METHOD AND DEVICE FOR CORRECTING STEADY-STATE PHASE ERROR

摘要

PURPOSE:To correct a DC phase error accurately and stably without malfunctions due to a stationary phase fluctuation and a sporadic disturbing input, by smoothing a phase error output to detect the DC phase error. CONSTITUTION:A phase comparator 28 outputs a digital signal (a binary bit signal train) corresponding to the phase difference between two input pulses (a reference pulse and a feedback phase control pulse). A latch output C of the phase comparator 28 has only DC components extracted by a digital low-pass filter (LPF) 26. The output of this LPF26 is connected to a preset circuit 32 of a speed control circuit 13, and a preset value P0 of a detecting counter 23 is changed in accordance with the change of the output of the LPF26. A preset value of a detecting counter 33 of the speed control circuit 13 is changed to change a speed control output J, thus correcting the steady-state phase error.