Television – Format conversion – Changing number of lines for standard conversion
Reexamination Certificate
2001-05-22
2004-03-09
Miller, John (Department: 2614)
Television
Format conversion
Changing number of lines for standard conversion
C348S531000, C348S704000, C315S364000, C315S367000, C315S368130
Reexamination Certificate
active
06704056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a horizontal deflection circuit and a television receiver comprising the same.
2. Description of the Prior Art
Recently, a television receiver tends to have a large screen. Further, the number of horizontal scanning lines forming a single screen tends to increase in order to improve picture quality. In addition, the television receiver is required to be capable of displaying a video signal such as a high-definition signal having a high horizontal scanning frequency.
The CRT (cathode ray tube) of the television receiver is provided with a horizontal deflection yoke and a vertical deflection yoke in order to deflect an electron beam, while a horizontal deflection circuit supplies a horizontal deflection current to the horizontal deflection yoke for horizontally scanning the electron beam and a vertical deflection circuit supplies a vertical deflection current to the vertical deflection coil for vertically scanning the electron beam.
Power consumption of the television receiver is increased following the aforementioned increase of the screen size and the number of the horizontal scanning lines, and hence reduction of power consumption is necessary. Particularly the horizontal deflection circuit consumes high power, and hence power consumption of the horizontal deflection circuit must be reduced.
In the horizontal deflection circuit, switching loss of the horizontal deflection current occupies most part of power consumption. In order to reduce power consumption of the horizontal deflection circuit, therefore, a power supply voltage for the horizontal deflection circuit may be increased for reducing the horizontal deflection current.
The horizontal deflection circuit has a transistor (hereinafter referred to as a horizontal output transistor) for supplying the horizontal deflection current to the horizontal deflection yoke. When the horizontal output transistor is switched, a large pulse voltage is generated on the collector in a horizontal blanking interval. This pulse voltage is applied across the collector and the emitter of the horizontal output transistor, and hence the withstand voltage across the collector and the emitter of the horizontal output transistor must be increased beyond the peak of the pulse voltage.
When the power supply voltage for the horizontal deflection circuit is increased for reducing the horizontal deflection current, therefore, the pulse voltage generated on the collector of the horizontal output transistor is increased. Therefore, the withstand voltage of the horizontal output transistor must be increased, to result in a high cost.
Accordingly, awaited is a technique of reducing the power consumption of the horizontal deflection circuit without increasing the withstand voltage of the horizontal output transistor.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a horizontal deflection circuit reduced in power consumption without increasing the withstand voltage of horizontal deflection current supply means supplying a horizontal deflection current to a horizontal deflection coil and a television receiver comprising the same.
A horizontal deflection circuit according to an aspect of the present invention comprises input means for inputting a video signal, video signal conversion means for deleting a prescribed number of horizontal scanning lines from a vertical blanking interval in the video signal input by the input means and assigning a time corresponding to the deleted horizontal scanning lines to horizontal blanking intervals of the remaining horizontal scanning lines thereby extending the horizontal blanking interval of each horizontal scanning line and horizontal deflection current supply means for supplying a horizontal deflection current to a horizontal deflection coil for retracing an electron beam in each horizontal blanking interval extended by the video signal conversion means.
In the horizontal deflection circuit according to this aspect, the video signal conversion means deletes the prescribed number of horizontal scanning lines from the vertical blanking interval and assigns the time corresponding to the deleted horizontal scanning lines to the horizontal blanking intervals of the remaining horizontal scanning lines thereby extending the horizontal blanking interval of each horizontal scanning line, whereby the pulse width of a pulse voltage generated on the horizontal deflection coil is expanded in the horizontal blanking interval. Thus, a power supply voltage can be increased without increasing the level of the pulse voltage generated on the horizontal deflection coil. In other words, a higher power supply voltage can be employed when the withstand voltage of the horizontal deflection current supply means supplying the horizontal deflection current to the horizontal deflection coil is left intact. Therefore, the power supply voltage can be increased for reducing the horizontal deflection current without increasing the withstand voltage of the horizontal deflection current supply means, thereby reducing power consumption of the horizontal deflection circuit.
The input means may include analog-to-digital conversion means for performing analog-to-digital conversion on the video signal and outputting a digital signal, and the video signal conversion means may include storage means for storing the digital signal output from the analog-to-digital conversion means, control means for controlling writing and reading of the digital signal in and from the storage means thereby deleting the prescribed number of horizontal scanning lines from the vertical blanking interval and extending the horizontal blanking interval of each horizontal scanning line and digital-to-analog conversion means for performing digital-to-analog conversion on the digital signal read from the storage means and outputting an analog signal.
In this case, the prescribed number of horizontal scanning lines can be deleted from the vertical blanking interval and the horizontal blanking interval of each horizontal scanning line can be extended by the simple function of controlling writing and reading of the digital signal in and from the storage means, whereby the horizontal deflection circuit is not complicated in structure.
The control means may include first synchronizing signal generation means for generating a vertical synchronizing signal and a first horizontal synchronizing signal, second synchronizing signal generation means for generating a second horizontal synchronizing signal having a lower frequency than the first horizontal synchronizing signal in response to the first horizontal synchronizing signal generated by the first synchronizing signal generation means, write control means for writing the digital signal output from the analog-to-digital conversion means in the storage means in response to the first horizontal synchronizing signal and the vertical synchronizing signal and read control means for reading the digital signal from the storage means while skipping digital signal components of the prescribed number of horizontal scanning lines in the vertical blanking interval in response to the second horizontal synchronizing signal and the vertical synchronizing signal.
A horizontal deflection circuit according to another aspect of the present invention comprises input means for inputting a video signal, video signal conversion means for reducing the number of horizontal scanning lines in an effective picture area of a vertical scanning interval by vertical interpolation in the video signal input by the input means and assigning a time corresponding to the reduced number of horizontal scanning lines to horizontal blanking intervals of the remaining horizontal scanning lines thereby extending the horizontal blanking interval of each horizontal scanning line and horizontal deflection current supply means for supplying a horizontal deflection current to a horizontal deflection coil for retracing an electron beam in each horizontal blanking interval extended
Gotanda Chikara
Kitahara Toshiaki
Nishikawa Yutaka
Uwabata Hideyo
Armstrong Kratz Quintos Hanson & Brooks, LLP
Matsushita Electric - Industrial Co., Ltd.
Miller John
Yenke Brian
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