Horizontal automatic frequency control circuit

Claim 2

A horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter connected between said phase sensitive detector and said horizontal oscillation circuit, switching means connected to said low-pass filter for disconnectably connecting said low-pass filter to the transmission path between said phase sensitive detector and said horizontal oscillation circuit, and means for controlling said switching means by vertical synchronizing pulses so as to disconnect said low-pass filter from said transmission path for a predetermined limited period of time following the appearance of the vertical synchronizing signal, so that the AC loop gain of said horizontal automatic frequency control circuit can be increased by the disconnection of said low-pass filter from said transmission path and the phase of said horizontal oscillation circuit can quickly respond to phase shift of the horizontal synchronizing signal.

Claim 3

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter consisting of a resistor and a capacitor connected in series, a switch for disconnecting said low-pass filter from the transmission path between said phase sensitive detector and said horizontal oscillation circuit, and means for controlling said switch by vertical synchronizing pulses so as to disconnect said low-pass filter from said transmission path for a predetermined limited period of time following the appearance of the vertical synchronizing signal, so that the AC loop gain of said horizontal automatic frequency control circuit can be increased by the disconnection of said low-pass filter from said transmission path and the phase of said horizontal oscillation circuit can quickly respond to phase shift of the horizontal synchronizing signal occurring every field.

Claim 4

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter consisting of a resistor and a capacitor connected in series, a switch for disconnecting said low-pass filter from the transmission path between said phase sensitive detector and said horizontal oscillation circuit, and means for controlling said switch by vertical synchronizing pulses so as to disconnect said low-pass filter from said transmission path for a predetermined limited period of time following the appearance of the vertical synchronizing signal, so that the AC loop gain of said horizontal automatic frequency control circuit can be increased by the disconnection of said low-pass filter from said transmission path and the phase of said horizontal oscillation circuit can quickly respond to phase shift of the horizontal synchronizing signal occurring every field.

Claim 5

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter connected between said phase sensitive detector and said horizontal oscillation circuit, a pulse generating circuit for generating pulses synchronous with vertical synchronizing pulses, a switch consisting of a monostable multivibrator arranged to be inverted in response to the application of said pulse and maintained in such a state for a predetermined limited period of time and at least two diodes connected in series across the output terminals of said monostable multivibrator, said low-pass filter being connected to the connection point between said two diodes in said switch, and means for connecting said low-pass filter to the transmission path between said phase sensitive detector and said horizontal oscillation circuit when said pulse is not applied to said monostable multivibrator and disconnecting said low-pass filter from said transmission path by said switch for a predetermined limited period of time when said pulse is applied to said monostable multivibrator, so that the AC loop gain of said horizontal automatic frequency control circuit can be increased during tHis period of time and the phase of said horizontal oscillation circuit can quickly respond to phase shift of the horizontal synchronizing signal occurring every field.

Claim 6

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter connected between said phase sensitive detector and said horizontal oscillation circuit, a pulse generating circuit for generating pulses synchronous with vertical synchronizing pulses, a switch consisting of a monostable multivibrator arranged to be inverted in response to the application of said pulse and maintained in such a state for a predetermined limited period of time and at least two diodes connected in series across the output terminals of said monostable multivibrator, said low-pass filter being connected to the connection point between said two diodes in said switch, and means for connecting said low-pass filter to the transmission path between said phase sensitive detector and said horizontal oscillation circuit when said pulse is not applied to said monostable multivibrator and disconnecting said low-pass filter from said transmission path by said switch for a predetermined limited period of time when said pulse is applied to said monostable multivibrator, so that the AC loop gain of said horizontal automatic frequency control circuit can be increased during tHis period of time and the phase of said horizontal oscillation circuit can quickly respond to phase shift of the horizontal synchronizing signal occurring every field.

Claim 7

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter consisting of a resistor and a capacitor connected in series, means for connecting one of the terminals of said low-pass filter to the transmission path between said phase sensitive detector and said horizontal oscillation circuit, means for obtaining pulses synchronous with vertical synchronizing pulses separated by said synchronizing signal separating circuit, a switch consisting of a monostable multivibrator arranged to be inverted in response to the application of said pulse and maintained in such a state for a predetermined limited period of time and at least two diodes connected across the output terminals of said monostable multivibrator, and means for connecting the other terminal of said low-pass filter to the connection point between said two diodes in said switch, whereby said monostable multivibrator can be inverted in response to the application of said pulse and said low-pass filter can be disconnected from said transmission path so that the AC loop gain of said horizontal automatic frequency control circuit can be increased during this period of time and the phase of said horizontal oscillation circuit can quickly respond to phase shift occurring every field.

Claim 8

In a still picture reproducing apparatus for obtaining a still picture by extracting a one-field picture signal from a television signal, recording the one-field picture signal and repeatedly reproducing this recorded signal, a horizontal automatic frequency control circuit comprising a synchronizing signal separating circuit for separating a synchronizing signal from a reproduced composite picture signal, a horizontal oscillation circuit, a horizontal deflection circuit for supplying deflection current to a horizontal deflection coil unit utilizing the signal applied from said horizontal oscillation circuit, a phase sensitive detector for comparing horizontal synchronizing pulses applied from said synchronizing signal separating circuit with phase comparing pulses derived from said horizontal deflection circuit thereby generating at the output thereof a control signal representative of the difference between the phase of the horizontal synchronizing pulses and the phase of the phase comparing pulses, means for applying said control signal to said horizontal oscillation circuit for controlling the phase of said horizontal oscillation circuit, a low-pass filter consisting of a resistor and a capacitor connected in series, means for connecting one of the terminals of said low-pass filter to the transmission path between said phase sensitive detector and said horizontal oscillation circuit, means for obtaining pulses synchronous with vertical synchronizing pulses separated by said synchronizing signal separating circuit, a switch consisting of a monostable multivibrator arranged to be inverted in response to the application of said pulse and maintained in such a state for a predetermined limited period of time and at least two diodes connected across the output terminals of said monostable multivibrator, and means for connecting the other terminal of said low-pass filter to the connection point between said two diodes in said switch, whereby said monostable multivibrator can be inverted in response to the application of said pulse and said low-pass filter can be disconnected from said transmission path so that the AC loop gain of said horizontal automatic frequency control circuit can be increased during this period of time and the phase of said horizontal oscillation circuit can quickly respond to phase shift occurring every field.