| 摘要 |
PURPOSE:To use one oscillator for generating a stable color signal, by making the center oscillation frequency of a VCO different between an NTSC and a PAL system, and equalizing the suppression range of variation in the oscillation frequency of the VCO on the former system to that on the latter system. CONSTITUTION:The center oscillation frequency fVCO of the VCO10 is 375fH for the PAL system and 378fH for the NTSC system. For example, pulse outputs are counted for a 1H (one horizontal scanning) period at certain intervals. In the PAL system, when the counted number of the pulses is 375, >=376, and <=374, a frequency counter 28 outputs 6c, 6e, and 6h respectively to control the oscillation frequency of the VCO10. In the NTSC system, the frequency counter 28 varies and when the counted number of pulses is 378, >=379, and <=376, the frequency counter 28 outputs 6c, 6e, and 6h respectively to control the oscillation frequency of the VCO10 as well as the PAL system. Consequently, only one oscillator is used for both systems and a stable color signal is regenerated. |
