Current control circuit for horizontal deflection coil of television receiver

A current control circuit comprising:

• first and second switching circuits;
• a first resonant circuit connected in parallel with said first switching circuit and including a first coil and a first capacitor;
• a second resonant circuit connected in parallel with said second switching circuit and including a second coil and a second capacitor;
• means defining a common current path for currents flowing through said first and second coils, respectively, and including a charging capacitor interposed in said path;
• means for applying first and second switching signals of the same frequency to said first and second switching circuits, respectively;
• means for varying the phase relation of said first and second switching signals and thereby controlling the voltage across said charging capacitor and, accordingly, a current flowing through one of said first and second coils;
• each of said first and second switching circuits including a switching transistor and a damper diode connected in parallel with each other;
• said first and second switching signals being applied to the switching transistors of said first and second switching circuits, respectively;
• said means for applying the first and second switching signals including an oscillator for generating an output with said frequency and being applied as said first switching signal to the transistor of said first switching circuit;
• said means for varying the phase relation of said first and second switching signals including phase control means receiving said output of the oscillator and providing a phase controlled output which is applied as said second switching signal to the transistor of said second switching circuit;
• and
• said phase control means including a monostable multivibrator and means for controlling the unstable time of said monostable multivibrator.

A current control circuit comprising:

• first and second switching circuits;
• a first resonant circuit connected in parallel with said first switching circuit and including a first coil and a first capacitor;
• a second resonant circuit connected in parallel with said second switching circuit and including a second coil and a second capacitor;
• means defining a common current path for currents flowing through said first and second coils, respectively, and including a charging capacitor interposed in said path;
• means for applying first and second switching signals of the same frequency to said first and second switching circuits, respectively, including an oscillator for generating an output with said frequency and which is applied as said first switching signal to said first switching circuit;
• means for varying the phase relation of said first and second switching signals and thereby controlling the voltage across said charging capacitor and, accordingly, a current flowing through one of said first and second coils, including phase control means receiving said output of the oscillator and providing a phase controlled output which is applied as said second switching signal to said second switching circuit;
• and
• said phase control means including a monostable multivibrator and means for controlling the unstable time of said monostable multivibrator.

A current control circuit comprising:

• first and second switching circuits;
• a first resonant circuit connected in parallel with said first switching circuit and including a first coil and a first capacitor;
• a second resonant circuit connected in parallel with said second switching circuit and including a second coil and a second capacitor;
• means defining a common current path for currents flowing through said first and second coils, respectively, and including a charging capacitor interposed in said path;
• means for applying first and second switching signals of the same frequency to said first and second switching circuits, respectively;
• means for varying the phase relation of said first and second switching signals and thereby controlling the voltage across said charging capacitor and, accordingly, a current flowing through one of said first and second coils;
• and
• said one of said first and second coils being a horizontal deflection coil of a television receiver, said frequency of the switching signal being the horizontal frequency of a video signal, and the phase relation of said first and second switching signals being varied parabolically with a repetition rate equal to the vertical frequency of said video signal so as to correct a side pincushion distortion of the raster of said television receiver.

In a horizontal deflection circuit of a television receiver having a horizontal deflection coil for horizontally deflecting an electron beam in response to a current flow through said coil;

• a side pin-cushion distortion correcting circuit comprising:
• first and second switching circuits;
• a first resonant circuit connected in parallel with said first switching circuit and including said horizontal deflection coil and a first capacitor;
• a second resonant circuit connected in parallel with said second switching circuit and including a second coil and a second capacitor;
• means defining a common current path for currents flowing through said horizontal deflection and second coils, respectively, and including a charging capacitor interposed in said path;
• means for applying first and second switching signals at the horizontal frequency of a video signal to said first and second switching circuits, respectively;
• and
• means for parabolically varying the phase relation of said first and second switching signals with a repetition rate equal to the vertical frequency of said video signal and the reby controlling the voltage across said charging capacitor and, accordingly, a current flowing through said horizontal deflection coil so as to correct side pin-cushion distortion of the electron beam raster.

In a television receiver having a cathode ray tube to which an anode voltage is applied and in which the size of the raster is varied with changes in said anode voltage upon variation of picture brightness;

• a circuit for stabilizing the raster size in the horizontal direction comprising a horizontal deflection coil through which a current is made to flow for horizontally deflecting an electron beam in said cathode ray tube, first and second switching circuits, a first resonant circuit connected in parallel with said first switching circuit and including said horizontal deflection coil and a first capacitor, a second resonant circuit connected in parallel with said second switching circuit and including a second coil and a second capacitor, means defining a common current path for currents flowing through said horizontal deflection and second coils, respectively, and including a charging capacitor interposed in said path, means for applying first and second switching signals of the horizontal frequency of a video signal to said first and second switching circuits, respectively, control means for varying the phase relation of said first and second switching signals and thereby controlling the voltage across said charging capacitor and, accordingly, the current flowing through said horizontal deflection coil, a flyback transformer having a primary winding connected with said coils so that currents flowing through the latter produce corresponding voltage pulses across said primary winding and a secondary winding at which stepped-up voltage pulses are obtained, rectifying means for obtaining a relatively high DC voltage from said stepped-up voltage pulses and which is employed as the anode voltage for the cathode ray tube, detecting means for detecting changes in said anode voltage with changes in picture brightness, and means for causing said control means to vary said phase relation of the first and second switching signals in response to detected changes in said anode voltage so as to stabilize the horizontal size of said raster.