Deflection control apparatus for a beam index color cathode ray tube

Deflection control apparatus for a beam index color television receiver of the type including a cathode ray tube adapted to display a video picture in response to a received color television signal, said cathode ray tube having index stripes disposed to be scanned by the electron beam of said cathode ray tube;

• detecting means for detecting when respective index stripes are scanned by said beam to produce an index signal, the frequency of said index signal varying from a predetermined frequency value when the scanning speed of said beam varies;
• oscillating means for generating an oscillating signal whose frequency is synchronized with said index signal;
• phase-locked loop means including comparing means for comparing said index signal to said oscillating signal to produce a control signal as a function of the difference therebetween and to adjust the frequency of said oscillating signal in accordance with said control signal;
• said control signal produced by said phase-locked loop means representing the variation of the scanning speed of said beam;
• and switching means for switching color information signals to modulate said beam in response to said oscillating signal;
• said deflection control apparatus comprising a main deflection yoke, transformer means having primary and secondary windings, one of which is coupled to said main deflection yoke, and amplifier means coupled to the other of said primary and secondary windings and responsive to said control signal to vary the current in said transformer means and thereby vary the current in said main deflection yoke so as to correspondingly vary the deflection speed of said beam.

Deflection control apparatus for a beam index cathode ray tube adapted to display a video picture, said cathode ray tube having index stripes disposed to be scanned by the electron beam of said cathode ray tube, a main deflection yoke for deflecting said beam along successive scanning traces, detecting means for detecting when respective index stripes are scanned by said beam to produce an index signal whose frequency varies from a predetermined frequency value when the scanning speed of said beam varies, oscillating means for generating an oscillating signal whose frequency is synchronized with said index signal, phase-locked loop means including a phase comparator for phase comparing the index and oscillating signals to produce a control signal as a function of the phase difference therebetween, said control signal representing the variation in the scanning speed of said beam and being operative to adjust the frequency of said oscillating signal, and switching means responsive to said oscillating signal for switching color information signals to modulate said beam, said deflection control apparatus comprising an auxiliary correcting deflection yoke responsive to deflection control signals supplied thereto to produce a correcting deflecting field so as to vary the deflection of said beam;

• gate means coupled to said phase locked loop means to pass the control signal produced by said phase comparator during a selected viewing interval in each scanning trace of said beam, and integrating means for integrating said passed control signal and supplying said integrated signal to said auxiliary correcting deflection yoke.

Deflection control apparatus for a beam index cathode ray tube adapted to display a video picture, said cathode ray tube having index stripes disposed to be scanned by the electron beam of said cathode ray tube, deflection yoke means including a deflection coil responsive to a deflection current flowing therein for deflecting said beam along successive scanning traces, detecting means for detecting when respective index stripes are scanned by said beam to produce an index signal whose frequency varies from a predetermined frequency value when the scanning speed of said beam varies, oscillating means for generating an oscillating signal whose frequency is synchronized with said index signal, phase-locked loop means including a phase comparator for phase comparing the index and oscillating signals to produce a control signal as a function of the phase difference therebetween, said control signal representing the variation in the scanning speed of said beam and being operative to adjust the frequency of said oscillating signal, and switching means responsive to said oscillating signal for switching color information signals to modulate said beam, said deflection control apparatus comprising deflection control signal generating means for generating a deflection control signal as a function of the control signal produced by said phase comparator and a variable impedance coupled to said deflection coil and responsive to said deflection control signal to exhibit a corresponding impedance, the amount of deflection current flowing through said deflection coil being a function of the variable impedance.