JP6270492B2 - Driving circuit - Google Patents

Description

  The present invention relates to a drive circuit for driving an organic EL (Electro Luminescence) display in an active matrix.

  Conventionally, in various display devices such as monitors for TVs and PCs (Personal Comuputers) or screens of mobile phones and tablet terminals, it has been common to display a high-definition image by arranging a large number of pixels on a matrix. It is necessary to apply an appropriate driving method according to the display element used.

  In organic EL displays that are self-luminous and have excellent visibility and are suitable for video display, as with liquid crystal displays, an active matrix drive system using thin film transistors (TFTs) is used to achieve high brightness. A high-definition and long-life display can be realized.

  Since the light emission intensity of the organic EL element is controlled by current, each pixel is basically driven by two TFTs, a selection TFT and a driving TFT. A capacitor is connected between the gate and source of the driving TFT, and a voltage corresponding to the pixel data is written from the selection TFT to the pixel, and the current value of the driving TFT is controlled to be constant, whereby the organic EL element is controlled. It is possible to emit light with a constant luminance.

  At this time, if the driving TFT characteristics vary, the current value largely fluctuates. Therefore, it is necessary to suppress the influence of the TFT characteristics variation using a compensation circuit. In particular, when the driving TFT is driven in a saturation region, since the current depends on the square of the threshold voltage of the TFT, how to suppress the fluctuation of the threshold voltage is important.

  The organic EL element generally has a configuration in which a driving TFT is connected to the anode side of the organic EL element due to restrictions on various materials and manufacturing processes, and various compensation circuits have been proposed so far. For example, as a compensation method called a voltage program, RMDawson et al. Have a compensation circuit that uses p-channel TFTs to show that a variation in emission luminance can be greatly reduced (for example, Non-Patent Document 1). And Patent Document 1).

  Furthermore, various techniques related to a compensation circuit that can be applied to an n channel have also been proposed (see, for example, Patent Documents 2 and 3).

  In recent years, process technology has been improved and attempts have been made to connect a cathode and a TFT of an organic EL, and a compensation circuit for that purpose has also been proposed (for example, see Patent Document 4).

Society for Information Display 1998, p.11

Special Table 2002-514320 JP 2005-345722 JP 2006-215213 JP JP 2010-160407 A

  However, the compensation circuit as described above has the following problems.

  A compensation circuit for a p-channel TFT cannot be applied to an n-channel TFT such as InGaZnO4 (IGZO), which is an oxide semiconductor material that has been researched and developed in recent years.

  Moreover, in the compensation circuit applicable to the n-channel TFT, since the source of the driving TFT is connected to the anode side, the voltage applied by the selection TFT is applied to both the capacitor and the organic EL element, and the input signal is appropriately set. Difficult to control.

  As a solution, for example, a new TFT can be connected to the anode and cathode of the organic EL element to cancel the voltage at the time of writing. However, in that case, it is necessary to form one extra TFT in addition to the compensation circuit, which not only makes the circuit configuration and driving method more complicated, but also makes the process complicated and affects the yield. .

  Furthermore, in the above-described circuit in which TFTs are connected to the anode and cathode of the organic EL element, a new TFT is required for the number of pixels in the entire display, and a large number of TFTs must be formed. There are many problems in terms of practicality, such as a reduction in the rate, a reduction in the yield of the manufacturing process, and an increase in cost.

  In particular, in a small and high-definition display, it is essential to reduce the number of TFTs for miniaturization.

  Accordingly, an object of the present invention is to provide a drive circuit that can be used for a high-definition organic EL display and that can be further miniaturized by reducing the number of TFTs.

The driving circuit according to the embodiment of the present invention includes an n-channel driving TFT in which a drain is connected to a cathode of an organic EL element and a source is connected to a reference potential point, and one of the drain or the source is connected to a data line. An n-channel type selection TFT, a first capacitor having one end connected to the other of the drain and source of the selection TFT and the other end connected to a reference potential point, and one end to the gate of the driving TFT A second capacitor having the other end connected to the one end of the first capacitor and the other of the drain or source of the selection TFT, and one of the drain or the source connected to the one end of the second capacitor. An adjustment TFT in which the other of the drain and the source is connected to the other end of the second capacitor, and one of the drain and the source is one of the second capacitors. And an n-channel setting TFT, the other of which is connected between the cathode of the organic EL element and the drain of the driving TFT, and is connected to the gate of the driving TFT. With the potential set to a predetermined data potential higher than a reference potential, the selection TFT and the adjustment TFT are turned on to charge the first capacitor from the data line, and after the charging period, While the potential of the data line is set to the predetermined data potential and the power supply to the organic EL element is cut off, the selection TFT and the setting TFT are turned on, and the driving TFT is diode-driven. performing driving by a set period to set the gate-source voltage of the driving TFT to the threshold voltage by the first capacitor and the second capacitor and

  A drive circuit that can be used for a high-definition organic EL display and can be further miniaturized by reducing the number of TFTs can be provided.

1 is a diagram illustrating a configuration of a drive circuit 100 included in an organic EL display according to Embodiment 1. FIG. 4 is a timing chart illustrating a driving method of the driving circuit according to the first embodiment. FIG. 1 is a diagram showing a drive circuit 1 connected to the cathode side of an organic EL element 10. FIG. FIG. 6 is a diagram illustrating a drive circuit 400 according to a second embodiment. FIG. 6 is a diagram illustrating a drive circuit 500 according to a third embodiment. FIG. 10 illustrates a drive circuit 600 according to a fourth embodiment. FIG. 10 is a diagram illustrating a timing chart for driving a drive circuit 600 according to a fourth embodiment. FIG. 10 shows a drive circuit 800 according to a fifth embodiment. FIG. 10 illustrates a drive circuit 900 according to a sixth embodiment. FIG. 10 is a diagram illustrating a timing chart for driving a drive circuit 900 according to a sixth embodiment. FIG. 20 shows a drive circuit 1100 according to a modification of the drive circuit 900 of the sixth embodiment. FIG. 10 shows a drive circuit 1200 according to a seventh embodiment. FIG. 20 shows a drive circuit 1300 according to a modification of the seventh embodiment. 8 is a timing chart schematically showing a relationship among a compensation period, a pixel data writing period, and a light emission period in an organic EL display using the drive circuit of Embodiments 1 to 7. 8 is a timing chart schematically showing a relationship among a compensation period, a pixel data writing period, and a light emission period in an organic EL display using the drive circuit of Embodiments 1 to 7.

  Embodiments to which the drive circuit of the present invention is applied will be described below.

<Embodiment 1>
FIG. 1 is a diagram illustrating a configuration of a drive circuit 100 included in the organic EL display according to the first embodiment, and FIG. 2 is a diagram illustrating a timing chart representing a drive method of the drive circuit according to the first embodiment. Note that a portion corresponding to one pixel of the organic EL display of Embodiment 1 is a portion including the drive circuit 100 and the organic EL element (OLED) 10. That is, one organic EL element 10 and one drive circuit 100 are disposed in each pixel of the organic EL display.

  The driving circuit 100 according to the embodiment includes a selection TFT 101, a capacitor C1 (102), a capacitor C2 (103), a driving TFT 104, and a setting TFT 105. Here, for the selection TFT 101 and the setting TFT 105, either of the left and right terminals may be a drain or a source. However, for convenience of explanation, the terminal located on the left side in the figure is the drain and on the right side in the figure. The description will be made assuming that the terminal located is the source.

  The selection TFT 101 has a drain connected to the terminal 100A, and a data voltage Vin is input through the data line. The source of the selection TFT 101 is connected to the capacitor C1 (102). The gate of the selection TFT 101 is connected to the selection line, and the selection voltage Vsel is input.

  One end of the capacitor C1 (102) is connected to the source of the selection TFT 101, and the other end is connected to the connection point A.

  The capacitor C2 (103) has one end connected to the connection point A and the other end connected to the terminal 100B. The terminal 100B is connected to the reference potential point and receives the voltage Vb. The voltage Vb is 0V as an example. That is, here, the reference potential is the ground potential.

  The driving TFT 104 has a drain connected to the connection point B, a source connected to the terminal 100B, and a gate connected to the connection point A. The driving TFT 104 is provided to allow a current to flow through the organic EL element 10.

  The setting TFT 105 has a drain connected to the connection point A, a source connected to the connection point B, and a gate to which the setting voltage Vc is input.

  The connection point A is a connection point between the other end of the capacitor C1 (102), one end of the capacitor C2 (103), and the drain of the setting TFT 105. The connection point B is a connection point of the cathode of the organic EL element 10, the drain of the driving TFT 104, and the source of the setting TFT 105.

  In addition, since the organic EL element 10 which is an insulator has a structure sandwiched between electrodes, it actually has an equivalent circuit configuration in which a capacitor is connected in parallel to a symbol of a diode. All notations in the figure relating to the capacitance associated with the EL element 10 are omitted.

  Next, driving of the organic EL element 10 by the driving circuit 100 according to the first embodiment will be described with reference to the timing chart of FIG. Here, time T1 to T8 is referred to as a compensation period, time T9 to T12 is referred to as a pixel data writing period, and time T13 and subsequent times are referred to as a light emission period.

  When Vb = Voff (0 V) is constant throughout the entire period, and when the selection TFT 101 is turned on by setting Vsel = Vh at time T1, the potential at the connection point between the capacitor C1 (102) and the selection TFT 101 becomes V1 = Voff. .

  Here, when Vd = Voff is changed to Vd = Vh1 at time T2, and when the voltage Vc is changed from VL to VH at T3 and the setting TFT 105 is turned on, the connection point B is changed from the connection point B to the connection point A through the organic EL element. A current flows and the potential is held by the capacitors C1 (102) and C2 (103), and the potential Va at the connection point A and the potential Vb at the connection point B are Va = Vb.

  At that time, Vh1 (> Vth) is set in advance so that the voltage is higher than the threshold voltage Vth of the driving TFT 104.

  When Vc = VL is set at time T4 and Vd = Voff is set at time T5, the potential at the connection point A is maintained, but the potential at the connection point B decreases due to the influence of the capacitance at both ends of the organic EL element.

  After that, when Vc = VH and the setting TFT 105 is turned on at time T6, a current flows from the connection point A to the connection point B and Va = Vb again. At this time, since the TFT 204 is turned on, the drain of the TFT 204 A current flows from D to the source S side and continues to flow until the gate-source voltage Vgs of the driving TFT 104 reaches the threshold voltage Vth.

  Here, the threshold voltage Vth of the driving TFT 104 is held in the capacitors C1 and C2, and compensation of the threshold voltage Vth of the driving TFT 104 can be realized.

  Vc = VL at time T7 and Vsel = Vl at time T8. After the setting TFT 105 and the selection TFT 101 are turned off, pixel data in consideration of the capacitance division of the capacitors C1 and C2 into Vin at times T9 to T12. When the potential Vx is input as a signal and the selection TFT 101 is turned on at Vsel = Vh at times T10 to T11, the voltage at the connection point between the capacitor C1 and the selection TFT 101 becomes Vx. Here, the potential Vy corresponding to the pixel data (voltage Vin) is written to the connection point A by the capacitive division of the capacitors C1 and C2, and Va = Vy + Vth.

  Finally, when Vd = Vh2 at time T13, the driving TFT 104 is turned on, a current corresponding to Vgs (= Vy + Vth) of the driving TFT 104 flows, and the organic EL element 10 remains constant until Vd = Voff. Emits light.

Here, the saturation current I of the driving TFT 104 is generally expressed by the following equation (1) using a coefficient α.
I = α (Vgs−Vth) ² (1)
For this reason, even if the threshold voltage Vth of the driving TFT 104 varies for each pixel (for each driving circuit 100 connected to each organic EL element 10), if Vgs = Vy + Vth is substituted, the term of Vth disappears. The influence of variation can be canceled.

  In order to obtain an appropriate compensation function in the driving circuit 100 of Embodiment 1, it is necessary to reduce the leakage current as much as possible when the selection TFT 101 and the setting TFT 105 are off. It is necessary to set the voltage Vsel and the voltage Vc to appropriate voltage values in order to surely turn off according to the characteristics.

  Therefore, the voltages VL and Vl that are the low-level voltages of the voltage Vsel and the voltage Vc do not need to be constant values in all the periods. For example, the voltage Vsel and the voltage Vc correspond to a decrease in the potential at the connection point B in the period from time T5 to T6. It is also possible to set the voltage VL to a lower value than other off states (for example, after T7).

  The voltage Vh1 of the pulse signal applied to the voltage Vd is set to a value necessary for threshold compensation, but is preferably set as low as possible in order to suppress power consumption, and the power supply circuit configuration is simple. Vh1 = Vh2 is desirable from the viewpoint of reducing power consumption, particularly in large displays.

  Further, Va = Vb when the setting TFT 105 is turned on at time T6, but it is indispensable that the driving TFT 104 is turned on and has a sufficient potential for current to flow for threshold compensation. Therefore, it is important to set a sufficiently large combined capacity of the capacitors C1 and C2 and accumulate sufficient charges during the period from time T3 to T4.

  Here, the driving circuit 1 for comparison will be described with reference to FIG.

  FIG. 3 is a diagram showing the drive circuit 1 connected to the cathode side of the organic EL element 10. The comparison drive circuit 1 shown in FIG. 3 includes terminals 1A and 1B, a selection TFT 301, a capacitor 302, and a drive TFT 303. Terminals 1A and 1B are terminals corresponding to terminals 100A and 100B of drive circuit 100 of the first embodiment shown in FIG. 1, respectively. The selection TFT 301 and the driving TFT 303 correspond to the selection TFT 101 and the driving TFT 104 of the driving circuit 100 of Embodiment 1 shown in FIG.

  When the voltage Vin corresponding to the input image is applied to the selection TFT 301, the voltage Vin is written into the capacitor 102, and the source-gate voltage Vgs of the driving TFT 303 is kept constant by the capacitor 102.

  At this time, the power supply voltage Vd is supplied to the anode side of the organic EL element 10, and the current flowing through the driving TFT 303 and the organic EL element 10 is controlled to be constant by Vgs, so that the organic EL element 10 emits light.

  At this time, if the threshold voltage Vth of the driving TFT 303 is varied, the current flowing through the driving TFT 303 is different for each pixel even with the same Vgs, so that the light emission intensity of the organic EL element 10 also varies.

  That is, in the comparative driving circuit 1, the threshold voltage of the driving TFT 303 cannot be compensated. Therefore, when the organic EL display is viewed as a whole, the emission intensity of each organic EL element 10 varies. . Therefore, it is necessary to have an appropriate compensation function like the drive circuit 100 of the first embodiment.

  In addition, as a circuit for compensating the threshold voltage of the driving TFT, it is considered that the threshold voltage can be easily compensated (corrected) as the number of TFTs is increased. However, increasing the number of TFTs increases the area required for wiring and TFTs, making it difficult to miniaturize and reducing the yield of organic EL display panels. Therefore, the number of TFTs included in the drive circuit It is important to minimize as much as possible.

  In this respect, the drive circuit 100 according to the first embodiment shown in FIG. 1 has only one TFT and one capacitor larger than the comparative drive circuit 1, so that there is a demand for miniaturization and miniaturization. It can respond enough.

  In the driving circuit 100 of Embodiment 1 (see FIG. 1), the source of the driving TFT 104 is connected to the wiring (terminal 100B) that becomes the reference potential Vb, and the source potential does not fluctuate. Therefore, the input of pixel data can be easily controlled by the potential Vin. This is the same in all embodiments described later.

<Embodiment 2>
FIG. 4 is a diagram illustrating a drive circuit 400 according to the second embodiment. The drive circuit 400 has a circuit configuration in which the connection relationship between the selection TFT 101 and the capacitors 102 and 103 is changed from the drive circuit 100 of Embodiment 1 (see FIG. 1). Since the drive circuit 400 of the second embodiment has a circuit configuration obtained by modifying the drive circuit 100 of the first embodiment, the components corresponding to the components of the drive circuit 100 of the first embodiment are the same as those in the 400 series. It shows with a code | symbol and duplication description is abbreviate | omitted.

  The drive circuit 400 includes terminals 400A and 400B, a selection TFT 401, a capacitor C1 (402), a capacitor C2 (403), a drive TFT 404, and a setting TFT 405.

  The connection point A is a connection point of one end of the capacitor C2 (403), the gate of the driving TFT 404, and the drain of the setting TFT 405. The connection point B is a connection point of the cathode of the organic EL element 10, the drain of the driving TFT 404, and the source of the setting TFT 405. The connection point R is a connection point between the source of the selection TFT 401, the other end of the capacitor C1 (402), and one end of the capacitor C2 (403).

  The capacitor C1 (402) and the capacitor C2 (403) are connected in series between the connection point A and the terminal 400B, and the source of the selection TFT 401 is connected at the connection point R between the capacitor C1 and the capacitor C2. Except for this point, the driving TFT 404, the setting TFT 405, and the organic EL element 10 have the same configuration as that of the driving circuit 100 of the first embodiment.

  Therefore, the drive circuit 400 of Embodiment 2 can be driven according to the drive timing chart shown in FIG.

  The operation mechanism different from the drive circuit 100 (see FIG. 1) of the first embodiment is a portion related to the potential held in the capacitors C1 and C2. That is, the threshold voltage Vth is written to the capacitor C2 (403) in the period (T1 to T8) in which the threshold voltage Vth is corrected, and Vx is written to the capacitor C1 (402) in the pixel data writing period (T9 to T12). .

  Therefore, unlike the drive circuit 100 of the first embodiment, the gate-source voltage Vgs of the driving TFT 404 is expressed as Vgs = Vx + Vth, and the potential of Vin can be written as it is. That is, as compared with the driving circuit 100 in the first embodiment, there is an advantage that the driving voltage can be easily set.

  When this gate-source voltage Vgs is substituted into equation (1), the term of the threshold voltage Vth disappears, so that even if the threshold voltage Vth of the driving TFT 404 varies, the current flowing through the organic EL element 10 is controlled to be constant. It becomes possible to do.

<Embodiment 3>
FIG. 5 is a diagram illustrating a drive circuit 500 according to the third embodiment. The drive circuit 500 has a circuit configuration in which a rectifying TFT 507 is inserted between the organic EL element 10 and the connection point B shown in FIG. The drive circuit 500 is the same as the drive circuit 100 of Embodiment 1 except that the gate and drain of the rectifying TFT 507 are connected and the TFT functions as a diode. Therefore, the drive circuit 500 of Embodiment 3 can be operated with the timing chart shown in FIG.

  In addition, the component corresponding to the component of the drive circuit 100 of Embodiment 1 is shown with the same code | symbol of 500 series, and duplication description is abbreviate | omitted.

  The drive circuit 500 includes a selection TFT 501, a capacitor C 1 (502), a capacitor C 2 (503), a drive TFT 504, a setting TFT 505, and a rectifying TFT 507.

  For example, in the driving circuit 100 of the third embodiment, in the driving circuit 100 shown in FIG. 1, the potential of the connection point B is reduced when the potential of the connection point B decreases relatively at time T5 shown in FIG. It is effective in suppressing the decrease. Except this, it is possible to operate almost the same as the operation mechanism of the drive circuit 100 of the first embodiment.

  The rectifying TFT 507 can be inserted between the organic EL element 10 of the second embodiment shown in FIG. 4 and the connection point B. In this case, the same effect can be imparted to the second embodiment. is there.

  In the third embodiment, since the rectifying TFT 507 is diode-connected, it is not necessary to take out a wiring for controlling the gate to the outside of the driving circuit 500, and it is not necessary to apply a signal from the outside.

  However, for the purpose of reducing the leakage current according to the characteristics of the rectifying TFT 507, the gate terminal of the rectifying TFT 507 may be made independent and driven by an external signal. The rectifying TFT 507 can also be applied to the following Embodiments 4, 5, 6, and 7 for the purpose of suppressing charging of the organic EL capacitor.

<Embodiment 4>
FIG. 6 is a diagram illustrating a drive circuit 600 according to the fourth embodiment. The drive circuit 600 has a circuit configuration in which a power supply TFT 608 having a gate and a drain connected to function as a diode is connected to a connection point B of the drive circuit 100 according to the first embodiment shown in FIG. The circuit configuration is the same as that of the first embodiment. Components corresponding to the components of the drive circuit 100 according to the first embodiment are denoted by the same reference numerals in the 600s, and redundant description is omitted.

  The driving circuit 600 includes terminals 600A and 600B, a selection TFT 601, a capacitor C1 (602), a capacitor C2 (603), a driving TFT 604, a setting TFT 605, and a power supply TFT 608.

  In the fourth embodiment, it is necessary to form one TFT more than in the first embodiment. However, since no current flows through the organic EL element 10 during the compensation period of the threshold voltage Vth, the long lifetime of the organic EL element 10 is achieved. In addition to being effective, the drive operation can be simplified.

  Further, although the correction power supply voltage Vp is required, it is a system different from the power supply voltage Vd of the organic EL element 10 and is low in voltage and constant, so that it can be easily driven by an external driver.

  FIG. 7 is a diagram illustrating a timing chart for driving the drive circuit 600 according to the fourth embodiment. In FIG. 7, times T21 to T26 are compensation periods, T27 to T30 are referred to as pixel data writing periods, and T31 and subsequent periods are referred to as light emission periods, and Vb = Voff is constant throughout the period.

  First, when Vsel = Vh at time T21, the connection point A has a circuit configuration in which a capacitor C1 (602) and a capacitor C2 (603) are connected in parallel. Here, when Vp = Vh1 at time T22, the potential at the connection point B increases, and when Vc = VH at time T23, the potentials at the connection point A and the connection point B (Va and Vb, respectively) become equal, and the capacitance C1 And the potential Va = Vb are written to C2 and the driving TFT 604 is turned on, and a current flows.

  At this time, the circuit operation at time T22 and time T23 is set to the operation at time T22 (Vp = Vh1) first.

  Next, when Vp = Voff at time T24, the electric charges written at the connection point A while maintaining Va = Vb continue to flow until the gate-source voltage Vgs of the driving TFT 604 reaches the threshold voltage Vth. Here, the threshold voltage Vth of the driving TFT 604 is held in the capacitors C1 and C2, and the threshold voltage Vth of the driving TFT 604 is compensated.

  The pixel data writing period and the light emission period after time T27 are the same as those in Embodiment 1, and thus are omitted here.

  Further, the drive circuit 600 of the fourth embodiment has capacitors C1 and C2 connected in series between the connection point A and the line of the potential Vb, similarly to the drive circuit 400 of the second embodiment (see FIG. 4). The selection TFT 601 may be connected to the connection portion between the capacitors C1 and C2. That is, the power supply TFT 608 is connected to the connection point B in the configuration of the drive circuit 400 (see FIG. 4) of the second embodiment, and in this case, the driving can be performed according to the timing chart of FIG.

  Since the power supply TFT 608 has a diode configuration with the gate and drain connected, when applying a pulse of the voltage Vp (of amplitude Vp) of the correction power source at times T22 to T24, the voltage Vp It is possible to perform drive control of the power supply TFT 608 with a voltage value.

  By applying a signal from another line by making the gate of the power supply TFT 608 independent of the drain, it is possible to internally drive the timing of the pulses at times T22 to T24. Since the configuration is complicated, it is basically preferable to use diode connection.

<Embodiment 5>
FIG. 8 shows a drive circuit 800 according to the fifth embodiment. The drive circuit 800 has a circuit configuration in which a power supply TFT 808 having a gate and a drain connected to function as a diode is connected to the connection point A of the drive circuit 100 of the first embodiment shown in FIG. These are the same as the circuit configuration of the first embodiment. Components corresponding to the components of the drive circuit 100 according to the first embodiment are denoted by the same reference numerals in the 800s, and redundant description is omitted.

  The drive circuit 800 includes terminals 800A and 800B, a selection TFT 801, a capacitor C1 (802), a capacitor C2 (803), a drive TFT 804, a setting TFT 805, and a power supply TFT 808.

  In FIG. 8, the power supply TFT 808 is illustrated as being connected at a point A ′ so that the power supply TFT 808 can be easily seen. However, the connection points A and A ′ may be considered to be the same contact point. A unified explanation will be given.

  The drive circuit 800 of the fifth embodiment has a configuration in which the connection point of the power supply TFT 608 of the drive circuit 600 of the fourth embodiment is changed from the connection point B to the connection point A. Therefore, like the drive circuit 600 of the fourth embodiment, it is necessary to form one more TFT as compared with the first embodiment, but no current flows through the organic EL element 10 during the compensation period of the threshold voltage Vth. Therefore, it is effective for extending the life of the organic EL element 10 and can further simplify the driving operation.

  Further, like the drive circuit 600 of the fourth embodiment, the correction power supply voltage Vp is required, but it is a separate system from the power supply voltage Vd of the organic EL element 10, and is low voltage and constant, so It can be easily driven by a driver.

  The operation of the drive circuit 800 of the fifth embodiment is basically the same as that of the drive circuit 600 (see FIG. 6) of the fourth embodiment, and can be explained by the timing chart shown in FIG. Hereinafter, FIG. 7 is used.

  First, when Vsel = Vh at time T21, the connection point A has a circuit configuration in which a capacitor C1 (602) and a capacitor C2 (603) are connected in parallel. Here, when Vp = Vh1 at time T22, the potential at the connection point A rises and is written in the capacitors C1 and C2.

  Further, when Vc = VH at time T23, the potentials of the connection point A and the connection point B (Va and Vb, respectively) are equal, and the potential written in the capacitors C1 and C2 is Va = Vb. As a result, the driving TFT 604 is turned on and a current flows.

  At this time, the circuit operation at the time T22 and the time T23 is set at the time T22 first. However, in the driving circuit 800 of the fifth embodiment, the circuit operation may be set to the reverse or the same timing.

  Next, when Vp = Voff at time T24, the drain-source connection is maintained until the gate-source voltage Vgs of the driving TFT 604 reaches the threshold voltage Vth due to the charge written to the connection point A while maintaining Va = Vb. Current continues to flow. Here, the threshold voltage Vth of the driving TFT 604 is held in the capacitors C1 and C2, so that the threshold voltage Vth of the driving TFT 604 is compensated.

  In the case of the driving circuit 800 of the fifth embodiment, unlike the driving circuit 600 of the fourth embodiment (see FIG. 6), when the power supply TFT 808 is turned on while the setting TFT 805 is turned off, the driving circuit 800 is connected to the connection point A. Since potentials are written in the capacitors C1 and C2, the circuit operations at time T23 and time T24 in FIG. 7 can be reversed.

  That is, even when the timing of setting Vp = Voff at time T24 is earlier than the timing of setting Vc = VH at time T23, it is possible to obtain the effect of compensating the threshold voltage Vth, and the drive circuit 600 according to the fourth embodiment. Compared to the above, it is possible to widen the drive time setting margin.

  Note that the pixel data writing period and the light emission period after time T27 are the same as those in Embodiment 1, and thus are omitted here.

  Similarly to the drive circuit 400 (see FIG. 4) of the second embodiment, the drive circuit 800 of the fifth embodiment connects capacitors C1 and C2 in series between the connection point A and the terminal 800B. The selection TFT 801 may be connected to the connection portion between C1 and C2. In other words, the power supply TFT 808 is connected to the connection point A of the circuit configuration of the second embodiment, and in this case also, the driving can be driven by the driving timing chart of FIG.

  Note that since the power supply TFT 808 has a diode configuration in which the gate and the drain are connected, when the voltage pulse is applied at times T22 to T24, the drive control of the power supply TFT 808 is performed with the voltage Vp. Is possible. It is possible to apply a signal from another line by making the gate of the power supply TFT 808 independent of the drain and to drive the power supply internally. However, in this case, the circuit configuration becomes complicated, such as an increase in wiring. Is preferably diode-connected.

<Embodiment 6>
FIG. 9 is a diagram illustrating a drive circuit 900 according to the sixth embodiment. FIG. 10 is a diagram illustrating a timing chart for driving the drive circuit 900 according to the sixth embodiment.

  In the drive circuit 900 according to the sixth embodiment, when a potential is written to the connection point A to compensate for the threshold voltage Vth, not the power supply line (Vd) to the organic EL element 10 (see FIG. 1), A method of writing from the selection TFT 901 is applied. That is, in the drive circuit 900 according to the sixth embodiment, a current necessary for compensation of the threshold voltage Vth is supplied through the data line (Vin).

  Except for this point, the drive circuit 900 according to the sixth embodiment has a circuit configuration obtained by modifying the drive circuits 100 and 400 according to the first and second embodiments. Therefore, the drive circuits 100 and 400 according to the first and second embodiments. Constituent elements corresponding to these constituent elements are denoted by the same reference numerals in the 900s, and redundant description is omitted.

  The drive circuit 900 includes terminals 900A and 900B, a selection TFT 901, a capacitor C1 (902), a capacitor C2 (903), a drive TFT 904, a setting TFT 905, and an adjustment TFT 909.

  In the driving circuit 900 according to the sixth embodiment, the voltage to be written for the compensation of the threshold voltage Vth may be a lower voltage as long as it is larger than Vth, and the current flowing through the driving TFT 904 during the compensation period is the maximum current required for light emission of the organic EL element 10. However, in order to ensure a sufficient current capacity, it is preferable to drive with an appropriate external driver.

  In this case, when writing to one scanning line, current flows through all the data lines. For example, a method of switching a low voltage power supply for correction with an external driver and connecting to the data line is applied. be able to.

  The drive circuit 900 of the sixth embodiment has a configuration in which an adjustment TFT 909 is connected between the connection point A and the R point in the drive circuit 400 of the second embodiment shown in FIG. In FIG. 9, although it is described as the R ′ point, since it is substantially the same point, it is described as the R point below.

  Also, T41 to T48 are referred to as a compensation period, T49 to T52 are referred to as a pixel data writing period, and T53 and subsequent periods are referred to as a light emission period, and Vb = Voff is constant (usually 0 V) in all periods. The operation of the drive circuit 900 is as follows.

  First, when Vin = Vz is set at time T41 and Vsel = Vh is set at time T42, when Vq = Vh1 is set at times T43 to T44, the selection TFT 901 and the adjustment TFT 909 are turned on, and the connection point The voltage Va at A and the voltage Vr at point R are Va = Vr = Vz and are written in the capacitors C1 (902) and C2 (903). Here, the voltage Vz is set to a voltage larger than the threshold voltage Vth of the driving TFT 904.

  Here, the operation at time T42 and time T43 may be the same timing regardless of which operation is earlier.

  When Vc = VH is set at time T45 and the TFT 905 is turned on, the selection TFT 901 is turned on, so that the driving TFT 904 is turned on while the voltage at the R point is kept at Vr = Vz. , Current flows until Va = Vb = Vth. At this time, Vr> Va.

  After this, Vc = VL is set at time T46 to turn off the setting TFT 905, Vsel = Vl is set at time T47, and Vin = Voff is set at time T48 to turn off the selection TFT 901. Then, the threshold voltage Vth is written in the series capacitance of the capacitors C1 and C2.

  Note that the pixel data writing period and the light emission period after time T29 are omitted here because they have the same operation mechanism as in the fourth embodiment, but the term of the threshold voltage Vth disappears in equation (1). As in the first to fifth embodiments, the threshold voltage Vth can be compensated. Note that the magnitude of the input voltage is basically set to Vin ≧ Vr.

  FIG. 11 is a diagram illustrating a drive circuit 1100 according to a modification of the drive circuit 900 according to the sixth embodiment. The drive circuit 1100 includes terminals 1100A and 1100B, a selection TFT 1101, a capacitor C1 (1102), a capacitor C2 (1103), a drive TFT 1104, a setting TFT 1105, and an adjustment TFT 1109.

  A drive circuit 1100 illustrated in FIG. 11 has a circuit configuration in which the adjustment TFT 909 illustrated in FIG. 9 is not connected to both ends of the capacitor C2 (903) but is connected between the connection point A and the terminal 1100A. For this reason, although the connection is different from FIG. 9, basically the same operation is realized. Accordingly, the operation can be performed according to the drive timing chart shown in FIG. 10, and the principle for compensation is the same as that in FIG.

<Embodiment 7>
FIG. 12 shows a drive circuit 1200 according to the seventh embodiment. In FIG. 12, an adjustment TFT 1209 is added in parallel between the connection point A of the drive circuit 100 of the first embodiment shown in FIG. 1 and the terminal 100A. In addition, although connection point A 'is shown in FIG. 12, since it is the same connection point as the connection point A, it is called the connection point A below.

  The drive circuit 1200 according to the seventh embodiment inputs the selection TFT 1201 not through the organic EL element 10 when writing a potential at the connection point A in order to compensate the threshold voltage Vth in the circuit according to the first embodiment. The potential is directly written using the data voltage from the side (terminal 1200A). That is, in the drive circuit 1200 according to the seventh embodiment, a current necessary for voltage compensation is supplied through the data line.

  Except for this point, the drive circuit 1200 according to the seventh embodiment has a circuit configuration obtained by modifying the drive circuit 100 according to the first embodiment. Therefore, the components correspond to the components of the drive circuit 100 according to the first embodiment. Are denoted by the same reference numerals in the 1200s, and redundant description is omitted.

  The drive circuit 1200 includes terminals 1200A and 1200B, a selection TFT 1201, a capacitor C1 (1202), a capacitor C2 (1203), a drive TFT 1204, a setting TFT 1205, and an adjustment TFT 1209.

  In Embodiment 7, the voltage written to the capacitors C1 (1202) and C2 (1203) in order to compensate the threshold voltage Vth may be a low voltage as long as it is larger than Vth, and the current flowing through the driving TFT 1204 during the compensation period is organic. It can be set smaller than the maximum current required for light emission of the EL element 10. However, in order to ensure a sufficient current capacity in writing to the capacitors C1 (1202) and C2 (1203) by the data voltage Vin, a countermeasure such as providing an appropriate external driver for the data line is performed as necessary. However, it is preferable to perform writing to the capacitors C1 (1202) and C2 (1203).

  In this case, when writing to one scanning line, current flows through all the data lines. For example, a method of switching a low voltage power supply for correction with an external driver and connecting to the data line is applied. be able to.

  Further, the drive circuit 1200 illustrated in FIG. 12 can be modified like the drive circuit 1300 illustrated in FIG.

  FIG. 13 shows a drive circuit 1300 according to a modification of the seventh embodiment.

  A drive circuit 1300 illustrated in FIG. 13 is obtained by switching the connection destination of the drain of the adjustment TFT 1209 of the drive circuit 1200 illustrated in FIG. 12 from the terminal 1200A to the source of the selection TFT 1301.

  The drive circuit 1300 includes terminals 1300A and 1300B, a selection TFT 1301, a capacitor C1 (1302), a capacitor C2 (1303), a drive TFT 1304, a setting TFT 1305, and an adjustment TFT 1309. A connection point between the source of the selection TFT 1301, one end of the capacitor C1 (1302), and the drain of the adjustment TFT 1309 is referred to as a connection point S.

  The drive circuit 1300 illustrated in FIG. 13 can be operated according to the drive timing chart illustrated in FIG. 10 in the same manner as the drive circuit 900 of Embodiment 6 (see FIG. 9). Note that the drive circuit 1200 illustrated in FIG. 12 can be substantially described based on the same operation principle, and thus the operation of the drive circuit 1300 illustrated in FIG. 13 is described here. Moreover, FIG. 10 is used here.

  First, in FIG. 10, when Vin = Vz is set at time T41 and Vsel = Vh is set at time T42, when Vq = Vh1 is set from time T43 to T44, the selection TFT 1301 and TFT 1309 are turned on and connected. The potential Va at the point A is Va = Vz. As a result, the voltage Vz is written to the capacitor C1 (1302) and the capacitor C2 (1303). Here, Vz is set to a voltage larger than the threshold voltage Vth of the driving TFT 1304.

  Here, as in the sixth embodiment, the operation at time T42 and T43 may be the same timing regardless of which operation is earlier.

  At time T45, when Vc = VH is set and the TFT 1305 is turned on, the selection TFT 1301 is in an on state. Therefore, the driving TFT 1304 is turned on while the potential at the S point is kept at Vs = Vz. Current flows until Vb = Vth. At this time, Vs> Va.

  After that, Vc = VL is set at time T46 to turn off the adjustment TFT 1305, Vsel = Vl is set at time T47, Vin = Voff is set at time T8, and the selection TFT 901 is turned off. And C2 is maintained in a state where Vth is written.

  Note that the pixel data writing period and the light emission period after time T29 are omitted here because they have the same operation mechanism as in the first embodiment, but the term of the threshold voltage Vth disappears in the equation (1). It is possible to compensate for Vth. Note that the magnitude of the data voltage Vin is basically set to Vin ≧ Vs.

[Common Driving Method of Embodiments 1 to 7]
Since the driver circuits (100, 400, 500, 600, 800, 900, 1100, 1200, 1300) of Embodiments 1 to 7 are configured with about three or four TFTs in one pixel, It has an advantageous circuit configuration for miniaturization and high-speed driving of an organic EL display, which is advantageous for pixel miniaturization and further can suppress a decrease in yield due to simplification of the manufacturing process.

  In the first to seventh embodiments, the source of the driving TFT (104, 404, 504, 604, 804, 904, 1104, 1204, 1304) is a wiring (via the terminals 100B, 400B, 500B, via the reference potential Vb, 600B, 800B, 900B, 1100B, 1200B, 1300B), and the source potential does not fluctuate. For this reason, input of pixel data can be easily controlled by the voltage Vin (via terminals 100A, 400A, 500A, 600A, 800A, 900A, 1100A, 1200A, 1300A).

  The first to seventh embodiments function by causing a current to flow into the gate of the driving TFT to hold the charge in the capacitor, and causing the current to flow out of the accumulated capacitor by diode-connecting the driving TFT. It has a circuit configuration for performing it efficiently and operates according to an appropriate drive timing chart.

  In the first to seventh embodiments, pixel data is written after the threshold voltage Vth of the driving TFT is compensated (corrected), and finally the light emitting period is reached when the power supply voltage Vd is turned on. Emits light. That is, the compensation period, the pixel data writing period, and the light emission period can be set independently.

  Therefore, in the driving circuits of Embodiments 1 to 7, various light emission periods can be provided after the compensation period and the pixel data writing period are completed. Here, how to set the compensation period, the pixel data writing period, and the light emission period for all the scanning lines will be described with reference to FIGS.

  14 and 15 are timing charts schematically showing the relationship between the compensation period, the pixel data writing period, and the light emission period in the organic EL display using the drive circuit of the first to seventh embodiments. The timing charts shown in FIGS. 14 and 15 are arranged in the vertical direction for all the scanning lines included in the organic EL display while shifting the timing chart for each scanning line shown in FIGS. Is.

  As shown in FIG. 14A, the compensation period, the pixel data writing period, and the light emission period may be performed for all the scanning lines while sequentially shifting the time. In this case, the organic EL elements 10 corresponding to the scanning lines emit light sequentially.

  Further, as shown in FIG. 14B, all the scanning lines are divided into a plurality of blocks, and the compensation period and the pixel data writing period are the same for all the scanning lines as in FIG. The light emission period may be performed simultaneously for each block by sequentially shifting the time. In this case, light emission is performed simultaneously for each block.

  Further, as shown in FIG. 14C, the compensation period and the pixel data writing period are performed while sequentially shifting the time with respect to all the scanning lines, and the light emitting period is performed simultaneously for all the scanning lines. Good. In this case, light emission is performed simultaneously for all the scanning lines.

  14A and 14B show the case where the writing time of all the pixel data is consumed for one field, the writing period and the light emitting period may be set freely.

  In addition, in the case where a method of emitting light in blocks or a method of simultaneously emitting light for all scanning lines is applied to the organic EL display using the drive circuit of Embodiments 1 to 7, as shown in FIG. A voltage compensation period is provided for each block, or provided simultaneously for all scanning lines, and then a pixel data writing period is provided for each block, or provided simultaneously for all scanning lines, and then a light emission period is provided for each block. Or all scanning lines can be provided simultaneously. In this case, since the threshold voltage compensation period can be shortened compared to the sequential light emission method shown in FIG. 14A, not only can the time required for threshold correction be set longer, but it is also used in the current television system. In the case of driving at a higher frame rate than the 60 Hz driving, for example, when applied to 120 Hz driving or 240 Hz driving, the effect is particularly exerted.

  In particular, Embodiments 1 to 7 can be applied to Super Hi-Vision with 4000 scanning lines, and high-quality moving image display can be performed using the driving method shown in FIGS. In addition, at a high frame rate (120 Hz or more), it is effective to apply not only the simultaneous light emission method but also the method of compensating the threshold voltage for each block or the previous pixel all at once as described above.

  In addition, when the first to seventh embodiments are applied to Super Hi-Vision as described above, the number of scanning lines increases and the time required per line is shortened, so the screen is divided into blocks and each block is divided. It is also possible to introduce a division method to investigate.

  In Embodiments 1 to 7, the light emission time in one frame may be freely set, such as effectively applying black insertion, as in the conventional driving method. In particular, in order to improve the moving image characteristics, it is desirable that the light emission time of the organic EL element 10 is 50% or less per frame. However, in consideration of the life of the organic EL element 10 and the light emission efficiency, 25% to 75%. It is desirable that the degree.

  Such black insertion can be easily controlled by the on-time of the power supply voltage Vd, but basically it can be turned on / off by an external circuit in units of one scanning line. ) And (C), it is possible to drive the power supply lines for each block or all the scanning lines simultaneously.

  Further, in the drive circuits (600, 800, 900, 1100, 1200, 1300) of the fourth to seventh embodiments, the power supply voltage Vd does not need to perform any on / off operation such as application of a pulse voltage during the compensation period. Therefore, since only the binary operation of on / off needs to be controlled during the light emission period, power consumption can be reduced and a simple external driver can be used.

  Further, in Embodiments 1 to 7, as in the conventional driving method, a reset period in which each potential or current in the previous field is returned to the initial state after the light emission period may be applied. In that case, after setting Vd = Voff at the end of the light emission period, a pulse voltage may be applied to each TFT to reset each TFT to an initial state.

  In particular, in FIGS. 14B and 14C, resetting is performed collectively by a plurality of scanning lines, so that the reset time can be set longer.

  In the first to seventh embodiments, the reset is preferably performed immediately after the end of the light emission period, but may be performed immediately before the compensation of the threshold voltage. In addition, a standby time may be provided after reset and threshold voltage compensation are performed after the end of the light emission period, and writing may be started at the start of the next field. That is, in this method, the compensation period of the threshold voltage Vth, the pixel data writing time, and the light emission period can be controlled independently, so that the timing and time distribution of each period can be freely set in each field including the reset period. be able to.

  In the first to seventh embodiments, in order to increase the response speed when applying Vsel = Vl, it is desirable to reduce the resistance of the wiring (data wiring) connected to Vin as much as possible. It is also possible to provide TFTs that connect the connection point with C1 and the wiring that becomes the reference voltage Vb as the source and drain, and supply Vb = Vl in synchronization with the time chart of Vc.

  In the drive timing chart examples of the first to seventh embodiments (FIGS. 2, 7, and 10), the selection TFT is set to Vin = Voff and Vsel = Vl at the end of the threshold voltage compensation period. In the pixel data writing period, when writing is performed immediately after compensation, it is possible to input Vin = Vx while keeping Vsel = Vl. In that case, Vx in FIG. 10 may be written without taking the state of Vz to Voff.

<Example>
As an example of the present invention, simulation was performed by applying n-channel polysilicon as a TFT model included in each of the driving circuits shown in the first to seventh embodiments.

  1, 4, 5, 6, 8, 9, 11, 12, and 13, each of the driving circuits (100, 400, 500, 600, 800, 900, 1100, 1200, 1300). ), Vd, Vsel, Vc, Vd, Vp, and Vq were appropriately set according to the characteristics of the TFT model, and the experiment was performed with the current flowing through the organic EL element 10 being constant. The TFT model was constructed by fitting based on the measured values of TFT characteristics. In addition, a simulation was performed for the comparative driving circuit 1 (see FIG. 3).

  First, in the driving circuit 1 for comparison shown in FIG. 3, the current value fluctuates by 20% or more when the threshold voltage of the driving TFT 303 fluctuates by 0.1V. , 400, 500, 600, 800, 900, 1100, 1200, 1300), it was confirmed that the current fluctuation can be suppressed to less than 1% by performing an appropriate circuit design.

  Furthermore, considering the case where 4000 scanning lines are driven at a frame frequency of 120 Hz (light emission aperture 50%), “a pixel data writing period is provided immediately after the threshold voltage compensation period, and a light emission period (4 ms) is provided after holding for 4 ms. ”(Condition (1))” and “when the pixel data writing period and light emission period (4 ms) are sequentially provided after holding for 4 ms after the end of the threshold voltage compensation period (condition (2))”. The current values flowing through the organic EL elements 10 were compared.

  These correspond to a method in which simultaneous (simultaneous) writing is performed and light is emitted simultaneously. Condition (1) corresponds to each pixel on the first line, and condition (2) corresponds to each pixel on the 4000th line. As a result of the simulation, the fluctuation of the current value is less than 1% for all the drive circuits (100, 400, 500, 600, 800, 900, 1100, 1200, 1300) of the first to seventh embodiments. It was found that the present invention can also be applied to a method of simultaneously emitting light at a frame rate of 120 Hz. In addition, the same result is obtained for the current obtained by simply dividing the set maximum current of the organic EL element 10 by 2, 10, 100, and 256, and there is a possibility that it can be applied to a case where gradation is expressed by 8 bits. This was confirmed by simulation experiments.

  As described above, according to the present invention, the source side of the driving TFT is directly connected to the reference potential point, the threshold voltage can be corrected in a state where the source potential does not vary, and the emission luminance of the organic EL element 10 is reduced. Variations can be greatly suppressed.

  Therefore, if the drive circuit of the present invention is applied to an organic EL display, it can support various light emission methods such as a simultaneous light emission method and a block light emission method, and realize a high image quality display panel such as realization of a high frame technology of Super Hi-Vision. The application of can be expected.

  The present invention constitutes a circuit capable of self-compensation even when the threshold voltage of the driving TFT fluctuates in the configuration in which the driving n-channel TFT is connected to the cathode side of the organic EL element. In other words, the present invention has a basic configuration in which at least one TFT is added between the gate and drain of an n-channel TFT for driving, and a capacitor is connected between the gate and source, and an appropriate current is input to and output from the gate. Has a circuit configuration. By directly connecting the source side of the driving TFT to a wiring serving as a reference potential, there is applied a means for applying a signal to each input terminal at an appropriate timing without causing a change in the source potential. This not only facilitates voltage control by the selection TFT at the gate of the driving TFT, but also enables appropriate current compensation for fluctuations and fluctuations in the threshold voltage of the driving TFT, thereby causing variations in the emission luminance of the organic EL. Can be greatly suppressed.

  The drive circuit according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and is not deviated from the scope of the claims. Various modifications and changes are possible.

100, 400, 500, 600, 800, 900, 1100, 1200, 1300 Driving circuit 100A, 100B, 400A, 400B, 500A, 500B, 600A, 600B, 800A, 800B, 900A, 900B, 1100A, 1100B, 1200A, 1200B 1300A, 1300B Terminal 101, 401, 501, 601, 801, 901, 1101, 1201, 1301 Selection TFT
102, 402, 502, 602, 802, 902, 1102, 1202, 1302 capacity C1
103, 403, 503, 603, 803, 903, 1103, 1203, 1303 capacity C2
104, 404, 504, 604, 804, 904, 1104, 1204, 1304 Driving TFT
105, 405, 505, 605, 805, 905, 1105, 1205, 1305 Setting TFT
507 Rectifier TFT
608, 808 TFT for power supply
909, 1109, 1209, 1309 Adjustment TFT

Claims (4)

An n-channel type driving TFT having a drain connected to the cathode of the organic EL element and a source connected to a reference potential point;
An n-channel type selection TFT in which either the drain or the source is connected to the data line;
A first capacitor having one end connected to the other of the drain or source of the selection TFT and the other end connected to a reference potential point;
A second capacitor having one end connected to the gate of the driving TFT and the other end connected to the one end of the first capacitor and the other of the drain or source of the selection TFT;
An adjustment TFT in which one of a drain or a source is connected to the one end of the second capacitor, and the other of the drain or the source is connected to the other end of the second capacitor;
One of the drain and the source is connected to one end of the second capacitor and the gate of the driving TFT, and the other is connected between the cathode of the organic EL element and the drain of the driving TFT. Including the setting TFT and
A charging period for charging the first capacitor from the data line by turning on the selection TFT and the adjustment TFT in a state where the potential of the data line is set to a predetermined data potential higher than a reference potential;
After the charging period, while setting the potential of the data line to the predetermined data potential, in a state where the power supply to the organic EL element is cut off, the selection TFT and the setting TFT are turned on, A driving circuit that drives a driving TFT by a diode and performs driving by a setting period in which a gate-source voltage of the driving TFT is set to a threshold voltage by the first capacitor and the second capacitor. Wherein instead of the other of the drain or source of the adjustment TFT is the other end of said second capacitor, wherein connected to the data line drive circuit according to claim 1, wherein. An n-channel type driving TFT having a drain connected to the cathode of the organic EL element and a source connected to a reference potential point;
An n-channel type selection TFT in which either the drain or the source is connected to the data line;
A first capacitor having one end connected to the other of the drain or source of the selection TFT and the other end connected to the gate of the driving TFT;
A second capacitor having one end connected to the gate of the driving TFT and the other end of the first capacitor and the other end connected to the reference potential point;
One of a drain and a source is connected to the data line, and the other is connected to the other end of the first capacitor and one end of the second capacitor;
One of the drain and the source is connected to the other end of the first capacitor, one end of the second capacitor, the other of the drain or source of the adjustment TFT, and the gate of the driving TFT, and the other of the drain or source is the An n-channel type setting TFT connected to the cathode of the organic EL element and the drain of the driving TFT,
A charging period in which the selection TFT and the adjustment TFT are turned on to charge the second capacitor from the data line in a state where the potential of the data line is set to a predetermined data potential higher than a reference potential;
After the charging period, while setting the potential of the data line to the predetermined data potential, in a state where the power supply to the organic EL element is cut off, the selection TFT and the setting TFT are turned on, A driving circuit that performs driving according to a setting period in which the driving TFT is diode-driven with the power obtained by the charging of the second capacitor and the gate-source voltage of the driving TFT is set to a threshold voltage. An n-channel type driving TFT having a drain connected to the cathode of the organic EL element and a source connected to a reference potential point;
An n-channel type selection TFT in which either the drain or the source is connected to the data line;
A first capacitor having one end connected to the other of the drain or source of the selection TFT and the other end connected to the gate of the driving TFT;
A second capacitor having one end connected to the gate of the driving TFT and the other end of the first capacitor and the other end connected to the reference potential point;
One of the drain and the source is connected to the other of the drain and the source of the selection TFT, and the other of the drain and the source is connected to the other end of the first capacitor and one end of the second capacitor. TFT for
One of the drain and the source is connected to the other end of the first capacitor, one end of the second capacitor, the other of the drain or source of the adjustment TFT, and the gate of the driving TFT, and the other of the drain or source is the An n-channel type setting TFT connected to the cathode of the organic EL element and the drain of the driving TFT,
A charging period in which the selection TFT and the adjustment TFT are turned on to charge the second capacitor from the data line in a state where the potential of the data line is set to a predetermined data potential higher than a reference potential;
After the charging period, while setting the potential of the data line to the predetermined data potential, in a state where the power supply to the organic EL element is cut off, the selection TFT and the setting TFT are turned on, A driving circuit that performs driving according to a setting period in which the driving TFT is diode-driven with the power obtained by the charging of the second capacitor and the gate-source voltage of the driving TFT is set to a threshold voltage.

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