• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 29 subscribers
  • Views 197 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

BOOSTXL-DRV8323RH: Electrical protection against bldc motor regen

biter terbi
Prodigy 160 points
Part Number: BOOSTXL-DRV8323RH
Other Parts Discussed in Thread: DRV8320, DRV8323

Hello! My name's Pedro and I'm working with this driver.
I have a BLDC motor that has magnetic coupling in both spinning directions, this allows the motor to be able to give electrical energy back every time its driven by an external force. This is great if you have the battery connected to the EVM, but if you happen to disconnect the battery this energy has no way to go.
We have the following circuit (simplified).



The issue with this circuit is when I disconnect the battery and spin the motor I run the risk of burning the voltage regulator (I had it actually happen to me haha)


So I propose the following fix:



There's a diode that stops the generated current from flowing back to the battery and the MCU, and a big capacitor to absorve the generated current.

I do not need the regenerative braking feature so I don't mind disconnecting the battery.

What do you think of this solution? Is there a way to do this just from the EVM configuration?

Any comments will be greatly appreciated.

Thank you in advance.

  • 0
    TI__Mastermind 22775 points

    Hey Pedro,

    Thanks for the questions and posting to the MD forum! Just a couple of questions. There is only one regulator being on this EVM, one is the integrated regulator on the DRV8323RH, but I see another regulator in your block diagram is the regulator being used to only power the MCU or are you using it to power both the DRV8320 and MCU off of the battery?

    When you say the regulator was damaged was this the devices internal regulator or the external regulator in your diagram?

    Just trying to make sure I understand the complete picture here. While your suggestion should work perfectly fine, besides my recommendation of perhaps adding more than one bulk capacitor and making sure that they are appropriately rated for the for the voltages you are expecting (we typically recommend 2x the expected voltage rating).

    If the regulator is only being used to power the MCU and the DRV8323 is being powered via the battery then I would recommend changing the position of the diode since it would give you the option to charge the battery. But this depends if you are trying to give yourself the option to run without the battery connected. You should be able to increase the capacitance on the EVM but I do not see a good way to add the diode to the VM path. Also ensure that the capacitors are able to handle the voltage as well, some of them are rated for 63V while others are rated to 80V.

    Looking forward to your response!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 160 points

    Hello Isaac! Sorry for the delayed response!
    That is an external voltage regulator, that just powers the MCU from the battery, the evm is directly connected to the battery. This was the regulator that was damaged, it seems that when I disconnected the battery and started spinning the motor by hand the voltage generated was too high for it.
    The only way this battery can be charged is by disconnecting it and charging it through an external power adapter, hence why I want to protect the rest of the circuit.
    I do not mind not having "regen braking" in this device, that's why I added the diode.

    So in conclusion you would recommend taking the diode away and adding a second capacitor?

    Thank you very much for your feedback!

  • +1 in reply to biter terbi
    TI__Mastermind 22775 points

    Hey Pedro,

    No worries, thanks for the response!

    Okay just wanted to check if you needed the option for regeneration to charge the battery. But no, your circuit should do the trick, I would just add another bulk capacitor to ground in parallel to the one shown in your figure. This should be enough to protect your regulator from being damaged.

    Best,

    Isaac