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LMG2100EVM-078: LMG2100EVM-078 reference design for bidirectional buck/boost converter

Fajar Budiman
Prodigy 40 points
Part Number: LMG2100EVM-078
Other Parts Discussed in Thread: LMG2100R044, INA229

Tool/software:

Dear TI expert,

I have tried this evaluation board and working with open loop control by giving PWM with certain duty cycle. I am now trying to design my own PCB with the sensor of INA229. I want to use it for bidirectional DC/DC converter to charge supercapacitor (two switch or halfbridge). I try to do simulation in simulink and psim with inductor, Cin, and Cout values in this evaluation board design, but it produces really high ripple current for the Current Control using PI with this 4.7uH inductor. I need to enlarged the inductor value. I have also have a look LMG2100R044 SIMPLIS MODEL but I have no idea to simulate with closed loop control. Can you help me with this issue? and can you provide the formulation and calculation for this development board, to choose to inductor, Cin, Cout, etc?

Best regards,

Fajar

  • 0
    TI__Expert 5935 points

    Hi Fajar,

    If the inductor current ripple is too high the switching frequency of the converter can be increased or the inductance of the inductor can be increased. The current ripple across the inductor will be decided by the equation following equation.

    V = L*di/dt

    V = voltage across the inductor

    L = inductance

    di = change in current 

    dt = change in time (time the voltage is applied the inductor)

    Best,

    Kyle

  • 0
    Prodigy 40 points

    Hi Kyle,

    Thanks for your response. Yes I have tried simulate to increase the inductor value amd reduce the ripple.

    What I don't get it is the reason of this evaluation board to choose 4.7uH, Fsw= 100kHz-500kHz since it will cause high ripple event with 500kHz switching frequency. 

    If you have some reference design related to this, I will be happy to refer.

    Best, 

    Fajar

  • 0 in reply to Fajar Budiman
    TI__Expert 5935 points

    Hi Fajar,

    The LMG2100R044 is capable of up to 10MHz switching frequency, so the 4.7uH inductor was selected to be able to support evaluation up to the MHz ranges as well. A larger inductor can be selected to optimize for lower switching frequencies in the 100-500kHz range.

    Best,

    Kyle Wolf