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Two Wire Brushless Motor Controller as Drop-in Replacement for Brushed DC

Casey Fordyce
Prodigy 30 points
Other Parts Discussed in Thread: DRV8801, DRV8313, DRV10983

I have a customer who is currently using a brushed DC motor to drive a fluid pump at 50psi.  The pump is closed loop controlled via a pressure sensor.  The motor speed is currently adjusted to maintain pressure with the use of a 30kHz PWM of 12VDC.  The kicker here may be that it operates with a low side switch, as in the 12VDC line is connected directly to the motor and the ground is switched on and off.  

What I am looking for is direction on whether it is feasible to use one of TI's brushless motor control chips as a stand alone device that turns on the motor as soon as power is applied and will vary the speed of the motor using the incoming 30kHz PWM power wires instead of power and a PWM signal wire.  This would allow them to run a brushless motor as a drop in replacement without changing the wiring harnesses.  The motor currently uses about .4A at 12VDC.  I would love it if one of the integrated chips would work like the DRV8313.

Thank you,

Casey

  • 0
    TI__Guru** 114905 points

    Hi Casey,

    It is possible. There is generally no problem switching ground on and off instead of the 12V line.

    The DRV8801 with a hall sensor to control the PH pin and the PWM to control the ENABLE pin sounds like it should work.

    By two wire brushless, can you provide a motor specification?

  • 0 in reply to Rick Duncan
    Prodigy 30 points
    Rick,

    By two wires I mean that the only wires going to the motor/controller combo are the existing power and ground. There would be the 12VDC and PWM'ed ground entering the motor controller and the brushless motor would still be connected to the controller with the conventional BLDC U, V, W motor leads. I don't have exact motor specs yet because my prototype hasn't been delivered yet but it is wound for 12V and KV of 740. It is an inrunner with a 12 slot stator and a 4 pole rotor.

    Thanks,

    Casey
  • 0 in reply to Casey Fordyce
    TI__Guru** 114905 points
    Hi Casey,

    Thanks for the clarification. Some of what I said previously no longer applies. The assumption was that the motor was a single or two phase BLDC, not a 3 phase BLDC.

    The DRV8313 should work in this application, although external logic will be required to commutate the motor.

    The DRV10983 may also be a good fit. It requires fewer external components, but requires the motor settings to be programmed into the device.

    EVMs of both are available at store.ti.com/default.aspx
  • 0 in reply to Rick Duncan
    Prodigy 30 points
    Rick,

    Just for my clarification, the DRV8313 needs an external control chip to provide it with logic signals required to commutate the motor, but the DRV10983 can function as a stand alone chip as long as you pre-program the motor settings prior to installing on the PCB. Is that correct? Also, can both of these chips can vary the speed of the motor with, I believe the method is called, power supply modulation where the incoming power is pulse width modulated to vary the incoming voltage? Would they require a cap on the input to smooth the incoming voltage ripples? I've seen several brushless motor controls for the R/C hobby world say not to power them from a SMPS because the supply cannot handle the back fed power generated by the motor coming to a stop. Should any supporting components be added to the incoming power lines to prevent the back feed? Thank you for your patience with a newbie!

    Casey