JP6565553B2 - Drive device for organic EL panel - Google Patents

Description

  The present invention relates to a drive device for an organic EL panel for driving a dot matrix type and passive drive type organic EL panel.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1, an organic EL (Electroluminescence) panel that is a dot matrix type and driven by a passive driving method is known. This type of organic EL panel is made of a conductive transparent film such as ITO (Indium Tin Oxide) on a support substrate, a plurality of anode lines (hereinafter referred to as drive lines) formed in stripes, and the drive lines. A plurality of cathode lines (hereinafter referred to as scanning lines) composed of an organic layer including an organic light emitting layer formed on the back surface of the substrate and a metal vapor deposition film such as aluminum formed on the back surface of the organic layer so as to be orthogonal to the drive line. And). In the organic EL panel, drive lines, scanning lines, and pixels (organic EL elements) configured by an organic layer located at the intersection of both lines are arranged in a matrix.

  For example, as illustrated in FIG. 7, the organic EL panel 100 includes a plurality of pixels E <b> 11 to Emn that are configured by organic EL elements. The driving device 110 that drives the organic EL panel 100 includes a cathode driving circuit 112, an anode driving circuit 113, and a display controller 114.

  The pixels E11 to Emn are provided at intersections between a plurality of scanning lines S1 to Sm provided in the horizontal direction and a plurality of drive lines D1 to Dn provided to be orthogonal to the scanning lines S1 to Sm. The pixels E11 to Emn are represented by an equivalent circuit including a diode component and a parasitic capacitance (capacitor) component arranged in parallel.

  The cathode driving circuit 112 includes a plurality of scanning switches 121 to 12m corresponding to the scanning lines S1 to Sm. The scanning switches 121 to 12m selectively connect the scanning lines S1 to Sm to the scanning voltage Vs or the ground voltage (0V) based on a control signal from the display controller 114. The display controller 114 applies the ground voltage to the scan lines S1 to Sm to be scanned by switching the scan switches 121 to 12m, and applies the scan voltage Vs to the scan lines S1 to Sm that are not to be scanned. The anode drive circuit 113 can switch whether to supply a drive current to each of the drive lines D1 to Dn based on a control signal from the display controller 114.

  The display controller 114 sequentially turns on the scan switches 121 to 12m to sequentially scan the scan lines S1 to Sm, and supplies a drive current to the drive lines D1 to Dn through the anode drive circuit 113, based on the image data. Characters, figures, etc. are displayed on the organic EL panel 100.

  Here, the pixels E11 to Emn made of organic EL elements have a predetermined capacitor component. For this reason, the pixels E11 to Emn can be turned on after the predetermined capacitor component is charged by the current from the drive lines D1 to Dn. Therefore, there is a problem that the lighting of the pixels E11 to Emn is delayed for the charging time.

  In order to solve this problem, for example, as described in Patent Document 2, a precharge driving method is known in which a predetermined precharge voltage is applied in advance to the pixels E11 to Emn to emit light to reduce the time required for charging. It has been.

JP 2007-57856 A Japanese Patent Laid-Open No. 11-45071

  However, in the precharge driving method described in Patent Document 2, the luminance of the pixels E11 to Emn varies depending on the lighting rate of the pixels E11 to Emn in the horizontal direction (the direction along the scanning lines S1 to Sm). There is.

  Specifically, as shown in FIG. 8A, the driving device 110 charges a predetermined precharge voltage Vp in the precharge period T1, and then, in the constant current supply period T2, the predetermined pixels E11 to E11 are charged. A constant current is supplied to Emn. The precharge voltage Vp is set to be equal to the voltage in the constant current supply period T2 when the lighting rate in the horizontal direction is 100%. Therefore, as shown in FIG. 8A, when the lighting rate in the horizontal direction is 100%, the pixels E11 to Emn are quickly turned on with desired luminance.

  On the other hand, for example, even when the lighting rate in the horizontal direction is 50%, the driving device 110 charges a constant precharge voltage Vp in the precharge period T1, as indicated by the solid line in FIG. To do. In this case, the precharge voltage Vp is ideally equal to the voltage in the constant current supply period T2, as indicated by the alternate long and short dash line in FIG. However, in practice, as shown by the solid line in FIG. 8B, the precharge voltage Vp is larger than the voltage in the constant current supply period T2, so that the luminance of each of the pixels E11 to Emn is higher than the desired luminance. .

  As described above, since the luminance of the pixels E11 to Emn increases as the lighting rate of the pixels E11 to Emn in the horizontal direction decreases, the luminance of the pixels E11 to Emn varies depending on the lighting rate of the pixels E11 to Emn. There's a problem.

  The present invention has been made in view of this problem, and an object of the present invention is to provide a drive device for an organic EL panel that reduces variations in pixel luminance due to a change in the lighting rate of the pixel in a direction along the drive line. .

In order to achieve the above object, an organic EL panel drive device according to the present invention includes a plurality of scan lines and a plurality of drive lines that intersect each other, and a plurality of scan lines and a plurality of drive lines that are arranged at the intersections of the drive lines. A constant current is supplied to the drive line corresponding to the organic EL element to be lit in the scanning of each scanning line, as well as being used in a passive matrix organic EL panel having an organic EL element. Before applying, a reference voltage from a reference voltage source is applied to the drive line, and then a precharge voltage from a precharge voltage source is applied to the drive line to which the reference voltage is applied a is, each scan line is a cathode line, and each drive line anode lines der A reference voltage varying unit capable of changing the reference voltage applied to the respective drive lines, based on the image data to be displayed on the organic EL panel and then arranged along the scanning lines for scanning The number of the organic EL elements to be turned on among the organic EL elements is acquired, and the reference voltage applied to each drive line is set lower through the reference voltage variable unit as the acquired number decreases. A control unit.

  According to the present invention, it is possible to reduce variations in pixel luminance due to a change in pixel lighting rate in the direction along the drive line.

1 is a circuit diagram illustrating an organic EL panel and an organic EL panel drive device according to an embodiment of the present invention. (A) which concerns on one Embodiment of this invention is the graph which showed the change of the anode voltage, (b) is the graph which showed the change of the scanning voltage. It is the flowchart which showed the control procedure of the display controller which concerns on one Embodiment of this invention. (A) which concerns on one Embodiment of this invention is a graph which showed the change of the anode voltage and scanning voltage when a horizontal lighting rate is high, (b) is the anode voltage when a horizontal lighting rate is low. 6 is a graph showing changes in scanning voltage. It is the graph which showed the change of the anode voltage and scanning voltage concerning the comparative example whose precharge voltage is variable. It is the graph which showed the change of the anode voltage which concerns on one Embodiment of this invention. It is the circuit diagram which showed the organic EL panel which concerns on background art, and the drive apparatus for organic EL panels. (A) which concerns on background art is a graph which showed the change of the anode voltage when the horizontal lighting rate is high, (b) is the graph which showed the change of the anode voltage when the horizontal lighting rate is low. is there.

  An embodiment of a drive device for an organic EL panel according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the organic EL panel 10 is configured in the same manner as the organic EL panel 100 in the background art, and is driven by a dot matrix type and a passive drive system. The organic EL panel 10 includes pixels E11 to Emn made of organic EL elements arranged in a matrix. The pixels (organic EL elements) E11 to Emn are a plurality of scanning lines S1 to Sm that extend in the horizontal direction and are arranged in the vertical direction, and a plurality of pixels that are orthogonal to the scanning lines S1 to Sm and arranged in the horizontal direction. It is provided at the intersection with the drive lines D1 to Dn.

  As shown in FIG. 1, the organic EL panel drive device 50 includes a cathode drive circuit 20, an anode drive circuit 30, and a display controller 40 that is an example of a control unit. In addition, in FIG. 1, although each part of the organic EL panel drive device 50 is shown separately, a control driver IC (Integrated Circuit) integrally including each part may be used.

  The cathode driving circuit 20 includes a plurality of scanning switches 21 to 2m corresponding to the scanning lines S1 to Sm. The scan switches 21 to 2m selectively connect the scan lines S1 to Sm to the scan voltage source Vc or the ground. That is, through the switching of the scanning switches 21 to 2m, the scanning lines S1 to Sm to be scanned are connected to the ground, and the scanning lines S1 to Sm that are not scanned are connected to the scanning voltage source Vc. The pixels E11 to Emn are connected to the scanning voltage source Vc through the scanning lines S1 to Sm, so that the negative voltage −Vs from the scanning voltage source Vc is applied to the pixels E11 to Emn. Note that the negative voltage indicates a state in which the anode voltage Vd of the drive lines D1 to Dn is lower than the scanning voltage Vs of the scanning lines S1 to Sm.

  The anode drive circuit 30 includes a constant current source A, a precharge voltage source V1 that can apply a precharge voltage Vp to each drive line D1 to Dn, and a reference voltage that can apply a reference voltage Vb to each drive line D1 to Dn. Voltage source V2, reference voltage variable unit 60 for changing reference voltage Vb, and drive lines D1 to Dn are selectively selected from constant current source A, precharge voltage source V1, and reference voltage voltage source V2. Drive switches 31 to 3n to be connected.

  The constant current source A is provided for each of the drive lines D1 to Dn. Each constant current source A is electrically connected to the first contact P1. The precharge voltage source V1 is electrically connected to a second contact P2 provided for each of the drive lines D1 to Dn. The reference voltage source V2 is electrically connected to one electric line L1. Further, a third contact P3 provided for each of the drive lines D1 to Dn and the reference voltage variable unit 60 are electrically connected to the electric line L1. The drive switches 31 to 3n select any one of the first to third contacts P1 to P3 and are electrically connected to any one of the selected first to third contacts P1 to P3. For example, when the drive switches 31 to 3n are connected to the third contact P3, the reference voltage Vb is applied to the electric line L1 and the drive lines D1 to Dn from the reference voltage voltage source V2. The reference voltage Vb can be changed by the reference voltage variable unit 60.

  The reference voltage variable unit 60 includes a plurality of Zener diodes Zd1 to Zdn, a ground connection line L2, and a reference voltage variable switch 61.

The plurality of Zener diodes Zd1 to Zdn have different Zener voltages (breakdown voltages) Vz. For example, the Zener voltage Vz of the Zener diode Zd1 is set to 2V, and the Zener voltage Vz of the Zener diode Zd2 is set to 1.2V. The anode side of each Zener diode Zd1 to Zdn is connected to the ground. The cathode side terminals of the Zener diodes Zd1 to Zdn are configured to be connectable to the reference voltage variable switch 61.
The ground connection line L2 has one end connected to the ground and the other end connected to the terminal P4.
The reference voltage variable switch 61 is electrically connected to the electric line L1 and electrically connected to any one of the terminals connected to the Zener diodes Zd1 to Zdn and the terminal P4 of the ground connection line L2 without the Zener diode. Connected.

  Each Zener diode Zd1 to Zdn is connected to the reference voltage variable switch 61, thereby setting the reference voltage Vb of the electric line L1 and each drive line D1 to Dn to its own Zener voltage Vz. When the reference voltage variable switch 61 is connected to the terminal P4 of the ground connection line L2, the reference voltage Vb is set to 0V.

  The display controller 40 performs lighting control of the pixels E11 to Emn by switching the scan switches 21 to 2m, the drive switches 31 to 3n, and the reference voltage variable switch 61. In brief, the display controller 40 sequentially scans the scan lines S1 to Sm by switching the scan switches 21 to 2m in order and temporarily switching from the scan voltage source Vc to the ground. The display controller 40 supplies the drive current to the drive lines D1 to Dn through the switching of the drive switches 31 to 3n when scanning the scan lines S1 to Sm, thereby lighting the pixels E11 to Emn based on the image data. Characters, figures, etc. are displayed on the organic EL panel 10.

(Display controller control procedure)
The control procedure of the display controller 40 will be described along the flowchart of FIG. The process according to this flowchart is repeated for each scan of the scan line. In the following description, the scanning is started from the time when scanning of the scanning line S2 is completed.

  After the scanning of the scanning line S2, the display controller 40 calculates the horizontal lighting rate from the number of lighting of the pixels E31 to E3n of the scanning line S3 to be scanned next based on the image data (S101). The horizontal lighting rate is calculated by “(the number of pixels to be lit in the predetermined scanning line Sx / the total number of pixels along the predetermined scanning line Sx) × 100 (%)”.

  Then, the display controller 40 connects the drive switches 31 to 3n corresponding to the pixels E31 to E3n to be lit to the third contact P3, and based on the lateral lighting rate calculated in step S101, the reference voltage variable switch The reference voltage Vb is set through the switching of 61 (S102). The display controller 40 connects the reference voltage variable switch 61 to the Zener diodes Zd1 to Zdn having the lower Zener voltage Vz as the lighting rate in the horizontal direction is lower. When the horizontal lighting rate is in the lowest range, the reference voltage variable switch 61 is connected. Is connected to the ground connection line L2 having no Zener diode. In step S102, the display controller 40 may connect the scanning switch 23 to either the scanning voltage source Vc or the ground, or may connect to the scanning voltage source Vc and the ground, and may be in a high impedance (open state).

  Next, the display controller 40 next switches on the precharge voltage Vp from the precharge voltage source V1 by switching the drive switches 31 to 3n corresponding to the pixels E31 to E3n to be lit to the second contact P2. Application is made to the pixels E31 to E3n (S103).

  Next, the display controller 40 switches the drive switches 31 to 3n corresponding to the pixels E31 to E3n to be lit to the first contact point P1, and connects the scanning switch 23 to the ground, whereby the constant current source A supplies the constant current. Are supplied to the pixels E31 to E3n that are turned on (S104). Thereby, the pixels E31 to E3n along the scanning line S3 can be turned on at a predetermined ratio. As described above, the display controller 40 ends the scanning of the scanning line S3, and then performs the scanning of the scanning line S4 according to the flowchart of FIG. 3 as described above.

(Relationship between reference voltage Vb and luminance)
Next, the relationship between the reference voltage Vb and the luminance of the pixels E11 to Emn will be described with reference to FIGS. 2 (a) and 2 (b).

  FIG. 2A shows changes in the anode voltage Vd applied to the drive lines D1 to Dn in the flowchart. The anode voltage Vd is set to the reference voltage Vb by the selected Zener diodes Zd1 to Zdn and the ground connection line L2 in the period Ta before precharging. For example, when the Zener diode Zd1 is selected by the reference voltage variable switch 61, the anode voltage Vd (reference voltage Vb) is 2V, which is the same as the Zener voltage Vz of the Zener diode Zd1, as shown by the solid line in FIG. Set to When the Zener diode Zd2 is selected by the reference voltage variable switch 61, the anode voltage Vd (reference voltage Vb) is the same as the Zener voltage Vz of the Zener diode Zd2 as shown by the one-dot chain line in FIG. Set to 1.2V. In the precharge period T1, the constant precharge voltage Vp is charged to the predetermined pixels E11 to Emn, so that the anode voltage Vd increases. In the constant current supply period T2, a constant current is supplied to the predetermined pixels E11 to Emn. By setting the reference voltage Vb low, the area when the anode voltage Vd in the constant current supply period T2 is integrated becomes small. For example, the area when the anode voltage Vd is integrated when the reference voltage Vb is 1.2 V is smaller by the area S than the area when the anode voltage Vd when the reference voltage Vb is 2 V is integrated. Since the luminance of the pixels E11 to Emn is determined by the area when the anode voltage Vd in the constant current supply period T2 is integrated, the luminance of the pixels E11 to Emn becomes lower as the reference voltage Vb is set lower.

The inventor of the present application sets the luminance of the pixel and the reference when the reference voltage Vb is set to 3 V under the same lateral lighting rate conditions (when a Zener diode having a Zener voltage Vz of 3 V is connected to the electric line L1). An experiment was performed to compare the luminance of the pixel when the voltage Vb was set to 0 V (when the ground connection line L2 was connected to the electric line L1). In this experiment, the luminance of the pixel when the reference voltage Vb is set to 3V is 20 cd / m ² higher than the luminance of the pixel when the reference voltage Vb is set to 0V. Therefore, it has been proved that there is a proportional relationship between the reference voltage Vb and the luminance of the pixel.

(Measures against short circuit of organic EL panel 10)
As shown in FIG. 1, the display controller 40 connects the scanning switches 21 to 2m to the scanning voltage source Vc, and connects the reference voltage variable switch 61 to the ground connection line L2, so that the pixels E11 to E11 are generated from the scanning voltage Vs. A reverse bias voltage (self-repair voltage) Ve is applied to Emn (organic EL element). With the current accompanying the reverse bias voltage Ve, foreign substances in the organic EL element can be removed, and the short circuit between the electrodes (drive line and scanning line) of the organic EL element can be suppressed. The application of the reverse bias voltage Ve is performed, for example, during the manufacturing process of the organic EL panel 10 or when the organic EL panel 10 is driven.

Here, since the scanning voltage Vs and the precharge voltage Vp are actually supplied from a common battery, they are set to the same voltage value. For example, as shown in FIG. 5 as a comparative example, in the configuration in which the precharge voltage Vp changes according to the lighting rate in the horizontal direction, the scanning voltage Vs also decreases as the precharge voltage Vp decreases. For this reason, in this comparative example, as the scanning voltage Vs decreases, the reverse bias voltage Ve applied to the pixels E11 to Emn (organic EL elements) decreases, and the above effects may not be sufficiently exhibited. As such a situation, for example, when an operation check test in the manufacturing process or when driving the organic EL panel 10, an image with a low lighting rate in the horizontal direction is displayed on the organic EL panel, so that the precharge voltage Vp is low. It is assumed that
In the present embodiment, the reference voltage Vb is variable, but the precharge voltage Vp is set constant. When the precharge voltage Vp is constant as in the present embodiment, as shown by the one-dot chain line in FIGS. 4A and 4B, the reference voltage Vb set according to the lighting rate in the horizontal direction is related. The scanning voltage Vs is constant. In FIG. 4A, the reference voltage Vb is set to 2.0V, and in FIG. 4B, the reference voltage Vb is set to 0V.
Therefore, in this embodiment, since the precharge voltage Vp is constant, the reverse bias voltage Ve applied to the pixels E11 to Emn (organic EL) is suppressed from decreasing. Therefore, the above effect can be sufficiently exhibited.

(Measures against heat generation in organic EL panel drive devices)
When the organic EL element is controlled to be lit, the capacitor component is repeatedly charged and discharged. In the present embodiment, as shown in FIG. 6, a voltage corresponding to the Zener voltage Vz is held as the reference voltage Vb, so that the voltage difference Vo during charging and discharging is reduced by the reference voltage Vb (Zener voltage Vz). can do. Therefore, it is possible to reduce the heat generated by the charge / discharge in the organic EL panel drive device 50, for example, the control driver IC.

(effect)
As mentioned above, according to one Embodiment described, there exist the following effects especially.

  (1) The organic EL panel drive device 50 is arranged at a crossing position of the plurality of scanning lines S1 to Sm and the plurality of drive lines D1 to Dn, and the scanning lines S1 to Sm and the drive lines D1 to Dn. And a plurality of pixels (organic EL elements) E11 to Emn, and is used in a passive drive type organic EL panel 10. The organic EL panel driving device 50 supplies the reference voltage Vb from the reference voltage source V2 before supplying a constant current to the drive lines D1 to Dn corresponding to the pixels E11 to Emn to be lit in the scans of the scan lines S1 to Sm. Is applied to any one of the drive lines D1 to Dn, and then the precharge voltage Vp from the precharge voltage source V1 is applied to the drive lines D1 to Dn to which the reference voltage Vb is applied. The organic EL panel driving device 50 is based on the reference voltage variable unit 60 that can change the reference voltage Vb applied to each of the drive lines D1 to Dn, and the image data to be displayed on the organic EL panel 10, based on the following. The horizontal lighting rate is calculated based on the number of pixels E11 to Emn that are scheduled to be lit among the pixels E11 to Emn arranged along the scanning lines S1 to Sm, and as the horizontal lighting rate decreases, the horizontal lighting rate decreases. And a display controller 40 that sets the reference voltage Vb applied to each of the drive lines D1 to Dn through the reference voltage variable unit 60 low. By setting the reference voltage Vb to be low in this way, the luminance of the pixels E11 to Emn can be reduced. Thereby, the dispersion | variation in the brightness | luminance of the pixels E11-Emn by the change of the horizontal direction lighting rate of the pixels E11-Emn can be reduced.

(2) The reference voltage variable unit 60 includes a plurality of Zener diodes Zd1 to Zdn having different Zener voltages Vz, and any one Zener selected from the plurality of drive lines D1 to Dn and the plurality of Zener diodes Zd1 to Zdn. And a reference voltage variable switch 61 for electrically connecting the diodes. The display controller 40 decreases the reference voltage Vb by connecting the reference voltage variable switch 61 to the Zener diodes Zd1 to Zdn having a lower Zener voltage among the plurality of Zener diodes Zd1 to Zdn as the lateral lighting rate decreases. Set. According to this configuration, the reference voltage Vb can be adjusted with a simple configuration by using the plurality of Zener diodes Zd1 to Zdn.
Further, the display controller 40 connects the reference voltage variable switch 61 to the ground when the horizontal lighting rate is in the minimum range. As a result, the reference voltage Vb can be set lower, and variations in luminance of the pixels E11 to Emn can be further reduced.

(Modification)
In addition, the said embodiment can be implemented with the following forms which changed this suitably.

In the above embodiment, the reference voltage variable unit 60 includes three or more Zener diodes Zd1 to Zdn and the ground connection line L2. However, the ground connection line L2 may be omitted, and the Zener diode may be There may be two. The reference voltage variable unit 60 may include a reference voltage variable switch 61, one Zener diode, and one ground connection line.
The reference voltage variable unit 60 is not limited to the circuit configuration of the above embodiment as long as the reference voltage Vb can be changed. For example, a resistor and a diode connected in series may be provided instead of the Zener diodes Zd1 to Zdn. Thereby, the reference voltage Vb can be set similarly to the said embodiment. Further, a resistor and a diode connected in series and a Zener diode may be used in combination.
Further, the reference voltage variable unit may be a converter that steps up or steps down the voltage from the constant current source A.

  In the above embodiment, the display controller 40 calculates the horizontal lighting rate, but without calculating the horizontal lighting rate, the pixels E11 to E1 of the scanning lines S1 to Sm to be scanned next based on the image data. The reference voltage Vb may be set based on the number of lights of Emn.

  In the above-described embodiment, the display controller 40 applies the reverse bias voltage Ve to remove foreign substances in the organic EL element and suppresses a short circuit between the electrodes of the organic EL element, but the reverse bias voltage Ve The structure which does not apply may be sufficient.

DESCRIPTION OF SYMBOLS 10 ... Organic EL panel 20 ... Cathode drive circuits 21-2m ... Scan switch 30 ... Anode drive circuits 31-3n ... Drive switch 40 ... Display controller (control part)
50 ... Organic EL panel drive device 60 ... Reference voltage variable section 61 ... Reference voltage variable switch E11-Emn ... Pixel (organic EL element)

Claims (2)

A dot matrix type comprising a plurality of scanning lines and a plurality of drive lines intersecting each other, and a plurality of organic EL elements arranged at the intersections of the respective scanning lines and the respective drive lines, and of a passive drive system A reference voltage from a reference voltage source is applied to the drive line before supplying a constant current to the drive line corresponding to the organic EL element that is used for the organic EL panel and is lit in scanning of each scan line. And a driving device for an organic EL panel that applies a precharge voltage from a precharge voltage source to the drive line to which the reference voltage is applied,
Each scan line is a cathode line, and each drive line is an anode line,
A reference voltage variable unit capable of changing the reference voltage applied to each drive line;
Based on the image data to be displayed on the organic EL panel, the number of the organic EL elements to be lit among the organic EL elements arranged along the scanning line to be scanned next is acquired, and the acquired number is A control unit that sets the reference voltage applied to each drive line through the reference voltage variable unit as it decreases.
An organic EL panel drive device characterized by the above. The reference voltage variable unit is:
A plurality of zener diodes having different zener voltages;
A reference voltage variable switch that electrically connects between the plurality of drive lines and any one of the plurality of Zener diodes,
The control unit is configured to connect the reference voltage variable switch to a Zener diode having a low Zener voltage among the plurality of Zener diodes as the number of the acquired organic EL elements decreases. Set the value lower,
The organic EL panel drive device according to claim 1, wherein:

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