| 摘要 |
PURPOSE:To fix the display size in the vertical direction even vertical scanning frequency is changed and to freely change the size by controlling the electric current value of a constant current source which decides the amplitude value of the output voltage of a vertical oscillating circuit based on the amplitude value of vertical deflecting current in a vertical deflecting coil. CONSTITUTION:Amplitude detecting means 131 - 135 detect the utmost amplitude value of the vertical deflecting current in the vertical deflecting coil 6, update the detected utmost amplitude value, for example, by every vertical cycle, and a comparing means 136 compares the detected utmost amplitude value with a standard value set by a setting means 139. Then, based on the compared result, the electric current value of the constant current source 4 of the vertical oscillating means 2 is controlled in order to permit the utmost amplitude value to be equal to the standard value. Thus, even when the vertical scanning frequency is changed, the display size in the vertical direction is always fixed and the size is freely changed to an optional size by changing the setting of the standard value. |
