Electricity: motive power systems – Open-loop stepping motor control systems
Patent
1982-11-02
1984-09-11
Truhe, J. V.
Electricity: motive power systems
Open-loop stepping motor control systems
318685, 318341, H02K 2904
Patent
active
044712839
ABSTRACT:
A circuit (30) for regulating the current level in a pulse width modulated stepper motor drive (10), the circuit (30) comprising a clock (26) for providing a signal output at a preset and predetermined frequency and duty cycle. A power supply (Vs) supplies current for energizing the windings (A-D) of a stepping motor, the circuit (30) chopping the current and controlling the chop duty cycle to maintain a predetermined current in stepping motor windings (A-D), the chop frequency being directly related to said clock frequency. The circuit (30) senses the current flowing through the windings (A-D) of the motor, and compares, in a differential amplifier (32), the sensed current to a predetermined current level (Vref). A sample/hold amplifier (35) samples at predetermined times dependent upon the duty cycle of said clock (26), the output of the differential amplifier (32), the output of said sample/hold amplifier (35) being a signal whose level is related to the difference between the actual sensed current the predetermined current level. A portion of the circuit 30 (comparator 45, latch 50) having an output signal turned on by a specific clock transition and turned off at a time related to the level of said output signal of said sample/hold circuit, pulse width modulates the chop of the motor current.
REFERENCES:
patent: 4074179 (1978-02-01), Kuo et al.
patent: 4306181 (1981-12-01), Welburn
patent: 4418304 (1983-11-01), Iwai
Bergmann Saul M.
Dick William J.
International Business Machines - Corporation
Truhe J. V.
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