| 摘要 |
PURPOSE:To reduce a voltage difference between a vertical blanking period and video period, and to reduce the meander of the upper part of a picture by impressing the vertical blanking pulse voltage of about 50% portion of the detection voltage of a white pattern picture,to the detection voltage. CONSTITUTION:The vertical blanking pulse of about 50% of the detection voltage obtained at a capacitor 8 through a diode 11 and a resistor 12 when the white pattern is being received and brightness is maximum, is impressed to the capacitor 8. At the time of considering the value of the resistor 10 to be large, pulse height is determined roughly by the values of the resistors 12, 7, 6, and the ripple portion of the voltage obtained at the capacitor 8, comes less. Then, the fall quantity of the AFC voltage of the vertical blanking period decreases, and in company with it, the voltage increment of the video period decreases. Thus, the voltage change of the AFC voltage, corresponding to the upper part of the picture, decreases, and the quantity of a right bend comes less. |
