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Horizontal Oscillator Synchronized With Phase Corrected Sync Pulse

IP.com Disclosure Number: IPCOM000086127D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Patten, MA: AUTHOR

Abstract

This horizontal synchronization circuit uses a triggered multivibrator to insure a wide frequency lock range. To compensate for changes in delays, the sync pulse is first delayed then used to trigger the multivibrator. A phase comparison between the trailing edge of the original sync pulse and the trailing edge of the flyback pulse is made to determine the necessary sync pulse delay. This phase comparison can be made quite sensitive, since it does not affect the locking or capture range of the circuit. Therefore, a high degree of accuracy can be maintained as to the phase relationship between sync pulse and forward sweep, since forward sweep immediately follows the trailing edge of the flyback pulse. This is accomplished without sacrificing capture range.

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Horizontal Oscillator Synchronized With Phase Corrected Sync Pulse

This horizontal synchronization circuit uses a triggered multivibrator to insure a wide frequency lock range. To compensate for changes in delays, the sync pulse is first delayed then used to trigger the multivibrator. A phase comparison between the trailing edge of the original sync pulse and the trailing edge of the flyback pulse is made to determine the necessary sync pulse delay. This phase comparison can be made quite sensitive, since it does not affect the locking or capture range of the circuit. Therefore, a high degree of accuracy can be maintained as to the phase relationship between sync pulse and forward sweep, since forward sweep immediately follows the trailing edge of the flyback pulse. This is accomplished without sacrificing capture range.

Incoming sync pulses 10, indicated by waveform A, are integrated in integrator 12 between two clamping levels +0.7 volt and - control voltage, to produce waveform B. A comparison is made between waveform B and the control voltage in compare 14 producing waveform E which is used to sync the multivibrator 16.

The rate of change of waveform B, as it goes in a negative direction, is determined by an exponential of a fixed time constant. Therefore, there exists a fixed relationship between the voltage differential between clamp levels (control voltage differential) and the integration time between clamp levels (delay time). By increasing the control voltage differential, the delay time is also increased and vice versa. Changing the delay time causes the phase relationship between waveform A (the sync pulse) and waveform E (multivibrator sync) to change. Waveform F is the output of the multivibrator 16. This signal...