Self-calibrating timing circuits for use in a sync separator
View Patent ↗Provided herein are self-calibrating timing circuits and methods for use in a sync separator. A comparator compares a video signal to a video reference voltage to produce a sliced sync signal that has a frequency that is equal to a scan frequency of a horizontal sync embedded in the video signal. A first converter converts the sliced sync signal to a control signal having an amplitude or magnitude that is inversely proportional to the scan period of the horizontal sync embedded the video signal. A second converter converts the voltage control signal to a timer signal that has timed intervals that are that are inversely proportional to the amplitude or magnitude of the control signal, and thus proportional to the scan period of the horizontal sync embedded in the video signal. These timed intervals produced in accordance with embodiments of the present invention are easily and precisely scalable, allowing them to be used to discriminate various timing features embedded in video signals. This abstract is not intended to be a complete description of, or limit the scope of, the invention.
1. A self-calibrating timing circuit for use in a sync separator, comprising:
a comparator to compare a video signal to a reference voltage to thereby produce a sliced sync signal indicative of sync features embedded in the video signal;
a first converter to convert the sliced sync signal to a control signal having an amplitude or magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
a second converter to convert the control signal to a timer signal that has timed intervals that are inversely related to the amplitude or magnitude of the control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
2. The circuit of claim 1 , wherein:
the control signal comprises a voltage control signal having an amplitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
the timer signal has timed intervals that are inversely related to the amplitude of the voltage control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
3. The circuit of claim 1 , wherein:
the control signal comprises a current control signal having a magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
the timer signal has timed intervals that are inversely related to the magnitude of the current control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
4. The circuit of claim 1 , wherein:
the amplitude or magnitude of the control signal is inversely related to the scan period by being inversely proportional to the scan period;
the timed intervals are inversely related to the amplitude or magnitude of the control signal by being inversely proportional to the amplitude or magnitude of the control signal; and
the timed intervals are related to the scan period by being proportion to the scan period.
5. The circuit of claim 1 , wherein an amplitude of the reference voltage is just above an amplitude of sync features embedded in the video signal.
6. The circuit of claim 1 , wherein the first converter comprises:
a one-shot circuit to receive the sliced sync signal and to produce a pulsed signal having a duty cycle that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
a low pass filter including an input and an output;
wherein the input of the low pass filter is selectively connected to one of a further reference voltage and ground, based on the pulsed signal; and
wherein an output of the low pass filter comprises the control signal.
7. The circuit of claim 1 , wherein:
the control signal comprises a voltage control signal having an amplitude that is inversely related to the scan period of the horizontal sync embedded in the video signal;
the timer signal has timed intervals that are inversely related to the amplitude of the voltage control signal, and thus related to the scan period of the horizontal sync embedded in the video signal; and
the second converter is configured to convert the voltage control signal to a current signal having a magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal, and to convert the current signal to the timer signal that has timed intervals that are inversely related to the amplitude of the voltage control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
8. The circuit of claim 1 , further comprising:
a detector to detect a standard of the video signal based on the amplitude or magnitude of the control signal.
9. The circuit of claim 1 , further comprising:
a detector to accept the control signal a to produce, based on the control signal, and detector output signal indicative of a standard of the video signal.
10. A method for producing a self-calibrated timing signal for use in a sync separator, comprising:
(a) comparing a video signal to a reference voltage to produce a sliced sync signal indicative of sync features embedded in the video signal;
(b) converting the sliced sync signal to a control signal having an amplitude or magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
(c) converting the control signal to a timer signal that has timed intervals that are inversely related to the amplitude or magnitude of the control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
11. The method of claim 10 , wherein:
the control signal comprises a voltage control signal having an amplitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
the timer signal has timed intervals that are inversely related to the amplitude of the voltage control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
12. The method of claim 10 , wherein:
the control signal comprises a current control signal having a magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
the timer signal has timed intervals that are inversely related to the magnitude of the current control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
13. The method of claim 10 , wherein:
the amplitude or magnitude of the control signal is inversely related to the scan period by being inversely proportional to the scan period; and
the timed intervals are inversely related to the amplitude or magnitude of the control signal by being inversely proportional to the amplitude or magnitude of the control signal; and
the timed intervals are related to the scan period by being proportion to the scan period.
14. The method of claim 10 , wherein an amplitude of the video reference voltage is just above an amplitude of sync features embedded in the video signal.
15. The method of claim 10 , wherein step (b) includes
(b.1) producing, based on the sliced sync signal, a pulsed signal having a duty cycle that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
(b.2) selectively connecting an input of a low pass filter to one of a further reference voltage and ground, based on the pulsed signal, to thereby produce the control signal at an output of the low pass filter.
16. The method of claim 10 , wherein the control signal comprises a voltage control signal having an amplitude that is inversely related to the scan period of the horizontal sync embedded in the video signal, and wherein step (c) includes:
(c.1) converting the voltage control signal to a current signal having a magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
(c.2) converting the current signal to the timer signal that has timed intervals that are inversely related to the amplitude of the voltage control signal, and thus related to the scan period of the horizontal sync embedded in the video signal.
17. The method of claim 10 , further comprising:
(d) detecting, based on the amplitude or magnitude of the control signal, a standard of the video signal.
18. The method of claim 17 , further comprising:
(e) outputting a signal that is indicative of the detected standard.
19. A self-calibrating circuit for use in a sync separator, comprising:
a comparator to compare a video signal to a reference voltage to thereby produce a sliced sync signal indicative of sync features embedded in the video signal;
a converter to convert the sliced sync signal to a control signal having an amplitude or magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
a detector to detect a standard of the video signal based on the amplitude or magnitude of the control signal.
20. The circuit of claim 19 , wherein the detector outputs a signal indicative of the detected standard.
21. A method for use in a sync separator, comprising:
(a) comparing a video signal to a reference voltage to produce a sliced sync signal indicative of sync features embedded in the video signal;
(b) converting the sliced sync signal to a control signal having an amplitude or magnitude that is inversely related to the scan period of the horizontal sync embedded in the video signal; and
(c) detecting, based on the amplitude or magnitude of the control signal, a standard of the video signal.
22. The method of claim 21 , further comprising:
(d) outputting a signal indicative of the detected standard.