• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 82 subscribers
  • Views 550 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMDSHVMTRPFCKIT: Ask for suggestions of shunt resistor

user4008740
Intellectual 915 points

Part Number: TMDSHVMTRPFCKIT
Other Parts Discussed in Thread: DRV8301

Dear TI experts:
For the shunt current feedback circuit, I carefully compare both circuits in TMDSHVMTRPFCKIT and DRV8301-HC-C2-KIT.
1. In TMDSHVMTRPFCKIT, the REF3118 is applied to obtain 1.8V, then the offset 1.65 is produced bu the OPA circuit.  But the related circuit is much simpler in DRV8301-HC-C2-KIT.
   I think TMDSHVMTRPFCKIT's design should be better, but I don't exactly know why? Could you kindly show me?
2. For the TMDSHVMTRPFCKIT's design, it uses "inverting" amplifier structure. That means Vout=3.3V when Ipeak= -10A, instead of Ipeak= +10A, right?  (Note: "non-inverting" amplifier structure in DRV8301-HC-C2-KIT)
3. In the TMDSHVMTRPFCKIT's design, the shunt resistor is 0.02Ohm and the Ipeak is 10A.
   If I change the shunt resistor to 0.005Ohm (8W), the Ipeak should be 40A.
   If I change the shunt resistor to 0.002Ohm (20W), the Ipeak should be 100A.
For my target application: PMSM, Vbus=86.4V, rated 3KW (peak 7.2KW), could you kindly suggest me how to choose the shunt resistor (including the Watt)?
Hope to hear from you soon.
I will appreciate your help so much~
Wish you the best!
Tang Han
  • 0
    TI__Guru** 117160 points
    1. Right, the offset voltage is produced by both reference voltage regulator and amplifier, so you need to calculate the resistors of the divided voltage and amplifying circuit to get a right offset voltage. Actually, the signal deal circuit ob both boards have a similar performance, you might refer to the DRV8301 board if there is an additional amplifier for the offset reference, that's more simple and easy to implement.
    2. Both boards are the same using negative feedback or the "inverting" you mentioned. The 3.3V should mean +10A input since shunt current of the low side used freewheel mode.
    3. The peak to peak current should be 19.89A if the shunt resistor is 20(mohm), 79.56A is for 4(mohm), 198.9A is for 2(mohm) if the gain of an amplifier is not changed.

    You might refer to DRV8301 boards, and change the gain of the amplify circuit to 10, and use a 1(mohm)/8(w) shunt resistor.
  • 0 in reply to Yanming Luo
    Intellectual 915 points

    Dear Mastermind:

    Thanks for your kind and professional reply.

    I got it and I will follow your valuable suggestions!

    Many thanks again!

    Sincerely yours,

    Tang Han