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,