Horizontal synchronization circuit
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorMiyuki Tachibana
Life of this patent
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Abstract
A horizontal synchronization circuit uses a standard decoder to generate a stable first signal locked in frequency and phase to horizontal synchronizing pulses in a composite video signal. A waveshaping circuit reshapes the first signal to generate a second signal for input to a synchronizing circuit. The synchronizing circuit generates a higher-frequency third signal. A timing generator divides the frequency of the third signal to generate a fourth signal having the same frequency as the first and second signals, and a fifth signal having a higher frequency. The fourth signal is fed back to the synchronizing circuit, and can also be used for synchronization of video signal processing. The fifth signal can be used for horizontal scanning at a rate higher than the standard horizontal frequency.
Claims12
A horizontal synchronization circuit, comprising:
- a decoder having an automatic frequency control circuit for receiving a composite video signal, separating therefrom horizontal synchronizing pulses having a certain horizontal frequency, generating a first signal also having said horizontal frequency, and locking said first signal in phase with said horizontal synchronizing pulses;
- a waveshaping circuit coupled to said decoder, for reshaping said first signal by reducing the duty cycle of said first signal to generate a second signal also having said horizontal frequency;
- a synchronizing circuit coupled to said waveshaping circuit, for receiving said second signal, generating a third signal with a frequency higher than said horizontal frequency, receiving a fourth signal, and controlling the frequency of said third signal according to a phase difference between said fourth signal and said second signal;
- and
- a timing generator coupled to said synchronizing circuit, for receiving said third signal and dividing the frequency thereof, thereby generating said fourth signal and a fifth signal, said fourth signal having said horizontal frequency and said fifth signal having a higher frequency.
Dependencies are inferred from the claim text.