| 摘要 |
PURPOSE:To start a protecting operation before a horizontal output circuit receives a stress by changing the lower limit of the incoming range of a PLL by a voltage proportional to an input synchronizing signal and smoothing the voltage change. CONSTITUTION:A one-shot multivibrator 2 is triggered by the input synchronizing signal and the output is integrated by a resistance 3 and a capacitor 4. The voltage of the capacitor 4 is applied to the base of a transistor 8 through a diode 5. When a PLL loop is operated and the base voltage of a transistor 9 is smaller than the base voltage (m) of the transistor 8, the transistor 8 is turned on and the transistor 9 is turned off. When the abnormality of the horizontal output circuit or the stop of the input synchronizing signal are detected, a transistor 31 is turned on, the base voltage (m) of the transistor 8 is raised to to turn on the transistor 8 and turn off the transistor 9, the PLL is disconnected and an oscillating frequency is elevated near to an upper limit. |
