protection MOSFETs.

    Everything you need to implement a solar charger is in this tool.
  • 0 in reply to Ed Walker
    Prodigy 70 points
    Hello EdWalker,
    Thank you so much for your prompt and detailed reply. We have actually considered this evaluation board, but the voltage and current specifications we require are much lower than what TIDA-00120 offers.
    Our specifications are as follows:
    Solar panel Vout(Boost Vin) = 2-6V
    Boost Vout(Battery voltage) = 7.2-8.4V
    Boost current input = upto 3.5A
    Boost output current = upto 2.5A
    Battery charging current = upto 1.5A

    Once again I would like to convey my heartfelt regards for your answer. I would kindly request a prompt reply again regarding suitable ICs for our operation as our testing phase is being held by this design.
  • 0 in reply to Parth Kharade
    Prodigy 5 points
    Hello Parth,
    I can not find a reference design that matches your needs.
    You should try looking here: www.ti.com/.../index.html
    TI reference designs

    There may be something that I might have missed.
    Or find some ideas on other aspects of your design.

    As I said before, boosting, at low Vin and MPPT currents is just not common.
    It is easier to put more panels in series and step down to charge.
    2 batteries in parallel have the same Watt-Hours as 2 in series.

    The BQ24650 is a MPPT charger.
    www.ti.com/.../BQ24650
    This is the most popular device for solar charging at the currents you design.
    It is buck step down as this is where the market has moved to.

    There are ways to implement MPPT with many converters.
    A dual stage may be considered where you first use a boost with MPPT, followed by a buck 2 cell series charger.
  • 0 in reply to Ed Walker
    TI__Guru**** 166916 points
    Hi Parth,

    Some other options:

    BQ25882 is a boost based charger that is close to your specifications. BQ25713 is a buck/boost battery charger that meets your specifications. You can use a microcontroller to dynamically change each charger's VINDPM set point, thereby implementing MPPT.