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DRV8872: Switching power supply protection from braking state into running state

Annie Liu
Genius 10295 points
Part Number: DRV8872

Hi Team,

There are 5 DRV8872 on the control board, each of which controls a DC motor. The rated power of the motor is 36W, it is powered by 24V, and the current limit of DRV8872 is 1.75A. The power of the switching power supply is 240W. The customer encountered the following problem：

If the two motors enter the running state from the brake state at the same time, the switching power supply will be protected.

If one motor enters the running state from the brake, there is no problem.

If the two motors enter the coasting state from the braking state at the same time, and then enter the running state, there is no problem.

Customer would like to know what caused this? Or what are the precautions for using DRV8872 to drive the motor?

Thanks,

Annie

  • +1
    TI__Guru 56650 points

    Annie,

    In brake mode, the coil terminal is shorted which could cause a high coil current due to the winding back EFM. In this condition, the current is sent back to the input source when the low side FET is off and the high side FET is on. So, the input power supply could trigger its input over voltage protection.

    "If one motor enters the running state from the brake, there is no problem."

    Would you try double the input bulk capacitor's capacitance to see if the issue is still there?

    "If the two motors enter the coasting state from the braking state at the same time"

    The coil current will drop quickly in the coast mode. 

    "If the two motors enter the coasting state from the braking state at the same time, and then enter the running state, there is no problem."

    I think we can use it as a solution.

    Regards,

    Wang Li