| 摘要 |
PURPOSE: A phase fixing loop for a horizontal synchronization performs a horizontal tracking with additional frequency value in a switching pulse generation period, enhances a fixing speed, and removes jitters of a horizontal synchronization signal of a video display device. CONSTITUTION: A phase fixing loop includes a horizontal tracking part which receives a synchronization signal and a system clock among video signals, checks a phase error of a synchronization signal every horizontal line, and generates a frequency value according to the phase error. A discrete time oscillator generates a specific frequency signal determined by the frequency value generated from the horizontal tracking part. Analog phase fixing loop receives an output signal of the discrete time oscillator, and reduces jitters of the output signal. The horizontal tracking part includes a synchronous signal comparator(52) which enabled when a VCR signal flag is at a inactivation level and generates a first phase error. A tracking filtering part(54) receives first and second phase errors, performs a predetermined operation, and outputs the frequency value. VCR signal detector(58) receives the frequency value, detects a phase error quantity repeated every field by a head switching pulse, and generates VCR signal flag. VCR synchronous signal comparator(60) is enabled when the VCR signal is at activation level, and provides the second phase error quantity to the tracking filtering part. |
