| 摘要 |
PURPOSE:To obtain a stable horizontal oscillation output by opening/closing a gate circuit by a signal outputted from a vertical oscillator to suppress the input of a vertically synchronizing signal from a synchronizing signal separating circuit to a phase comparator. CONSTITUTION:The synchronizing signal separating circuit 1 separates only a synchronizing signal from an inputted TV signal and the separated synchronizing signal is inputted to the vertical oscillator 2. The gate circuit 3 is opened/ closed by an input from the oscillator 2 and outputs the synchronizing signal to a phase comparator 4. The synchronizing signal (a) inputted from the circuit 1 to the circuit 3 is outputted to the phase comparator 4 only for the closed period of the gate circuit 3. When the gate circuit 3 is opened and the synchronizing signal is not inputted to the comparator 4, the output signal of the comparator 4 is not applied to a low pass filter 5 and a capacitor 7 holds its potential, so that voltage fed back to a horizontal oscillator 6 is not changed. Consequently, unstable operation in the vertically synchronizing signal period of the horizontal oscillator 6 can be removed and stable horizontal oscillation characteristics can be obtained. |
