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1. (WO1983002695) STEPPER MOTOR CONTROL CIRCUIT

Pub. No.:    WO/1983/002695    International Application No.:    PCT/GB1983/000027
Publication Date: Aug 4, 1983 International Filing Date: Feb 2, 1983
IPC: H02P 8/12
Applicants: LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
TURVEY, Simon
Inventors: TURVEY, Simon
Title: STEPPER MOTOR CONTROL CIRCUIT
Abstract:
A stepper motor control circuit includes a waveform generator circuit (301, 302, 303, 304, 305) which produces two identical substantially stepless symmetrical waveforms (preferably of triangular configuration) at a frequency which can be varied on demand. Each waveform is used as a current demand signal for a pulse width modulator with a push-pull output stage (Q301, Q302) controlling current in the motor windings (310, 311). The pulse width modulator runs at a fixed frequency an order of magnitude higher than the maximum required stepping frequency. A current sensing resistor (R301) provides a feedback signal which is fed back to input of the modulator to balance the demand signal.