JP2007093729A - Organic electroluminescence driving circuit, organic electroluminescence display device and driving method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of high frequency noise by suppressing a surge current when reset driving of an organic electroluminescence (OEL) element. <P>SOLUTION: A current limit resistor 4 is provided between each of scanning electrodes Row<SB>1</SB>to Row<SB>4</SB>, and GND. Thereby, the surge current is suppressed by the current limit resistor 4 and a peak value of the surge current is suppressed. In concrete terms, when starting reset, the surge current flowing through all scanning electrodes Row<SB>1</SB>to Row<SB>4</SB>is limited and when releasing the reset, the surge current flowing through the scanning electrodes Row<SB>1</SB>to Row<SB>4</SB>in which scanning electrode selecting switches RS<SB>1</SB>to RS<SB>4</SB>remain OFF is limited. Consequently, the occurrence of the high frequency noise caused by the surge current is prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving circuit for causing an organic EL element to emit light, an organic EL display, and a driving method thereof.

  In the organic EL display, a desired display is performed by switching and driving a light emitting pixel (an organic EL element that is a light emission target) every predetermined period. When driving the organic EL element in this way, charges are stored in the parasitic capacitance of each organic EL element during the scanning period. For example, as shown in Patent Document 1, the organic EL element that emits light is switched at the timing of switching. Then, reset driving is performed to discharge the electric charge.

  When the reset drive is used, when a certain scan moves to the next scan line, all the scan lines (cathode lines) and all the data lines (anode lines) are once dropped to the ground potential (0 V) and reset. Thereby, the charge charged in the parasitic capacitance of the organic EL element in the previous scanning period is discharged, and the charging period for the parasitic capacitance of the light emitting pixel in the next scanning is shortened. In other words, since the charge period becomes longer if the polarity of the charge charged in the parasitic capacitance is opposite to the polarity of the voltage applied in the next scanning period, the charge charged in the parasitic capacitance is discharged. The charging period of the parasitic capacitance in the next scanning period can be shortened. Thereby, the rise of the waveform of the light emitting pixel is made fast.

  A method for driving the conventional organic EL element will be described with reference to FIGS. 16 to 19 are operation explanatory diagrams of an organic EL drive circuit for driving a so-called simple matrix type organic EL element. Actually, the organic EL elements corresponding to the number of pixels are arranged in a matrix, but here a 4 × 4 matrix is shown for simplicity.

In FIGS. 16 to 19, first, the scan electrode Row ₁ is scanned to light the organic EL elements E _1,1 and E _1,2, and then, after a reset period, the next scan is performed, and the scan electrode Row _{2 is} scanned. Is shown, and the organic EL elements E _2,3 and E _2,4 are illuminated to perform a light emission operation. FIG. 20 is a timing chart showing voltage waveforms of the scan electrodes Row ₁ and Row ₂ , the data electrodes Col ₁ and Col _2, and the data electrodes Col ₃ and Col ₄ in this case, and FIGS. This corresponds to the state of each part in the organic EL drive circuit at the timings (1) to (4).

[Timing (1): Pre-reset state (light emitting pixel selection period)]
In the pre-reset state shown in FIG. 16, the scan selection switch RS ₁ is turned on (selected) and fixed at the ground potential (0 V). The other scan electrode selection switches RS _{2 to} RS ₄ are turned off (not selected), and the reverse bias voltage Vrow is applied.

Further, the data selection switches CS ₁ and CS ₂ are turned on (light emission), and a forward bias is applied from the constant current control circuits CC ₁ and CC ₂ . The other data selection switches CS ₃ and CS ₄ are turned off (non-emission) and fixed to the ground potential (0 V).

At this time, the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₁ ) and the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₁ and CS ₂ ). For the parasitic capacitances C _1,1 , C _{1,2 of} the pixels existing in the voltage drop from the potential difference Vcol ′ (= Vcol to the constant current sources CC _{1 to} CC ₄ , and the data side and the scanning side, respectively. Is charged by subtracting the voltage drop due to the wiring resistance.

Further, among the scan electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₂ to RS ₄ ) and those that are not selected among the data selection switches CS _{1 to} CS ₄ (CS ₃ , CS ₄ ) ₄ ) The parasitic capacitances C _2,3 , C _2,4 , C _3,3 , C _3,4 , C _4,3 , C _{4,4 of} the pixels present at the intersections of the pixels are charged with the potential difference Vrow. Yes.

And among the scanning electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₂ to RS ₄ ) and among the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₁ , CS _2). ) With respect to the parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , and C _{4,2 of} the pixels existing at the intersections of ()). May be negatively charged with respect to Vrow.

At this time, since (Vrow−Vcol ′) is about several V, parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 The charge of the pixel is very small compared to the charge of the pixel charged with the potential difference Vcol ′ including the parasitic capacitance C _2,3 and the potential difference row.

Note that the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₁ ) and the data selection switches CS _{1 to} CS ₄ that are not emitting light (CS ₃ and CS ₄ ). Since the potential difference is substantially 0 V with respect to the parasitic capacitances C _1,3 and C _{1,4 of} the pixels existing in FIG.

[Timing (2): Start reset]
In the reset start state shown in FIG. 17, the scan selection switch RS ₁ remains fixed and is fixed at the ground potential (0 V). The other scan electrode selection switches RS _{2 to} RS ₄ are all turned off and are fixed to the ground potential (0 V). In the data selection switch, CS ₁ and CS ₂ are turned off (non-light emitting), and are fixed to the ground potential (0 V). Other data selection switches are fixed to the ground potential (0 V) while being off (non-light emitting).

At this time, the forward bias charges accumulated in the parasitic capacitances C _1,1 and C _1,2 are transferred from the scan electrode Row ₁ to the data electrodes Col ₁ and Col ₂ through the scan electrode drive circuit 2 side. It goes out to the electrode drive circuit 1 side (see broken line). The reverse bias charges accumulated in the parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 are obtained from the data electrodes Col ₁ , Col _2. In a path through the scan electrodes Row _{2 to} Row ₄ , the data electrode drive circuit 1 side exits from the scan electrode drive circuit 2 side (see the alternate long and short dash line). Further, the reverse bias charges accumulated in the parasitic capacitances C _2,3 , C _2,4 , C _3,3 , C _3,4 , C _4,3 , C _4,4 are stored in the data electrodes Col ₃ , Col. in path through the scan electrode Row ₂ ～Row ₄ from ₄ goes from the data electrode driving circuit 1 side missing from the scanning electrode driving circuit 2 side (see chain lines d point).

[Timing (3): Reset period]
During the reset period shown in FIG. 18, since all the scan electrodes Row _{1 to} Row ₄ and the data electrodes Col _{1 to} Col ₄ are fixed to the ground potential (0 V), no charge movement occurs anywhere.

[Timing (4): Reset release]
In the reset release state shown in FIG. 19, the scan selection switch RS ₂ remains fixed and is fixed at the ground potential (0 V). The other scan electrode selection switches RS ₁ , RS ₃ , and RS ₄ are all turned off, and application of the reverse bias voltage Vrow is started. The data selection switches CS ₁ and CS ₂ are fixed to the ground potential (0 V) while being off (non-light emitting). The data selection switches CS ₃ and CS ₄ that switch to light emission are switched from OFF (non-light emission) to ON, and forward bias application starts from the constant current control circuits CC ₃ and CC ₄ .

At this time, the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₂ ) and the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₃ and CS ₄ ). For the parasitic capacitances C _2,3 and C _{2,4 of} the pixels existing in the pixel, the forward bias charges are charged with the potential difference Vcol ′ through the path from the data electrodes Col ₃ and Col ₄ to the scan electrode Row _2. Go (see dashed line).

Scan electrode selection switches RS _{1 to} RS ₄ that are not selected (RS ₁ , RS ₃ , RS ₄ ) and data selection switches CS _{1 to} CS ₄ that are light emitting (CS ₃ , CS ₄ ) ₄ ) For the parasitic capacitances C _1,3 , C _1,4 , C _3,3 , C _3,4 , C _4,3 , C _{4,4 of} the pixels present at the intersection of the scanning electrodes Row ₁ , The reverse bias charges are charged through the path from Row ₃ and Row ₄ through the data electrodes Col ₃ and Col ₄ (see the alternate long and short dash line). Thus, finally the parasitic capacitance _{C 1,3, C 1,4, C 3,3} , C 3,4, C 4,3, C 4,4 is charged with a potential difference (Vrow-Vcol ').

Further, among the scanning electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₁ , RS ₃ , RS ₄ ) and those that are not selected among the data selection switches CS _{1 to} CS ₄ (CS ₁ , CS ₂ ) for the parasitic capacitances C _1,1 , C _1,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 In the path from the scan electrodes Row ₁ , Row ₃ , and Row ₄ to the data electrodes Col ₁ and Col ₂ , the charge of reverse bias is charged with the potential difference Vrow (see the two-dot chain line).

The intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₂ ) and the data selection switches CS _{1 to} CS ₄ that are not emitting light (CS ₁ and CS ₂ ). Since the potential difference is substantially 0 V with respect to the parasitic capacitances C _2,1 and C _{2,2 of} the pixels existing in the pixel, no charge is charged.

As described above, the organic EL element is driven. Figure 21 is a timing chart showing the relationship between the current flowing in scan electrodes Row ₁ ~Row ₄ and data electrodes Col ₁ ~Col potential scan electrode Row ₁ ~Row ₄ of ₄ in the series of timing.
Japanese Patent No. 3314046

  However, when the above-described reset driving is used, a surge-like current as shown in FIG. 21 flows in order to discharge the charge charged in the parasitic capacitance of the organic EL element every scan. Further, at the moment when the reset is released, a surge current flows in order to charge the forward-biased charge to the pixel that shifts to light emission. For example, when driven at the timing shown in FIG. 21, if a reset period of about 5 μS is set, high-frequency noise of 200 kHz due to the surge current is generated. Therefore, when an organic EL is used as a vehicle-mounted display, radiation noise to a car radio or the like becomes a problem.

  In view of the above points, an object of the present invention is to prevent generation of high-frequency noise by suppressing a surge current when performing reset driving of an organic EL element.

To achieve the above object, the present invention, during the reset period, through the plurality of scanning electrodes (Row ₁ ~Row _4), which discharges the electric charge charged in the parasitic capacitance (C _1,1 ~C _4,4) It is characterized in that current limiting means (4, 4a to 4d, 5) is provided in a path through which current flows.

  Thus, by providing the current limiting means (4, 4a to 4d, 5) in the path through which the discharge current flows, it becomes possible to suppress the peak value of the surge current that is generated when shifting to the reset period. As a result, it is possible to prevent high-frequency noise from being generated due to the surge current.

In addition, current limiting means (4, 4a to 4d, 5) may be provided in a path for applying a predetermined voltage (Vrow) to the plurality of scan electrodes (Row _{1 to} Row ₄ ). Even in this case, the same effect as described above can be obtained.

In these cases, as a drive unit (1-3), with a scanning electrode selecting switch for switching the voltages applied to the plurality of scanning electrodes _{(Row 1 ~Row 4) (RS} 1 ~RS 4) scanning A configuration in which the electrode driving circuit (2) is provided and the current limiting means (4, 4a to 4d, 5) is provided in the scanning electrode driving circuit (2) can be adopted.

In this case, if the scan electrode selection switches (RS _{1 to} RS ₄ ) in the scan electrode drive circuit (2) are formed in the IC, a plurality of current limiting means (4, 4a to 4d, 5) are provided inside the IC. scan electrode (Row ₁ ~Row ₄₎ may be configured which are formed for each.

  As the current limiting means, for example, a current limiting resistor (4, 4a to 4d) or an inductor (5) can be applied.

Further, the present invention can also be applied to an organic EL display that performs display on an organic EL panel constituted by a plurality of organic EL elements (E _{1,1 to} E _4,4 ). In this case, each pixel (10) constituting the organic EL panel is configured by a plurality of subpixels (10a to 10c), and each of the plurality of subpixels (10a to 10c) includes a plurality of organic EL elements ( E _{1,1 to} E _4,4 ). With such a configuration, the plurality of subpixels (10a to 10c) selectively emit light so that the total area of the subpixels (10a to 10c) increases as the brightness around the organic EL panel increases. Then, it becomes possible to appropriately perform gradation and light control.

  In this case, if the plurality of sub-pixels (10a to 10c) are all configured with different areas, the total number of sub-pixels (10a to 10c) that emit light can be changed simply by changing which of the sub-pixels (10a to 10c) emits light. The area can be changed.

  Such an organic EL display is particularly preferably applied to a device in which the brightness of the surroundings is greatly changed, such as being mounted on a vehicle.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
FIG. 1 is a circuit diagram showing a schematic configuration of an organic EL drive circuit to which the first embodiment of the present invention is applied. Hereinafter, the organic EL drive circuit of the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the organic EL drive circuit includes a data electrode drive circuit 1, a scan electrode drive circuit 2 and a control circuit 3 corresponding to a drive unit, and a plurality of scan lines and a plurality of data extracted from these. A plurality of organic EL elements E _{1,1 to} E _4,4 in a matrix form are provided at each intersection of lines. The plurality of organic EL elements E _{1,1 to} E _4,4 are actually arranged in a matrix form for the number of pixels, but are shown here as a simplified 4 × 4 matrix.

The data electrode drive circuit 1 is for controlling the potential applied to the data electrodes Col _{1 to} Col ₄ . The data electrode driving circuit 1 includes a data electrode Col ₁ ~Col ₄ constant current source CC ₁ to CC ₄ provided for the respective data electrode selecting switch CS ₁ to CS ₄ is provided.

The constant current sources CC _{1 to} CC ₄ form a constant current based on the voltage applied from the predetermined power source 1a. The data electrode selection switches CS _{1 to} CS ₄ are movable contacts on the data electrodes Col _{1 to} Col ₄ side, a fixed contact connected to GND (0 V) and a fixed contact connected to the constant current sources CC _{1 to} CC _4. A movable contact can be brought into contact with either one of these.

The scan electrode drive circuit 2 is for controlling the potential applied to the scan electrodes Row _{1 to} Row ₄ . The scan electrode drive circuit 2 is provided with a current limiting resistor 4 corresponding to current limiting means in addition to the data electrode selection switches CS _{1 to} CS ₄ .

Scanning electrode selecting switch RS ₁ to RS _4, each scan electrode Row ₁ ~Row ₄ side is a movable contact, applying a fixed contact and a predetermined voltage Vrow connected to GND (0V) via a current limiting resistor 4 The movable contact can be brought into contact with either one of the fixed contacts connected to the predetermined power source 2a.

The control circuit 3 is for driving on and off of the scanning electrode selecting switch RS ₁ to RS ₄ in the data electrode selecting switch CS ₁ to CS ₄ and the scanning electrode driving circuit 2 in the data electrode driving circuit 1. Specifically, on / off of the data electrode selection switches CS _{1 to} CS ₄ and the scan electrode selection switches RS _{1 to} RS ₄ is controlled so that the pixels selected as the light emitting pixels emit light and other pixels do not emit light. .

Next, a method for driving the organic EL elements E _{1,1 to} E _4,4 by the organic EL driving circuit of the present embodiment will be described with reference to FIGS.

2 to 5, first, the scan electrode Row ₁ is scanned to light up the organic EL elements E _1,1 and E _1,2, and then, after a reset period, the next scan is performed, and the scan electrode Row _{2 is} scanned. Is shown, and the organic EL elements E _2,3 and E _2,4 are illuminated to perform a light emission operation. FIG. 6 is a timing chart showing voltage waveforms of the scan electrodes Row ₁ and Row ₂ , the data electrodes Col ₁ and Col _2, and the data electrodes Col ₃ and Col ₄ in this case, and FIGS. This corresponds to the state of each part in the organic EL drive circuit at the timings (1) to (4).

[Timing (1): Pre-reset state (light emitting pixel selection period)]
In the pre-reset state shown in FIG. 2, the scan selection switch RS ₁ is turned on (selected) and fixed at the ground potential (0 V). The other scan electrode selection switches RS _{2 to} RS ₄ are turned off (not selected), and the reverse bias voltage Vrow is applied.

Further, the data selection switches CS ₁ and CS ₂ are turned on (light emission), and a forward bias is applied from the constant current control circuits CC ₁ and CC ₂ . The other data selection switches CS ₃ and CS ₄ are turned off (non-emission) and fixed to the ground potential (0 V).

Thereby, currents i _1,1 and i _1,2 flow through the organic EL elements E _1,1 and E _1,2 selected as the light emitting pixels, and these emit light.

At this time, the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₁ ) and the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₁ and CS ₂ ). For the parasitic capacitances C _1,1 , C _{1,2 of} the pixels existing in the voltage drop from the potential difference Vcol ′ (= Vcol to the constant current sources CC _{1 to} CC ₄ , and the data side and the scanning side, respectively. Is charged by subtracting the voltage drop due to the wiring resistance.

Further, among the scan electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₂ to RS ₄ ) and those that are not selected among the data selection switches CS _{1 to} CS ₄ (CS ₃ , CS ₄ ) ₄ ) The parasitic capacitances C _2,3 , C _2,4 , C _3,3 , C _3,4 , C _4,3 , C _{4,4 of} the pixels present at the intersections of the pixels are charged with the potential difference Vrow. Yes.

And among the scanning electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₂ to RS ₄ ) and among the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₁ , CS _2). ) With respect to the parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , and C _{4,2 of} the pixels existing at the intersections of ()). Is charged.

At this time, since (Vrow−Vcol ′) is about several V, parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 The charge of the pixel is very small compared to the charge of the pixel charged with the potential difference Vcol ′ including the parasitic capacitance C _2,3 and the potential difference row.

Note that the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₁ ) and the data selection switches CS _{1 to} CS ₄ that are not emitting light (CS ₃ and CS ₄ ). Since the potential difference is substantially 0 V with respect to the parasitic capacitances C _1,3 and C _{1,4 of} the pixels existing in FIG.

[Timing (2): Start reset]
In the reset start state shown in FIG. 3, the scan selection switch RS ₁ remains fixed and is fixed at the ground potential (0 V). The other scan electrode selection switches RS _{2 to} RS ₄ are all turned off and are fixed to the ground potential (0 V). In the data selection switch, CS ₁ and CS ₂ are turned off (non-light emitting), and are fixed to the ground potential (0 V). Other data selection switches are fixed to the ground potential (0 V) while being off (non-light emitting).

At this time, the forward-biased charges accumulated in the parasitic capacitances C _1,1 and C _1,2 are scanned along the path from the scan electrode Row ₁ to the data electrodes Col ₁ and Col ₂ via the current limiting resistor 4. It escapes from the electrode drive circuit 2 side to the data electrode drive circuit 1 side (see broken line). The reverse bias charges accumulated in the parasitic capacitances C _2,1 , C _2,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 are obtained from the data electrodes Col ₁ , Col _2. A path that passes through the scan electrodes Row _{2 to} Row ₄ and the current limiting resistor 4 passes from the data electrode drive circuit 1 side to the scan electrode drive circuit 2 side (see the alternate long and short dash line). Further, the reverse bias charges accumulated in the parasitic capacitances C _2,3 , C _2,4 , C _3,3 , C _3,4 , C _4,3 , C _4,4 are stored in the data electrodes Col ₃ , Col. ₄ passes through the scan electrodes Row ₂ to Row ₄ and the current limiting resistor 4 from the data electrode drive circuit 1 side to the scan electrode drive circuit 2 side (see the two-dot chain line).

As described above, all the currents flowing through the scan electrodes Row _{1 to} Row ₄ flow through the current limiting resistor 4. For this reason, it is possible to prevent a large charging current from flowing from each of the parasitic capacitances C _{1,1 to} C _4,4 .

[Timing (3): Reset period]
During the reset period shown in FIG. 4, since all the scan electrodes Row _{1 to} Row ₄ and the data electrodes Col _{1 to} Col ₄ are fixed to the ground potential (0 V), no charge movement occurs anywhere.

[Timing (4): Reset release]
In the reset release state shown in FIG. 5, the scan selection switch RS ₂ remains fixed and is fixed at the ground potential (0 V). The other scan electrode selection switches RS ₁ , RS ₃ , and RS ₄ are all turned off, and application of the reverse bias voltage Vrow is started. The data selection switches CS ₁ and CS ₂ are fixed to the ground potential (0 V) while being off (non-light emitting). The data selection switches CS ₃ and CS ₄ that switch to light emission are switched from OFF (non-light emission) to ON, and forward bias application starts from the constant current control circuits CC ₃ and CC ₄ .

Accordingly, currents i _2,3 and i _2,4 flow through the organic EL elements E _2,3 and E _2,4 selected as the light emitting pixels, and these emit light.

At this time, the intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₂ ) and the data selection switches CS _{1 to} CS ₄ that are emitting light (CS ₃ and CS ₄ ). The parasitic capacitances C _2,3 and C _{2,4 of} the pixels existing in the pixel are forward-biased by the potential difference Vcol ′ through the path from the data electrodes Col ₃ and Col ₄ to the scan electrode Row ₂ and the current limiting resistor 4. Go to charge (see dashed line).

Scan electrode selection switches RS _{1 to} RS ₄ that are not selected (RS ₁ , RS ₃ , RS ₄ ) and data selection switches CS _{1 to} CS ₄ that are light emitting (CS ₃ , CS ₄ ) ₄ ) For the parasitic capacitances C _1,3 , C _1,4 , C _3,3 , C _3,4 , C _4,3 , C _{4,4 of} the pixels present at the intersection of the scanning electrodes Row ₁ , The reverse bias charges are charged through the path from Row ₃ and Row ₄ through the data electrodes Col ₃ and Col ₄ (see the alternate long and short dash line). Thus, finally the parasitic capacitance _{C 1,3, C 1,4, C 3,3} , C 3,4, C 4,3, C 4,4 is charged with a potential difference (Vrow-Vcol ').

Further, among the scanning electrode selection switches RS _{1 to} RS ₄ , those that are not selected (RS ₁ , RS ₃ , RS ₄ ) and those that are not selected among the data selection switches CS _{1 to} CS ₄ (CS ₁ , CS ₂ ) for the parasitic capacitances C _1,1 , C _1,2 , C _3,1 , C _3,2 , C _4,1 , C _4,2 In the path from the scan electrodes Row ₁ , Row ₃ , and Row ₄ to the data electrodes Col ₁ and Col ₂ , the charge of reverse bias is charged with the potential difference Vrow (see the two-dot chain line).

The intersection of the scan electrode selection switches RS _{1 to} RS ₄ that are selected (RS ₂ ) and the data selection switches CS _{1 to} CS ₄ that are not emitting light (CS ₁ and CS ₂ ). Since the potential difference is substantially 0 V with respect to the parasitic capacitances C _2,1 and C _{2,2 of} the pixels existing in the pixel, no charge is charged.

As described above, the organic EL element is driven. Figure 7 is a timing chart showing the relationship between the current flowing in scan electrodes Row ₁ ~Row ₄ and data electrodes Col ₁ ~Col potential scan electrode Row ₁ ~Row ₄ of ₄ in the series of timing.

As shown in this figure, in the reset start state (timing (2) in FIG. 6) and reset release state (timing (4) in FIG. 6), a surge occurs in the path through each of the scan electrodes Row _{1 to} Row _4. Current will flow.

However, as described above, since the current limiting resistor 4 is provided between each of the scan electrodes Row _{1 to} Row ₄ and GND, the surge current is suppressed by the current limiting resistor 4 and the peak value of the surge current is suppressed. It is done. Specifically, in the case of the present embodiment, the surge current flowing through all the scan electrodes Row _{1 to} Row ₄ can be limited when the reset start state is set, and the scan electrode selection switch RS _{1 is set} when the reset is released. The surge current that flows through the scan electrodes Row _{1 to} Row ₄ can be limited although it is kept off among the RS ₄ .

  As a result, it is possible to prevent high-frequency noise from being generated due to the surge current. And when an organic electroluminescent element is used as a vehicle-mounted display, it can prevent that the radiation noise to a car radio etc. becomes a problem.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 8 is a diagram showing only the scan electrode drive circuit 2 in the organic EL drive circuit of the present embodiment. In the present embodiment, the form of the current limiting resistor 4 in the first embodiment is changed. Since other configurations are the same as those in the first embodiment, only different portions from the first embodiment will be described.

As shown in FIG. 8, in this embodiment, current limiting resistors 4a to 4d are provided for each line to which the scan electrodes Row _{1 to} Row ₄ are connected. That is, the scan electrode selection switches RS _{1 to} RS _{4 and the} like in the scan electrode drive circuit 2 are constituted by ICs, but the current limiting resistors 4a to 4d are provided inside the ICs.

Thus, it is also possible to provide the current limiting resistors 4a to 4d for each line to which the scan electrodes Row _{1 to} Row ₄ are connected.

(Third embodiment)
A second embodiment of the present invention will be described. FIG. 9 is a diagram showing only the scan electrode drive circuit 2 in the organic EL drive circuit of the present embodiment. In the present embodiment, the place where the current limiting resistor 4 in the first embodiment is provided is changed. Since other configurations are the same as those in the first embodiment, only different portions from the first embodiment will be described.

As shown in FIG. 9, in the present embodiment, in the path from the predetermined power source 2a of the scan electrode drive circuit 2 to each of the scan electrode selection switches RS _{1 to} RS ₄ , that is, the voltage supply line to which the voltage Vrow is supplied. The current limiting resistor 4 is provided.

As described above, when the current limiting resistor 4 is provided in the path from the predetermined power source 2a to each of the scan electrode selection switches RS _{1 to} RS ₄ , each of the scan electrode selection switches RS _{1 to} RS ₄ is turned on (selected). It becomes possible to suppress the peak value of the surge current that occurs when the switch is turned off (non-selected) and when the switch is kept off.

Therefore, as in the present embodiment, even when the current limiting resistor 4 is provided in the path from the predetermined power supply 2a to each of the scan electrode selection switches RS _{1 to} RS ₄ , the same effect as that of the first embodiment can be obtained. Obtainable.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. FIG. 10 is a diagram showing only the scan electrode drive circuit 2 in the organic EL drive circuit of the present embodiment. In the present embodiment, the form of the current limiting resistor 4 in the third embodiment is changed. Since other configurations are the same as those of the third embodiment, only different portions from the third embodiment will be described.

As shown in FIG. 10, in this embodiment, current limiting resistors _{4 a} to ₄ d are provided for each power supply line to which the scan electrodes Row _{1 to} Row ₄ are connected. That is, the scan electrode selection switches RS _{1 to} RS _{4 and the} like in the scan electrode drive circuit 2 are constituted by ICs, but the current limiting resistors 4a to 4d are provided inside the ICs.

Thus, it is also possible to provide the current limiting resistors 4a to 4d for each power supply line to which the scan electrodes Row _{1 to} Row ₄ are connected.

(Fifth embodiment)
A fifth embodiment of the present invention will be described. This embodiment shows a preferable form as an organic EL display to which the organic EL drive circuit shown in the first to fourth embodiments is applied.

  In a simple matrix organic EL display, when a pulse application period (pulse width) applied to a scanning line or a data line is increased or decreased, and a current driving element (such as an organic EL or a light emitting diode) is driven. In general, gradation and dimming are established by increasing or decreasing the current flowing through the light emitting element.

  Further, as a general simple matrix display gradation and dimming method, there are some which perform pulse width control (PWM control) and current control.

  However, in these methods, the load on the driver IC varies depending on the number of light emitting pixels shining per scanning line, the area, and the size of the screen, the variation of the light emitting elements, and the variation of the driving transistors inside the driver IC. There is a limit to dimming and dimming. In particular, when the current limiting resistors 4, 4 a to 4 d are provided as in the above embodiments, it takes time to rise and fall of the pulse. For example, even if it is attempted to narrow the pulse width in pulse width control, the rise of the pulse In addition, it is necessary to allow for a fall time, and gradation and dimming cannot be performed appropriately.

  In addition, the indicator used by the driver in a special environment where it is exposed to ambient light during the daytime and darkened at night or inside a tunnel, such as when mounted on a vehicle. In order to achieve optimal performance, it is necessary to greatly change the brightness of day and night. In that case, simply performing pulse width control or current control deteriorates the display quality such as lack of linearity in gradation and dimming performance. Let

  Therefore, in this embodiment, an organic EL display suitable for the organic EL drive circuit shown in the first to fourth embodiments will be described.

  FIG. 11 illustrates several pixels (here, four pixels) of an organic EL panel in a monochromatic organic EL display mounted on a vehicle, and FIG. (B) shows a display form at night, and indicates that the hatched portion in the figure emits light.

As shown in FIG. 11, each pixel 10 is composed of an aggregate of sub-pixels 10a and 10b having two different areas. The sub-pixels 10a, one of 10b one but corresponds to each one of the organic EL element E _{1, 1} to E _{4, 4} shown in the first to fourth embodiments described above, the sub-pixels 10a, 10b Each of these is configured to emit light independently.

  When such an organic EL display is used, each pixel can obtain different luminance depending on whether only one of the sub-pixels 10a and 10b emits light or both of the sub-pixels 10a and 10b. It is possible to perform gradation and dimming depending on which of 10b emits light.

  In particular, if the organic EL display is mounted on a vehicle, the brightness of the surroundings changes greatly between day and night. However, the subpixels 10a and 10b can be made to emit light as in this embodiment. Tone and dimming can be easily done by simply changing.

  Therefore, the organic EL display according to the present embodiment can appropriately perform gradation and dimming, and can prevent display quality from deteriorating.

  In driving the organic EL display as in the present embodiment, information on the brightness around the organic EL display is input to the control circuit 3 so that the light emission pixel selection by the control circuit 3 is selected. Can be performed according to the brightness of the surrounding area. For example, if an on / off signal of a vehicle headlamp switch is input to the control circuit 3 as information relating to the brightness around the organic EL display, it is possible to perform display according to day and night by the organic EL display.

(Sixth embodiment)
A sixth embodiment of the present invention will be described. FIG. 12 illustrates several pixels (here, four pixels) of the organic EL panel in the monochromatic organic EL display of the present embodiment, and FIG. b) shows a display form at night, and indicates that the hatched portion in the figure emits light.

  In the present embodiment, the number of subpixels is changed with respect to the fifth embodiment. Since other configurations are the same as those of the fifth embodiment, only different portions from the fifth embodiment will be described.

As shown in FIG. 12, each pixel is composed of a collection of sub-pixels 10a, 10b, and 10c having three large, medium, and small areas. Those subpixel 10a, 10b, one of the 10c one is corresponding to each one of the organic EL element E _{1, 1} to E _{4, 4} shown in the first to fourth embodiments described above, the sub-pixels 10a Each of 10b, 10c is configured to emit light independently.

  If such an organic EL display is used, each pixel can obtain different luminance depending on whether only one of the sub-pixels 10a, 10b, or 10c emits light or when all the pixels emit light. Depending on which of the pixels 10a, 10b, and 10c emits light, gradation and dimming can be performed. Thus, even if the number of subpixels 10a, 10b, and 10c is increased, the same effect as in the fifth embodiment can be obtained.

(Seventh embodiment)
A seventh embodiment of the present invention will be described. FIG. 13 is a diagram showing a schematic configuration of the organic EL drive circuit of the present embodiment. In this embodiment, in addition to the line connected to GND via the current limiting resistor 4, another line connected to GND without passing through the current limiting resistor 4 is different from the first embodiment. It is added. Since other configurations are the same as those in the first embodiment, only different portions from the first embodiment will be described.

As shown in FIG. 13, in this embodiment, each of the scan electrode selection switches RS _{1 to} RS ₄ is a three-point contact switch, and one of the fixed contacts is connected to GND without passing through the current limiting resistor 4. Connected to the line.

As described above, the peak value of the surge current can be suppressed by providing the current limiting resistor 4, but it takes time to rise and fall of the pulse by providing the current limiting resistor 4. Become. For this reason, when it is desired to shorten the pulse rise and fall times, the scan electrodes Row _{1 to} Row ₄ may be directly connected to the GND by the scan electrode selection switches RS _{1 to} RS ₄ . .

(Other embodiments)
In the first to fourth embodiments, the current limiting resistors 4 and 4a to 4d have been described as examples of current limiting means. However, other current limiting means may be applied. For example, the current limiting resistors 4 and 4a to 4d shown in the first to fourth embodiments may be replaced with an inductor 5 as shown in FIGS.

  Moreover, although the display example in the organic EL panel in an organic EL display was shown in the said 5th, 6th embodiment, it does not restrict to these. Specifically, the total area of the sub-pixels 10a, 10b, and 10c that emit light during the daytime and at night may be changed so that the total area is larger in the daytime than in the nighttime.

  For example, FIGS. 15A and 15B show a daytime display mode and a nighttime display mode in the case of the organic EL panel shown in the fifth embodiment, respectively. As shown in this figure, only the sub-pixel 10a having a large area can emit light during the daytime, and only the sub-pixel 10b having a small area can emit light at night.

  Of course, the number of subpixels shown in these embodiments is merely an example, and each pixel can be composed of three or more subpixels. Moreover, although the monochromatic organic electroluminescence display was mentioned as an example in the said embodiment, this invention is applicable also to a color organic electroluminescence display. However, in the case of a color organic EL display, the number of subpixels is very large, and the circuit configuration of the organic EL drive circuit becomes complicated. For this reason, it is preferable to use a single color.

1 is a circuit diagram illustrating a schematic configuration of an organic EL drive circuit according to a first embodiment of the present invention. It is the figure which showed the operation | movement of the state before reset of the organic electroluminescent drive circuit shown in FIG. It is the figure which showed the operation | movement of the reset start state of the organic electroluminescent drive circuit shown in FIG. It is the figure which showed the operating state in the reset period of the organic electroluminescent drive circuit shown in FIG. It is the figure which showed the operation state of the reset cancellation | release state of the organic EL drive circuit shown in FIG. 6 is a timing chart showing voltage waveforms of scan electrodes Row ₁ and Row ₂ , data electrodes Col ₁ and Col _2, and data electrodes Col ₃ and Col ₄ when the operations of FIGS. 2 to 5 are performed. Is a timing chart showing the relationship between the current flowing from before reset state to a set of scan electrodes Row ₁ in the timing ～Row ₄ and data electrodes Col ₁ potential of ～Col ₄ and the scanning electrodes Row ₁ ~Row ₄ leading to the reset release state . It is the figure which showed only the scanning electrode drive circuit 2 in the organic electroluminescent drive circuit of 2nd Embodiment of this invention. It is the figure which showed only the scanning electrode drive circuit 2 in the organic electroluminescent drive circuit of 3rd Embodiment of this invention. It is the figure which showed only the scanning electrode drive circuit 2 in the organic electroluminescent drive circuit of 4th Embodiment of this invention. It is an enlarged view for several pixels of the organic EL panel in the monochrome organic EL display shown in the fifth embodiment of the present invention. It is an enlarged view for several pixels of the organic EL panel in the monochrome organic EL display shown in the sixth embodiment of the present invention. It is the figure which showed schematic structure of the organic electroluminescent drive circuit of 7th Embodiment of this invention. It is the figure which showed schematic structure of the organic electroluminescent drive circuit shown in other embodiment. It is an enlarged view for several pixels of the organic EL panel in the monochrome organic EL display shown in the fifth embodiment of the present invention. It is the figure which showed the operation | movement of the state before reset of the conventional organic EL drive circuit. It is the figure which showed the operation | movement of the reset start state of the conventional organic EL drive circuit. It is the figure which showed the operating state in the reset period of the conventional organic EL drive circuit. It is the figure which showed the operation state of the reset cancellation | release state of the conventional organic EL drive circuit. FIG. 20 is a timing chart showing voltage waveforms of scan electrodes Row ₁ and Row ₂ , data electrodes Col ₁ and Col _2, and data electrodes Col ₃ and Col ₄ when the operations of FIGS. 16 to 19 are performed. Is a timing chart showing the relationship between the current flowing from before reset state to a set of scan electrodes Row ₁ in the timing ～Row ₄ and data electrodes Col ₁ potential of ～Col ₄ and the scanning electrodes Row ₁ ~Row ₄ leading to the reset release state .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Data electrode drive circuit, 1a ... Power supply, 2 ... Scan electrode drive circuit, 2a ... Power supply,
3 ... Control circuit, 4, 4a to 4d ... Current limiting resistor, 5 ... Inductor,
E _{1,1 to} E _4,4 ... Organic EL element, C _{1,1 to} C _4,4 ... Parasitic capacitance, CC _{1 to} CC ₄ ... Constant current source,
CS _{1 to} CS ₄ ... data electrode selection switch, Col _{1 to} Col ₄ ... data electrode,
RS _{1 to} RS ₄ ... Scan electrode selection switch, Row _{1 to} Row ₄ .

Claims (10)

A matrix is formed at each intersection of a plurality of scanning lines connected to each of the plurality of scanning electrodes (Row _{1 to} Row ₄ ) and a plurality of data lines connected to each of the plurality of data electrodes (Col _{1 to} Col ₄ ). A plurality of organic EL elements (E _{1,1 to} E _4,4 ) arranged in
By controlling the voltage applied to the plurality of scan electrodes (Row _{1 to} Row ₄ ) and the plurality of data electrodes (Col ₁ to Col ₄ ), the plurality of scan lines and the plurality of data lines are passed through. Then, a driving voltage is applied to a selected one of the plurality of organic EL elements (E _{1,1 to} E _4,4 ), and the organic EL element (E _1,1 to which the driving voltage is applied) is applied. , E _4,4 ), and driving units (1 to 3) for emitting light,
The driving unit (1-3), during the scan period to emit light selected ones of the plurality of organic EL elements (E _{1, 1} to E _{4, 4)} and the subsequent scanning period, the There is a reset period for discharging charges charged in the parasitic capacitances (C _{1,1 to} C _4,4 ) formed in the plurality of organic EL elements (E _{1,1 to} E _4,4 ) during the scanning period. A simple matrix organic EL drive circuit,
During the reset period, the plurality of through scan electrode (Row ₁ ~Row _4), the parasitic capacitance (C _1,1 ~C _4,4) current limiting means in the path of the current flowing to discharge the charge stored in the (4, 4a-4d, 5) is provided, The organic EL drive circuit characterized by the above-mentioned. A matrix is formed at each intersection of a plurality of scanning lines connected to each of the plurality of scanning electrodes (Row _{1 to} Row ₄ ) and a plurality of data lines connected to each of the plurality of data electrodes (Col _{1 to} Col ₄ ). A plurality of organic EL elements (E _{1,1 to} E _4,4 ) arranged in
By controlling the voltage applied to the plurality of scan electrodes (Row _{1 to} Row ₄ ) and the plurality of data electrodes (Col ₁ to Col ₄ ), the plurality of scan lines and the plurality of data lines are passed through. Then, a driving voltage is applied to a selected one of the plurality of organic EL elements (E _{1,1 to} E _4,4 ), and the organic EL element (E _1,1 to which the driving voltage is applied) is applied. , E _4,4 ), and driving units (1 to 3) for emitting light,
The driving unit (1-3), during the scan period to emit light selected ones of the plurality of organic EL elements (E _{1, 1} to E _{4, 4)} and the subsequent scanning period, the There is a reset period for discharging charges charged in the parasitic capacitances (C _{1,1 to} C _4,4 ) formed in the plurality of organic EL elements (E _{1,1 to} E _4,4 ) during the scanning period. A simple matrix organic EL drive circuit,
Wherein a plurality of scanning electrodes (Row ₁ ~Row _4), in the path of the charging current for applying a predetermined voltage (Vrow) to the parasitic capacitance (C _{1, 1} -C _{4, 4),} the current limiting means (4, 4a to 4d and 5) are provided. The driving unit (1-3), said plurality of scanning electrodes (Row ₁ ~Row ₄₎ scan electrode driving circuit provided with a scan electrode selection switch for switching the voltage applied (RS ₁ to RS ₄₎ against The organic EL according to claim 1 or 2, wherein the current limiting means (4, 4a to 4d, 5) is provided in the scan electrode driving circuit (2). Driving circuit. The scan electrode selection switches (RS _{1 to} RS ₄ ) in the scan electrode drive circuit (2) are formed in an IC, and the current limiting means (4, 4a to 4d, 5) are provided in the IC. _4. The organic EL driving circuit according to claim 3, wherein the organic EL driving circuit is formed for each of the scanning electrodes (Row _{1 to} Row ₄ ). 5. The organic EL driving circuit according to claim 1, wherein the current limiting means is a current limiting resistor (4, 4a to 4d). 5. The organic EL drive circuit according to claim 1, wherein the current limiting means is an inductor (5). An organic EL driving circuit according to any one of claims 1 to 6 is provided, and display is performed on an organic EL panel composed of the plurality of organic EL elements (E _{1,1 to} E _4,4 ). An organic EL display,
Each pixel (10) that constitutes the organic EL panel includes a plurality of subpixels (10a to 10c), and each of the plurality of subpixels (10a to 10c) includes the plurality of organic pixels. It is composed of each EL element (E _{1,1 to} E _4,4 ),
The plurality of subpixels (10a to 10c) are configured to selectively emit light such that the total area of the subpixels (10a to 10c) increases as the brightness of the periphery of the organic EL panel increases. An organic EL display device characterized by that. The organic EL display according to claim 7, wherein the plurality of sub-pixels (10a to 10c) are all configured with different areas. The organic EL display according to claim 7 or 8, wherein the organic EL display is mounted on a vehicle. An organic EL panel having a plurality of pixels (10) is provided,
Each pixel (10) constituting the organic EL panel is composed of a plurality of subpixels (10a to 10c), and each of the plurality of subpixels (10a to 10c) is an organic EL element (E). _{1,1 to} E _4,4 ), the organic EL display driving method,
The plurality of sub-pixels (10a to 10c) are selectively caused to emit light so that the total area of the sub-pixels (10a to 10c) increases as the brightness of the periphery of the organic EL panel increases. Driving method of organic EL display.

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