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DRV8312: 8312 Basic speed control - (not max or constant torque)

Part Number: DRV8312

1 - Example of the 1xPWM command - is this a constant value ie - the bus voltage percent to apply or should this be a waveform? How to control speed? (adjust value down until desired speed is measured). This is more like a constant power/torque input and not very stable, right?
2 - Example of 3xPWM command - these should be sin waves that are 120 deg out of phase, right?
3 - How to Minimize Power Losses (core/switching/EMI)  - double ramp example? Do we need to measure current with a ground "R" … can it be lower/smaller, can we move it to just the gate? (look into)… how much power is lost in each element?
4 - Any Recommendations on making the spin speed more stable/repeatable?

  • Hey Nelson,

    Thank you for the question. We will aim to provide an update this week.

    Best,
    Akshay

  • Hi Nelson,

    1 - Example of the 1xPWM command - is this a constant value ie - the bus voltage percent to apply or should this be a waveform? How to control speed? (adjust value down until desired speed is measured). This is more like a constant power/torque input and not very stable, right?

    1xPWM command typically involves applying a constant duty cycle to control the motor. This could represent a constant voltage or a waveform, depending on your control strategy. The duty cycle may be adjusted to regulate the speed, but keep in mind that this approach might result in less stable speed control compared to more advanced methods.

    2 - Example of 3xPWM command - these should be sin waves that are 120 deg out of phase, right?

    Yes, for the 3xPWM command, you typically generate three sinusoidal waveforms that are 120 degrees out of phase to control the three phases of the motor. (for a visual there are application curves in the datasheet)

    3 - How to Minimize Power Losses (core/switching/EMI)  - double ramp example? Do we need to measure current with a ground "R" … can it be lower/smaller, can we move it to just the gate? (look into)… how much power is lost in each element?

    Power losses can be attributed to an array of variables how ever yes implementing techniques like double ramp control would help minimize power losses however I don't have an example unfortunately. to calculate power losses you can take a look at the following E2E post that discusses calculating power loss:

    https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1067600/drv8328-about-power-losses-calculate/3950945?tisearch=e2e-sitesearch&keymatch=power%25252525252520losses%25252525252520calculation#3950945

    4 - Any Recommendations on making the spin speed more stable/repeatable?

    consider implementing closed-loop control using feedback from encoders or sensors. This allows the controller to adjust the motor drive in real-time to maintain a more stable and repeatable speed.

    Regards,

    Yara