Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
1999-02-08
2001-03-13
Hjerpe, Richard A. (Department: 2774)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C345S211000, C345S098000
Reexamination Certificate
active
06201535
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for FLAT PANEL DISPLAY APPARATUS HAVING AUTO TRACKING CONTROL FUNCTION earlier filed in the Korean Industrial Property Office on the 6
th
day of February 1998 and there duly assigned Ser. No. 03511/1998, a copy of which is annexed hereto.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention concerns a flat panel display apparatus, and more particularly a flat panel display apparatus with an automatic tracking control.
2. Related Art
The flat panel display apparatus receives an analog video signal and synchronous signal from a host such as a computer system. Then the flat panel display apparatus uses an analog to digital converter (A/D converter) to convert the analog video signal to corresponding digital video signal to display. In this case, the sampling clock signal supplied to the A/D converter varies in its frequency depending on the characteristics of the synchronous signal.
Computer systems are information handling systems that are utilized by many individuals and businesses today. A computer system can be defined as a microcomputer that includes a central processing unit (CPU), a volatile memory, a non-volatile memory such as read only memory (ROM), a display monitor, a keyboard, a mouse or other input device such as a trackball, a floppy diskette drive, a compact disc-read only memory (CD-ROM) drive, a modem, a hard disk storage device, and a printer. A computer system's main board, which is a printed circuit board known as a motherboard, is used to electrically connect these components together. A computer system can be a desktop computer, a portable computer such as a notebook computer or palm-sized computer, or other type of computer. The central processing unit is often described as a microprocessor. The microprocessor is an electronic component having internal logic circuitry handling most, if not all, the data processing in the computer system. The internal logic circuitry of microprocessors is typically divided into three functional parts known as the input/output (I/O) unit, the control unit, and the arithmetic-logic unit (ALU). These three functional parts interact together and determine the power and performance of the microprocessor. The combination of the control unit and the arithmetic-logic unit can be referred to as the central processing unit. Also, the combination of the input/output unit, the control unit, and the arithmetic-logic unit can be referred to as the central processing unit. One example of non-volatile memory is read only memory (ROM). Information stored in non-volatile memory can remain unchanged even when there is a power failure. The information stored in non-volatile memory will stay there until it is changed. Read only memory is used to store important information such as instructions for the central processing unit. There are different types of read only memory including electrically-erasable-programmable-read-only-memory (EEPROM) chip and flash-read-only-memory (flash-ROM). The flash-ROM can also be referred to as flash memory. Computer systems include a basic input output system (BIOS) which is an especially important program stored in read only memory. The basic input output system tests a computer every time the computer is powered on. The basic input output system can allocate a computer system's resources automatically, making adjustments needed to accommodate new hardware. Also, the basic input output system governs how system board components interact. When the computer system is powered on, the basic input output system immediately takes control of the computer system and its components. The first duty of the basic input output system is to perform a series of diagnostic routines called the power on self test (POST) routine, which ensures that every part of the computer system's hardware is functioning properly.
Meanwhile, the point at which the A/D converter performs a sampling on the analog video signal differs according to the phase of the sampling clock signal. Hence, when the sampling clock signal has a frequency suitable for the synchronous signal but with a phase difference, the proper sampling point is not secured, resulting in distorted video data and thus degradation of the picture quality. In order to resolve such problems, the flat display apparatus is provided with a tracking control, which is to adjust the phase of the sampling clock signal to achieve the optimum sampling point at which the effective parts of the analog signal may be sampled. This is also called the fine control, and has been manually preformed.
Such tracking control should be repeated whenever the display mode is changed, and it is very hard for a general user to manually perform the tracking adjustment control. Moreover, the manual control components can be so sensitive to factors such as heat that they may change a delay time and cause the analog video signal to be incorrectly converted into the digital video signal.
I have found that manual adjustments to tracking signals can be inconvenient and inefficient. Efforts have been made with reference to display devices, tracking signals, and synchronizing signals.
Exemplars of recent efforts in the art include U.S. Pat. No. 5,748,252 issued to Draves, U.S. Pat. No. 5,333,019 issued to Okamoto, U.S. Pat. No. 5,155,417 issued to Tateishi, U.S. Pat. No. 5,021,719 issued to Arai, et. at, U.S. Pat. No. 4,491,925 issued to Richards, U.S. Pat. No. 4,483,599 issued to MacRae, et. al, and U.S. Pat. No. 4,323,924 issued to Flasza.
While these recent efforts provide advantages, I note that they fail to adequately provide a flat panel display apparatus with automatic tracking control.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a flat panel display apparatus with means to automatically perform the tracking adjustment.
According to an embodiment of the present invention, a flat panel display apparatus comprises a sampling clock generator for generating a sampling clock signal with a frequency corresponding to a synchronous signal supplied from a host, a delay circuit for delaying the sampling clock signal, a level converter for converting an analog video signal supplied from the host to have a given digital voltage level, a phase detector for detecting the phase difference between the digital voltage level video signal from the level converter and the sampling clock signal delayed by the delay circuit to generate a phase difference data, a comparator for comparing the phase difference data with a delay data corresponding to the synchronous signal, a micro-controller for generating the delay data to increase or decrease the delay time of the delay circuit to adjust the phase of the sampling clock signal in response to the output of the comparator, and an analog to digital converter for converting the analog video signal into corresponding digital video signal in response to the delayed sampling clock signal.
Preferably, the delay circuit comprises a shift register for delaying the sampling clock signal according to a high frequency clock signal with a higher frequency than that of the sampling clock signal, and a multiplexer for selectively generating one of the outputs of the shift register under the control of the micro-controller. The level converter comprises a buffer for receiving the analog video signal, and a zener diode connected between the input of the buffer and ground. The phase detector comprises a counter for counting a clock signal with a higher frequency than that of the sampling clock signal, a latch for latching the output of the counter, and a flip-flop for enabling or disabling the counter and latch according as the level converter supplies the video signal or the delay circuit supplies the delayed sampling clock signal. There is further provided a high frequency clock generator for supplying a clock signal with a higher frequency than that of the sampling clock signal.
Bushnell , Esq. Robert E.
Dinh Duc Q.
Hjerpe Richard A.
Samsung Electronics Co,. Ltd.
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