Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2001-03-12
2002-09-17
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S387000, C315S408000
Reexamination Certificate
active
06452347
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a deflection system and a deflection method of a horizontal reciprocating deflection mode scanning an electron beam in a reciprocating manner.
BACKGROUND TECHNIQUE
A deflection system of a horizontal reciprocating deflection mode scanning an electron beam in a reciprocating manner is recently proposed in the field of a display unit for a television set or the like, in order to make display of a high resolution. In the deflection system of the horizontal reciprocating deflection mode, a forward scanning line and a backward scanning line must be parallelized with each other.
FIGS.
4
(
a
) to
4
(
d
) are waveform diagrams for illustrating a vertical deflection current and a horizontal deflection current employed in the horizontal reciprocating deflection mode for parallelizing forward and backward scanning lines with each other. FIG.
4
(
a
) shows a first sawtooth wave current SI
1
for generating a vertical deflection magnetic field moving an electron beam from the top to the bottom of a screen of a television set or the like and thereafter returning the electron beam to the top of the screen again. When performing reciprocating scanning with the first sawtooth wave current SI
1
shown in FIG.
4
(
a
), the forward and backward scanning lines are not parallelized with each other. Therefore, inclination of a vertical deflection current must be nulled in forward scanning and backward scanning in order to parallelize the forward and backward scanning lines with each other.
Therefore, a second sawtooth wave current SI
2
shown in FIG.
4
(
b
) is added to the first sawtooth wave current SI
1
shown in FIG.
4
(
a
), for generating a vertical deflection current VI shown in FIG.
4
(
c
). The second sawtooth wave current SI
2
shown in FIG.
4
(
b
) has the same frequency as a horizontal scanning frequency, and the inclination of the second sawtooth wave current SI
2
in forward scanning and backward scanning is so set that inclination of the composited vertical deflection current VI in forward scanning and backward scanning is nulled.
A horizontal deflection current HI shown in FIG.
4
(
d
) has the waveform of a frequency half the horizontal scanning frequency for performing reciprocating scanning.
FIGS.
5
(
a
) and
5
(
b
) are conceptual diagrams showing parallelized reciprocating deflection scanning. When performing reciprocating scanning with the vertical deflection current VI shown in FIG.
4
(
c
) and the horizontal deflection current HI shown in FIG.
4
(
d
), such ideal reciprocating scanning that a scanning line
21
performs reciprocating scanning in parallel on a screen
20
is implemented as shown in FIG.
5
(
a
). When supplying the vertical deflection current VI shown in FIG.
4
(
c
) to a vertical deflection coil while supplying the horizontal deflection current HI shown in FIG.
4
(
d
) to a horizontal deflection coil, however, the scanning line maybe distorted. When a current component resulting from the horizontal deflection current HI is induced from the horizontal deflection coil to the vertical deflection coil and superposed on the vertical deflection current VI shown in FIG.
4
(
c
), a scanning line
22
is distorted as shown in FIG.
5
(
b
), to distort a displayed image.
In a conventional deflection system, the following method, for example, is carried out in order to cancel a current component induced to flow in a vertical deflection coil from a horizontal deflection coil by a horizontal deflection current: A transformer is serially connected to the vertical deflection coil for supplying the vertical deflection coil with a current 180° out of phase with the horizontal deflection current flowing in the horizontal deflection coil through the transformer. Thus, the current component induced to the vertical deflection coil is canceled. In this case, the transformer serially connected to the vertical deflection coil must be of a standard suitable to the large vertical deflection current, and hence the manufacturing cost is increased. Further, power consumed in a driving circuit for driving the transformer is disadvantageously increased.
An object of the present invention is to provide a deflection system and a deflection method capable of performing reciprocating deflection without distorting a scanning line and reducing the cost as well as power consumption.
DISCLOSURE OF THE INVENTION
A deflection system according to an aspect of the present invention, performing reciprocating scanning by horizontally deflecting an electron beam in a reciprocating manner in response to a vertical synchronizing signal and a horizontal synchronizing signal, comprises a vertical deflection coil, a horizontal deflection coil, a horizontal deflection current supply circuit supplying a horizontal deflection current for horizontally deflecting the electron beam in a reciprocating manner, an induced current detection circuit detecting a current component induced to the vertical deflection coil by the horizontal deflection current flowing in the horizontal deflection coil, a sawtooth wave voltage generation circuit generating a sawtooth wave voltage synchronous with the vertical synchronizing signal, a first current supply circuit receiving the sawtooth wave voltage generated by the sawtooth wave voltage generation circuit and supplying a first sawtooth wave current for vertically deflecting the electron beam to the vertical deflection coil, a second current supply circuit supplying a second sawtooth wave current for parallelizing forward and backward scanning lines with each other to the vertical deflection coil, and a correction voltage addition circuit adding a correction voltage for canceling the current component detected by the induced current detection circuit to the sawtooth wave voltage generated by the sawtooth wave voltage generation circuit.
In the deflection system, the induced current detection circuit detects the current component induced to the vertical deflection coil by the horizontal deflection current flowing in the horizontal deflection coil. The correction voltage addition circuit adds the correction voltage to the sawtooth wave voltage on the basis of the detected current component, and the first current supply circuit supplies the current component responsive to the correction voltage to the vertical deflection coil.
Thus, the current component induced to the vertical deflection coil by the horizontal deflection current flowing in the horizontal deflection coil can be canceled. Therefore, reciprocating deflection can be performed without distorting the scanning lines. In this case, no transformer may be serially connected to the vertical deflection coil for supplying a current component for canceling the current component induced to the vertical deflection coil. Therefore, the cost for the deflection system as well as power consumption can be reduced.
The induced current detection circuit may generate an output voltage responsive to the current component, and the correction voltage addition circuit may include a regulating circuit regulating the amplitude and the phase of the output voltage from the induced current detection circuit and outputting the regulated output voltage as the correction voltage and an addition circuit adding the correction voltage output from the regulating circuit to the sawtooth wave voltage generated by the sawtooth wave voltage generation circuit.
In this case, the induced current detection circuit generates the output voltage responsive to the current component induced to the vertical deflection coil, while the regulating circuit regulates the amplitude and the phase of the output voltage and outputs the correction voltage having proper relation to the phase of the current component induced to the vertical deflection coil. Further, the addition circuit adds the correction voltage to the sawtooth wave voltage generated by the sawtooth wave voltage generation circuit. Thus, the first current supply circuit supplies a current component of opposite polarity to the current component in
Kobayashi Masa-aki
Nakatsuji Masanori
Tanaka Masanobu
Ueda Akira
Yamate Kazunori
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