Display apparatus having a horizontal screen size adjusting circuit in step-up type

An apparatus, comprising:

• a video display conveying varying visual information to a user, said video display forming a screen having a vertical screen size and a horizontal screen size, said visual information appearing on said screen, and said video display including an electron gun emitting a beam of electrons;
• a signal generating unit receiving a first signal and a feedback signal, generating a second signal in accordance with said first signal and said feedback signal, and outputting said second signal, wherein said first signal corresponds to a horizontal screen size adjusting signal and said second signal corresponds to a pulse width modulation signal;
• an adjusting unit receiving said second signal from said signal generating unit, said adjusting unit being driven by said second signal, said adjusting unit outputting a third signal to adjust said horizontal screen size;
• a driving circuit receiving a fourth signal and generating a fifth signal, said fourth signal corresponding to a horizontal oscillation frequency signal;
• an output unit having a switch selectively turning said output unit on and off, said output unit receiving said third signal from said adjusting unit, said output unit receiving said fith signal from said driving circuit, said fifth signal switching said switch, said output unit selectively discharging a voltage in accordance with said fifth signal, said output unit comprising:
• a first transistor having a control electrode receiving said fifth signal from said driving circuit, a first electrode of a principal electrically conducting channel receiving said third signal from said adjusting unit, and a second electrode of said principal electrically conducting channel, said switch corresponding to said first transistor, said feedback signal being output from said second electrode of said first transistor to said signal generating unit;
• a resistor connecting said second electrode of said first transistor to a reference potential;
• and
• a diode restricting current flow having a cathode connected to said adjusting unit and an anode connected to the reference potential;
• a first inductor receiving a sixth signal from said output unit, said first inductor deflecting said electron beam in accordance with said sixth signal;
• and
• a first capacitor being coupled in series to said first inductor, said first capacitor correcting a linearity of said screen;
• and
• said adjusting unit further comprising:
• a transformer having an input terminal receiving said second signal, a first output terminal, and a second output terminal;
• a second transistor having a control electrode connected to said first output terminal of said transformer, a first electrode of a principal electrically conducting channel receiving a first power, and a second electrode of said principal electrically conducting channel connected to said second output terminal of said transformer;
• a second inductor adjusting said horizontal screen size in accordance with said third signal supplied through said second transistor;
• and
• a step-up converting unit maintaining a back electromotive force generated at said second inductor, said step-up converting unit comprising:
• a backward current cutting-off unit preventing current from flowing backward due to the back electromotive force generated at said second inductor;
• and
• a charging unit preventing a surge current due to the back electromotive force generated at said second inductor and smoothing the back electromotive force.

A method, comprising:

• conveying varying visual information to a user utilizing a video display forming a screen having a vertical screen size and a horizontal screen size, said visual information appearing on said screen, and said video display including an electron gun emitting a beam of electrons;
• receiving a horizontal screen size adjusting signal and a feedback signal;
• generating a pulse width modulation signal in accordance with said horizontal screen size adjusting signal and said feedback signal;
• receiving said pulse width modulation signal in an adjusting unit comprised of:
• a matching transformer having an input terminal disposed to receive said pulse width modulation signal, a first output terminal, and a second output terminal;
• and
• a transistor having a control electrode connected to said first output terminal of said matching transformer, a first electrode of a principal electrically conducting channel receiving power, and a second electrode of said principal electrically conducing channel connected to said second output terminal of said matching transformer;
• generating a first signal in accordance with said received pulse width modulation signal to adjust said horizontal screen size;
• preventing current from flowing backward in said adjusting unit due to a back electromotive force generated at a first inductor in said adjusting unit;
• preventing a surge current due to the back electromotive force and smoothing the back electromotive force;
• receiving a horizontal oscillation frequency signal and generating a second signal;
• receiving said first and second signals at an outputting circuit;
• outputting from said outputting circuit a third signal in accordance with said first and second signals;
• switching a switch on and off in accordance with said second signal, said switch being included in said outputting circuit, said switch corresponding to a transistor, said transistor having a control electrode receiving said second signal, a first electrode of a principal electrically conducting channel receiving said first signal, and a second electrode of said principal electrically conducting channel connected to a reference potential through a resistor, said second electrode outputting said feedback signal in accordance with said first and second signals;
• outputting from said outputting circuit said feedback signal, in accordance with said first and second signals;
• receiving said third signal and deflecting said electron beam in accordance with said third signal, said deflecting being performed by a second inductor;
• and
• correcting a linearity of said screen, said correcting being performed by a correcting unit disposed between said second inductor and a reference potential.

An apparatus, comprising:

• a video display conveying varying visual information to a user, said video display forming a screen having a vertical screen size and a horizontal screen size, said visual information appearing on said screen, and said video display including an electron gun emitting a beam of electrons;
• a pulse width modulation signal generating unit receiving a horizontal screen size adjusting signal and a feedback signal, and accordingly generating a pulse width modulation signal, said pulse width modulation signal generating unit outputting said pulse width modulation signal;
• a horizontal screen size adjusting unit being driven by said pulse width modulation signal and generating a first signal adjusting said horizontal screen size in accordance with a step-up type, said horizontal screen size adjusting unit comprising:
• a matching transformer unit, comprising:
• a first capacitor having a first terminal receiving said pulse width modulation signal, and having a second terminal;
• a transformer having an input terminal coupled to said second terminal of said first capacitor, and having a first output terminal and a second output terminal;
• and
• a second capacitor having a first termina coupled to said first output terminal of said transformer, and having a second terminal;
• a first transistor having a control electrode connected to said second terminal of said second capacitor, a first electrode of a principal electrically conducting channel receiving power, and a second electrode of said principal electrically conducting channel connected to said second output terminal of said transformer;
• a step-up converting unit comprising:
• a first diode restricting current flow having an anode and a cathode, said anode being connected to said second output terminal of said transformer;
• and
• a third capacitor being disposed between said cathode of said first diode and a reference potential;
• a horizontal screen size adjusting inductor having an input terminal connected to said cathode of said first diode;
• a horizontal driving circuit being driven by a horizontal oscillation frequency signal and generating a second signal;
• a horizontal outputting circuit comprising:
• a switch, said second signal activating said switch, said horizontal outputting circuit receiving said first signal from said horizontal screen size adjusting unit and said second signal, said feedback signal being transmitted from said switch to said pulse width modulation signal generating unit;
• and
• a second diode restricting current flow having a cathode connected to said horizontal screen size adjusting inductor and an anode connected to the reference potential, said horizontal outputting circuit selectively outputting said first signal to said pulse width modulation signal generating unit in accordance with said second signal;
• a horizontal deflection inductor receiving said first signal, said horizontal deflection inductor horizontally deflecting said electron beam in accordance with said first signal;
• and
• a last capacitor being coupled in series to said horizontal deflection inductor, said last capacitor correcting a linearity of said screen.