• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 29 subscribers
  • Views 123 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.

DRV8812: Motor Driver for capacitive type devices

Shibin Varghese
Intellectual 835 points
Part Number: DRV8812

Hi Team,
I am using a blower in one of my designs.
I was initially planning to use the motor driver DRV8812PWPR to drive the blower.
But my blower is capacitive load type.
If my understanding is correct, the chip uses current regulations.
The xl0 and xl1 pins are used to control the current.
But the capacitive load requires voltage regulation.
Are there any solutions to drive such a capacitive load?
One thing we figured out is to change the voltage provided to the H bridge (if we are using MOSFETs to build the H Bridge only).
We use a boost converter to boost the voltage from 3.7V to 40V to be provided at the VM pin of the chip.
The output voltage of the boot converter can be adjusted using my MCU.
If I am using this DRV8812PWPR as the driver, is there any problem to change the voltage at the VM pin to adjust the power of the blower?
Driver Should provides:
• AC drive waveform of 20-22 kHz at 0 to 40 V peak.
• 0 to 1 W into pump (continuous).

  • 0
    TI__Guru 56650 points

    Hello, Shibin,

    According to your description, I would think there are two challenges for the drivers:

    a.  the capacitive load requires voltage regulation

    b. the capacitive load would have a high current and voltage spike if the driver switch is turned on to charge this capacitive load. So, we have to put an inductor in series with this capacitive load to limit the high current and voltage spike. 

    So, I think you need a DC/DC convert to achieve the above goal. DRV8812 is not right device. I think if you post the requirement on DC to DC switching converter forum, you could get a quick answer.

    Regards,

    Wang Li

  • 0 in reply to Wang5577
    Intellectual 835 points

    Hi Wang5577,
    Thank you for your reply.
    My load is a piezo blower.
    The vendor of the blower uses an H bridge. 
    The supply of the H Bridge is from a boost converter. The boost converter voltage can be adjusted using an MCU like the below circuit.

    So, if I am using this DRV8812PWPR as the driver, is there any problem to change the voltage at the VM pin to adjust the power of the blower just like the above setup?.

  • 0 in reply to Shibin Varghese
    TI__Guru 56650 points

    Shibin,

    In this case, the motor driver device doesn't need to do the voltage regulation. Changing VM voltage is OK to me.

    Regards,

    Wang Li

  • 0 in reply to Wang5577
    Intellectual 835 points

    Hi Wang5577,
    Thank you for your reply.
    We have no power supply pins other than the VM pin.
    I VM pin can have a voltage range between 8V to 45V.
    However, will changing the VM voltage create any problem with the internal LDO or internal reference voltage ??.
    changing the VM voltage using the adjustable boost converter seems like the best solution I can take.
    Looking forward to hearing from you.

  • +1 in reply to Shibin Varghese
    TI__Guru 56650 points

    Shibin,

    I don't see any problem if the VM is in the recommended range. Since the motor driver circuit is included in boost converter feedback loop, I would think you may need to use EVMs to test system before finalizing the solution.

    Regards,

    Wang

  • +1 in reply to Wang5577
    Intellectual 835 points

    Thank you @Wang5577