BACKGROUNG ART LED is one of the flat panel displays being widely used for displaying information and messages. Some of the reasons for LED popularity may include reduced operation voltage and current requirements, greater durability, a higher level of brightness and greater optical efficiency as compared to other types of display panels. Since, however, it is difficult to manufacture very large LED display panels, conventional LED display devices are constructed by using an array of LED modules, each including a control circuit and an LED array having a plurality of LED elements.

Referring to Fig. 1, there is illustrated a schematic block diagram of one of the LED modules included in such a conventional dot-matrix LED display device (see, e. g., disclosed in U. S. Pat. No. 5,717,417 issued to Takahashi et al. and entitled"DOT-MATRIX LED DISPLAY DEVICE HAVING BRIGHTNESS CORRECTION CIRCUIT AND METHOD FOR CORRECTING BRIGHTNESS USING THE CORRECTION CIRCUIT"). As shown in Fig.

1, a dot-matrix LED module 10 includes an LED array having M x N LED elements, a data conversion circuit 14, a data output circuit 16 and a column decoder 18. Input data and control signals are inputted to the LED module 10 from a main controller (not shown). The input data is provided sequentially on a pixel-by-pixel basis. In response to the control signals, the serial pixel data is converted into parallel data for all the pixels to be displayed on one

column of the LED array 12. The converted parallel data is provided to the rows of the LED array 12 through the data output circuit 16 and the columns of the LED array 12 are scanned by the column decoder 18 under the control of the control signals.

As disclosed above, each LED display module included in the conventional LED device employs therein a data conversion circuit for converting the serial pixel data into a parallel format, complicating the circuitry in each LED module and increasing the manufacturing cost thereof.

DISCLOSURE OF THE INVENTION It is, therefore, an object of the present invention to provide an LED (light emitting diode) display device and simplified control method therefor.

In accordance with one aspect of the present invention, there is provided an LED display device comprising: an LED display unit having therein P number of LED modules, each LED module including an LED array having M x N LED elements, P, M and N being positive integers greater than 1; one or more buses coupled to the LED display modules; and a control unit for providing display data on the buses, the display data including P number of segment data sets being sequentially provided one of on the buses, wherein each segment data set includes data to be displayed by LED elements on a display line, the display line being one of the rows and the columns of each LED array, and the data included in each segment data set is provided on the buses simultaneously.

In accordance with another aspect of the invention, there is provided a display device comprising: a display unit having therein a plurality of display modules, each display module including a display array having more than one display element arranged in a pattern having one or more rows and one or more columns; and a control unit for

sequentially providing a multiple number of data sets, wherein each data set includes data to be displayed by more than one display element on a display line, the display line being one of the rows and the columns of each display array, and the data included in each data set is provided simultaneously.

In accordance with still another aspect of the present invention, there is provided a method for use in a display device including a plurality of display modules, each display module having a display array containing more than one display elements arranged in a pattern having one or more rows and one or more columns, the method comprising the steps of: sequentially providing a multiplicity of data sets, wherein each data set includes data to be displayed by more than one display element on a display line, the display line being one of the rows and the columns of each display array, and the data included in each data set is provided in parallel; storing a data set in a corresponding display module; and selecting the display line of each display array to thereby display the data sets on the display arrays.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiment given in conjunction with the accompanying drawings, in which: Fig. 1 represents a schematic block diagram of a conventional dot-matrix LED display module; Fig. 2 exemplifies a schematic block diagram of an LED display device in accordance with the present invention; Fig. 3 presents a block diagram of one of LED display modules included in the LED display device; Fig. 4 illustrates a timing diagram explaining the operation of the LED display device; and Fig. 5 depicts a flow chart explaining the operation

of the LED display device in accordance with the present invention.

MODES OF CARRING OUT THE INVENTION The preferred embodiment of the present invention will now be described with reference to Figs. 2 to 5B.

Referring to Fig. 2, there is provided a schematic block diagram of an LED display device 20 in accordance with the present invention. As shown in Fig. 2, the LED display device 20 comprises an external manipulation unit (EMU) 210, a control unit 220 and an LED display unit 230, wherein the LED display unit 230 includes a plurality of LED display modules, e. g., 232-1 to 232-n, n being a positive integer greater than 1. Each LED module includes an LED array having a multiplicity of, e. g., 16 x 16, LED elements. The control unit 220 includes therein a memory 222, a controller 224, a buffer 226 and a display control block 228 and is coupled to the LED display unit 230 through buses 240,250 and 260.

The EMU 210 can be, e. g., a computer, a key matrix, a keyboard, a touch screen, or a combination thereof; and serves to revise data pre-stored in the memory 222, input new data into the memory 222, and/or generate an operation start signal via the controller 224 in response to inputs by an operator.

The controller 224 serves to control the memory 222, the buffer 226 and the display control block 228. The display control block 228 controls the overall operation of the LED display unit 230.

The memory 222 is made of, e. g., a non-volatile memory device such as an EEPROM and a flash memory, whereas the buffer 226 is made of, e. g., a volatile memory device such as an SRAM or a DRAM. The memory 222 stores various alphanumeric and/or graphic data sets provided by the EMU 210 through the controller 224. Upon receiving an operation

start signal, which includes a designation signal indicating a data set to be displayed, from the EMU 210, the controller 224 retrieves a portion of the data set from the memory 222 and temporarily stores same in the buffer 226 prior to providing same to the display control block 228.

The portion of the data set corresponds to pixel data of one line (a column or a row) of an LED array included in each LED module. After storing the pixel data for each LED module, the controller 224 provides a data write signal (/DATA WR) shown in Fig. 4 and the pixel data to the display control block 228. In response thereto, the display control block 228 provides display data (DISDATA) on the bus 240, a data hold signal (DATAHOLD) and a latch enable signal (/LATCHEN) on the bus 260, and a line selection signal (LINE-SEL), a power driver enable signal (/PDEN) and a data scan clock signal (SC-CLK) on the bus 250. The data and signals provided on the buses 240 to 260 will be described in detail with reference to Figs. 3 to 5.

Referring to Fig. 3, there is illustrated a block diagram of one of the LED display modules, e. g., 232-1 of the LED display unit 230, in accordance with the present invention. The structures of the LED display modules 232-1 to 232-n are identical each other. As shown in Fig. 3, each of the LED display modules 232-1 to 232-n includes an LED array 310, a latch 320, a gradation control circuit 325 and a power driver 330, wherein the LED array 310 includes, e. g., 16 x 16 LED elements, each corresponding to one pixel. As well known in the art, one pixel may include R, G, B elements and in that case one LED element include three diodes. For the sake of simplicity, the present invention will be described assuming that one pixel is composed of one LED. It is to be understood to those skilled in the art, however, that the subject invention is not limited to such a case but can be readily extended to the pixels having RGB elements.

The display data DIS DATA is comprised of sets of

pixel data sequentially provided on the bus 240 by the display control block 228, wherein each set of pixel data corresponds to pixel data of one pixel line of an LED array and pixel data in one set is provided in parallel on the bus 240. For instance, if one pixel is expressed by m bits, m being a positive integer, and one line of a LED array to be displayed at the same time has 16 pixels, 16 x m bits are simultaneously provided in one set of pixel data for an LED array and the respective sets of pixel data for the LED arrays are sequentially provided on the bus 240.

The latch 320 is connected to data lines numbered [1] to [16] of the LED array 310, wherein the data lines [1] to [16] are connected to respective rows (or columns) of the LED array 310 through the gradation control circuit 325.

The gradation control circuit 325 serves to convert the m bit data on each data line into one of 2m gradation levels to be displayed on the LED array 310. If m=1, i. e., each LED element is merely controlled on and off, a gradation level control may not be necessary and thus the output from the latch 320 can be directly coupled to the LED array 310 without having to employ the gradation control circuit 325.

The power driver 330 is connected to the LED array 310 through power lines numbered [1] to [16], each of which is connected to corresponding columns (or rows) of the LED array 310.

A more detailed description of the operation of the LED display device 20 will be described with reference to Figs. 2 to 5. Fig. 4 and Fig 5 respectively represent a timing diagram and a flow chart explaining the operation of the LED display device 20 in accordance with the present invention.

At step S502, the controller 224 checks whether or not an operation start signal is inputted from the EMU 210, wherein the operation start signal includes a designation signal indicating a data set to be displayed among one or more data sets stored in the memory 222. The data set

represents data to be displayed on the whole LED display unit 230. The data set may correspond to a still image and/or a text, a motion picture, or a text scrolling across the LED display unit 230. The data set is displayed on the LED display unit 230 on, e. g., a frame-by-frame basis, one frame including n x 16 x 16 pixels in this example. If the data set is of a still image and/or a text, the frames thereof would be identical each other. If the data set is of a motion picture or a scrolling text, the frames thereof would be different from each other.

If the result at step S502 is positive, the procedure proceeds to step S504; and, if otherwise, the controller 224 returns to a stand-by mode until an operation start signal is inputted. At step S504, the controller 224 retrieves from the memory 222 a first data segment of the first frame of the data set indicated by the designation signal and stores same in the buffer 226. The first data segment includes n sets of pixel data, each set of pixel data including data for the 16 pixels of the first column of the LED array included in one of the LED modules 232-1 to 232-n.

Similarly, an ith data segment includes n sets of pixel data, wherein each set of pixel data includes data for the 16 pixels of an ith column of the LED array included in each of the LED modules 232-1 to 232-n, i being 1 to 16.

At step S506, the controller 224 stores the first data segment in the buffer 226. Address data may be appended to each set of pixel data. The address data designates an LED array on which each set of pixel data is to be displayed.

At step S508, the controller 224 issues at T1 the first data write signal/DATAWR as shown in Fig. 4 and simultaneously provide the display control block 228 with the sets of pixel data included in the data segment stored in the buffer 226.

In response to/DATAWR from the controller 224 at step S510, the display control block 228 generates display data (DIS DATA) on bus 240, a latch enable signal

(/LATCHEN) and a data hold signal (DATAHOLD) on bus 260, and a line selection signal (LINE-SEL), a power-driver enable signal (/PDEN) and a data scan clock signal (SCCLK) on bus 250 as shown in Fig. 4.

In Fig. 4, it is assumed that the LED display unit 230 includes 6 LED modules, i. e., n=6. As shown in Fig. 4, DISDATA includes the sets of pixel data Dj's (j= 1 to 6) sequentially provided on bus 240, starting from D1. On the other hand, pixel data in each Dj are simultaneously provided on bus 240, as described hereinabove. DHj in DATA HOLD activates a latch in an j th LED module if/LATCH EN is in the logic low state. Therefore, a set of pixel data Dj is simultaneously latched into a latch of an j th LED module under the control of DATAHOLDand/LATCHEN. As shown in Fig. 4, it may be preferable that the logic low state of/LATCHEN is asserted ahead of Di by the interval T, to T2 and also DHj is issued prior to Du boy the interval T to T2 in order to ensure the latching of Dj into the latch of the ith LED module. Also, all the sets of pixel data in DISDATA should be latched during the interval T1 to T3 during which/LATCHEN is in the low state (step S512).

At step S514, the power driver 330 is activated when /PD_EN is in the logic low state and SC-CLK is in the logic high state; and the output from the power driver 330 is provided to an ith column of every LED array in response to LINESEL LSi (i being 1 to 16) to thereby turn on the ith columns of the LED arrays to display DIS_DATA on the ith columns of the LED arrays. LSi designates the it column of each LED array to be activated. The"XX"marked portions of DISDATA, DATAHOLD and LINE SEL represents''Don't Care Data"or"Don't Care Signal".

At step S516, it is checked by the controller 224 whether the display operation is to be terminated.

Termination of display may be determined in response to a display termination signal provided from the EMU 210 by the operator or can be done automatically after a preset time

period from the onset of the operation start signal. If none of such cases applies, the process returns to step S504 and the display operation described above will be repeated for next data segments of the current frame and its subsequent frames until one of such case applies.

Although the preferred embodiment of the present invention has been described with respect to the LED device, it should be appreciated to those skilled in the art that the invention can be equally applied to other flat panel displays, e. g., fluorescent displays, liquid crystal displays, plasma display panels or the like.

It is also to be appreciated that each set of pixel data included in DISDATA may not necessarily contain data for all the pixels on one row or column. Each set of pixel data may contain a fraction of pixels (but more than one pixel) on one row or column. Also, the number of pixel data sets in DISDATA need not be identical to the number of LED modules.

The circuitry included in each of the LED modules of the invention is relatively simple compared to those of the conventional LED modules since the pixel data of one column is supplied simultaneously and all the control signals are provided from the control unit. As a result, the circuitry in each LED module can be placed on one board or in one package together with the control unit, or each LED module can be constructed so that an LED element or an LED array in trouble can be readily replaced with a new one.

It is to be noted that the data write signal/DATA WR, the latch enable signal/LATCH_EN and the power driver enable signal/PDEN can have logic high-activated states.

It is also to be appreciated by one skilled in the art that DIS DATA and the output of the power driver 330 can be applied to columns and rows of the LED arrays, respectively, in lieu of rows and columns as in the preferred embodiment of the invention.

It is also to be understood that if the display device

20 is employed as a sign board or panel mounted in a vehicle, the display device 20 can be constructed to automatically initiate the display operation, e. g., when a driver brakes the car.

While the present invention has been described with respect to certain preferred embodiments only, other modifications and variations may be made without departing from the spirit and scope of the present invention as set forth in the following claims.