Hi,

I am trying to drive a unipolar stepper motor (with 6 leads) using a bipolar drive. the drive consists of 4 sets of half bridges (high and low side switches using MOSFETs). I am planning to use only the low side switches to drive the 4 coil end of the stepper motor. The centre-tappings of the coils will be connected to Vsupply as usual.
I am attaching the diagram for you to have an idea.
My concern is whether the unused high side switch protection diode (in pink) will cause failure of the coil due to some transformer action.
Hope it's not too confusing...
I will be waiting for your feedback.

Regards,
Anj.

Attached Images

Motor Drive Circuit.jpg (68.4 KB, 24 views)

 

Search the Allegro site for this app note. ApplyinganA3967toaUnipolarStepperMotorApplication. PDF (I may have renamed it on my computer) It says you can but since the PWM is on the high side, you don’t get micro stepping, only full and half step. I did it and works fine.

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Anj.

I suggest that you connect and drive the unipolar stepper motor just like a bipolar, just ignore the centre-tap wires. Do not connect the centre taps to V+. Leave them open.

Bob