Title of Invention	"HORIZONTAL FOCUS CONTROLLING APPARATUS FOR CATHODE-RAY TUBE"
Abstract	The present invention relates to a horizontal focus controlling apparatus which compensates for a distortion generated on a screen of a computer or a TV set. The apparatus includes select signal generating means for dividing the period of a sawtooth signal into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions and parabola signal generating means for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal according to the selections of the first, second, or third select signals.

Title of Invention

"HORIZONTAL FOCUS CONTROLLING APPARATUS FOR CATHODE-RAY TUBE"

Abstract

The present invention relates to a horizontal focus controlling apparatus which compensates for a distortion generated on a screen of a computer or a TV set. The apparatus includes select signal generating means for dividing the period of a sawtooth signal into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions and parabola signal generating means for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal according to the selections of the first, second, or third select signals.

Full Text	Background of the Invention The present invention relates to a horizontal focus controlling apparatus for compensating a distortion generated on a cathode-ray tube (CRT) screen such as a computer or a TV set, and more particularly, to a horizontal focus controlling apparatus for making a horizontal parabola signal coincide with a phase of a flyback pulse (FBP) signal. The horizontal focus controlling means compensates for the distortion of the CRT screen by generating a parabola signal corresponding to a curved surface on the CRT screen and outputting it with a horizontal scan signal. A horizontal parabola signal synchronized with a flyback pulse is required for controlling such a horizontal focus. Since a horizontal portion of the CRT has a higher operating frequency than a vertical portion of the CRT, an output gain and a phase of the parabola signal should hardly change. Also, since the CRT operates in a multi-synchronizing method, the above-mentioned conditions should be met with respect to all the horizontal synchronizing signal frequencies. However, there is a problem that the output gain and the phase of the parabola signal change according to the input synchronizing signal frequency in a conventional technology. Summary of the Invention It is an object of the present invention to provide a horizontal focus controlling apparatus for making a parabola output signal coincide with the phase of a FBP signal by generating a predetermined select signal in ord'er to control a horizontal focus in a CRT. To achieve the above object, there is provided a horizontal focus controlling apparatus for a cathode-ray tube, comprising: select signal generating means for dividing the period of a sawtooth signal into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and parabola signal generating means for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal according to the selections of the first, second, or third select signals. According to the present invention there is provided a horizontal focus controlling apparatus for a cathode-ray tube for generating a parabola signal applied to control the horizontal focus, said apparatus comprising: select signal generator for dividing the period of a sawtooth signal into a falling portion, a rising portion located before a central point of a positive pulse of the flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and parabola signal generator for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal responsive to the selections of the first, second, or third select signals. Brief Description of the Accompanying Drawings The above objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: FIG. 1 shows a block diagram of a horizontal focus controlling apparatus for a cathode-ray tube according to the present invention; FIG. 2 shows a circuit diagram of the select signal generating portion shown in Fig. 1; IGS. 3A to 3E show a relationship between an input signal and an output signal of the select signal generating portion shown in FIG. 2; FIG. 4 shows the parabola signal generating portion shown in FIG. 1; and FIGS. 5A to 5E show a relationship between an input signal and an output signal of the parabola signal generating portion shown in FIG. 4. Detailed Description of the Invention Hereinafter, a preferred embodiment of the present invention is described with reference to the attached drawings. FIG. 1 shows a block diagram of a horizontal focus controlling apparatus for a cathode-ray tube according to the present invention. The horizontal focus controlling apparatus includes a select signal generating portion 1 which inputs a sawtooth signal SAWTOOTH INPUT and a pulse signal OSC INPUT which is synchronized with a falling portion of the sawtooth signal SAWTOOTH INPUT for dividing the period of the sawtooth signal SAWTOOTH INPUT into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point and generating first, second, and third select signals SELECT1, SELECT2 and SELECT3 synchronized with the respective portions and a parabola signal generating portion 2 for generating a parabola signal PARABOLA OUTPUT which is synchronized with the flyback pulse signal by controlling the sawtooth signal SAWTOOTH INPUT according to the selections of the first, second, or third select signals SELECT1, SELECT2 or SELECTS. The detailed description of the operation of the horizontal focus controlling apparatus will be followed with reference to FIG. 2, FIGS. 3A-3E, FIG. 4 and FIGS. 5A-5E. FIG. 2 shows a circuit diagram of the select signal generating portion 1 shown in FIG. 1. In FIGS. 3A to 3E show a relationship between an input signal and an output signal of the signal generating portion 1 shown in FIG. 2. FIGS. 3A, 3B, 3C, 3D and 3E show waveforms of the sawtooth signal SAWTOOTH INPUT and a flyback pulse signal, the first select signal SELECT1, a comparator output signal, the second select signal SELECT2, and the third select signal SELECTS, respectively. Referring to FIG. 2 a comparator 11 outputs a signal which results when the sawtooth signal SAWTOOTH INPUT is compared with a threshold voltage Ref corresponding to a position of 0.375T thereof. A first NOR gate 12 performs a logic NOR operation with respect to the output signal of the comparator 11 and the pulse signal (OSC INPUT) synchronized with a falling portion of the sawtooth signal SAWTOOTH INPUT and outputs the result. A second NOR gate 13 performs a logic NOR operation with respect to the output signal of the first NOR gate 12 and the pulse signal (OSC INPUT) synchronized with the falling portion of the sawtooth signal SAWTOOTH INPUT and outputs the result. By doing so, the pulse signal (OSC INPUT) synchronized with the falling portion of the sawtooth signal SAWTOOTH INPUT, the output signal of the first NOR gate 12, and the output signal of the second NOR gate 13 respectively serve as the first select signal SELECT1, the second select signal SELECT2 and the third select signal SELECT3. FIG. 4 shows a circuit diagram of the parabola signal generating portion 2 shown in FIG. 1 and FIGS. 5A-5E show a relationship between an input signal and an output signal of the signal generating portion 2 shown in FIG. 4. FIGS. 5A, 5B, 5C, 5D and 5E show waveforms of the sawtooth signal SAWTOOTH INPUT, a fourth amplifier output signal, an inverted signal of the fourth amplifier output signal, the parabola output signal PARABOLA OUTPUT, and the flyback pulse signal. A reference voltage generator (not shown) generates a reference voltage Ref for controlling a direct current offset. A first amplifier 31 amplifies the sawtooth signal SAWTOOTH INPUT by unity gain and a first switch 34 outputs the output of the first amplifier 31 to a fourth amplifier 37 during a section selected by the first select signal SELECT1. A second amplifier 32 controls the direct current offset of the sawtooth signal SAWTOOTH INPUT according to the input reference voltage Ref and the sawtooth signal SAWTOOTH INPUT, and then inverts and amplifies it by a predetermined unit of gain and a second switch 35 outputs the output of the second amplifier 32 to the fourth amplifier 37 during a section selected by the second select signal SELECT2. A third amplifier 33 controls the direct current offset of the sawtooth signal SAWTOOTH INPUT according to the input reference voltage Ref and the sawtooth signal SAWTOOTH INPUT, and then inverts and amplifies it by a predetermined unit of gain and a third switch 36 outputs the output of the third amplifier 33 to the fourth amplifier 37 during a section selected by the third select signal SELECT 3. The fourth amplifier 37 inverts and amplifies the output signal of the first, second or third switch 34, 35 or 36 which is output according to the first, second or third select signal SELECT1, SELECT2 or SELECTS by a gain based on the ratio of the rising section to the falling section of the sawtooth signal SAWTOOTH INPUT during the section in which the first select signal SELECT1 is activated and by a predetermined unit of gain during the other sections, and outputs the result. An inverter 38 inverts and outputs the output signal of the fourth amplifier 37. A multiplier 39 multiplies the output signal of the fourth amplifier 37 by that of the inverter 38 and generates the desired parabola signal PARABOLA OUTPUT. Here, reference characters R1-R8 indicate resistors and reference character Cl indicates a capacitor. Referring to FIGS. 5A and 5B, it is noted that a sawtooth signal having uniform rising and falling portions can be used to generate a sawtooth signal having no falling section by the switching of a select signal. Referring FIGS. 5D and 5E, it is noted that the non-distorted parabola signal whose phase coincides with that of the flyback pulse signal can be generated by doing so. According to the horizontal focus controlling apparatus for a cathode-ray tube according to the present invention, it is possible to generate the non-distorted parabola signal whose phase coincides with that of the flyback pulse signal and to utilize it to control the horizontal focus of the CRT screen by generating the parabola signal after generating the sawtooth signal having no falling section by dividing the section of a predetermined sawtooth signal and generating a select signal corresponding thereto. -We claim: 1. A horizontal focus controlling apparatus for a cathode-ray tube for generating a parabola signal applied to control the horizontal focus, said apparatus comprising: select signal generator for dividing the period of a sawtooth signal into a falling portion, a rising portion located before a central point of a positive pulse of the flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and parabola signal generator for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal responsive to the selections of the first, second, or third select signals. 2. A horizontal focus controlling apparatus for a cathode-ray tube as claimed in claim 1, wherein said select signal generator comprises: a signal generator for generating a pulse signal which is synchronized with a falling portion of the sawtooth signal as the first select signal; a comparator for outputting a signal which results when the sawtooth signal is compared with a threshold voltage corresponding to a predetermined position of the sawtooth signal; a first NOR gate for performing a logic NOR operation with respect to the compared signal and the pulse signal and outputting the result as the second select signal; a second NOR gate for performing a logic NOR operation with respect to the output signal of said first NOR gate and the pulse signal and outputting the result as the third select signal. 3. A horizontal focus controlling apparatus for a cathode-ray tube as claimed in any of the preceding claims, wherein said parabola signal generator comprises: reference voltage generator for generating a reference voltage for controlling a direct current offset; first amplifier (31) for amplifying the sawtooth signal by a predetermined unit of gain during a section selected by the first select signal; second amplifier (32) for controlling the direct current offset of the sawtooth signal according to the input reference voltage and the input sawtooth signal and then inverting and amplifying it by a predetermined unit of gain during the section selected by the second select signal; third amplifier (33) for controlling the direct current offset of the sawtooth signal according to the input reference voltage and the input sawtooth signal and then inverting and amplifying it by a predetermined unit of gain during the section selected by the third select signal; fourth amplifier (37) for inverting and amplifying the output signal of one of said first, second and third amplifier by a gain based on the ratio of the rising section to the falling section of the sawtooth signal during the section in which the first select signal is activated and by a predetermined unit of gain during the other sections and outputs the result; inverter (38) for inverting the output of said fourth amplifier; and multiplier (39) for generating the parabola signal by multiplying the output signal of said fourth amplifier by the output of said inverter. 4. A horizontal focus controlling apparatus for a cathode-ray tube for generating a parabola signal applied to control the horizontal focus, substantially as hereinbefore described with reference to the accompanying drawings.

Full Text

Background of the Invention
The present invention relates to a horizontal focus controlling apparatus for compensating a distortion generated on a cathode-ray tube (CRT) screen such as a computer or a TV set, and more particularly, to a horizontal focus controlling apparatus for making a horizontal parabola signal coincide with a phase of a flyback pulse (FBP) signal.
The horizontal focus controlling means compensates for the distortion of the CRT screen by generating a parabola signal corresponding to a curved surface on the CRT screen and outputting it with a horizontal scan signal. A horizontal parabola signal synchronized with a flyback pulse is required for controlling such a horizontal focus. Since a horizontal portion of the CRT has a higher operating frequency than a vertical portion of the CRT, an output gain and a phase of the parabola signal should hardly change. Also, since the CRT operates in a multi-synchronizing method, the above-mentioned conditions should be met with respect to all the horizontal synchronizing signal frequencies. However, there is a problem that the output gain and the phase of the parabola signal change according to the input synchronizing signal frequency in a conventional technology.
Summary of the Invention
It is an object of the present invention to provide a horizontal focus controlling apparatus for making a parabola
output signal coincide with the phase of a FBP signal by generating a predetermined select signal in ord'er to control a horizontal focus in a CRT.
To achieve the above object, there is provided a horizontal focus controlling apparatus for a cathode-ray tube, comprising:
select signal generating means for dividing the period of a sawtooth signal into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and
parabola signal generating means for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal according to the selections of the first, second, or third select signals.
According to the present invention there is provided a horizontal focus controlling apparatus for a cathode-ray tube for generating a parabola signal applied to control the horizontal focus, said apparatus comprising:
select signal generator for dividing the period of a sawtooth signal into a falling portion, a rising portion located before a central point of a positive pulse of the flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and
parabola signal generator for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal responsive to the selections of the first, second, or third select signals.
Brief Description of the Accompanying Drawings
The above objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which:
FIG. 1 shows a block diagram of a horizontal focus controlling apparatus for a cathode-ray tube according to the present invention;
FIG. 2 shows a circuit diagram of the select signal generating portion shown in Fig. 1;
IGS. 3A to 3E show a relationship between an input signal and an output signal of the select signal generating portion shown in FIG. 2;
FIG. 4 shows the parabola signal generating portion shown in FIG. 1; and
FIGS. 5A to 5E show a relationship between an input signal and an output signal of the parabola signal generating portion shown in FIG. 4.
Detailed Description of the Invention
Hereinafter, a preferred embodiment of the present invention is described with reference to the attached drawings.
FIG. 1 shows a block diagram of a horizontal focus controlling apparatus for a cathode-ray tube according to the present invention. The horizontal focus controlling apparatus includes a select signal generating portion 1 which inputs a sawtooth signal SAWTOOTH INPUT and a pulse signal OSC INPUT which is synchronized with a falling portion of the sawtooth signal SAWTOOTH INPUT for dividing the period of the sawtooth signal SAWTOOTH INPUT into a falling portion, a rising portion located before the central point of the positive pulse of a flyback pulse signal, and a rising portion after the central point and generating first, second, and third select signals SELECT1, SELECT2 and SELECT3 synchronized with the respective portions and a parabola signal generating portion 2 for generating a parabola signal PARABOLA OUTPUT which is synchronized with the flyback pulse signal by controlling the
sawtooth signal SAWTOOTH INPUT according to the selections of the first, second, or third select signals SELECT1, SELECT2 or SELECTS. The detailed description of the operation of the horizontal focus controlling apparatus will be followed with reference to FIG. 2, FIGS. 3A-3E, FIG. 4 and FIGS. 5A-5E.
FIG. 2 shows a circuit diagram of the select signal generating portion 1 shown in FIG. 1. In FIGS. 3A to 3E show a relationship between an input signal and an output signal of the signal generating portion 1 shown in FIG. 2. FIGS. 3A, 3B, 3C, 3D and 3E show waveforms of the sawtooth signal SAWTOOTH INPUT and a flyback pulse signal, the first select signal SELECT1, a comparator output signal, the second select signal SELECT2, and the third select signal SELECTS, respectively.
Referring to FIG. 2 a comparator 11 outputs a signal which results when the sawtooth signal SAWTOOTH INPUT is compared with a threshold voltage Ref corresponding to a position of 0.375T thereof. A first NOR gate 12 performs a logic NOR operation with respect to the output signal of the comparator 11 and the pulse signal (OSC INPUT) synchronized with a falling portion of the sawtooth signal SAWTOOTH INPUT and outputs the result. A second NOR gate 13 performs a logic NOR operation with respect to the output signal of the first NOR gate 12 and the pulse signal (OSC INPUT) synchronized with the falling portion of the sawtooth signal SAWTOOTH INPUT and outputs the result. By doing so, the pulse signal (OSC INPUT) synchronized with the falling portion of the sawtooth signal SAWTOOTH INPUT, the output signal of the first NOR gate 12,
and the output signal of the second NOR gate 13 respectively serve as the first select signal SELECT1, the second select signal SELECT2 and the third select signal SELECT3.
FIG. 4 shows a circuit diagram of the parabola signal generating portion 2 shown in FIG. 1 and FIGS. 5A-5E show a relationship between an input signal and an output signal of the signal generating portion 2 shown in FIG. 4. FIGS. 5A, 5B, 5C, 5D and 5E show waveforms of the sawtooth signal SAWTOOTH INPUT, a fourth amplifier output signal, an inverted signal of the fourth amplifier output signal, the parabola output signal PARABOLA OUTPUT, and the flyback pulse signal.
A reference voltage generator (not shown) generates a reference voltage Ref for controlling a direct current offset. A first amplifier 31 amplifies the sawtooth signal SAWTOOTH INPUT by unity gain and a first switch 34 outputs the output of the first amplifier 31 to a fourth amplifier 37 during a section selected by the first select signal SELECT1. A second amplifier 32 controls the direct current offset of the sawtooth signal SAWTOOTH INPUT according to the input reference voltage Ref and the sawtooth signal SAWTOOTH INPUT, and then inverts and amplifies it by a predetermined unit of gain and a second switch 35 outputs the output of the second amplifier 32 to the fourth amplifier 37 during a section selected by the second select signal SELECT2. A third amplifier 33 controls the direct current offset of the sawtooth signal SAWTOOTH INPUT according to the input reference voltage Ref and the sawtooth signal SAWTOOTH INPUT, and then inverts and amplifies it by a predetermined unit of
gain and a third switch 36 outputs the output of the third amplifier 33 to the fourth amplifier 37 during a section selected by the third select signal SELECT 3. The fourth amplifier 37 inverts and amplifies the output signal of the first, second or third switch 34, 35 or 36 which is output according to the first, second or third select signal SELECT1, SELECT2 or SELECTS by a gain based on the ratio of the rising section to the falling section of the sawtooth signal SAWTOOTH INPUT during the section in which the first select signal SELECT1 is activated and by a predetermined unit of gain during the other sections, and outputs the result. An inverter 38 inverts and outputs the output signal of the fourth amplifier 37. A multiplier 39 multiplies the output signal of the fourth amplifier 37 by that of the inverter 38 and generates the desired parabola signal PARABOLA OUTPUT. Here, reference characters R1-R8 indicate resistors and reference character Cl indicates a capacitor.
Referring to FIGS. 5A and 5B, it is noted that a sawtooth signal having uniform rising and falling portions can be used to generate a sawtooth signal having no falling section by the switching of a select signal. Referring FIGS. 5D and 5E, it is noted that the non-distorted parabola signal whose phase coincides with that of the flyback pulse signal can be generated by doing so.
According to the horizontal focus controlling apparatus for a cathode-ray tube according to the present invention, it is possible to generate the non-distorted parabola signal whose phase coincides with that of the flyback pulse signal
and to utilize it to control the horizontal focus of the CRT screen by generating the parabola signal after generating the sawtooth signal having no falling section by dividing the section of a predetermined sawtooth signal and generating a select signal corresponding thereto.

-We claim:
1. A horizontal focus controlling apparatus for a cathode-ray tube for generating a
parabola signal applied to control the horizontal focus, said apparatus comprising:
select signal generator for dividing the period of a sawtooth signal into a falling portion, a rising portion located before a central point of a positive pulse of the flyback pulse signal, and a rising portion after the central point of the positive pulse of the flyback pulse signal and generating first, second, and third select signals synchronized with the respective portions; and
parabola signal generator for generating a parabola signal which is synchronized with the flyback pulse signal by controlling the sawtooth signal responsive to the selections of the first, second, or third select signals.
2. A horizontal focus controlling apparatus for a cathode-ray tube as claimed in
claim 1, wherein said select signal generator comprises:
a signal generator for generating a pulse signal which is synchronized with a falling portion of the sawtooth signal as the first select signal;
a comparator for outputting a signal which results when the sawtooth signal is compared with a threshold voltage corresponding to a predetermined position of the sawtooth signal;
a first NOR gate for performing a logic NOR operation with respect to the compared signal and the pulse signal and outputting the result as the second select signal;
a second NOR gate for performing a logic NOR operation with respect to the output signal of said first NOR gate and the pulse signal and outputting the result as the third select signal.
3. A horizontal focus controlling apparatus for a cathode-ray tube as claimed in any
of the preceding claims, wherein said parabola signal generator comprises:
reference voltage generator for generating a reference voltage for controlling a direct current offset;
first amplifier (31) for amplifying the sawtooth signal by a predetermined unit of gain during a section selected by the first select signal;
second amplifier (32) for controlling the direct current offset of the sawtooth signal according to the input reference voltage and the input sawtooth signal and then inverting and amplifying it by a predetermined unit of gain during the section selected by the second select signal;
third amplifier (33) for controlling the direct current offset of the sawtooth signal according to the input reference voltage and the input sawtooth signal and then inverting and amplifying it by a predetermined unit of gain during the section selected by the third select signal;
fourth amplifier (37) for inverting and amplifying the output signal of one of said first, second and third amplifier by a gain based on the ratio of the rising section to the falling section of the sawtooth signal during the section in which the first select signal is activated and by a predetermined unit of gain during the other sections and outputs the result;
inverter (38) for inverting the output of said fourth amplifier; and
multiplier (39) for generating the parabola signal by multiplying the output signal of said fourth amplifier by the output of said inverter.
4. A horizontal focus controlling apparatus for a cathode-ray tube for generating a parabola signal applied to control the horizontal focus, substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

2040-del-1997-abstract.pdf

2040-del-1997-claims.pdf

2040-del-1997-correspondence-others.pdf

2040-del-1997-correspondence-po.pdf

2040-del-1997-description (complete).pdf

2040-del-1997-drawings.pdf

2040-del-1997-form-1.pdf

2040-del-1997-form-19.pdf

2040-del-1997-form-2.pdf

2040-del-1997-form-3.pdf

2040-del-1997-form-4.pdf

2040-del-1997-form-6.pdf

2040-del-1997-gpa.pdf

2040-del-1997-petition-138.pdf

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Patent Number

214884

Indian Patent Application Number

2085/DEL/1997

PG Journal Number

10/2008

Publication Date

07-Mar-2008

Grant Date

18-Feb-2008

Date of Filing

25-Jul-1997

Name of Patentee

SAMSUNG ELECTRONICS COMPANY LIMITED

Applicant Address

416, MAETAN-DONG, PALDAL-GU, SUWON-CITY, KYUNGKI-DO, REPUBLIC OF KOREA

Inventors:

#	Inventor's Name	Inventor's Address
1	YONG-SUB KIM	401, DAEDONG VILLA, 12-12 SONGPA 1-DONG, SONGPA-GU, SEOUL, REPUBLIC OF KOREA

PCT International Classification Number

H04N 3/22

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	96-46321	1996-10-16	Republic of Korea