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Original question:

DRV10987: DRV10987 no motor Reliability test

DRV10987: AC Volt detection

Lin Joey71
Prodigy 100 points
Part Number: DRV10987
Other Parts Discussed in Thread: DRV10983

Hi

I have a design need for detection AC Volt to set BLDC speed.

I am currently planning AC in using the resistor divider to ADC or Volt Comparator, but I want to know to have else solution.

  • 0
    TI__Expert 6065 points
    Hey Lin,

    I want to make sure I understand your requirement.
    To my understanding, you want to control bldc speed with an AC voltage. You are thinking about using a resistor divider to an adc or voltage comparator to then decide what speed cmd to send (presumably through a microcontroller or some other solution), but you want to know what other solutions are there. Please correct me if I'm wrong.

    To control speed, DRV10987 has an analog speed mode, where voltage on the SPEED pin between 0V and 3.3V scales to a pwm speed cmd of 0% to 100% duty cycle. So I would recommend scaling the AC voltage somehow to a range between 0V and 3.3V and giving it to the SPEED pin, maybe put a resistor divider. Also put precautions to make sure voltage doesnt exceed the absolute max of the SPEED pin.
  • 0 in reply to Sanmesh Udhayakumar
    Prodigy 100 points

    hi

    Attached is my system AC volt in, after bridge rectifier volt data, how can I use convert into ADC, my switch on AC line can't change



  • 0 in reply to Lin Joey71
    TI__Expert 6065 points
    1) What does the AC voltage look like, and what about the AC voltage changes to indicate different speed? Is it just amplitude, or is it frequency? What is the range these parameters change for your desired speed range? Giving more details about the AC voltage will help me recommend a solution for you.
    2) In your table, my understanding is just that the 272V amplitude AC signal becomes 308V DC when rectified? I dont think that seems right, so please correct my understanding.
  • 0 in reply to Sanmesh Udhayakumar
    Prodigy 100 points
    I can accept any solution. Because we can only judge from the L line monitor the AC voltage change to set speed range.
    if TI have any AC/DC(PFC,under 100W, 90V~300V to 24V/3A) solution
  • 0 in reply to Lin Joey71
    TI__Expert 6065 points
    1) To see if TI has a AC/DC(PFC,under 100W, 90V~300V to 24V/3A) solution, I would ask on the appropriate e2e forum. As per TI designs that incorporate both the ac/dc stage and DRV10x drivers, i would look at the below designs. They are for DRV10983, which is pin to pin compatible with the DRV10987.
    www.ti.com/.../TIDA-01417
    www.ti.com/.../TIDA-00652
    2) So is this AC voltage the voltage that comes straight from your outlet?
    3) I'm assuming you're using this AC voltage to both power the DRV device and control the speed of the motor. Is this right?
    4) Can you control speed with just a DC voltage? If so, just use the 3.3V regulator V3P3 as the supply, and use a resistor divider with a potentiometer to control speed and set the Speed pin to analog mode. You will control speed then through the voltage on the speed pin from 0V to 3.3V