Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-03
2001-11-20
Jankus, Almis R. (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S066000, C345S068000, C345S210000, C345S214000
Reexamination Certificate
active
06320561
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a drive circuit for a display panel, disposed with a common electrode and an individual electrode in each of a plurality of display cells arranged in a matrix configuration, for controlling gas discharges in each display cell by applying display pulses to a common electrode to perform display operations and by individually applying control voltages to individual electrodes to control the discharge in each display cell.
2. Description of the Related Art
Heretofore, display panels, such as plasma displays, are known for performing display operations by controlling the gas discharge of each display cell. In such display panels, it is necessary to continually maintain a favorable state for discharge of the stored charge in order to perform normal discharge. Accordingly, initialization is performed periodically in all display cells, such as by erasing the stored charge that causes discharge.
Japanese Patent Laid-Open Publication Nos. Hei 10-143106(1998/05/29), 8-278766(1996/10/22), 7-40927(1995/06/02), 9-325736(1997/12/16), and 8-212930(1996/08/20) disclose this sort of initialization.
Although various types of initialization methods have been proposed in this manner, if the discharge conditions change, for example, a different method must be adopted.
RELATED APPLICATION
The present applicant has proposed an invention concerning a display panel with a novel drive method in an international application (application number PCT/JP98/01444) of the Patent Cooperation Treaty. This display panel comprises individual display cell electrodes and a common electrode. The individual electrodes are driven individually for every display cell and the common electrodes are driven together for a plurality of display cells. The discharge is then controlled for each display cell so as to control the overall display by applying a positive display pulse to the common electrode and by individually controlling the application of a positive control voltage to the individual electrodes.
The drive for the common electrode in this display panel employs display pulses having voltage that changes in two levels. One two-level display pulse performs discharge for storing charge and discharge for erasing charge. Theoretically, therefore, erasure of the charge is performed automatically, even though display discharge is repeated. However, storage of the charge due to insufficient voltage application when the power is turned on or storage of charge due to repetition of discharges does occur. In order to eliminate this, a positive pulse (initialization pulse) is supplied, once per frame, to all individual electrodes so as to invert the display cell charges to perform initialization.
This sort of initialization can solve the problem of inappropriate charge storage and maintain normal discharge. However, this method requires that a-sufficiently large positive voltage be applied to the individual electrodes. The voltage application onto the individual electrodes drives a control element (ex. transistor) corresponding to each display cell. Thus, the entire drive circuitry for the individual electrodes must be adapted for high voltages. Furthermore, the insertion of initialization pulses raises the frequency for driving the individual electrodes, resulting in the problem that the power consumption of the drive circuitry is increased.
SUMMARY OF THE INVENTION
The object of this invention is to solve the above-mentioned problems by providing display panel drive circuit capable of driving the individual electrodes at low voltages and low frequencies.
The display panel drive circuit of this invention applies a reset pulse having a polarity opposite to that of the display pulse in gaps between applied display pulses to the common electrode. Thus, the control of the individual electrode is unaffected even if reset pulses are inserted. Accordingly, it is sufficient to have one on-off operation of the individual electrode in one frame necessary to determine when to halt the discharge. Therefore, the individual electrode can be driven at a low frequency so as to achieve a reduction in power consumption of this drive circuit. Furthermore, a high voltage initialization pulse (reset pulse) for the individual electrode is unnecessary, making it possible to eliminate the need for handling high voltages in the drive circuit for the individual electrode.
The above-mentioned display pulse is formed from voltages of two levels and the voltage rises and lowers in a stepwise fashion. It is preferable for the absolute voltage value of the above-mentioned reset pulse to be greater than or equal to the first level voltage value of the display pulse. With this type of display pulse, one display pulse can cause two discharges, one for storing charge and another for erasing the stored charge. When a stable discharge is performed, the insertion of the reset pulse becomes unnecessary.
It may also be preferable to apply the above-mentioned reset pulse either once for one frame or once for a plurality of frames. This enables frames to be created without inserting the reset pulse and results in reduced processing requirements.
It may also be preferable to provide a sequence memory for storing a plurality of sequences for driving the above-mentioned common electrode and individual electrode, and to control the drive of the common electrode on the basis of the sequence data read out from the sequence memory. This enables repetitive output of the same display pulse to be easily performed.
Furthermore, it may be preferable to provide a loop memory for storing the sequence readout order from the above-mentioned sequence memory, and to read out the sequence data from the sequence memory on the basis of the data read out from the loop memory. This raises the degree of freedom of sequence use and permits various types of drive with a small storage capacity. In particular, the operation of the sequence of insertion of the reset pulse through the loop memory can be performed as desired.
This invention is composed as described above and achieves the effects given below.
(i) Control of the individual electrode remains unaffected, even if a reset pulse is inserted, because the reset pulse having a polarity opposite to that of the display pulse is applied in the interval between applied display pulses to the common electrode. Accordingly, one on-off operation of the individual electrode in one frame is sufficient to determine when to halt the discharge. Therefore, it is sufficient to drive the individual electrode at an extremely low frequency so as to achieve a reduction in power consumption of this drive circuit. Furthermore, a high voltage initialization pulse for the individual electrode is unnecessary, making it possible to lower the load in the drive circuit for the individual electrode and sufficiently lower the voltages to be handled.
(ii) The above-mentioned display pulse is formed from voltages of two levels and the voltage rises and lowers in a stepwise fashion. It may be preferable for the absolute voltage value of the above-mentioned reset pulse to be greater than or equal to the first level voltage value of the display pulse. With this sort of display pulse, one display pulse can cause two discharges, one for storing charge and another for erasing the stored charge. When a stable discharge is performed, the insertion of the reset pulse becomes unnecessary.
(iii) It may be preferable to apply the above-mentioned reset pulse once for one frame or once for a plurality of frames. This enables frames to be created without inserting the reset pulse and results in lighter processing requirements.
(iv) It may be preferable to provide a sequence memory for storing a plurality of sequences for driving the above-mentioned common electrode and individual electrode, and to control the drive of the common electrode on the basis of the sequence data read out from the sequence memory. This enables the drive to repetitively output the same display pulse to be easily performed.
(v) It may
Arimoto Hironobu
Ito Atsushi
Jankus Almis R.
Mitsubishi Denki & Kabushiki Kaisha
Rothwell Figg Ernst & Manbeck
Tran Henry N.
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