JPS5622256A - Control unit for disc rotating speed - Google Patents

Abstract

PURPOSE:To keep constant the line speed of disc track, by detecting the data processing position at the radial direction of disc, and controlling the phase locked loop with the synchronizing signal included in the data during disc track revolution according to the position of detection. CONSTITUTION:The output pulse of the rotary encoder 2 directly coupled to the disc rotating motor 1 is one input to the phase comparator 3. Another input of the comparator 3 is fed from the output pulse of the divider 4. The dividing operator 4 makes frequency division for the reference pulse input with the divisor designation input from the divisor designation source 5. In response to the location of disc radial direction by the radius detector 8 of the divisor designation source 5, synchronizing signal included in the data during disc track rotation from the synchronizing signal generator 9 is produced to be the divisor designation input to the divider operator 4. The compared output of the phase comparator 3 controls the motor 1 via LPF6 and motor drive amplifier 7. Thus, the line speed of disc track can be kept constant.