JP2006308845A - Electronic circuit, light emitting device, driving method thereof, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variation of gradation of a light emitting element resulting from drop of potential of a power feeder. <P>SOLUTION: A light emission control circuit P1 supplies drive current Ie1 according to voltage between a first node N1 and a second node N2 from the power feeder 42 to an OLED element 17. Holding capacity Cs holds voltage between a first electrode La1 and a second electrode La2. A control circuit P2 includes a switching element SW1 which conducts the first electrode La1 to any of a data line 15 and the first node N1 to which data potential Vdata is supplied and a switching element SW2 which conducts the second electrode La2 to any of a ground line 44 and the second node N2 to which ground potential VL is supplied. In a writing period P<SB>WRT</SB>, the first electrode La1 is connected to the data line 15 and the second line La2 is connected to the ground line 44. In a light emission period P<SB>EL</SB>following the writing period, the first electrode La1 is connected to the first node N1 and the second electrode La2 is connected to the second node N2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for controlling the behavior of a light emitting element such as an organic light emitting diode (hereinafter referred to as “OLED (Organic Light Emitting Diode)”) element.

  An active matrix light-emitting device has a structure in which a plurality of unit circuits (pixel circuits) each including a light-emitting element are arranged in a matrix. FIG. 16 is a circuit diagram illustrating a so-called voltage programming unit circuit Pa in which a current (hereinafter referred to as “driving current”) Iel supplied to the OLED element 17 is set according to the potential of the data line 15 (for example, Patent Document 1). As shown in the figure, one unit circuit Pa includes a power supply line 42 supplied with a higher potential (hereinafter referred to as “power supply potential”) VH of a power supply and a ground line 44 supplied with a lower potential VL. And an OLED element 17 and a transistor (hereinafter referred to as “driving transistor”) Tdr interposed therebetween. The gate of the driving transistor Tdr is connected to the data line 15 through a transistor (hereinafter referred to as “selection transistor”) Tsw which is turned on by a low level signal S. A capacitive element C is interposed between the gate and source of the drive transistor Tdr.

  When the selection transistor Tsw shifts to the ON state under the above configuration, the data potential Vdata supplied to the data line 15 at that time is supplied to the gate of the driving transistor Tdr and the data potential Vdata is set according to the data potential Vdata. The voltage (that is, the voltage Vgs between the gate and the source of the driving transistor Tdr) is held in the capacitive element C. Therefore, the voltage held in the capacitive element C is applied between the gate and the source of the drive transistor Tdr even during the period in which the selection transistor Tsw is turned off and the unit circuit Pa is electrically disconnected from the data line 15. As a result, the drive current Iel corresponding to the data potential Vdata can be continuously supplied to the OLED element 17.

The drive current Iel supplied to the OLED element 17 under this configuration is expressed by the following equation (1).
Iel = (β / 2) (Vgs−Vth) ²
= (Β / 2) {(Vdata−VH) −Vth} ² (1)
However, “Vth” in Equation (1) is the threshold voltage of the drive transistor Tdr, and “β” is the gain coefficient of the drive transistor Tdr. “Vgs” is a voltage between the gate and the source of the driving transistor Tdr. That is, the voltage Vgs corresponds to the difference (Vgs = Vdata−VH) between the power supply potential VH and the data potential Vdata.
JP 2002-156923 A (FIG. 2)

  Under the configuration shown in FIG. 16, a large amount of current flows through the feeder line 42 in order to supply the drive current Iel to the OLED element 17. In addition, the feed line 42 has its own resistance. Therefore, the power supply potential VH supplied to each unit circuit Pa drops according to the position of the unit circuit Pa (more specifically, the path length from the power supply circuit that is the supply source of the power supply potential VH to the unit circuit Pa). . Since the drive current Iel supplied to the OLED element 17 depends on the power supply potential VH as shown in the equation (1), in the conventional configuration shown in FIG. 16, the drive current Iel is reduced to the extent of the drop of the power supply potential VH. Accordingly, there is a problem that the unit circuit Pa differs, and the gradation varies for each unit circuit Pa due to the difference in the drive current Iel. The present invention has been made in view of such circumstances, and an object of the present invention is to solve the problem of suppressing variations in gradation of light emitting elements due to a drop in the potential of a feeder line.

  In order to solve this problem, the electronic circuit according to the present invention applies a current corresponding to the voltage between the first node and the second node from the power supply line (for example, the power supply line 42 shown in FIG. 2) to the light emitting element. A light emission control circuit to be supplied, a storage capacitor that holds the voltage between the first electrode and the second electrode (for example, the storage capacitor Cs shown in FIG. 2), and the gradation specified for the light emitting element A first state in which a data line to which a data potential is supplied is electrically connected to the first electrode and a reference wiring that is a wiring other than the power supply line is electrically connected to the second electrode; and the first electrode and the first node; And a control circuit that is in any one of the second states for conducting the second electrode and the second node. The control circuit includes, for example, a first switching means (for example, the switching element SW1 in FIG. 2) that makes the first electrode conductive to either the data line or the first node, and the second electrode to either the reference wiring or the second node. 2nd switching means (for example, switching element SW2 of FIG. 2).

  According to this configuration, the data potential is held in the holding capacitor when the control circuit is in the first state. Further, when the control circuit transits to the second state, the voltage held in the storage capacitor is applied between the first node and the second node, whereby a current corresponding to the data potential is supplied to the light emitting element. . In this configuration, for example, the voltage between the first node and the second node that determines the amount of current flowing through the light emitting element even if the potential of the feeder line fluctuates with the supply of drive current to the other light emitting elements. Is not affected by fluctuations in the potential of the feeder line. Therefore, according to the present invention, it is possible to suppress variations in gradation of the light emitting elements due to a drop in the potential of the feeder line.

  If a wiring having a smaller potential variation than the power supply line is used as the reference wiring to which the second electrode of the storage capacitor is connected, the expected effect of suppressing the variation in the current supplied to the light emitting element is even more remarkable. Become. In a more desirable mode, a wiring having a substantially constant potential is used as the reference wiring. According to this aspect, since the substantially constant potential is supplied to the second electrode of the storage capacitor when the control circuit is in the first state, the voltage corresponding to the data potential is taken into the storage capacitor with higher accuracy. Can do. The reference wiring may be a wiring formed separately from other elements. However, if the wiring that conducts to the unit circuit and other peripheral elements is used as the reference wiring, the configuration can be simplified and the manufacturing cost can be reduced. Is reduced. For example, in a configuration in which a light emitting element is interposed between a ground line to which a ground potential is supplied and a power supply line, a wiring that conducts to the ground line can be used as a reference wiring.

  However, the reference wiring is not limited to a wiring to which a substantially constant potential is supplied. For example, an auxiliary data line (for example, the second data line 152 shown in FIG. 10) in which the potential is set so that the voltage between the data lines becomes a voltage corresponding to the gradation specified for the light emitting element. It may be used as a reference wiring. According to this aspect, since the gradation of the light emitting element is designated by the difference value between the data line and the auxiliary data line, it is possible to reduce the influence of noise and crosstalk generated on the data line and the auxiliary data line. A specific example of this aspect will be described later as a fifth embodiment (FIG. 10).

  The light emission control circuit according to the present invention may be a circuit that supplies a current corresponding to the voltage between the first node and the second node from the power supply line to the light emitting element, and a specific mode thereof is arbitrary. For example, a light emission control circuit according to one aspect is a transistor interposed between a power supply line and a light emitting element, and one of a source and a gate is connected to a first node, and the other of the source and the gate is a second. A drive transistor connected to the node is provided. According to this aspect, since the current of the light emitting element can be adjusted by adjusting the gate potential of the driving transistor, the configuration is simplified and the current of the light emitting element can be easily and reliably controlled. . Specific examples of this aspect will be described later as second to fifth embodiments. In a more specific aspect, the driving transistor is an n-channel transistor having a source connected to the light emitting element and the second node, a drain connected to the power supply line, and a gate connected to the first node. . According to this aspect, since the voltage between the gate and the source of the driving transistor can be determined to be the voltage held in the storage capacitor, the light emitting element can be used regardless of variations in characteristics (particularly voltage-current characteristics) of the light emitting element. Can be emitted with high accuracy according to the data potential. A specific example of this aspect will be described later as a third embodiment (FIG. 5).

  Note that in the configuration in which the current supplied to the light emitting element is controlled by the drive transistor, the variation in the threshold voltage of the drive transistor becomes a problem. Therefore, a function for compensating for variations in the threshold voltage of the drive transistor is added to the light emission control circuit of a more desirable mode. For example, a light emission control circuit having this function includes a driving transistor that controls a current flowing from a power supply line to a light emitting element according to a gate potential, and conduction between one of a source and a drain of the driving transistor and the gate of the driving transistor. And a switching element for switching non-conduction, and a capacitor interposed between the gate of the driving transistor and one of the first node and the second node. According to this aspect, when one of the source or drain of the driving transistor and the gate of the driving transistor are brought into conduction by the switching element being turned on, the potential of the gate of the driving transistor becomes a level corresponding to the threshold voltage. The variation can be compensated. A specific example of this aspect will be described later as a fourth embodiment (FIG. 7).

  The present invention is also specified as a method of driving the electronic circuit of each aspect described above. That is, according to this driving method, the voltage between the first electrode and the second electrode and the light emission control circuit that supplies a current corresponding to the voltage between the first node and the second node from the power supply line to the light emitting element are set. A method of driving an electronic circuit having a storage capacitor for holding a data line to which a data potential corresponding to a specified gray scale is supplied to a light emitting element and a first electrode in a first period. In addition, the reference wiring, which is a wiring other than the power supply line, and the second electrode are made conductive, and the first electrode and the first node are made conductive in the second period after the first period, and the second electrode and the second electrode are made conductive. This is a method for conducting a node. According to the present invention, for the reason described above with respect to the electronic circuit of the present invention, it is possible to suppress the variation in the current of the light emitting element due to the fluctuation of the potential of the feeder line.

  The first period and the second period may be continuous periods, or a predetermined gap may be sandwiched between them. In a more desirable mode, a pause period is inserted between the first period and the second period. In this idle period, the first electrode is not connected to either the data line or the first node, and the second electrode is not connected to any of the reference wiring and the second node. That is, both the first electrode and the second electrode of the storage capacitor are in a floating state. According to this aspect, since the light emitting element can emit light while maintaining the charge accumulated in the storage capacitor in accordance with the data potential with high accuracy, it is possible to further reliably suppress uneven gradation of the light emitting element. it can.

  The light emission control circuit of the electronic circuit according to the present invention has a function of compensating the threshold voltage of the driving transistor as described above. In other words, the light emission control circuit in this configuration includes a driving transistor that controls the current flowing from the power supply line to the light emitting element according to the potential of the gate, and conduction and non-conduction between one of the source or drain of the driving transistor and the gate of the driving transistor. A switching element for switching conduction, and a capacitor interposed between the gate of the driving transistor and one of the first node and the second node. In the case of driving an electronic circuit including the light emission control circuit having this configuration, the gate of the driving transistor is set to a potential corresponding to the threshold voltage of the driving transistor by turning on the switching element in the first period. In two periods, it is desirable to turn off the switching element. According to this aspect, the gate voltage of the driving transistor is set to a potential corresponding to the threshold voltage prior to the supply of the current to the light emitting element, whereby the variation in the threshold voltage of the driving transistor can be compensated.

  The present invention is also specified as a light emitting device including the electronic circuit of each aspect described above. That is, the light emitting device includes a plurality of electronic circuits each connected to a data line, a data supply means for supplying a data potential to each of the plurality of data lines, and a selection for sequentially selecting each of the plurality of electronic circuits. Each of the plurality of electronic circuits includes: a light emission control circuit that supplies a current corresponding to a voltage between the first node and the second node from the power supply line to the light emitting element; A storage capacitor for holding a voltage between the first electrode and the second electrode, a first switching means for conducting the first electrode to either the data line or the first node, and a reference wiring or the second node And a second switching means for conducting the second electrode, the selecting means for the electronic circuit selected by the selecting means so that the first electrode is conducted to the data line and the second electrode is conducted to the reference wiring. 1 switch Controlling the switching means and the second switching means, and for the non-selected electronic circuit, the first switching means and the second switching so that the first electrode is conducted to the first node and the second electrode is conducted to the second node. Control means. According to this configuration, for the reason described above with respect to the electronic circuit of the present invention, it is possible to suppress the variation in the current of the light emitting element due to the fluctuation of the potential of the feeder line.

  In a desirable mode of the light emitting device according to the present invention, a ground line is provided which is constituted by a conductive film body distributed continuously over a plurality of electronic circuits and is supplied with a substantially constant ground potential. The reference line is electrically connected to the ground line, and is interposed between the line and the feeder line. According to this aspect, since the reference wiring is electrically connected to the ground line, the configuration can be simplified as compared with the configuration in which the reference wiring is formed independently from the unit circuit or its peripheral elements. In addition, since the ground line in this aspect is a conductive film body that is continuously distributed over a plurality of electronic circuits, the impedance can be easily reduced as compared with the feeder line. Accordingly, it is possible to sufficiently suppress the fluctuation of the potential in the ground line and to surely suppress the variation in the current of the light emitting element.

  The light emitting device according to the present invention is used in various electronic devices. A typical example of this electronic device is a device that uses a light emitting device as a display device. Examples of this type of electronic device include a personal computer and a mobile phone. However, the use of the light emitting device according to the present invention is not limited to image display. For example, the light emitting device of the present invention can also be applied as an exposure device (exposure head) for forming a latent image on an image carrier such as a photosensitive drum by irradiation of light. In this exposure apparatus, since a large number of electronic circuits are arranged linearly over the entire width of the paper on which an image is formed, the potential of the feeder line in the electronic circuit located at the end of the arrangement and the central part of the arrangement It is likely to be different from the potential of the feeder line in the electronic circuit located. Therefore, the present invention that can suppress the variation in current due to the fluctuation of the potential of the feeder line is particularly preferably employed for this type of electronic apparatus.

<A: First Embodiment>
FIG. 1 is a block diagram showing a configuration of a light emitting device according to the first embodiment of the present invention. As shown in the figure, the light emitting device D includes a pixel array unit 10, a selection circuit 21, a data supply circuit 25, a control circuit 31, and a power supply circuit 35. Among these, m control lines 11 extending in the X direction and n data lines 15 extending in the Y direction orthogonal to the X direction are formed in the pixel array unit 10. A unit circuit P is arranged at a position corresponding to each intersection of the control line 11 and the data line 15. Therefore, these unit circuits P are arranged in a matrix of m rows × n columns.

  The selection circuit 21 is means for sequentially selecting the unit circuits P of the pixel array unit 10. The selection circuit 21 in the present embodiment selects each unit circuit P in units of rows for each horizontal scanning period. On the other hand, the data supply circuit 25 generates a data potential Vdata corresponding to each of the unit circuits P for one row (n) selected by the selection circuit 21 in each horizontal scanning period, and outputs the data potential Vdata to each data line 15. . The data potential Vdata supplied to the data line 15 in the j-th column (j is an integer satisfying 1 ≦ j ≦ n) is the luminance specified for the unit circuit P in the j-th column belonging to the selection row by the selection circuit 21. It is a level according to (gradation).

  The control circuit 31 controls each circuit by supplying various signals such as a clock signal to the selection circuit 21 and the data supply circuit 25, and outputs image data specifying the luminance of each unit circuit P to the data supply circuit 25. To do. On the other hand, the power supply circuit 35 generates a higher potential (hereinafter referred to as “power supply potential”) VH and a lower potential (hereinafter referred to as “ground potential”) VL. As shown in FIG. 1, a feed line (power supply line) 42 extending in the Y direction along each column of the unit circuits P is formed in the pixel array unit 10. The power supply potential VH generated by the power supply circuit 35 is supplied to each unit circuit P through these power supply lines 42. In the pixel array section 10, a conductive film body (so-called solid pattern) continuous over all the unit circuits P is formed as a ground line 44 so as to overlap the entire area. The ground potential VL generated by the power supply circuit 35 is supplied in common to all unit circuits P via the ground line 44.

  Next, the configuration of each unit circuit P will be described with reference to FIG. In the drawing, only one unit circuit P in the j-th column belonging to the i-th row (i is an integer satisfying 1 ≦ i ≦ m) is shown, but the other unit circuits P have the same configuration. is there. A typical example of each transistor shown in FIG. 2 and the following drawings is a thin film transistor using low-temperature polysilicon as a semiconductor layer, but the form and material of each transistor are arbitrary.

  As shown in FIG. 2, one unit circuit P includes a light emission control circuit P1 and a control circuit P2. Among these, the light emission control circuit P 1 includes the OLED element 17 electrically inserted between the power supply line 42 and the ground line 44. The OLED element 17 is an element that emits light with a luminance corresponding to the drive current Iel flowing in the forward direction, and has a structure in which a light emitting layer made of an organic EL material is interposed in the gap between the anode and the cathode. The cathodes of the OLED elements 17 in all the unit circuits P are commonly connected to the ground line 44. The light emission control circuit P1 is means for controlling the drive current Iel flowing from the power supply line 42 via the OLED element 17 into the ground line 44 in accordance with the voltage between the first node N1 and the second node N2.

  The OLED element 17 of the present embodiment is formed, for example, by discharging a droplet of an organic EL material from an inkjet head and drying it. As the material of the light emitting layer of the OLED element 17, an organic light emitting material such as a low molecular weight polymer or a dendrimer is used. However, the OLED element 17 is only an example of a light emitting element. For example, instead of the OLED element 17, an inorganic EL element, a field emission (FE) element, a surface-conduction electron (SE) element, a ballistic electron surface emitting (BS) element Various self-luminous elements such as LED (Light Emitting Diode) elements, electrophoretic elements, electrochromic elements, and the like may be used.

  The control circuit P2 shown in FIG. 2 is means for controlling the voltage between the first node N1 and the second node N2 in accordance with the data potential Vdata of the data line 15, and includes the first electrode La1 and the second electrode La2. And a switching capacitor SW1 and a switching device SW2. The switching element SW1 is means for selectively conducting the first electrode La1 of the storage capacitor Cs to either the data line 15 or the first node N1, and the switching element SW2 grounds the second electrode La2 of the storage capacitor Cs. Means for selectively conducting either the line 44 or the second node N2. The switching element SW1 and the switching element SW2 are controlled by a control signal S [i] supplied to the control line 11. That is, if the control signal S [i] is at a high level, the first electrode La1 of the storage capacitor Cs is connected to the data line 15 and the second electrode La2 is connected to the ground line as shown by the solid line in FIG. If the control signal S [i] is at a low level, the first electrode La1 is connected to the first node N1 and the second electrode La2 is the second as shown by the broken line in FIG. Connected to node N2.

  In the above configuration, the selection circuit 21 causes each of the control signals S [1] to S [m] to transition to the high level in order for each horizontal scanning period. That is, the control signal S [i] is at a high level during the i-th horizontal scanning period in one vertical scanning period, and is at a low level during other periods. In a period during which the control signal S [i] is maintained at a high level (hereinafter referred to as “writing period”), the first electrode La1 of the storage capacitor Cs is connected to the data line 15 and the second electrode La2 is connected to the ground line 44. Therefore, the storage capacitor Cs holds a voltage corresponding to the data potential Vdata (a voltage corresponding to the difference between the data potential Vdata and the ground potential VL). In a period in which the control signal S [i] transitions to a low level following this writing period (hereinafter referred to as “light emission period”), the first electrode La1 is connected to the first node N1 and the second electrode La2 is Connected to the second node N2. Therefore, in the light emission period, the voltage held in the holding capacitor Cs in the immediately preceding writing period is applied between the first node N1 and the second node N2, and the drive current Iel corresponding to this voltage is supplied. As a result, the OLED element 17 emits light with a luminance corresponding to the data potential Vdata. The brightness control as described above is executed for each unit circuit P, whereby a desired image is displayed on the pixel array unit 10.

  By the way, when a drive current Iel is supplied to the OLED element 17 of each unit circuit P, a potential drop occurs in the power supply line 42 in proportion to the amount of current and the resistance associated with the power supply line 42. Therefore, under the conventional configuration in which the storage capacitor C is connected to the power supply line 42 as illustrated in FIG. 16, when the data potential Vdata is taken into one unit circuit Pa, the drive current Iel is supplied to the other unit circuit Pa. Is supplied, the voltage held in the holding capacitor C varies according to the degree of the potential drop of the feeder line 42. The degree of the potential drop varies depending on the position of the unit circuit Pa (more specifically, the path length from the supply source of the power supply voltage to the unit circuit Pa). Even if specified, there is a problem that the actual luminance of each unit circuit Pa varies depending on the position of the unit circuit Pa. This variation in luminance is recognized as display unevenness in, for example, an electronic device that uses a light emitting device as display means.

  On the other hand, in the present embodiment, the second electrode La2 is connected to the ground line 44 in the writing period in which the data potential Vdata is supplied to the first electrode La1 of the storage capacitor Cs. Therefore, even if the potential of the feeder line 42 fluctuates (drops) due to the supply of the drive current Iel to the OLED element 17, the voltage (or charge amount) corresponding to the data potential Vdata is not affected by this fluctuation. Can be held in the holding capacitor Cs with high accuracy. Since the drive current Iel supplied to the OLED element 17 is controlled according to the voltage held in the holding capacitor Cs, according to the present embodiment, each OLED element 17 regardless of the fluctuation of the potential of the feeder line 42. Can be controlled to a desired brightness with high accuracy.

  2, even if the ground potential VL of the ground line 44 conducting to the second electrode La2 of the storage capacitor Cs is different for each unit circuit P, the luminance variation of the OLED element 17 occurs. it's possible. However, since the ground line 44 in this embodiment is a continuous film body over all the unit circuits P, the impedance is extremely low (that is, the potential drop) as compared with the power supply line 42 formed linearly for each column. Is small). Therefore, when compared with the conventional configuration in which the storage capacitor C is connected to the power supply line 42, the effect of suppressing the variation in luminance of each unit circuit P is certainly exhibited by the present embodiment. In other words, the connection destination of the second electrode La2 of the storage capacitor Cs in the writing period is a wiring (for example, a wiring having a low impedance) whose potential fluctuation is smaller than that of the power supply line 42 that is the supply source of the driving current Iel. It is desirable. For example, a configuration in which a substantially constant potential is supplied to the data supply circuit 25 as a reference potential of the data potential Vdata (for example, a reference potential of a D / A converter that generates the data potential Vdata from image data) via a predetermined wiring. In this case, the second electrode La2 of the storage capacitor Cs may be connected to this wiring in the writing period.

<B: Second Embodiment>
Next, a second embodiment of the present invention will be described. In addition, among each embodiment described below, elements having the same operations and functions as those of the first embodiment are denoted by common reference numerals, and the description thereof is appropriately omitted.

  FIG. 3 is a circuit diagram showing a configuration of the unit circuit P in the present embodiment. As shown in the figure, the control line 11 shown as one wiring in FIG. 1 includes a first control line 111 and a second control line 112 as shown in FIG. 3 in this embodiment. . A first control signal Sa [1] to Sa [m] that defines a writing period during which the data potential Vdata is taken into the unit circuit P of the row is supplied from the selection circuit 21 to the first control line 111 of each row. Further, the second control lines 112 of each row are supplied from the selection circuit 21 with second control signals Sb [1] to Sb [m] that define a light emission period during which the OLED element 17 of the unit circuit P of the row emits light. The The specific waveform of each signal and the operation of the unit circuit P corresponding to this will be described later.

  As shown in FIG. 3, the control circuit P2 in this embodiment includes a storage capacitor Cs and four p-channel transistors (SW1a, SW1b, SW2a, SW2b) similar to those in FIG. Among these, the transistors SW1a and SW1b are means for switching the connection destination of the first electrode La1 of the storage capacitor Cs to either the data line 15 or the first node N1, similarly to the switching element SW1 of FIG. More specifically, the transistor SW1a is a switching element having a source connected to the data line 15 and a drain connected to the first electrode La1. On the other hand, the transistor SW1b is a switching element having a source connected to the first node N1 and a drain connected to the first electrode La1. On the other hand, the transistors SW2a and SW2b are means for switching the connection destination of the second electrode La2 to either the ground line 44 or the second node N2, similarly to the switching element SW2 of FIG. More specifically, the transistor SW2a has a source connected to the second electrode La2 and a drain connected to the ground line 44, and the transistor SW2b has a source connected to the second electrode La2 and a drain connected to the second electrode La2. Connected to node N2.

  The gates of the transistors SW1a and SW2a are connected to the first control line 111. Therefore, if the first control signal Sa [i] is at a high level, both the transistors SW1a and SW2a are turned off, and the storage capacitor Cs is electrically disconnected from the data line 15 and the ground line 44. If the signal Sa [i] is at a low level, both the transistors SW1a and SW2a are turned on so that the first electrode La1 is connected to the data line 15 and the second electrode La2 is connected to the ground line 44. On the other hand, the gates of the transistors SW1b and SW2b are connected to the second control line 112. Therefore, if the second control signal Sb [i] is at a high level, both the transistors SW2a and SW2b are turned off, and the holding capacitor Cs is electrically disconnected from the light emission control circuit P1, and the second control signal Sb [ If i] is at a low level, both the transistors SW2a and SW2b are turned on so that the first electrode La1 is connected to the first node N1 and the second electrode La2 is connected to the second node N2.

  As shown in FIG. 3, the light emission control circuit P1 in the present embodiment includes a drive transistor Tdr and a transistor T1 in addition to the OLED element 17 similar to that in FIG. The conductivity type of the drive transistor Tdr and the transistor T1 is a p-channel type. The drive transistor Tdr is a means for adjusting the drive current Iel supplied from the power supply line 42 to the OLED element 17 in accordance with the gate potential, and its source is connected to the power supply line 42 and the first node N1. The gate is connected to the second node N2. The drain of the driving transistor Tdr is connected to the anode of the OLED element 17. The cathode of the OLED element 17 is connected to the ground line 44. On the other hand, the transistor T1 is a switching element for controlling the state of electrical connection between the gate and the source of the driving transistor Tdr (that is, switching between conduction and non-conduction), and the source is the source of the driving transistor Tdr. The drain is connected to the gate (and the second node N2) of the driving transistor Tdr.

Next, the operation of this embodiment will be described with reference to FIG. As shown in FIG. 4, the second control signals Sb [1] to Sb [m] are sequentially set to the high level every horizontal scanning period. More specifically, the second control signal Sb [i] is at a high level from the start point t0 to the end point t3 of the i-th horizontal scanning period in one vertical scanning period (1V), and light emission in the other period. It becomes a low level during the period P _EL . On the other hand, the first control signals Sa [1] to Sa [m] are sequentially set to the low level every horizontal scanning period. More specifically, the first control signal Sa [i] is transmitted from the time point t1 when a predetermined time length has elapsed from the starting point t0 of the i-th horizontal scanning period in one vertical scanning period, to the end point t3 of the horizontal scanning period. Becomes a low level in the writing period P _WRT that is a period up to a time point t2 before a predetermined time length, and becomes a high level in other periods. Thus, from the interval (writing period P _WRT the light emission period P _EL writing period the first control signal Sa [i] becomes the low level P _WRT and the second control signal Sb [i] is made the low level by the time) migrating from and the light emission period P _EL when shifts to the light emission period P _EL in the writing period P _WRT, both the first control signal Sa [i] and the second control signal Sb [i] and the high level A period POFF (hereinafter referred to as “pause period”) is inserted. In the idle period P _OFF , all the transistors (SW1a, SW1b, SW2a, SW2b) constituting the control circuit P2 are turned off. That is, both the first electrode La1 and the second electrode La2 of the storage capacitor Cs are in a floating state.

As described above, in the writing period P _WRT , the first control signal Sa [i] maintains a low level. Therefore, the first electrode La1 of the storage capacitor Cs is connected to the data line 15 when the transistor SW1a is turned on, and the second electrode La2 is connected to the ground line 44 when the transistor SW2a is turned on. Is done. In addition, since the second control signal Sb [i] is maintained at a high level, the transistors SW1b and SW2b are turned off, whereby the holding capacitor Cs is electrically disconnected from the light emission control circuit P1. Therefore, the storage capacitor Cs holds a voltage corresponding to the difference between the data potential Vdata and the ground potential VL. On the other hand, the transistor T1 is turned on by the low-level first control signal Sa [i]. Therefore, the power supply potential VH is supplied to the gate of the drive transistor Tdr. Thus, the transistor T1 functions as means for supplying (initializing) a predetermined potential to the gate of the driving transistor Tdr.

Next, in the light emission period P _EL , the first control signal Sa [i] maintains a high level and the second control signal Sb [i] maintains a low level. Therefore, when the transistor SW1b is turned on, the first electrode La1 of the storage capacitor Cs is connected to the first node N1 (and further the source of the driving transistor Tdr), and the transistor SW2b is turned on to turn on the second. The electrode La2 is connected to the second node N2 (and the gate of the driving transistor Tdr). Further, since the transistors SW1a and SW2a are turned off, the holding capacitor Cs is electrically disconnected from the data line 15 and the ground line 44. On the other hand, since the transistor T1 is turned off by the high-level first control signal Sa [i], the supply of the power supply potential VH from the power supply line 42 to the drive transistor Tdr is stopped. With the above operation, in the light emission period P _EL , the voltage held in the holding capacitor Cs in the immediately preceding write period P _WRT is transferred between the gate and the source of the drive transistor Tdr. As a result, the OLED element 17 Light is emitted with luminance according to the data potential Vdata.

As described above, also in the present embodiment, since the second electrode La2 of the storage capacitor Cs is connected to the ground line 44 in the write period _PWRT , the same effect as that of the first embodiment is achieved. In addition, in the present embodiment, the storage capacitor Cs is electrically connected from any of the data line 15, the ground line 44, and the light emission control circuit P1 in the pause period P _OFF between the writing period P _WRT and the light emission period P _EL. Therefore, there is an advantage that the voltage held in the holding capacitor Cs can be maintained at a desired level with high accuracy. For example, it is assumed that the writing period P _WRT and the light emission period P _EL are continuous without an interval. In this case, due to the delay of the first control signal Sa [i] and the second control signal Sb [i], the waveform dullness, and the like, there is a possibility that the periods in which both signals are at the low level overlap each other. There is. When both the first control signal Sa [i] and the second control signal Sb [i] are at a low level, the first electrode La1 of the storage capacitor Cs is connected to both the data line 15 and the first node N1. The second electrode La2 is connected to both the ground line 44 and the second node N2. Therefore, even though charges corresponding to the data potential Vdata are accumulated in the holding capacitor Cs in the writing period P _WRT , the charge in the holding capacitor Cs escapes prior to the light emission of the OLED element 17 in the light emission period P _EL . As a result, the expected supply of the drive current Iel to the OLED element 17 may be hindered. On the other hand, in the present embodiment, the storage capacitor Cs is reliably insulated from the data line 15, the ground line 44, and the light emission control circuit P1 in the pause period P _OFF between the writing period P _WRT and the light emission period P _EL. Therefore, such a problem can be prevented and the OLED element 17 can emit light with the desired brightness with high accuracy. However, even if there is a period in which both the first control signal Sa [i] and the second control signal Sb [i] are at a low level, there is no particular problem (for example, the light emitting device D is used for displaying an image). In the case where there is almost no influence on the image quality in the display device, or when duplication of these signals is avoided by some method, a configuration in which the pause period P _OFF is not provided (that is, the writing period P _WRT and the light emission period P _EL May be a continuous configuration).

<C: Third Embodiment>
Next, a third embodiment of the present invention will be described. In the second embodiment, the case where the light emission control circuit P1 and the control circuit P2 are configured by p-channel transistors has been exemplified. On the other hand, in the unit circuit P of the present embodiment, the light emission control circuit P1 and the control circuit P2 are configured by n-channel transistors.

  FIG. 5 is a circuit diagram showing a configuration of the unit circuit P according to the present embodiment. As shown in the figure, the conductivity type of the four transistors (SW1a, SW1b, SW2a, SW2b) constituting the control circuit P2 of the unit circuit P is an n-channel type. The conductivity type of the drive transistor Tdr that controls the drive current Iel and the transistor T1 that controls conduction between the source and drain of the drive transistor Tdr are also n-channel types. The source of the driving transistor Tdr is connected to the anode of the OLED element 17 and the second node N2, and the drain thereof is connected to the power supply line. The gate of the driving transistor Tdr is connected to the first node N1. Each of the first control signal Sa [i] and the second control signal Sb [i] supplied to the unit circuit P of the present embodiment has a waveform in which the high level and the low level of each signal shown in FIG. It becomes.

Also in this configuration, since the second electrode La2 of the storage capacitor Cs is connected to the ground line 44 in the writing period _PWRT , the same effect as that of the first embodiment is achieved. In addition, according to the present embodiment, the voltage held in the holding capacitor Cs can be applied between the gate and the source of the driving transistor Tdr. There is an advantage that variation in luminance can be suppressed. This effect will be described in detail as follows.

  Now, consider a configuration in which each transistor of the unit circuit Pa shown in FIG. 16 is replaced with an n-channel transistor. As shown in FIG. 6, in this configuration, the source of the n-channel type driving transistor Tdr is connected to the anode of the OLED element 17 (source follower), and the gate is connected to the selection transistor Tsw and the capacitive element C. Is done. When the selection transistor Tsw is turned on, the data potential Vdata supplied to the data line 15 is supplied to the gate of the drive transistor Tdr and held in the capacitor C. In this configuration, the source potential of the drive transistor Tdr varies according to the characteristics (particularly voltage-current characteristics) of the OLED element 17. Since the drive current Iel supplied to the OLED element 17 has a current amount corresponding to the voltage between the gate and the source of the drive transistor Tdr, the fluctuation of the potential of the source of the drive transistor Tdr varies (and moreover the OLED element 17 brightness variations).

  On the other hand, in the unit circuit P of the present embodiment, the source of the drive transistor Tdr is connected to the second electrode La2 of the storage capacitor Cs via the second node N2, and therefore, between the gate and source of the drive transistor Tdr. The voltage is determined to be a voltage held by the holding capacitor Cs. Therefore, regardless of the voltage-current characteristics of the OLED element 17, the drive current Iel having a current amount corresponding to the data potential Vdata can be supplied to the OLED element 17 with high accuracy. Since the luminance of the OLED element 17 is proportional to the drive current Iel, according to the present embodiment, even if the voltage-current characteristics of the OLED element 17 of each unit circuit P are different, Brightness unevenness can be suppressed.

<D: Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described.
The characteristics (particularly the threshold voltage Vth) of the drive transistor Tdr included in the light emission control circuit P1 of each unit circuit P may be different for each unit circuit P. The light emission control circuit P1 in this embodiment has a function of compensating for such a variation in the threshold voltage Vth of the drive transistor Tdr.

  FIG. 7 is a circuit diagram showing a configuration of the unit circuit P according to the present embodiment. As shown in the figure, the light emission control circuit P1 of this embodiment includes four p-channel transistors (Tdr, Tel, T1, and T2), and a first electrode Lb1 and a second electrode Lb2 that face each other. And a capacitive element C0.

  The source of the drive transistor Tdr is connected to the feeder line 42 and the first node N1. The drain of the drive transistor Tdr is connected to the source of a transistor (hereinafter referred to as “light emission control transistor”) Tel for controlling the period during which the OLED element 17 actually emits light. The gate of the light emission control transistor Tel is connected to the second control line 112 and the drain thereof is connected to the anode of the OLED element 17.

  The first electrode Lb1 of the capacitive element C0 is connected to the gate of the driving transistor Tdr. The second electrode Lb2 of the capacitive element C0 is connected to the second node N2 and the drain of the transistor T1. The transistor T1 is a switching element for controlling the state of electrical connection between the second electrode Lb2 of the capacitive element C0 and the feed line 42 (that is, switching between conduction and non-conduction between them), and the source thereof is the feed line 42. (And the first node N 1) and the gate is connected to the first control line 111. Therefore, when the first control signal Sa [i] becomes low level, the transistor T1 is turned on, and the power supply potential VH is supplied to the second electrode Lb2 of the capacitive element C0.

  The transistor T2 is a switching element that switches between conduction and non-conduction between the gate and drain of the drive transistor Tdr, and is interposed between the gate and drain of the drive transistor Tdr. The gate of the transistor T2 is connected to the first control line 111. Therefore, when the first control signal Sa [i] transitions to the low level, the transistor T2 is turned on, and thus the driving transistor Tdr functions as a diode.

Next, the operation of this embodiment will be described with reference to FIG. As shown in the figure, the first control signal Sa [i] in this embodiment is the end point of the horizontal scanning period from the time point t0 that is a predetermined time length before the starting point t1 of the i-th horizontal scanning period. It becomes a low level in a period up to a time point t2 that is a predetermined time before t3 and becomes a high level in other periods. Hereinafter, the period from the time t0 when the first control signal Sa [i] falls to the low level to the start point of the horizontal scanning period (the time when the second control signal Sb [i] rises) t1 is referred to as “reset period P _RES ”. The period from the start point t1 of the horizontal scanning period to the time point t2 when the first control signal Sa [i] rises to the high level is referred to as “writing period P _WRT ”. Note that, as in the second embodiment, the second control signal Sb [i] maintains a high level from the start point t1 to the end point t3 of the i-th horizontal scanning period, and the light emission period P, which is the other period. Low level at _EL . Between the writing period P _WRT and the light emission period P _EL , as in the second embodiment, a pause period in which both the first control signal Sa [i] and the second control signal Sb [i] are at a high level. P _OFF is inserted.

As shown in FIG. 8, in the reset period _PRES , both the first control signal Sa [i] and the second control signal Sb [i] are at a low level. Therefore, the transistor T1 is turned on, and a substantially constant power supply potential VH is supplied to the second electrode Lb2 of the capacitive element C0. Further, the transistor T2 is turned on, the drive transistor Tdr is diode-connected, and the light emission control transistor Tel is turned on. As a result, the potential of the drain of the driving transistor Tdr (and the potential of the gate conducting to the drain via the transistor T2) is sufficiently lowered. In the reset period _PRES , the light emission control transistor Tel is turned on, so that the OLED element 17 emits light. However, since the reset period P _RES is set to a sufficiently short time length compared to the light emission period P _EL (that is, the time length during which the drain of the drive transistor Tdr is lowered to a predetermined level), the light emission in the reset period P _RES is performed. Has almost no influence on the luminance of the OLED element 17. On the other hand, the output of the data supply circuit 25 is set to high impedance during the reset period _PRES .

Next, in the writing period P _WRT , the data supply circuit 25 supplies the data lines 15 with the data potential Vdata having a level corresponding to the luminance of each OLED element 17 in the i-th row selected by the selection circuit 21. In the writing period P _WRT , the selection circuit 21 maintains the first control signal Sa [i] at a low level and changes the second control signal Sb [i] to a high level. As a result, the transistors SW1a and SW2a are turned on, so that the data potential Vdata is supplied to the first electrode La1 of the storage capacitor Cs and the ground potential VL is supplied to the second electrode La2. Therefore, the storage capacitor Cs holds a voltage corresponding to the difference between the data potential Vdata and the ground potential VL.

On the other hand, in the light emission control circuit P1, the light emission control transistor Tel is turned off by the high-level second control signal Sb [i], and the transistors T1 and T2 are turned on by the low-level first control signal Sa [i]. Maintain state. Therefore, the potential Vg of the gate of the drive transistor Tdr rises from the level lowered in the reset period, and finally converges to the level expressed by the equation (1).
Vg = VH- | Vth | (1)
Note that the transistor potential is generally expressed with reference to the source potential. Since the drive transistor Tdr is a p-channel type, the threshold voltage Vth is a negative number. This is why equation (1) includes the absolute value of the threshold voltage Vth.

Next, in the light emission period P _EL , as shown in FIG. 8, the first control signal Sa [i] maintains a high level and the second control signal Sb [i] transitions to a low level. Therefore, the transistors T1 and T2 are turned off. Further, when the transistors SW1b and SW2b are turned on, the connection destination of the storage capacitor Cs is changed from the data line 15 and the ground line 44 to the first node N1 and the second node N2. That is, between the first node N1 and the second node N2, a storage capacitor Cs in a state of holding a voltage “ΔV (= Vdata−VL)” corresponding to the difference between the data potential Vdata and the ground potential VL is connected. Is done. At this time, the potential of the first electrode Lb1 of the capacitive element C0 (the potential Vg of the gate of the driving transistor Tdr) is only “k · ΔV” from the potential “Vdd− | Vth |” set in the writing period P _WRT . Change. However, “k” is a numerical value corresponding to the capacitance ratio of the holding capacitor Cs, the capacitance of the capacitive element C0, the gate capacitance of the driving transistor Tdr, and other parasitic capacitances. Therefore, the potential Vg of the gate of the driving transistor Tdr is expressed by the following equation (2).
Vg = VH− | Vth | −k · ΔV (2)

In the light emission period P _EL , the light emission control transistor Tel is turned on by the low-level second control signal Sb [i]. Therefore, the OLED element 17 has a drive current Iel corresponding to the gate potential Vg of the drive transistor Tdr. Is supplied. Assuming that the drive transistor Tdr operates in the saturation region, the drive current Iel is expressed by the following equation (3).
Iel = (β / 2) (Vgs−Vth) ² (3)
“Vgs” in Expression (3) is the gate potential of the drive transistor Tdr when the source potential is used as a reference. Further, considering that the power supply potential VH is supplied to the source of the driving transistor Tdr and the equation (2), the voltage Vgs is expressed by the following equation (4). However, in the expression (4), the absolute value of the threshold voltage Vth is removed and expressed as “+ Vth”.
Vgs = Vg-VH
= (VH + Vth−k · ΔV) −VH
＝ Vth−k ・ ΔV …… (4)

When this equation (4) is substituted, equation (3) is transformed into the following equation (5).
Iel = (β / 2) {k · ΔV} ² (5)
As shown in the equation (5), the drive current Iel supplied to the OLED element 17 is determined only by the difference ΔV (= Vdata−VL) between the data potential Vdata and the ground potential VL, and the threshold of the drive transistor Tdr. It does not depend on the voltage Vth. Therefore, uneven brightness due to variations in threshold voltage Vth is suppressed.

As described above, the potential Vg at the gate of the driving transistor Tdr to determine the driving current Iel in the light emission period P _EL has a level corresponding to the voltage stored in the storage capacitor Cs at the writing period P _WRT. Since the second electrode La2 of the storage capacitor Cs is connected to the ground line 44, similarly to the first embodiment, the OLED element 17 can be caused to emit light with an intended luminance regardless of the fluctuation of the potential of the feeder line 42. it can. Although FIG. 7 illustrates the configuration in which the capacitive element C0 is disposed at the gate of the drive transistor Tdr, the capacitive element C0 is not necessarily an independent element. For example, a capacitance parasitic to other elements such as the gate capacitance of the driving transistor Tdr may be used as the capacitive element C0.

Incidentally, US Pat. No. 6,229,506 discloses a unit circuit Pb as shown in FIG. 9A as a configuration for compensating for variations in the threshold voltage Vth of the drive transistor Tdr. In this unit circuit Pb, compensation of the threshold voltage Vth of the drive transistor Tdr is realized by diode-connecting the drive transistor Tdr with the transistor Tb while fixing one electrode L of the capacitive element C1 to a specific reference potential Vref. The More specifically, first, as shown in FIG. 9B, in the reset period _PRES , the light emission control transistor Tel and the transistor Tb are turned on, and the drain and gate potentials of the drive transistor Tdr are set to a sufficiently low level. Pull it down. In the subsequent compensation period P ₁ , the transistor Tb is turned on and the drain and gate of the driving transistor Tdr are made conductive, thereby converging the potential of the gate of the driving transistor Tdr to “VH− | Vth |”. In this compensation period P ₁ , the reference potential Vref is supplied from the data line 15 to the electrode L of the capacitive element C ₁ via the transistor Ta in the on state. In the writing period P ₂ following the compensation period P ₁ , the transistor Tb is turned off to release the diode connection of the driving transistor Tdr, and then the data potential Vdata is supplied to the data line 15. As a result, the gate potential of the drive transistor Tdr is lowered from “VH− | Vth |” in accordance with the data potential Vdata. More specifically, the difference between the reference potential Vref and the data potential Vdata is divided according to the capacitance ratio between the capacitive element C1 and the capacitive element C2, and supplied to the gate of the drive transistor Tdr. In the light emission period P _EL , the light emission control transistor Tel is turned on and the drive current Iel is supplied to the OLED element 17.

Here, in the operation of compensating the threshold voltage Vth (that is, the operation of converging the gate potential of the drive transistor Tdr to “VH− | Vth |” in the guarantee period P ₁ in FIG. 9B), the gate of the drive transistor Tdr Since the potential is in the vicinity of the threshold voltage Vth, the operation takes a relatively long time. However, in the unit circuit Pb shown in FIG. 9A, since it is necessary to capture both the reference potential Vref and the data potential Vdata from the data line 15, the potential of the data line 15 is taken as the reference potential within one horizontal scanning period. It is necessary to switch alternately between Vref and data potential Vdata. Therefore, there is a problem that it is difficult to secure a sufficient time for compensation of the threshold voltage Vth. On the other hand, according to the present embodiment, since the power supply potential VH substantially plays a role as the reference potential Vref in the configuration of FIG. 9A, the potential of the data line 15 is changed to the reference potential Vref. There is no need. Therefore, it is possible to reliably execute these operations while securing a sufficient time for writing the data potential Vdata and compensating the threshold voltage Vth.

<E: Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described. In the above respective embodiments, in the writing period P _WRT, second electrode La2 of the storage capacitor Cs is illustrated a structure which is connected to the wiring to be maintained at a substantially constant potential (ground line 44). However, connection of the second electrode La2 of the storage capacitor Cs in the writing period P _WRT is not limited to this type of line. In the present embodiment, the second electrode La2 of the storage capacitor Cs is connected to a wiring to which a potential corresponding to the luminance of the OLED element 17 is supplied.

FIG. 10 is a circuit diagram showing a configuration of the unit circuit P according to the present embodiment. As shown in the figure, the data line 15 illustrated as one wiring in FIG. 1 includes a first data line 151 and a second data line 152 in the present embodiment. The source of the transistor SW1a of the unit circuit P is connected to the first data line 151. On the other hand, the transistor SW2a is interposed between the second electrode La2 of the storage capacitor Cs and the second data line 152. Therefore, when the first control signal Sa [i] transitions to the low level in the writing period P _WRT , the second electrode La2 of the storage capacitor Cs is brought into conduction with the second data line 152.

A data potential Vdata 1 is supplied from the data supply circuit 25 to the first data line 151. Similarly, the data potential Vdata2 is supplied from the data supply circuit 25 to the second data line 152. The levels of the data potentials Vdata1 and Vdata2 are selected so that the voltage Vdata (= Vdata1−Vdata2) corresponding to the difference is a voltage corresponding to the luminance of each OLED element 17. Therefore, when the transistors SW1a and SW2a are turned on in the writing period P _WRT , the holding capacitor Cs holds the voltage Vdata (that is, Vdata1−Vdata2) corresponding to the luminance specified for the OLED element 17.

  Also in the present embodiment, since the second electrode La2 of the storage capacitor Cs is connected to a wiring other than the power supply line 42, the OLED element 17 is placed regardless of the fluctuation of the potential of the power supply line 42 as in the first embodiment. Light can be emitted with the brightness of the period. Furthermore, in the present embodiment, since the luminance of the OLED element 17 is determined according to the potential difference between the first data line 151 and the second data line 152, luminance unevenness due to noise or crosstalk can be suppressed. There is an advantage. For example, even if the potentials of both the first data line 151 and the second data line 152 fluctuate by “Δ” simultaneously due to noise, the potential difference Vdata between the first data line 151 and the second data line 152 does not fluctuate at all ( Vdata = (Vdata 1 + Δ) − (Vdata 2 + Δ) = Vdata 1 −Vdata 2), and no influence of noise appears on the luminance of the OLED element 17.

  In the present embodiment, the configuration in which the first data line 151 and the second data line 152 are formed for each column is illustrated, but the data line 15 in the other column is the first data line 151 and the second data line. A configuration may also be used as one of the lines 152. For example, in FIG. 11, the first data line 151 is formed along the array of the unit circuits P in the odd columns, and the second data line 152 is formed along the array of the unit circuits P in the even columns. The configuration is illustrated. With this configuration, in the unit circuit P in the j-th column that is an odd-numbered column, the transistor SW1a is connected to the first data line 151 corresponding to the column, while the (j + 1) th adjacent to the transistor SW1a. The transistor SW2a is connected to the second data line 152 in the column. Similarly, in the unit circuit P of the (j + 1) -th column that is an even-numbered column, the transistor SW2a is connected to the second data line 152 of that column, while the first j-th column of the j-th column adjacent thereto is connected. The transistor SW1a is connected to the data line 151.

In this configuration, the first control signal Sa [i] that defines the writing period P _WRT is supplied to each unit circuit P as two systems of signals, the control signal Sa1 [i] and the control signal Sa2 [i]. That is, the control signal Sa1 [i] is supplied to each unit circuit P in the odd-numbered column via the control line 11a, and the control signal Sa2 [i] is supplied to each unit circuit P in the even-numbered column via the control line 11b. The Although the first control signal Sa [i] has been described here, the second control signal Sb [i] has the same configuration. As shown in FIG. 12, the control signal Sa1 [i] and the control signal Sa1 [i] are at a low level (active level) in a period that does not overlap each other. On the other hand, the data potential Vdata1 and the data potential Vdata2 supplied to the first data line 151 have a difference value Vdata (= Vdata1-Vdata2) in a period in which the control signal Sa1 [i] is at a low level. The level is determined according to the gradation specified for the unit circuit P in the odd-numbered column in the i-th row, and the unit circuit P in the even-numbered column in the i-th row is specified during the period when the control signal Sa2 [i] is at the low level. Each level is selected so as to have a level corresponding to the gradation, and is supplied from the data supply circuit 25 to each data line (151/152).

  Also in the configuration of FIG. 11, since the potential difference (Vdata) between the first data line 151 and the second data line 152 is taken into each unit circuit P, the same effect as in the fifth embodiment is achieved. In addition, according to this configuration, since it is sufficient to form one data line (151 or 152) for each column of the unit circuit P, the first data line 151 and each column as shown in FIG. Compared with a configuration in which both of the second data lines 152 are formed, there is an advantage that the configuration can be simplified by reducing the total number of wirings.

<F: Application example>
Next, an electronic apparatus using the light emitting device D according to the present invention will be described. FIG. 13 is a perspective view showing the configuration of a mobile personal computer that employs the light-emitting device D according to any one of the embodiments described above as a display device. The personal computer 2000 includes a light emitting device D as a display device and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002. Since the light emitting device D uses the OLED element 17 as a light emitting element, it is possible to display an easy-to-see screen with a wide viewing angle.

  FIG. 14 shows a configuration of a mobile phone to which the light emitting device D according to the embodiment is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and a light emitting device D as a display device. By operating the scroll button 3002, the screen displayed on the light emitting device D is scrolled.

  FIG. 15 shows a configuration of a personal digital assistant (PDA) to which the light emitting device D according to the embodiment is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and a light emitting device D as a display device. When the power switch 4002 is operated, various kinds of information such as an address book and a schedule book are displayed on the light emitting device D.

  Electronic devices to which the light emitting device D according to the present invention is applied include those shown in FIGS. 13 to 15, digital still cameras, televisions, video cameras, car navigation devices, pagers, electronic notebooks, electronic papers, Examples include calculators, word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, devices equipped with touch panels, and the like. The application of the light emitting device D according to the present invention is not limited to image display. For example, in an image forming apparatus such as an optical writing type printer or an electronic copying machine, a writing head that exposes a photosensitive member according to an image to be formed on a recording material such as paper is used. However, the light emitting device of the present invention is used. The electronic circuit referred to in the present invention is a concept including a unit circuit that constitutes a pixel of a display device as in each embodiment, and a circuit that is a unit of exposure in an image forming apparatus.

It is a block diagram which shows the structure of the light-emitting device which concerns on 1st Embodiment. It is a circuit diagram which shows the structure of a unit circuit. It is a circuit diagram which shows the structure of the unit circuit which concerns on 2nd Embodiment. It is a timing chart which shows the waveform of each signal supplied to a unit circuit. It is a circuit diagram which shows the structure of the unit circuit which concerns on 3rd Embodiment. It is a comparative circuit diagram for explaining the effect of the third embodiment. It is a circuit diagram which shows the structure of the unit circuit which concerns on 4th Embodiment. It is a timing chart which shows the waveform of each signal supplied to a unit circuit. It is a timing chart which shows the composition of the unit circuit concerning a proportionality, and the waveform of each signal. It is a circuit diagram which shows the structure of the unit circuit which concerns on 5th Embodiment. It is a circuit diagram which shows the structure of the unit circuit which concerns on the other aspect of 5th Embodiment. It is a timing chart which shows the waveform of each signal. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a circuit diagram which shows the structure of the conventional unit circuit.

Explanation of symbols

D: Light emitting device, 10: Pixel array unit, P: Unit circuit, 11: Control line, 111: First control line, 112: Second control line, 15: Data line, 151: First data line 152... Second data line 17... OLED element 21... Selection circuit 25... Data supply circuit 31. 44... Ground line, P1... Emission control circuit, P2... Control circuit, SW1... Switching element, SW2... Switching element, Cs. T1, T2, SW1a, SW1b, SW2a, SW2b ...... transistors, P _WRT ...... writing period, P _EL ...... emission period, P _RES ...... reset period, P _OFF ...... rest period, Sa [i] ...... 1st control signal, Sb [i] ... 2nd control signal, Vdata ... Data potential, VH ... Power supply , VL ... ground potential.

Claims (14)

A light emission control circuit for supplying a current corresponding to a voltage between the first node and the second node from the feeder line to the light emitting element;
A storage capacitor for holding a voltage between the first electrode and the second electrode;
A data line to which a data potential corresponding to a specified gradation is supplied to the light emitting element is electrically connected to the first electrode, and a reference wiring other than the power supply line is electrically connected to the second electrode. And a control circuit which is in any one of a second state in which the first electrode is electrically connected to the first node and the second electrode is electrically connected to the second node. Electronic circuit provided. The electronic circuit according to claim 1, wherein the reference wiring is a wiring to which a substantially constant potential is supplied. The light emitting element is interposed between a ground line to which a ground potential is supplied and the power supply line,
The electronic circuit according to claim 2, wherein the reference wiring is a wiring that conducts to the ground line. 2. The electron according to claim 1, wherein the reference wiring is an auxiliary data line in which a potential is set so that a voltage between the data line and the data line becomes a voltage corresponding to a gradation specified for the light emitting element. circuit. The control circuit includes: a first switching unit that causes the first electrode to conduct to either the data line or the first node; and a second switching unit that causes the second electrode to conduct to either the reference wiring or the second node. The electronic circuit according to claim 1, further comprising: 2 switching means. The light emission control circuit is a transistor interposed between the power supply line and the light emitting element, and one of a source and a gate is connected to the first node, and the other of the source and the gate is connected to the second node. The electronic circuit according to claim 1, further comprising a connected driving transistor. 7. The n-channel transistor having a source connected to the light emitting element and the second node, a drain connected to the power supply line, and a gate connected to the first node. The electronic circuit described. The light emission control circuit includes:
A driving transistor for controlling a current flowing from the feeder line to the light emitting element according to a potential of a gate;
A switching element that switches between conduction and non-conduction between one of the source or drain of the drive transistor and the gate of the drive transistor;
The electronic circuit according to claim 1, further comprising: a capacitor interposed between a gate of a driving transistor and one of the first node and the second node. A light emission control circuit that supplies a current corresponding to a voltage between the first node and the second node to the light emitting element from a power supply line, and a storage capacitor that holds a voltage between the first electrode and the second electrode. A method for driving an electronic circuit comprising:
In the first period, the data line to which the data potential corresponding to the designated gradation is supplied to the light emitting element is electrically connected to the first electrode, and the reference wiring that is a wiring other than the power supply line and the first wiring Conduction between two electrodes,
A method for driving an electronic circuit, wherein, in a second period after the first period, the first electrode and the first node are made conductive and the second electrode and the second node are made conductive. In the rest period between the first period and the second period,
The electronic circuit drive according to claim 9, wherein the first electrode is not conducted to any of the data line and the first node, and the second electrode is not conducted to any of the reference wiring and the second node. Method. The light emission control circuit includes a driving transistor that controls a current flowing from the power supply line to the light emitting element according to a gate potential, and conduction and non-conduction between one of a source or a drain of the driving transistor and a gate of the driving transistor. A switching element for switching between, and a capacitor interposed between the gate of the driving transistor and one of the first node and the second node,
In the first period, the gate of the driving transistor is set to a potential corresponding to the threshold voltage of the driving transistor by turning on the switching element.
The method for driving an electronic circuit according to claim 9, wherein the switching element is turned off in the second period. A plurality of electronic circuits each connected to a data line; data supply means for supplying a data potential to each of the plurality of data lines; and selection means for sequentially selecting each of the plurality of electronic circuits. A light emitting device,
Each of the plurality of electronic circuits includes a light emission control circuit that supplies a current corresponding to a voltage between the first node and the second node from the power supply line to the light emitting element, and a first electrode and a second electrode. A holding capacitor for holding a voltage, first switching means for conducting the first electrode to either the data line or the first node, and conducting the second electrode to any of the reference wiring and the second node Second switching means for causing
In the electronic circuit selected by the selection unit, the selection unit includes the first switching unit and the second switching unit such that the first electrode is connected to the data line and the second electrode is connected to the reference line. The first switching means and the second switching so that the first electrode is electrically connected to the first node and the second electrode is electrically connected to the second node for a non-selected electronic circuit while controlling the means. Light-emitting device that controls the means. Comprising a ground wire configured by a conductive film body distributed continuously over the plurality of electronic circuits and supplied with a substantially constant ground potential;
The light emitting element is interposed between the ground line and the power supply line,
The light-emitting device according to claim 12, wherein the reference wiring is a wiring that conducts to the ground line. An electronic apparatus comprising the light emitting device according to claim 12.

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