JP2007033584A - Current drive type display device and driving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase lifetime of a current drive type display device which performs duty drive. <P>SOLUTION: A display data comparator circuit 50 detects a line with the same content as that of a line selected next by a scanning circuit 21 among pieces of display data stored in a display RAM 14. A line drive circuit 20 controls line wiring of the detected line to be selected in addition to line wiring of the line being selected when a line with the same content as that of the line being selected by the scanning circuit 21 is detected by the display data comparator circuit 50. Thus, since frequencies that current flowing to an organic EL element increase, however, an amount of current flowing to the organic EL element decreases, deterioration of the organic EL element which is easier to be deteriorated as it is radiated at higher luminance is delayed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a matrix display device, and more particularly, to a current drive display device that performs duty drive and a driving method thereof.

  Conventionally, a display device including an organic electroluminescence (hereinafter abbreviated as EL) element is known. In this display device, the organic EL element is driven with a constant current by static driving, duty driving, or active driving.

  FIG. 7 is a block diagram showing a configuration of a conventional display device that performs duty driving. The display device shown in FIG. 7 performs screen display on the organic EL panel 40 based on the display data stored in the display RAM 14. The organic EL panel 40 includes row wirings R1 to Rn, column wirings C1 to Cm, and (m × n) organic EL elements formed at intersections of both wirings.

  The row driving circuit 90 includes a scanning circuit 21 and a switch circuit 22. The scanning circuit 21 sequentially selects a row of organic EL elements every one line time, and outputs n scanning signals in which only one has a value (for example, 1) indicating selection to the switch circuit 22. The switch circuit 22 controls the row wirings R1 to Rn to either the selected state or the non-selected state according to the scanning signal output from the scanning circuit 21. The scanning circuit 21 switches the selected row every line time. As a result, the voltages of the row wirings R1 to Rn are controlled to be in a selected state (here, a low level voltage) for each line time as shown in FIG.

  The row driving circuit 90 notifies the display RAM 14 of the row selected by the scanning circuit 21. The display RAM 14 outputs the display data of the row notified from the row driving circuit 90. The column driving circuit 30 supplies a necessary amount of current corresponding to the display data output from the display RAM 14 to the column wirings C1 to Cm. When the row wiring Rj (j is an integer of 1 to n) is in a selected state, the current supplied from the column drive circuit 30 via the column wirings C1 to Cm flows through the organic EL element in the jth row. . At this time, the organic EL element in the j-th row emits light with a luminance corresponding to the amount of current flowing through each organic EL element. In the display device shown in FIG. 7, a process of controlling one row wiring to a selected state and supplying a necessary amount of current according to display data to the column wiring is performed for each row of the organic EL elements. In this way, screen display based on the display data stored in the display RAM 14 is performed.

The invention related to the present invention is disclosed in the following documents. Patent Document 1 discloses a method for reducing the power consumption of a display device by reducing the horizontal resolution or the vertical resolution. This method can be applied when displaying characters or the like at a low resolution, but cannot be applied when displaying photos or the like at a high resolution. Patent Document 2 discloses a method for extending the lifetime of a display device by simultaneously scanning a plurality of adjacent scanning lines. In this method, the scanning lines that are scanned simultaneously are fixed. Patent Document 3 discloses a method for extending the life of a display device by reducing the current flowing through the organic EL element when a still image is displayed. This document does not disclose simultaneously selecting a plurality of row wirings.
JP 2000-181394 A JP 2004-302173 A JP 2005-62485 A

  In general, a self-luminous display element deteriorates faster as light is emitted with higher luminance. For example, it is empirically known that the half-life of the organic EL element (the time required for the luminance to drop to half of the original) is inversely proportional to the square of the luminance. For this reason, when duty driving is performed in a display device including an organic EL element, there is a problem that the lifetime of the organic EL element is shortened as compared with the case where static driving or active driving is performed.

For example, it is assumed that the half-life L1 of an organic EL element that emits light with luminance X by static driving or active driving is given by the following formula (1) (where T is a proportional constant).
L1 = T / X ² (1)
On the other hand, when duty driving is performed with a duty number P (P is an integer of 2 or more), the light emission time is 1 / P, but in order to obtain the same brightness, light is emitted with P times the luminance. Therefore, the half-life L2 of the organic EL element is as shown in the following formula (2).
L2 = T / (PX) ² × P = T / PX ² = L1 / P (2)
As described above, when the duty drive is performed in the display device including the organic EL element, the half life is 1 / P compared with the case where the static drive or the active drive is performed.

  Therefore, an object of the present invention is to extend the life of a current-driven display device that performs duty driving.

A first invention is a matrix type display device that performs duty driving based on given display data,
A display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings;
A row driving circuit for controlling a row wiring selected from the row wirings to a selected state;
A column driving circuit for supplying a necessary amount of current to each of the column wirings based on the display data for one row;
A display data comparison circuit for detecting lines of the same content from the display data,
The row driving circuit controls a row wiring corresponding to the detected row to a selected state simultaneously when a row having the same content is detected by the display data comparison circuit.

According to a second invention, in the first invention,
The row driving circuit sequentially selects one row wiring per line time from the row wiring,
The display data comparison circuit sets, as a reference row, a row corresponding to a row wiring selected at the next line time by sequential selection in the row driving circuit, and sets a row having the same content as the reference row from the display data. It is detected every line time.

According to a third invention, in the second invention,
The display data comparison circuit includes:
A first line memory for storing display data of the reference row;
A second line memory that can store the display data for one row, and in which display data of each row other than the reference row is sequentially written;
A comparison circuit that checks whether or not the storage content of the first line memory matches the storage content of the second line memory each time the storage content of the second line memory is updated. It is characterized by.

According to a fourth invention, in the second invention,
The display data comparison circuit includes:
A line memory for storing display data of the reference line;
And a comparison circuit for sequentially checking whether or not display data of each line other than the reference line matches the stored contents of the line memory.

According to a fifth invention, in the second invention,
The row driving circuit includes:
A scanning circuit that stores values indicating row wirings to be sequentially selected for each row, and shifts the stored contents for each line time;
Based on the comparison result by the display data comparison circuit, a comparison result storage circuit that stores, for each row, a value indicating whether or not the content is the same as the reference row;
A row selection signal generation circuit for obtaining a row selection signal by performing a logical operation for each row on the value stored in the scanning circuit and the value stored in the comparison result storage unit;
And a switch circuit that selectively controls the row wiring to a selected state based on the row selection signal.

A sixth invention is the second invention, wherein:
The display data comparison circuit detects a line having the same content as the reference line from the display data for one screen.

According to a seventh invention, in the second invention,
The display data comparison circuit detects a line having the same content as the reference line from the display data of less than one screen.

In an eighth aspect based on the first aspect,
The display panel is composed of an organic electroluminescence panel.

According to a ninth aspect of the present invention, there is provided a matrix type display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings. A drive circuit for duty driving based on
A row driving circuit for controlling a row wiring selected from the row wirings to a selected state;
A column driving circuit for supplying a necessary amount of current to each of the column wirings based on the display data for one row;
A display data comparison circuit for detecting lines of the same content from the display data,
The row driving circuit controls a row wiring corresponding to the detected row to a selected state simultaneously when a row having the same content is detected by the display data comparison circuit.

According to a tenth aspect of the present invention, there is provided a matrix type display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings. A driving method for duty driving based on
Controlling a row wiring selected from among the row wirings to a selected state;
Supplying a necessary amount of current to each of the column wirings based on the display data for one row;
Detecting a line having the same content from the display data,
The step of controlling the state of the row wiring is characterized in that when a row having the same content is detected from the display data, the row wiring corresponding to the detected row is simultaneously controlled to be in a selected state. .

  According to the first, ninth, or tenth invention, when the display data includes a row having the same content, a plurality of row wirings are simultaneously controlled to be in a selected state. When a row wirings are controlled to be in the selected state at the same time, the amount of current flowing through the display element is 1 / a, so that the display element emits light with a luminance of 1 / a. Accordingly, it is possible to delay the deterioration of the display element, which is likely to be deteriorated as light is emitted with high luminance. Further, since the display element emits light with a frequency a, the screen can be displayed with a desired luminance. Thus, the life of the display panel or display device can be extended without impairing the screen display function.

  According to the second aspect of the invention, the display data comparison circuit operates in synchronization with the sequential selection of the row wirings in the row drive circuit, so that the storage amount of the result obtained by the display data comparison circuit can be reduced.

  According to the third aspect of the present invention, by storing both comparison target data, data input and comparison can be performed at any timing.

  According to the fourth aspect of the present invention, it is possible to prevent repeated input of the same data by storing one of the comparison target data.

  According to the fifth aspect of the present invention, a row driving circuit can be easily obtained by adding a circuit for storing a value for each row and a small amount of logic circuit to a conventional circuit including a scanning circuit and a switch circuit. Can do.

  According to the sixth aspect, the effect of extending the life can be enhanced by detecting rows having the same contents from a wide range.

  According to the seventh aspect, by limiting the range in which lines having the same content are detected, the effect of extending the life can be achieved with a small amount of calculation.

  According to the eighth aspect of the invention, the lifetime of the display device including the organic electroluminescence panel can be extended.

  FIG. 1 is a block diagram showing a configuration of a display device according to an embodiment of the present invention. The display device shown in FIG. 1 includes display RAMs 14a and 14b, a row drive circuit 20, a column drive circuit 30, an organic EL panel 40, and a display data comparison circuit 50. This display device performs screen display on the organic EL panel 40 by performing constant current duty driving based on display data stored in the display RAMs 14a and 14b.

  The organic EL panel 40 includes n row wirings R1 to Rn extending in the row direction and m column wirings C1 to Cm extending in the column direction. A total of (m × n) organic EL elements are formed at the intersections of the row wirings R1 to Rn and the column wirings C1 to Cm. The organic EL element emits light with luminance corresponding to the amount of flowing current and functions as a display element.

Hereinafter, i is an integer from 1 to m, j is an integer from 1 to n, and an organic EL element formed at the intersection of the row wiring Rj and the column wiring Ci is referred to as P _ij . In a general duty drive, in order to emit the organic EL elements P _ij at a desired luminance, it is assumed that electric current I _ij to the organic EL element P _ij. Note that the organic EL panel 40 may perform two-tone monochrome display, multi-gradation display, or color display. The values of m and n may be arbitrary. As an example, m is set to 128 and n is set to 64.

The display RAM 14a stores display data for one screen. The display RAM 14b stores display data having the same contents as the display RAM 14a, separately from the display RAM 14a. When the organic EL element emits light with s-level luminance, the display RAMs 14a and 14b store at least (m × n × t) -bit display data as display data for one screen. However, s is an integer greater than or ^equal to 2, and t is the minimum integer satisfying s ≦ 2 ^t .

  The display device shown in FIG. 1 further includes a host interface circuit (hereinafter referred to as a host I / F circuit) 12 and an instruction decoder 13, and is connected to a host CPU (not shown) via a system bus 11. . When updating the display data stored in the display RAMs 14a and 14b, the host CPU issues a command for that purpose (hereinafter referred to as a drawing command). The host I / F circuit 12 receives a drawing command issued from the host CPU and outputs it to the command decoder 13. The instruction decoder 13 analyzes the drawing instruction output from the host I / F circuit 12, updates the display data stored in the display RAM 14a, and updates the display data stored in the display RAM 14b.

  The display device shown in FIG. 1 is configured so that display data of a screen is not updated while a screen is displayed. More specifically, this display device is provided with display RAMs 14a and 14b for two screens, one of which is used for screen display and the other is used for screen update, and the role of both is when the display of one screen is completed. Can be switched to. Upon receiving a drawing command from the host I / F circuit 12, the command decoder 13 immediately updates only the display data stored in the display RAM for screen update, and the display of one screen is completed. Is switched to the display RAM for updating the screen, the display data stored in the display RAM is updated. Hereinafter, unless otherwise specified, the display RAM for display on the display RAMs 14 a and 14 b is simply referred to as “display RAM”.

  The row drive circuit 20, the column drive circuit 30, and the display data comparison circuit 50 form a drive circuit for the organic EL panel 40. As shown in FIG. 1, the row driving circuit 20 includes a scanning circuit 21, a switch circuit 22, a comparison result storage circuit 23, and a row selection signal generation circuit 24. The display data comparison circuit 50 includes a reference line memory 51, A comparison line memory 52 and a comparison circuit 53 are included.

  The scanning circuit 21 sequentially selects a row of organic EL elements every one line time, and outputs n scanning signals in which only one has a value indicating selection (for example, 1) to the row selection signal generation circuit 24. The row driving circuit 20 notifies the display RAM of the row selected by the scanning circuit 21 and notifies the display data comparison circuit 50 of the next row selected by the scanning circuit 21.

  The reference line memory 51 and the comparison line memory 52 have a capacity capable of storing display data for at least one row. The comparison circuit 53 has an exclusive OR circuit, and compares the content stored in the reference line memory 51 with the content stored in the comparison line memory 52 using the exclusive OR circuit. The display data comparison circuit 50 executes a comparison process (FIG. 5), which will be described later, so that the row notified from the row drive circuit 20 (that is, the next in the scanning circuit 21) from the display data stored in the display RAM. A line having the same contents as the reference line is detected. When performing the comparison process, the display data comparison circuit 50 outputs a comparison result 61 indicating whether or not each row of display data has the same content as the next row selected by the scanning circuit 21. The comparison result storage circuit 23 stores the comparison results 61 output from the display data comparison circuit 50 for n rows.

  The row selection signal generation circuit 24 generates n row selection signals based on the scanning signal output from the scanning circuit 21 and the comparison result stored in the comparison result storage circuit 23. The row selection signal is a value indicating selection (for example, 1) when the corresponding scanning signal is a value indicating selection, or when the corresponding comparison result is a value indicating “same content”. In other cases, the row selection signal is a value indicating non-selection (for example, 0).

  The switch circuit 22 controls the row wirings R1 to Rn to either the selected state or the non-selected state according to the row selection signal output from the row selection signal generation circuit 24. As described above, in the display device shown in FIG. 1, when the scanning circuit 21 selects the j-th row, the row wiring Rj and the row wiring having the same content as the j-th row are simultaneously controlled to be in a selected state. .

On the other hand, the display RAM outputs display data of a row notified from the row driving circuit 20 (that is, a row selected by the scanning circuit 21). The column driving circuit 30 supplies a necessary amount of current corresponding to the display data output from the display RAM to the column wirings C1 to Cm. For example, when the scanning circuit 21 selects the j-th row, the column driving circuit 30 supplies the necessary amounts of currents I _{1j to} I _mj corresponding to the display data of the j-th row read from the display RAM to the column wirings C1 to C1. Supply to Cm.

When only one row wiring among the row wirings R1 to Rn is controlled to be selected when the scanning circuit 21 selects the jth row, the organic EL element in the jth row has Currents I _{1j to} I _mj supplied from the column drive circuit 30 flow as they are. Therefore, the organic EL element in the j-th row emits light with a luminance corresponding to the currents I _{1j to} I _mj .

On the other hand, when the scanning circuit 21 is selecting the j-th row, if a row wirings (a is an integer of 2 or more) among the row wirings R1 to Rn are controlled to be in the selected state, the column The currents I _{1j to} I _mj supplied from the drive circuit 30 are divided by a, and 1 / a of the currents I _{1j to} I _mj flows through the organic EL element in the j-th row. Accordingly, the organic EL element in the j-th row emits light with luminance corresponding to the currents I _1j / a to I _mj / a. At this time, the organic EL elements other than the j-th row also emit light with the same luminance (that is, with luminance corresponding to the currents I _1j / a to I _mj / a) if the row wiring is controlled to the selected state.

  A specific example of the operation of the display circuit shown in FIG. 1 will be described with reference to FIGS. Here, as an example, in the display data stored in the display RAM, the contents of the second and fourth lines are the same, and the contents of the other lines are different from each other. Hereinafter, the process of detecting a line having the same content as the display data of the j-th line is referred to as “j-th line comparison process”, and the period during which the scanning circuit 21 selects the j-th line is referred to as “j-th line time”. .

  FIG. 2 is a timing chart showing voltage changes of the row wirings R1 to Rn. In the n-th line time, the display data comparison circuit 50 performs the comparison process for the first row. A comparison result that there is no line having the same content as the first line is obtained by the comparison process of the first line. Based on the comparison result, the row driving circuit 20 controls only the row wiring R1 to a selected state (here, a low level voltage) in the first line time, as shown in FIG.

  In the first line time, the display data comparison circuit 50 performs comparison processing for the second row. By the comparison process of the second line, a comparison result that the fourth line has the same contents as the second line is obtained. Based on the comparison result, the row driving circuit 20 controls the row wiring R2 and the row wiring R4 to be in a selected state at the same time in the second line time, as shown in FIG.

  Similarly, based on the comparison result that there is no row having the same content as the third row, only the row wiring R3 is controlled to be in the selected state in the third line time. Further, based on the comparison result that the second row has the same contents as the fourth row, the row wiring R4 and the row wiring R2 are simultaneously controlled to be in the selected state during the fourth line time.

  FIG. 3 is a diagram showing how current flows through the organic EL panel 40 during the first line time, and FIG. 4 is a diagram showing how current flows through the organic EL panel 40 during the second line time. 3 and 4, a diode represents an organic EL element formed in the organic EL panel 40.

  As shown in FIGS. 3 and 4, the switch circuit 22 includes n switches corresponding to the n row wirings R1 to Rn. The switch corresponding to the row wiring Rj connects the row wiring Rj to a ground voltage that is a low level voltage when the corresponding row selection signal is a value indicating selection, and otherwise the row wiring Rj. Is connected to a high level voltage. The column drive circuit 30 includes n switches and n constant current sources corresponding to the column wirings C1 to Cm. A constant current source corresponding to the column wiring Ci supplies a necessary amount of current according to display data read from the display RAM. The switch in the column driving circuit 30 has a function of connecting a constant current source to the column wirings C1 to Cm for a predetermined time.

In the first line time (see Figure 3), row wirings R1 only selected (here, the low-level voltage) of the row wirings R1~Rn is controlled, the column wiring C1~Cm current I ₁₁ ~I _m1 is supplied. In this case, the current I ₁₁ flows into the row wiring R1 via the organic EL element P ₁₁ . Accordingly, the organic EL element P ₁₁ emits light with a luminance corresponding to the current I ₁₁ . Similarly, the other organic EL elements P _{21 to} P _m1 arranged in the first row also emit light with luminance corresponding to the currents I _{21 to} I _m1 , respectively.

On the other hand, in the second line time (see Figure 4), and the row wiring R2 and the row wiring R4 is controlled to be simultaneously selected, the column wiring C1~Cm current I ₁₂ ~I _{m @ 2} is supplied. Of current I ₁₂ supplied to the column wiring C1, half flows into the row wire R2 via the organic EL element P _12, the other half flows into the row wire R4 via the organic EL element P _14. Therefore, the organic EL element P ₁₂ is half the current I ₁₂ which is supplied to the column wiring C1 (i.e., current I _12/2) emits light at a luminance corresponding to the same time, also the organic EL organic EL element P ₁₄ to the same brightness as the element P _12. Similarly, second line arranged other organic EL elements P ₂₂ to P _{m @ 2} also emits light at luminance corresponding to current I ₂₂ / 2~I _m2 / _2, respectively, at the same time, arranged in the fourth row The other organic EL elements P _{24 to} P _m4 thus emitted emit light with the same luminance as the organic EL elements P _{22 to} P _m2 , respectively.

Similarly, in the third line time, the organic EL elements P _{13 to} P _{m3 in the} third row emit light with luminance corresponding to the currents I _{13 to} I _m3 , respectively. In the fourth line time, the organic EL element P ₁₄ to P _m4 in the fourth row emits light at a luminance corresponding to the current I ₁₄ / 2~I _m4 / 2, respectively, and at the same time, the second row of the organic EL element P _{12 to} P _m2 also emit light with the same luminance as the organic EL elements P _{14 to} P _m4 .

Thus, the organic EL element in the first row emits light with luminance corresponding to the currents I _{11 to} I _m1 in the first line time, and the organic EL element in the third row has the currents I ₁₃ to I in the third line time. _Emits light with a luminance corresponding to Im3. Further, the organic EL element of the second row, after light emission at a luminance corresponding to the current I ₁₂ / 2~I _m2 / ₂ in the second line time, the current in the fourth line time I ₁₄ / 2~I _m4 / 2 It emits light with a brightness corresponding to. The organic EL element in the fourth row emits light with the same luminance at the same time as the organic EL element in the second row.

Therefore, the organic EL elements in the first row and the third row emit light with luminance according to the display data. Further, since the second and fourth lines of the display data have the same contents, the currents I _{12 to} I _m2 and the currents I _{14 to} I _m4 are equal. Therefore, the organic EL element of the second line, the second line time and the fourth line time, will emit light at a luminance corresponding to current I ₁₂ / 2~I _m2 / _2, respectively, the second row of the organic EL The same result is obtained as when the element emits light with a luminance corresponding to the currents I _{12 to} I _m2 in the second line time. Therefore, the organic EL elements in the second row also emit light with a luminance corresponding to the display data. Similarly, the organic EL elements in the fourth row also emit light with luminance corresponding to the display data. As described above, according to the display device shown in FIG. 1, it is possible to perform screen display on the organic EL panel 40 with desired luminance based on the display data stored in the display RAM.

  Hereinafter, the display device shown in FIG. 1 will be described in detail with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing the comparison process of the j-th row executed by the display data comparison circuit 50. In the comparison process illustrated in FIG. 5, the variable k is used to specify a row to be compared.

  In the comparison process for the j-th row, first, the display data for the j-th row among the display data stored in the display RAM is transferred to the reference line memory 51 (step S101). Next, (j + 1) is set to k. However, if j is equal to n (the number of row wirings), 1 is set to k (step S102). Next, the display data of the kth row among the display data stored in the display RAM is transferred to the comparison line memory 52 (step S103).

  Next, it is determined whether or not the contents of the reference line memory 51 and the comparison line memory 52 are the same (step S104). Step S <b> 104 is performed using the comparison circuit 53. If the contents are the same, the value 1 is written as the kth comparison result in the comparison result storage circuit 23 (step S105). If the contents are different, the value 0 is stored in the comparison result storage circuit 23 as the kth comparison result. Is written (step S106).

  Next, it is determined whether or not k is equal to j (step S107). If both are equal, the process ends. If they are not equal, 1 is added to k. However, if k before addition is equal to n, 1 is set to k (step S108). Thereafter, the comparison process for the j-th row proceeds to step S103.

  When the comparison process shown in FIG. 5 is executed, the reference line memory 51 stores display data of a row notified from the row driving circuit 20 (that is, a row selected next by the scanning circuit 21). In the comparison line memory 52, display data of rows other than the row notified from the row drive circuit 20 (that is, rows other than the row selected next by the scanning circuit 21) is sequentially written. The comparison circuit 53 checks whether or not the storage content of the reference line memory 51 matches the storage content of the comparison line memory 52 every time the storage content of the comparison line memory 52 is updated. Therefore, by executing the comparison process shown in FIG. 5, it is possible to easily detect a line having the same content as a certain line with a small circuit amount.

  FIG. 6 is a circuit diagram of the row driving circuit 20. The comparison result storage circuit 23 is configured using, for example, n flip-flops. The comparison result 61 output from the comparison circuit 53 is given to the data input terminal of each flip-flop. The k-th completion signal Ek is given to the clock terminal of the k-th flip-flop (k is an integer of 1 to n). When executing the step S105 or S106 of the comparison process (FIG. 5), the display data comparison circuit 50 outputs the comparison result 61 between the j-th row and the k-th row of the display data and the k-th completion signal Ek. Is output. Therefore, at the time when the comparison processing for the j-th row is completed, the comparison result storage circuit 23 stores, for each row, a value obtained by the display data comparison circuit 50 indicating whether or not the content is the same as that of the j-th row. Yes.

  In the example shown in FIG. 6, the comparison result storage circuit 23 is configured using n flip-flops. However, any circuit that can store n-bit information is used as the comparison result storage circuit 23. Also good. For example, the comparison result storage circuit 23 may be configured using SRAM, DRAM, or the like.

  The scanning circuit 21 is configured using, for example, n flip-flops connected so that data can be cyclically shifted. Of the outputs of the n flip-flops, only one output has a value indicating selection (here, 1). Further, a horizontal synchronizing signal output at a predetermined time interval from a timer circuit (not shown) is given to the data input terminal of each flip-flop. The scanning circuit 21 configured as described above stores a value indicating whether or not a selection is being made for each row, and cyclically shifts the stored content every line time.

  In the example shown in FIG. 6, the scanning circuit 21 cyclically shifts the stored content. However, the scanning circuit only needs to have at least a function of shifting the stored content. A signal having a predetermined value (for example, 1) may be supplied every frame time to the first flip-flop of the scanning circuit configured as described above.

  The row selection signal generation circuit 24 is configured using n logic gates (here, OR gates). Each OR gate obtains, for each row, a logical sum of the n signals output from the comparison result storage circuit 23 and the n scanning signals output from the scanning circuit 21, and the obtained logical sum is obtained for n rows. It outputs to the switch circuit 22 as a selection signal. As described above, the switch included in the switch circuit 22 connects the row wiring Rj to the low level voltage when the row selection signal has a value indicating selection, and otherwise connects the row wiring Rj. Connect to high level voltage.

  Such a row drive circuit 20 can be easily obtained by adding a circuit for storing values for each row and a small amount of logic circuits to the conventional row drive circuit 90 (FIG. 7).

  Hereinafter, a specific effect produced by the display device shown in FIG. 1 will be described. In this display device, when the display data includes a row having the same content, a plurality of row wirings are simultaneously controlled to be in a selected state. Therefore, when a row wirings (a is an integer of 2 or more) are controlled to be in a selected state at the same time, the amount of current flowing through the organic EL elements in each row is the amount of current a supplied from the column driving circuit 30. The organic EL elements in each row have a luminance corresponding to the current that is 1 / a of the current supplied from the column driving circuit 30 (that is, 1 / a when performing general duty driving). ).

Generally, it is empirically known that a self-luminous display element degrades faster as it emits light with higher luminance. For example, the half-life of an organic EL element is inversely proportional to the square of luminance. In the display device shown in FIG. 1, each row of organic EL elements emits light during the a-line time within one frame time. As described above, since the organic EL element emits light with a frequency a times as compared with the case where general duty driving is performed, the influence on the life of the organic EL element is also a times. However, as compared with the case of performing a general duty driving, since the amount of current flowing through the organic EL element becomes 1 a partial effect on the lifetime of the organic EL element is one of a ² min. When both are combined, in the display device shown in FIG. 1, the influence on the lifetime of the organic EL element is 1 / a in the case of performing general duty driving. Therefore, according to the display device shown in FIG. 1, the lifetime of the organic EL element, the organic EL panel, and the display device can be extended.

For example, when the number m of row wirings is 64, if the light emission of the organic EL panel 40 at a luminance of 100 cd / m ^2, in a typical duty driving, emit each organic EL element at a luminance of 6400cd / m ² It is necessary to let On the other hand, in the display device shown in FIG. 1, when two rows having the same contents are included in the display data, the organic EL elements in each row emit light with a luminance of 3200 cd / m ² and display. When four rows having the same contents are included in the data, the organic EL elements in each row emit light with a luminance of 1600 cd / m ² . For this reason, the influence which it has on the lifetime of an organic EL element becomes 1/2 or 1/4, respectively. Therefore, the lifetime of the organic EL element, the organic EL panel, and the display device can be extended.

  As described above, according to the display device according to the present embodiment, when the display data includes a row having the same content, a plurality of row wirings are controlled to be in a selected state at the same time. When the row wiring is controlled to be in the selected state at the same time, the organic EL element emits light with a luminance of 1 / a. Therefore, it is possible to delay the deterioration of the organic EL element that is more likely to be deteriorated as light is emitted with higher luminance. In addition, since the organic EL element emits light at a frequency, the screen can be displayed with a desired luminance. Thus, the life of the organic EL element, the organic EL panel and the display device can be extended without impairing the screen display function.

  In addition, since the display data comparison circuit 50 detects the line having the same content as the reference line with the next line selected by the row driving circuit 20 as the reference line, the storage amount of the result obtained by the display data comparison circuit 50 Can be reduced. In addition, since the display data comparison circuit 50 stores both data to be compared, data input and comparison can be performed at any timing. In addition, since the display data comparison circuit 50 detects lines having the same content from the display data for one screen, the line having the same contents can be detected from a wide range, and the effect of extending the life can be enhanced.

  Various modifications can be configured for the display device according to the present embodiment. In the above description, the display data comparison circuit 50 performs the comparison process for the next row selected by the row driving circuit 20. However, the display data comparison circuit only needs to complete the comparison process of the row before the row driving circuit 20 selects a row, and the configuration of the display data comparison circuit may be arbitrary as long as the condition is satisfied. .

  For example, the display data comparison circuit may detect a row having the same content as the next selected row by the row driving circuit 20 from display data of less than one screen. By limiting the range in which lines having the same contents are detected in this way, the effect of extending the life can be achieved with a small amount of calculation. Such a display data comparison circuit can be obtained by limiting the possible range of k in the comparison process shown in FIG.

  Alternatively, the display data comparison circuit includes only the reference line memory 51 as a line memory, and the comparison circuit sequentially checks whether or not the display data of each row stored in the display RAM matches the stored contents of the reference line memory 51. It is good as well. By storing one of the comparison target data in this way, it is possible to prevent the same data from being repeatedly input.

  Further, as long as the display data of the screen is not updated during the display of one screen, the display device does not necessarily have the display RAM for two screens. For example, in a display device having a display RAM for one screen, a time zone for reading display data for screen display and a time zone for screen update may be divided.

It is a block diagram which shows the structure of the display apparatus which concerns on one Embodiment of this invention. FIG. 2 is a timing chart showing a voltage change of a row wiring of the display device shown in FIG. 1. In the display apparatus shown in FIG. 1, it is a figure which shows a mode (1st example) that an electric current flows into an organic electroluminescent panel. In the display apparatus shown in FIG. 1, it is a figure which shows a mode that a current flows into an organic electroluminescent panel (2nd example). It is a flowchart which shows the comparison process in the display apparatus shown in FIG. It is a circuit diagram of the row drive circuit of the display apparatus shown in FIG. It is a block diagram which shows the structure of the conventional display apparatus. It is a timing chart which shows the voltage change of the row wiring of the conventional display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... System bus 12 ... Host I / F circuit 13 ... Instruction decoder 14 ... Display RAM
DESCRIPTION OF SYMBOLS 20 ... Row drive circuit 21 ... Scan circuit 22 ... Switch circuit 23 ... Comparison result memory circuit 24 ... Row selection signal generation circuit 30 ... Column drive circuit 40 ... Organic EL panel 50 ... Display data comparison circuit 51 ... Reference line memory 52 ... Comparison Line memory 53 ... Comparison circuit 61 ... Comparison result

Claims (10)

A matrix type display device that performs duty driving based on given display data,
A display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings;
A row driving circuit for controlling a row wiring selected from the row wirings to a selected state;
A column driving circuit for supplying a necessary amount of current to each of the column wirings based on the display data for one row;
A display data comparison circuit for detecting lines of the same content from the display data,
The row driving circuit controls a row wiring corresponding to the detected row to a selected state simultaneously when a row having the same contents is detected by the display data comparison circuit. The row driving circuit sequentially selects one row wiring per line time from the row wiring,
The display data comparison circuit sets, as a reference row, a row corresponding to a row wiring selected at the next line time by sequential selection in the row driving circuit, and sets a row having the same content as the reference row from the display data. The display device according to claim 1, wherein detection is performed every line time. The display data comparison circuit includes:
A first line memory for storing display data of the reference row;
A second line memory that can store the display data for one row, and in which display data of each row other than the reference row is sequentially written;
A comparison circuit that checks whether or not the storage content of the first line memory matches the storage content of the second line memory each time the storage content of the second line memory is updated; The display device according to claim 2. The display data comparison circuit includes:
A line memory for storing display data of the reference line;
The display device according to claim 2, further comprising: a comparison circuit that sequentially checks whether display data of each line other than the reference line matches the storage content of the line memory. The row driving circuit includes:
A scanning circuit that stores values indicating row wirings to be sequentially selected for each row, and shifts the stored contents for each line time;
Based on the comparison result by the display data comparison circuit, a comparison result storage circuit that stores, for each row, a value indicating whether or not the content is the same as the reference row;
A row selection signal generation circuit for obtaining a row selection signal by performing a logical operation for each row on the value stored in the scanning circuit and the value stored in the comparison result storage unit;
The display device according to claim 2, further comprising: a switch circuit that selectively controls the row wiring to a selected state based on the row selection signal.   The display device according to claim 2, wherein the display data comparison circuit detects a line having the same content as the reference line from the display data for one screen.   The display device according to claim 2, wherein the display data comparison circuit detects a line having the same content as the reference line from the display data of less than one screen.   The display device according to claim 1, wherein the display panel is an organic electroluminescence panel. Drive for duty-driving a matrix type display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings based on given display data A circuit,
A row driving circuit for controlling a row wiring selected from the row wirings to a selected state;
A column driving circuit for supplying a necessary amount of current to each of the column wirings based on the display data for one row;
A display data comparison circuit for detecting lines of the same content from the display data,
The row driving circuit controls a row wiring corresponding to the detected row to a selected state simultaneously when a row having the same content is detected by the display data comparison circuit. Drive for duty-driving a matrix type display panel including a plurality of row wirings, a plurality of column wirings, and a plurality of display elements formed at intersections of the row wirings and the column wirings based on given display data A method,
Controlling a row wiring selected from among the row wirings to a selected state;
Supplying a necessary amount of current to each of the column wirings based on the display data for one row;
Detecting a line having the same content from the display data,
The step of controlling the state of the row wiring is characterized in that when a row having the same content is detected from the display data, the row wiring corresponding to the detected row is simultaneously controlled to be in a selected state. Driving method.

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