Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
1996-05-02
2003-01-07
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C345S010000, C345S215000, C348S730000, C315S106000, C315S107000
Reexamination Certificate
active
06504534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CRT display unit and a power supply control method therefor, and more particularly, it relates to power supply control for extending the life of a CRT.
2. Description of the Background Art
A CRT display unit is connected to a central unit, such as a host computer, which generates a synchronizing signal and a video signal, to display an image of the video signal. In this case, it is recommended that power is applied to the CRT display unit independently of a power supply for the computer. If the power supply for the computer is also employed for applying power to the CRT display unit, this may lead to an excessive capacity of a power supply switch for the computer. Further, the CRT display unit is often installed in a position separated from the computer.
Under such circumstances, there have been proposed some CRT display units, whose power supplies are controlled to the power supplies on and off on the basis of signals from computers.
Japanese Patent Application Laying-Open No. 64-33586 (1989) describes a technique of detecting presence/absence of a video signal from a computer for on-off controlling a power supply for a CRT display unit on the basis of the result of the detection. In such a power supply control method, however, no video signal is present when a CRT intentionally displays a homogeneous black picture image, and hence the power supply for the CRT display unit is disadvantageously and erroneously turned off in this case.
On the other hand, each of Japanese Patent Application Laying-Open Nos. 60-1982 (1985) and 1-257893 (1989) describes a technique of detecting presence/absence of a synchronizing signal from a computer for on-off controlling a power supply for a CRT display unit on the basis of the result of the detection. In this power supply control method, however, the computer regularly transmits a synchronizing signal and hence, the power supply for the CRT display unit cannot be turned off unless a power supply for the computer is turned off or the CRT display unit is disconnected from the computer.
Further, there has been developed a technique of switching the screen of a CRT to display a homogeneous black image when the same display image continuously appears on the CRT for a constant period, in order to prevent burning of a fluorescent material which is applied to the screen of the CRT. Such switching of the display to a black picture image is often carried out by application software called a “screen saver”, for example. When the “screen saver” operates in such a manner, however, it is difficult to distinguish the screen of the CRT from that in a cutoff state of the CRT display unit. On the other hand, the power supply for the CRT display unit is not turned off upon such operation of the “screen saver”. Consequently, the CRT display unit may be left intact in an ON state of the power supply therefor. This leads to wasteful power consumption, as well as to reduction in life of the CRT because of a continuous ON state of a heater provided therein.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to eliminate the aforementioned disadvantage in a CRT display unit provided with a “screen saver”.
According to the present invention, as hereinafter described in detail, a power supply control method is provided for a CRT display unit which is adapted to turn off a power circuit after a lapse of a predetermined period of time, as well as, to turn off a heater after a further lapse of a predetermined period of time when a “screen saver” operates so that a CRT displays a homogeneous black picture image, in order to eliminate the aforementioned disadvantage.
However, the aforementioned “screen saver”, which has been developed in order to prevent a CRT screen from burning, may be adapted to display various patterns of animations for the purpose of amusement, in addition to display of a homogeneous black picture image. A typical system of such a “screen saver” is provided with tens of types of patterns, for example, while the user can produce such patterns himself in response to his liking.
In such circumstances, an applicable range of such a power supply control method is inevitably narrowed if the factor for starting the control for turning off the power supply for the CRT display is restricted to only the display of a homogeneous black picture image. Further, the software of the “screen saver”, which has dependence on an operating system, requires dedicated programs for various systems such as DOS, Windows, OS/2, UNIX and the like, for example.
When the same image is displayed on the CRT for a constant period of time and it is necessary to drive the “screen saver”, all input operations for the computer which are made by an operator are interrupted. There have been proposed some devices for detecting such an interrupted state of the input operations in a hardware manner and displaying a homogeneous black picture image, for example, in order to prevent the CRT screen from burning. According to Japanese Utility Model Publication No. 2-6467 (1990), for example, a CRT display unit includes a timer so that a video signal is converted to a blank signal if no input operation is carried out for a period of time which is previously set in the timer.
In order to implement the “screen saver” in the aforementioned hardware manner, however, it is necessary to extensively modify the interior of the computer. Thus, a relatively high cost is required for such a modification. Further, such a modification is difficult to make for people other than a computer manufacturer.
Accordingly, a second object of the present invention is to implement a “screen saver” in a hardware manner, with no need for an extensive modification of a computer body.
The present invention is first directed to a CRT display unit which is adapted to be connected to a central unit which generates a synchronizing signal and a video signal, for displaying an image of the video signal on the CRT display unit. This CRT display unit includes a power supply circuit which includes a main power supply and an auxiliary power supply, a power circuit, which is driven by the main power supply, including a high voltage circuit, a deflection circuit and a video circuit, a synchronous processing circuit for processing a synchronizing signal received from the central unit and supplying the processed synchronizing signal to the high voltage circuit and the deflection circuit, a video input processing circuit, which includes a video signal detector for detecting at least one of the presence or absence of a video signal output from the central unit, for processing the video signal and supplying the processed video signal to the video circuit, and a CRT having an anode which is supplied with a high dc voltage from the high voltage circuit, a deflecting yoke which is supplied with a deflecting current from the deflection circuit, a cathode which is supplied with a cathode drive signal from the video circuit, and a heater which is supplied with a current from the auxiliary power supply. According to each of first and second aspects as described below, the CRT display unit according to the present invention preferably includes the aforementioned elements in common.
According to the first aspect of the present invention, the CRT display unit further includes a main power supply controller for controlling the main power supply to turn on or turn off the power circuit when the video signal detector detects either the presence or absence of the video signal, a first timer for timing at least a period of time when the power circuit is turned off, and auxiliary power supply controllor for controlling the auxiliary power supply to turn off the heater after a lapse of a period of time previously set in the first timer.
According to the aforementioned first aspect of the present invention, the power circuit is first turned off when the “screen saver” operates such that the CRT displays a homogeneous black picture image, i.e.,
Katada Hideo
Komatsu Yuichi
Konishi Kazuhiro
Takase Katsuhisa
Tanabe Toshihisa
Lao Lun-Yi
Nanao Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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