GB1450434A - Phase control apparatus for a rotary member - Google Patents

Abstract

1450434 Automatic control of phase and speed SONY CORP 14 Dec 1973 [18 Dec 1972] 58000/73 Heading G3R In a phase control apparatus for a rotary member e.g. a video tape recording head, first and second signals are generated when the motor reaches predetermined angular positions. A squarewave is generated that has a pre-set phase relationship with the first signal, and is compared with the second signal. The comparator is thus in one of three conditions, according to whether the second signal is lagging, leading or coincident with the squarewave. The rotation of the rotary member is controlled according to the comparator condition, a reference phase signal and at least one of the first and second signals. As shown, the first and second pulse signals are generated by position detectors 12a, 12b. The first signals from detector 12a sequentially triggers multi-vibrators 15, 16, and if a pulse from detector 12b occurs whilst multi-vibrator 16 is triggered on, a vertical synchronizing signal Sv passes via time delay 2 and NAND gates 4, 5 to integrator 6. The integration is sampled and held by 7 at the next pulse from either detector 12a, 12b whose outputs are summed by mixer 13. The held signal produces a motor control e.g. braking signal for motor 9 which may drive a rotary head in a video tape recorder, or drive a tape capstan. If the pulse from detector 12b occurs whilst multi-vibrator 15 is triggered on, or after the multi-vibrators have both reverted to their off state, the output from NAND gate 5 to the integrator 6 is respectively a '1' (overspeed) or '0' (underspeed) signal, producing a low or high motor control signal. The motor may be a D.C. or eddy current type, or a synchronous motor fed from a variable frequency oscillator.