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BOOSTXL-DRV8323RH: 1x PWM Mode

ANIKET SHIGWAN
Prodigy 40 points
Part Number: BOOSTXL-DRV8323RH
Other Parts Discussed in Thread: DRV8323

I amtrying to drive a 3 phase BLDC motor using BOOSTXL-DRV8323RH EVM Board. The motor runs smoothly when INHA pin is fed an analog voltage via onboard potentiometer pot.

When I supply the voltage to INHA Pin via Arduino PWM the motor rotates with a rough noise. Only when PWM Duty cycle approaches close to 90% does the motor show smooth rotation.

(Arduino freq is 490 Hz).

Please shed some light on the cause and probable rectifications. Thank You.

  • +1
    TI__Mastermind 26046 points

    Hi Aniket,

    1x PWM mode requires obviously requires 1 PWM signal to commutate the motor. The frequency and duty cycle of the PWM input yield the gate driver output frequency and PWM duty cycle. When you feed an analog voltage, the DRV8323 sees this as a 100% PWM duty cycle as long as the analog voltage is above VIH. 

    Sounds like your motor requires a large speed at the VM supply voltage you are giving it for it to spin. For instance, if you are giving it 90% at VM = 12V for the motor to spin smoothly, then the average voltage for the motor phase PWM is around 12*0.9 = 10.8V. You may need to use a higher supply voltage so that the motor spins with a lower input PWM duty cycle. For instance, if VM = 24V, and the motor spins with an average voltage of 10.8V, then you should only need a 45% duty cycle to spin the motor. 

    Also, I recommend a PWM frequency of around 20kHz or higher so that there is no audible noise. Low frequencies produce audible noise. 

    Thanks,
    Aaron

  • 0
    Prodigy 40 points

    Hello Aaron, thanks a lot for your valuable input. In my case I was able to achieve smooth rotation simply by raising the PWM frequency as per your suggestion. Thanks again. 

  • +1 in reply to ANIKET SHIGWAN
    TI__Mastermind 23306 points

    Hello Aniket,

    Glad to hear that it worked out. If this has resolved your issue then please mark the thread as 'Resolved'.

    Best Regards,

    Akshay