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PMP21529: Increase Reference Design Current Capability

Part Number: PMP21529
Other Parts Discussed in Thread: UCD3138

Hello everyone,

We are working on BMS for 48V li-ion battery, therefore, we are evaluating the need of bidirectional DC/DC converter located on its input to control the battery current flow. Browsing Texas Instruments reference designs, we found PMP21529. Based on "4. Performance Specification" data located in the document "Test Report: PMP21529 4-Switch Buck-Boost Bi-directional DC-DC Converter Reference Design", this design intends to work with 2A in Battery Charge Mode and 10A in Backup Supply Mode.

Out intention is to rise its current capabilty to 100A on both directions.

I am not an expert on DC/DC converter topologies, so, I would like some guidance. Is it feasible to rise PMP21529 current capability just working on the hardware components and firmware parameters? Or is it better to implement such converter with a new topology, with higher efficiecy (altough this one has >95% efficiency)?

Many thanks in advance.

Kind regards,

Felipe Marques.

  • Felipe,  hello and thank you for your interest in Texas Instruments.  We will be on company holiday vacation Thursday, November 28th and Friday,November 29th.  We will resume normal business operation hours Monday, December 2nd.  Your query has been forwarded to our Power Design Services Team for review and answer.  Please allow us until Monday, December 2nd at the earliest for a response from the team. 

    Best Regards,

    J. Fullilove

    Reference Design Operations

    Texas Instruments

  • Felipe,

    Does your BMS system have the same 48Vin to 48Vout specification? Or it's a 48V to 12V system?

    If it's a 48V to 48V system, then you will still need to use the 4-sw buck-boost.

    If it's a 48V to 12V system, then you just need to use a synchronous buck converter.

    For such high current, you might want to interleave your power stage to lower the ripple current.

    I have involved the designer - Bosheng Sun - to this thread in case he has additional comments.


    Sheng-Yang Yu 

  • Hello Sheng-Yang,

    Thank you for the reply.

    Yes, this is a 48V to 48V system. When you say interleaving the power stage, do you mena by interleaving power switches, mosfet drivers, inductor and capacitors?

    Best regards,

    Felipe Lima.

  • Hi Felipe,

    Both sides are 48V battery? The firmware of PMP21529 assumes only one side is battery, the other side is DC source, therefore it only do voltage mode control when in backup mode. In your case, if both sides are battery, you will need constant current control on both direction, then you will need to write your own firmware, but you can use PMP21529 firmware as your starting point.

    Interleaving means 2 or more phases run in parallel, each phase like PMP21529, they are controlled by a single controller.





  • Hi Bosheng,

    Thanks for the reply.

    No, this battery must be a backup power system; therefore, one side is the battery and the other is the charges or a DC source, similar to the application indicated in the reference design.

    So, does interleaving this system only require a UCD3138 controller?

    One last question, please. According to "Performance Specifications", this design is intended to work with 2A in battery charge mode. But the components employed may tolerate current levels above 2A. In order to have 10A in both modes, does it need a firmware adjustment?

    Best regards,

    Felipe Lima.

  • Hi Felipe,

    Yes, the interleaved power stages only need 1 UCD3138 to control them. UCD3138 has 8 PWM outputs, each phase of the 4-switch buck boost needs 4 PWM, so you can only interleave 2 power stages. You will need to modify the code to support the 2nd stage, and also do current balancing.

    The hardware of PMP21529 supports 10A on both sides, you need to modify the code to support 10A in batter charging mode.