Hi All,
A question regarding microstepping control of a 3 phase hybrid
stepper motor (4 wire star wiring.)
A have a microstepping controller which produces 3 phases of 50/50
PWM, and I need to design an amplifier circuit.
What I'm thinking is that I need something like the following (per
phase.)
+Vs _________
|
R1
|
__|
|
|__
|
|________PHASE 1 WINDING __________ 0V
|
__|
|
|__
|
|
R2
-Vs ____|______
The above diagram is supposed to represent a half bridge, with two
current sensing resistors (R1, R2.) The star point on the motor is
connected to ground.
In this scheme we can split the PWM 50/50 into direction and magnitude
signals. The direction signal (ANDed with the chopper controller)
turns on either the top transistor, or the bottom transistor. The
magnitude is used as a reference voltage input to the chopper.
My application is quite cost sensitive and I'm not sure how to do this
cheaply.
Additionally, I have two motors to drive, and not a lot of space on
the board.
It looks like I need per motor...
3 half bridges with sense resisitors
Level shifting on each of voltages comming from the resistors
3 chopper controllers (or do I need six?)
A bit of logic (couple of and gates on the transistors)
Mosfet drivers
What would be the best way to do this?
I'm not expecting a full solution but any ideas would be gratefully
appreciated.
All the best,
Jim Donaldson