JPH0410638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device, and more particularly to a display device in which an AC type gas discharge display panel, a so-called plasma display panel, is driven by a time division driving method.

A plasma display panel consists of two sets of electrodes arranged in a matrix, facing each other with a dischargeable gas medium in between, and the surface of each electrode in contact with the gas medium is covered with a dielectric layer. The externally applied voltage is configured to couple to the gas medium via the capacitance.

Therefore, in order to cause a desired gas cell to discharge and emit light, an AC voltage is applied between a pair of opposing electrodes sandwiching the gas cell, and as the polarity of the applied voltage changes, the cell discharges intermittently once. , emit light. To drive this type of plasma display panel in a time-division manner, first a voltage pulse train consisting of a plurality of pulses is applied to each electrode in either rows or columns facing each other in turn. is applied sequentially and scanned at a repetition rate of about 60 times or more per second. When a voltage pulse train is applied to a certain electrode among these electrodes and it is in a selected state, all the opposing cells that are to be emitted in accordance with the display data content are selected from among the gas cell group in a row determined by this electrode. By applying a voltage pulse train of opposite polarity to the above pulse train to the other electrode to bring it into a selected state, only a desired cell can be caused to discharge and emit light. By repeating the above operation each time each electrode in the former electrode group is scanned one by one, the desired display will appear over the entire surface. If the number of repetitions of scanning is a constant value R times, and the number of pulses assigned to each electrode in one scan is a, then the number of pulses applied to the cell to discharge light is Ra per second. As mentioned above, the gas cell discharges and emits light every time the polarity of the applied voltage changes, so one pulse voltage discharges twice, and therefore one
Discharges 2Ra times per second. The luminance of each gas cell's light emission is proportional to the capacitance of the dielectric layer covering the electrode, but in order to prevent breakdown of the dielectric layer, the dielectric layer must have a certain thickness, and the capacitance will not exceed a certain value. Therefore, there is a limit to the luminance of light emitted per discharge, and at present, in order to obtain a level of luminance that can be put to practical use, it is necessary to discharge about 5,000 times per second. On the other hand, if the number of electrodes to be scanned is n, in order to make the gas cell discharge 2Ra times per second,
The repetition frequency of the voltage pulse is nRa (Hz),
For example, in order to put a plasma display panel with 120 scanning electrodes into practical use, the frequency nRa is nRa = n2Ra/2 = 120 x 5000/2 = 300 (kHz), which is the current level of plasma display panels. Considering that the drive voltage is approximately 150V, the power consumption required for high frequency switching in the driver section is quite large. This power consumption increases as the switching frequency increases.
In other words, the higher the luminance of the light-emitting cell, the more it increases. Furthermore, when the luminance is constant, it increases in proportion to the number of cells emitting light.

When such a plasma display panel is used as a monitor for a keyboard input device or the like, an input method is generally used in which data is input on the bottom line and when the input is completed, the data is shifted up one line. Operators currently pay special attention to the lines they are typing, but they pay little attention to the lines that have been completed and shifted. However, in conventional display devices, the last or two previous input lines emit light with the same brightness as the currently input line, so the larger the display capacity of the plasma display panel, the lower the power consumption. growing. Another drawback is that if the brightness is increased sufficiently to make it easier for the operator to check, the power consumption will also increase accordingly.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a plasma display device that consumes less power and is easy for an operator to confirm.

According to the present invention, current processing is performed in a monitoring device that drives a plasma display panel in a time-sharing manner, which has two sets of electrode groups facing each other and arranged in a matrix through a dielectric material and a discharge space. A display device is obtained which is characterized in that it is equipped with means for increasing the display brightness only for the line that is being executed and decreasing the brightness for the portion that has been processed. An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of the present invention.
In FIG. 1, 1 is a clock oscillation circuit, 2 is a program counter, 3 is a row number counter, 4 is a row number counter, 5 is a bottom row detection circuit, 6 is a memory, and 7
1 is a character energy router, 8 is a toggle oscillation circuit, 9 and 10 are shift registers, 11 is a latch, 12 is a scanning electrode driver, 13 is a data electrode driver, 14 is a plasma display.
It is a panel. A program counter 2 and a bottom row detection circuit 5 are parts added to the conventional display device according to the present invention.

Clock oscillation circuit 1 is a clock oscillation circuit that serves as a reference for the operation of the present invention. The clock oscillated here is sent to the program counter 2. The program counter 2 is normally provided to divide the input clock to a frequency suitable for time-division driving of the plasma display panel 14. However, when the bottom row detection circuit 5 detects the bottom row and outputs a signal, the program counter 2 counts two to three times the normal number.

This output signal of the program counter 2 corresponds to the display time of one scan electrode, so the count number is 2 to 3 times larger, which means that the display time is 2 to 3 times larger.
This means that the number of pulses assigned to each electrode in one scan will be doubled or tripled for the bottom row only, as explained in the principle of time-division drive method of plasma display panels, and the brightness of the bottom row will be increased by 3 times. becomes 2 to 3 times brighter than other rows.

The column number counter 3 is provided to count the output signal of the program counter 2 by the number of display columns of the plasma display panel, and this column number counter also receives an output signal specifying the column address of the memory 6, Outputs a scanning signal for scanning electrodes.

The row number counter 4 receives the output signal of the column number counter,
It is inserted to count the number of lines on the plasma display panel 14. This row number counter also outputs a signal specifying the row address of the memory 6. The bottom row detection circuit 5 detects whether the row number counter has reached the bottom row or not, and outputs an output signal when the row number counter reaches the bottom row to change the count number of the program counter 2. Memory 6 is plasma
It is inserted to store information to be displayed on the display panel 14. Further, the memory 6 outputs address information determined by the column number counter 3 and the row number counter 4 to the character generator 7. The character generator converts the output signal from the memory 6 into a character pattern and inputs it to the shift register 10 for output. Toggle oscillation circuit 8
is input to oscillate a torque for converting the output waveforms of the scan electrode driver 12 and data electrode driver 13 into a pulse train.

The scanning side shift register 9 is input to shift the scanning signal. Data side shift register 10
is inserted to parallelize the serial information of the character patterns generated by the character generator 7. The latch 11 stores the display information parallel-converted by the shift register 10 in order to hold it for a display time. The scan electrode driver 12 and the data electrode driver 13 transfer the output signals of the shift register 9 and latch 10 to the plasma display panel 14.
Input to convert to the driving voltage. The plasma display panel display device configured as described above naturally adopts a display method in which data is input from the bottom line, and when one line input is completed, the data is shifted up one line and new data is input from the bottom line. 40
In the case of a plasma display panel display device with a display capacity of 12 lines of characters, power consumption was reduced by 45% compared to a conventional display device with constant brightness. Furthermore, if the bottom row detection circuit 5 is configured to be able to detect any row other than the bottom row, it is possible to increase the brightness of only any row.

In the above embodiment, the matrix type has been described, but the same can be applied to the segment type.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a display device of a plasma display panel according to an embodiment of the present invention. 5... Bottom line detection circuit, 14... Plasma display panel.

Claims (1)

[Claims] 1. In a display device in which a plasma display panel having a group of electrodes facing each other across a discharge space is driven in a time-division manner, the display brightness is increased only for the electrode that is performing display processing, and the display processing is completed. 1. A plasma display panel display device, characterized in that the electrode is provided with means for reducing brightness.