| 摘要 |
PURPOSE:To prevent local baking of a fluorescent screen by providing an internal synchronizing signal generating circuit outputting an internal synchronizing signal having a reference frequency and using the internal synchronizing signal so as to drive a horizontal output circuit only when the frequency of the horizontal synchronizing signal inputted externally is at the outside of the permissible frequency range. CONSTITUTION:When a frequency fH is increased, since an output voltage Vo of a voltage control circuit 25 rises, a maximum value Vs of a terminal voltage Vs of a horizontal deflection coil 3 is unchanged. That is, the frequency voltage characteristic is set so that an output voltage Vo is obtained so as not to change the maximum value Vs. When the maximum value Vs is unchanged, since the maximum value of an exciting current iH is unchanged, an electron beam 7 is scanned up to a horizontal position before the frequency fH is changed. Thus, a voltage Vcc (output voltage Vo) of a power supply 13 is changed so as not change the maximum value Vs of the terminal voltage vs in response to the change in the frequency fH of the horizontal synchronizing signal (a) thereby controlling the horizontal scanning range of the electron beam 7 to be within a prescribed range at all times. |
