| 摘要 |
PURPOSE:To correct variance in hue, by correcting unlocked APC operation into lockable state, through the detection of unlocked APC operation due to jutter. CONSTITUTION:For an unlocked state where a color burst signal to a phase comparator 15 and a phase comparison reference signal are not in coincidence with the phase shift direction, first the oscillating frequency is gradually increased by a charging circuit 30. Since no signal P3 is applied to a current conversion circuit 28 while a signal G2 is zero, the oscillation frequency of a variable frequency oscillator 12 is not controlled to generate a signal S2. This signal S2 becomes to a signal S2' via a gate circuit 34 and counted. When the output S4 of a counter 35 is ''1'', the control signal of a phase inverting circuit 38 is inverted with an output signal S5 of an FF36. Thus, the direction of phase shift at every horizontal scanning of the phase comparison reference signal and the color burst signal to a phase comparator 15 is coincident and the APC operation can be locked. |
