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Help to Choose Best IC For Design

Grimal Patel
Prodigy 70 points
Other Parts Discussed in Thread: PMP9656, UCC2897A, PMP10215, LM5021, LM5015

Hello,

For one project i need to design Isolated DC-DC Converter.

My Design Specs: Vin = 48 V and Vout = 24 V. and Iout = 12.5 Amp Power = 300 W. Cost is not the constraint , Size Is one Constraints.

Can you suggest that which Isolated converter i can choose and Which Controller IC Related to that Converter?

Thank You
Grimal
GE Helathcare

  • 0
    TI__Mastermind 26225 points

    Hi Grimal,

    I think active clamp forward would be a good option for your design requirements. ACForward is a soft switching topology and you can also use self driven SR on the secondary to help maximize the efficiency and limit the amount of heat generated by the converter. This will help you meet your size constraints. I would suggest taking a look at UCC2897A and reference design PMP9656 which is a 12Vout/250W ACForward achieving 95.5% efficiency. The reference design is not quite on the dot for your design spec but it will give you an idea of what is achievable.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 70 points

    Hi,

    Thank you for your suggestions. I have one confusion between Two switch Forward Topology and Active clamp forward topology. Among this two which will be less costly?. and can you suggest some PWM Controller for two switch forward converter topology for my project requirements?

    Thanks in advance
    Grimal
    GE Healthcare

  • 0 in reply to Grimal Patel
    TI__Mastermind 26225 points

    Hi Grimal,

    The two switch forward requires a bit more circuitry to properly bias the high side drive as you can't simply bootstrap the voltage (both FETs are on at the same time). Two switch forward does enjoy a reputation as a very robust topology however (no danger of shoot through). Ultimately, I would say the cost is going to come down to the PFET of the active clamp forward vs NFET + additional high side bias circuitry. You can take a look at PMP10215 to get an idea for what is needed for the high side bias circuitry. LM5021 would be a good choice to consider for two switch forward as well.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 70 points

    Hi Sir,

    Thank you for your guidance.

    As you suggested me to use Active clamp forward converter topology and suggested me to use UCC2897A Controller and PMP9656 for Reference Design. But This design is for 12 V Output. So will it wok for My Vo= 24 V. ?? Design Calculation I will Carry out. That is not the Problem.

    Thank You Sir
    Grimal
    GE Healthcare

  • 0 in reply to Grimal Patel
    TI__Mastermind 26225 points

    Hi Grimal,

    As I mentioned earlier, it's not on the dot for your design spec, it is of similar power level to what you are looking for and could serve as a reference point as you design your power stage. 

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 70 points

    Hi Sir,

    As you suggested me to refer LM5021 to use for two switch topology and ask me to refer PMP10215. But can you see and confirm me because LM5021 is suitable for only one mosfet circuitary as written in datasheet(Ideal for flyback) and In PMP10215 design, there is no higher side mosfet is used. Please confirm me that it can be really useful for two switch or other are also available ?

    Thank You

  • 0 in reply to Grimal Patel
    TI__Mastermind 26225 points

    Hi Grimal,

    The OUT pin of LM5021 is fed to both pins of a half bridge driver to drive both high side and low side FETs (page 2 of the schematic). LM5021 is used twice in PMP10215. One is a flyback, the other is a two switch forward. The datasheet is very much geared towards flyback but LM5021 can also work as a two switch forward.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 70 points

    Hi,

    thanks for your suggestions.

    I found out one controller LM5015 for two switch topology. can I use for my application as an my Input side current is more than 1 A (Around 6 A)?

    and can you suggest any other controller same as LM5015 for a source current more than or 6 A?

    Thanks in advance
    Grimal
    GE Healthcare

  • 0 in reply to Grimal Patel
    TI__Mastermind 26225 points

    Hi Grimal,

    The internal cycle by cycle current limit would not be able to support >1A MOSFET current so this converter would not be able to deliver full load power for your design spec. I would suggest using external FETs + LM5021 for 300W as the power dissipation will be much easier to manage using external FETs. To my knowledge, TI does not have a controller with integrated MOSFETs that would be able to support two switch forward at this power level.

    Best Regards,

    Ben Lough