Motor driving circuit

Details Motor driving circuit Motor driving circuit

1991-03-11

1995-05-23

Shoop, Jr., William M.

Electricity: motive power systems

Induction motor systems

Primary circuit control

318685, 318696, 318569, 318600, 3885075, H02P 528

Patent

active

054184436

ABSTRACT:
In a motor driving circuit for generating sine wave signals for driving a focusing step motor in a video camera or the like, sine wave data stored in a ROM are accessed in response to an address signal generated by an address generator. A desired sine wave frequency is set by bit-shifting the address signal supplied from the address generator. The address generator counts horizontal sync pulses in which, prior to counting, a predetermined number of the sync pulses are removed at substantially equal intervals so that the counted number of pulses per frame is equal to a power product of 2. The order in which the sine wave data are accessed is inverted every quarter frame period, and the sine wave data read out of the ROM in a vertical period in the order established by the inverter device are processed so as to form sine wave signals having respective phases for supply to the step motor. Sine wave data having a relatively large amplitude are read out from the ROM at the start of the rotation of the step motor so as to obtain a predetermined torque, and, after the step motor has started rotating, sine wave data having a smaller amplitude are read out so as to reduce the power consumption.

REFERENCES:
patent: 4647760 (1987-03-01), Bardwell
patent: 4926104 (1990-05-01), King et al.
patent: 5252905 (1993-10-01), Wills et al.

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