| 摘要 |
PURPOSE:To quicken the lead-in of an ACC circuit by comparing the average value of a chrominance signal with a reference value and feeding back a value corresponding to the difference. CONSTITUTION:A signal from an input terminal 1 is extracted to an output terminal 3 via a multiplication circuit 2. The output signal of the multiplication circuit 2 is applied to a detection circuit 4 detecting the maximum and minimum peak value of the burst period. The average value of the detected value is applied to a subtraction circuit 5 and applied to an adder circuit 7 while being subtracted from the reference value. A signal from the adder circuit 7 is stored in a D flip-flop 8 in the timing of a horizontal pulse of an input terminal 9 and this stored value is applied to the multiplication circuit 2. A value in response to the magnitude of the difference with the reference value is extracted from the subtraction circuit 5 and a control value is revised at a time from this value. |
