U.S. Philips Corporation

Kurt J Johannes

Jurgen Ruprecht

The invention relates to a gated control circuit for controlling an input signal, for example the chrominance signal formed by the color synchronizing signal and the color difference signal of a FBAS signal. The chrominance signal is controlled in dependence on the amplitude of the color synchronizing signal. To that end the color synchronizing signal is applied to an amplitude detector (3), the difference between the output signal of the amplitude detector (3) and a desired value is formed and the result is stored in a register (5). The output signal of the register (5) is applied to a control member (6) having an integrating behavior and including a counter whose counting rate can be changed in dependence on the value of the comparator circuit (4). The chrominance signal and the output signal of the control member (6) are applied to an adjusting member (1, 2), so that the chrominance signal is changed in accordance with the control deviation.

Gated control circuit

A circuit for detecting the vertical blanking period in a picture signal, having a pulse interval detector and a subsequent pulse shaping stage. A composite synchronizing signal, which contains pulses in a predetermined sequence, is applied to the pulse interval detector. The pulse interval detector supplies an output signal change when the interval between the pulses falls short of a predetermined time threshold. The output signal is applied to the pulse shaping stage which, in response thereto, produces a vertical synchronizing signal. With such a circuit arrangement, a vertical synchronizing signal is obtained substantially without delay with respect to the composite synchronizing signal, while at the same time, the circuit design effort and cost are reduced, because of the fact that the pulse interval detector constitutes the time threshold with a predetermined multiple of a period of a periodical clock signal and that the pulse shaping stage forms the vertical synchronizing signal at the occurrence of given pulses in the sequence of pulses of the composite synchronizing signal after the occurrence of the change in the output signal.

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Hamburg, Germany

Kurt J Johannes