JP2005331933A - Organic el display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display which reduces luminance variation of each pixel and can reduce lowering of an aperture ratio to a small level. <P>SOLUTION: The organic EL display comprises: a light emitting part; a current control part for controlling a current made to flow through the light emitting part; a 1st switching part for performing switching between transmission and non-transmission of the current controlled by the current control part; a current detection part for detecting a transmitted and controlled current value as a voltage; a comparison amplifying part for carrying out a comparison of a voltage value corresponding to the detected current with a voltage value corresponding to an image signal and amplifying the resultant value; a 2nd switching part for performing switching between transmission and non-transmission of the voltage resulting from the comparison and amplification; and an image signal holding capacitor which is charged and discharged according to the voltage transmitted from the 2nd switching part. The current control part controls the current made to flow through the light emitting part according to the charging voltage of the image signal holding capacitor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic EL display device that performs display by using self-emitting organic EL (electroluminescence) elements in pixels and arranging them in a matrix, and is particularly suitable for reducing luminance variation for each pixel. The present invention relates to an organic EL display device.

  A display device using an organic EL element has a feature that an LCD (Liquid Crystal Display) does not have a backlight because the organic EL element is a self-light-emitting element and does not require a backlight. In addition, since it has characteristics of a high-speed response and a wide viewing angle, and since the element itself is solid, it has any advantages that can be applied to flexible applications.

  As a driving method of the organic EL display device, PM (passive matrix) driving and AM (active matrix) driving can be performed in the same manner as the LCD. However, a thin film transistor (TFT) is provided for each pixel to control the pixel individually. The AM method has become mainstream. As a result, higher definition, longer life, and further lower power consumption are considered.

By the way, in order to control the light emission of each pixel of the organic EL display device without variation, it is necessary to align the current value of each pixel with respect to a certain image signal. In particular, this is important in the case of a method in which an image signal is given as an analog signal and the pixel emits light in accordance with the analog value. An example of an organic EL display device aiming at reducing luminance unevenness under such premise is, for example, one disclosed in Patent Document 1.
JP 2002-91377 A

  In the display device disclosed in the above document, a configuration is used in which negative feedback is performed so that the pixel current matches the image signal. As a result, even if there is a variation in the characteristics of the input voltage versus the output current of the current control circuit, this is absorbed and a current value that is uniform between pixels for a certain image signal is obtained. However, inevitably, it is necessary to build an error amplification circuit necessary for negative feedback for each pixel, so that there is a disadvantage in terms of display aperture ratio (ratio of net light emitting area to display area). It is done.

  The present invention has been made in consideration of the above-described circumstances. In an organic EL display device that performs display by using organic EL elements that self-emit light in pixels and arranging them in a matrix, the luminance variation of each pixel is reduced. An object of the present invention is to provide an organic EL display device which is reduced and has a small sacrifice in aperture ratio.

  In the organic EL display device according to the present invention, a plurality of pixels are arranged in a matrix, a pixel is selected from the plurality of pixels according to a pixel selection signal, and the selected pixel is caused to emit light according to an image signal. A display device comprising: a light emitting unit; a current control unit that controls a current that flows through the light emitting unit; and first / non-transmission switching of current controlled by the current control unit according to the pixel selection signal. A switching unit, a current detection unit that detects the value of the controlled current transmitted by the first switching unit as a voltage, a voltage value corresponding to the detected current, and a voltage value corresponding to the image signal And a second switching unit that switches between transmission and non-transmission of the voltage value that is the result of the comparison and amplification in accordance with the pixel selection signal. And an image signal holding capacitor that is charged and discharged by the voltage value transmitted from the second switching unit, and the current control unit uses the charging voltage of the image signal holding capacitor to emit the light emitting unit. To control the current flowing through.

  In this configuration, the image signal is input to one of the comparison amplification units, and a voltage is applied to the other input from the current detection unit that detects the current transmitted by the first switching unit. The output of the comparison amplification unit is supplied to the image signal holding capacitor and the current control unit via the second switching unit. In such a configuration, it is easily achieved that the first switching unit of each pixel is used for the multiplexer and the second switching unit of each pixel is used for the demultiplexer. That is, since only one set of the comparison amplification unit and the current detection unit is necessary for a plurality of pixels, it is not necessary to provide the comparison amplification unit and the current detection unit for each pixel. Therefore, a factor that decreases the aperture ratio can be eliminated. In addition, since negative feedback is performed by the comparison amplifier, even if there is a variation in the input voltage vs. output current characteristics of the current controller, this is absorbed and the current value that is aligned between pixels for a certain image signal. Is obtained.

  According to the organic EL display device of the present invention, the current detection unit and the comparison amplification unit are provided for negative feedback. However, the current detection unit and the comparison amplification unit are not provided for each pixel. Variations can be reduced and the sacrifice can be made extremely small in terms of aperture ratio.

  As an embodiment of the present invention, the current detection unit is a resistor or a Hall element inserted and connected between a power supply and the first switching unit, and the light emitting unit is between the current control unit and ground. Inserted and connected. A resistor or a Hall element having an easy configuration is used as the current detection unit. Further, the light emitting portion is formed with reference to the ground.

  Here, the current detection unit may detect the value of the controlled current as a voltage using an on-resistance of a thin film transistor inserted and connected between a power source and the first switching unit. . According to this, it is not necessary to build a resistor, and there is an advantage in the manufacturing process.

  Further, the current control unit is an n-channel thin film transistor, and outputs the current flowing through the light emitting unit as a drain / source current, and the control of the current is supplied to the gate of the image signal holding capacitor. A configuration in which the charging voltage is applied can be employed. In this configuration, an n-channel thin film transistor is used for the current control unit.

  Further, the current control unit is a p-channel thin film transistor, outputs the current flowing through the light emitting unit as a source / drain current, and the control of the current is based on the charging voltage of the image signal holding capacitor supplied to the gate. It can also be configured to be made. In this configuration, a p-channel thin film transistor is used for the current control unit.

  Further, as an embodiment, the current detection unit is a resistor or a Hall element inserted and connected between a ground and the first switching unit, and the light emitting unit is interposed between the current control unit and a power source. It can be inserted and connected. A resistor or a Hall element, which is an easy configuration as a current detection unit, is used, and a light emitting unit is formed on the basis of a power source.

  Here again, the current control unit is an n-channel thin film transistor, outputs the current flowing through the light emitting unit as a drain-source current, and the charge of the image signal holding capacitor supplied to the gate is controlled by the current. It can be set as the structure made by.

  Further, as an embodiment, the light emitting unit, the current control unit, the first switching unit, the second switching unit, and the image signal holding capacitor are provided in each of the plurality of pixels, and the comparative amplification Each of the matrix-like pixel columns, and a connection from the first switching unit to the current detection unit is included in the pixel column to which the current detection unit belongs. It is assumed that the connection from the comparison amplification unit to the second switching unit is made to all the pixels included in the pixel column to which the comparison amplification unit belongs. This is a configuration in which the use of the first and second switching units described above as multiplexers or demultiplexers is summarized for each column of matrix pixels. According to this, only one set of the current detection unit and the comparison amplification unit is required for each column, and the number of current detection units and comparison amplifiers to be formed can be minimized.

  Based on the above, embodiments of the present invention will be described below with reference to the drawings. First, prior to the description of the embodiment, the cause of luminance unevenness in each pixel in the organic EL display device will be described with reference to FIGS. 30A and 30B. FIG. 30A and FIG. 30B are equivalent circuit diagrams each showing a configuration of each pixel of an organic EL display device as a comparative example. 30A shows a configuration using p-channel transistors 56 and 58 as thin film transistors (TFTs), and FIG. 30B shows a configuration using n-channel transistors 56a and 58a as thin film transistors.

  In the case shown in FIG. 30A, the organic EL element 54 which is a light emitting portion is formed with reference to the ground, and in the case shown in FIG. 30B, the organic EL element 54a is formed with reference to the power source. Reference numerals 57 and 57a denote image signal holding capacitors, reference numeral 51 denotes a power supply line, reference numeral 52 denotes an image signal line, and reference numeral 53 denotes a scanning line. Although not shown, the image signal line 52 is commonly connected to other pixels in the vertical (column) direction, and the scanning line 53 is commonly connected to other pixels in the horizontal (row) direction.

  An image signal is supplied to the image signal line 52 with an analog value (voltage), and a pixel selection signal is supplied to the scanning line 53 in synchronization therewith. When the pixel selection signal is supplied to the scanning line 53, the transistor 58 (58a) is turned on to charge and discharge the image signal holding capacitor 57 (57a) according to the voltage of the image signal on the image signal line 52. Capacitor 57 (57a) then holds that voltage until transistor 58 (58a) becomes conductive. The transistor 56 (56a) controls its drain current by the voltage held in the capacitor 57 (57a).

Here, the input voltage (gate-source voltage Vgs) of the transistor 56 (56a) versus the output current (drain current Ids, particularly in the case of the p-channel transistor 56, the source / drain current, the n-channel transistor 56a The case is also referred to as a drain-source current). That is, Ids = (1/2) · μ · Cox · (W / L) · (Vgs−Vth) ² . Here, μ is the carrier mobility, Cox is the gate capacity per unit area, W is the channel width, L is the channel length, and Vth is the threshold voltage. As can be seen from this equation, when the threshold voltage Vth varies from pixel to pixel, the output current (drain current Ids) varies in a square characteristic (that is, very sensitive) with respect to the same input voltage (gate-source voltage Vgs). Understand. The drain current Ids is a current that flows through the organic EL element 54 (54a) as it is, resulting in a current variation, that is, a luminance variation.

  For the TFT as the transistor 56 (56a), polycrystalline silicon having an excellent current driving capability is often used as the channel material. However, the threshold voltage Vth varies depending on the characteristics of the device, for example, about several tens of mV. . Therefore, in the configurations of these comparative examples, luminance variations for each pixel as a display device cannot be avoided. In addition, it is not preferable to employ a design in which the center value of Vth is reduced in order to reduce the variation in the drain current Ids, because the drain current Ids increases and the power consumption cannot be reduced as an organic EL display device.

  On the other hand, FIG. 1 is a block diagram showing a configuration of a specific pixel in the organic EL display device according to the embodiment of the present invention. As shown in FIG. 1, a power line 1, an image signal line 2, and a scanning line 3 are connected to this pixel, and a light emitting unit 4, a current detection unit 5, a current control unit 6, and an image signal holding capacitor 7. , First switching unit 8, second switching unit 9, and comparison amplification unit 10. Although not shown, the scanning line 3 is commonly connected to other pixels in the horizontal (row) direction.

  The light emitting unit 4 is an organic EL element formed on the basis of the ground, and its anode side is connected to the current output terminal of the current control unit 6. The current control unit 6 controls the current flowing from the current detection unit 5 to the light emitting unit 4 via the first switching unit 8, and the control input terminal is controlled so as to follow the voltage held by the voltage holding capacitor 7. Is connected to one end of the capacitor 7.

  The first switching unit 8 is provided between the current control unit 6 and the current detection unit 5, and transmits / not transmits the current flowing through the current control unit 6 to the current detection unit 5 based on the pixel selection signal from the scanning line 3. The transmission is switched. The current detection unit 5 is connected between the power supply line 1 and the first switching unit 8 and detects a current as a result of being controlled by the current control unit 6 through the first switching unit 8. The detected current is guided to the inverting input terminal of the comparison amplification unit 10 as a voltage value. The second switching unit 9 is provided between the output of the comparison amplification unit 10 and one end of the image signal holding capacitor 7 and the control input terminal of the current control unit 6, and transmits / receives based on the pixel selection signal from the scanning line 3. The non-transmission is switched, and the output voltage of the comparison amplification unit 10 is guided to one end of the image signal holding capacitor 7 and the control input terminal of the current control unit 6 during transmission.

  The comparison amplifier 10 has a function of subtracting the voltage of the inverting input terminal from the voltage of the non-inverting input terminal and amplifying the result with a large gain and outputting the result. The image signal from the image signal line 2 is supplied to the non-inverting input terminal of the unit 5 or the second switching unit 9. A broken line 2B drawn from the first switching unit 8, a broken line 2A drawn from the output of the comparison amplifier 10, and a long broken line 20 drawn from the image signal line 2 will be described later.

  According to the pixel of the organic EL display device having the configuration shown in FIG. 1, an image signal is given to the image signal line 2, and a pixel selection signal is given to the scanning line 3, so that the first and second switching units 8, 9 In the closed state, a voltage substantially equal to the image signal becomes the output voltage of the current detection unit 5. This is because a negative feedback path is formed by the loop of the current detection unit 5, the comparison amplification unit 10, the second switching unit 9, the current control unit 6, the first switching unit 8, and the current detection unit 5. This is because the relationship between the inverting input and the inverting input is a so-called imaginary short state.

  Therefore, the current in the current detection unit 5 is a value that matches the image signal applied to the image signal line 2, and the matched current flows to the light emitting unit 4 via the first switching unit 8 and the current control unit 6. . Therefore, variation in current flowing through the light emitting unit 4 is eliminated in principle. Therefore, the luminance variation for each pixel is eliminated. In other words, a voltage is generated in the image signal holding capacitor 7 by the negative feedback path so as to make the current value of the light emitting unit 4 constant regardless of variations in the characteristics of the input voltage versus the output current of the current control unit 6.

  As a display device, it is the easiest configuration to arrange such pixel configurations in the vertical (column) and horizontal (row) directions. In this case, the image signal line 2 is provided so as to extend like a long broken line 20 and be connected in common to other pixels in the vertical (column) direction. No conducting wire corresponding to the broken lines 2A and 2B is provided. However, in this case, it is necessary to provide the current detection unit 5 and the comparison amplification unit 10 in addition to the first and second switching units 8 and 9 for each pixel. This is disadvantageous in terms of the ratio of the light emitting area.

  Therefore, a configuration in which the current detection unit 5 and the comparison amplification unit 10 do not need to be provided in each pixel is also conceivable. It is provided with a broken line 2B drawn from the first switching unit 8 and a broken line 2A drawn from the output of the comparison amplifier 10 as conducting wires, and these conducting wires are connected in common to each pixel in the column direction. Do. No conducting wire corresponding to the long broken line 20 is provided. In each pixel (not shown) to which the broken lines 2B and 2A are connected, the current detection unit 5 and the comparison amplification unit 10 are not provided.

  In this configuration, that is, the first switching unit 8 becomes a multiplexer for selecting the control current by the current control unit 6 of each pixel in the column direction, and the second switching unit 9 is a capacitor for holding an image signal of each pixel in the column direction. 7 is a demultiplexer that distributes the output of the comparison amplification unit 10 to 7. These selection and distribution are performed by a pixel selection signal given to the scanning line 3. According to such a configuration, it is sufficient that at least one pair of the current detection unit 5 and the comparison amplifier 10 is provided in each column, and it is possible to eliminate the need to build in a display surface as a display device. Is obtained. A configuration in which one set is provided for each pixel in a plurality of rows in each column instead of one set in each column may be employed.

  FIG. 2 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 2, the same reference numerals are given to the same components as in FIG. In this example, a resistor 5a is used for the current detection unit 5, and n-channel transistors 6a, 8a, and 9a are used for the current control unit 6, the first switching unit 8, and the second switching unit 9, respectively. As is well known, the transistors 6a, 8a and 9a can be thin film MOS transistors formed on a glass substrate. Among these, the thin film MOS transistor can be a so-called amorphous silicon transistor. In such a circuit of FIG. 2, since the detection polarity of the resistor 5a as the current detection unit is inverted, the input terminal of the comparison amplification unit 10 is opposite to that shown in FIG.

  Supplementing the connection of the n-channel transistors 6a, 8a, 9a is as follows. The transistor 6a has a source connected to the anode of the light emitting unit 4 and a drain connected to the source of the transistor 8a. The gate is connected to one end of the image signal holding capacitor 7. The transistor 8a has a gate connected to the scanning line 3, a drain connected to one end of the resistor 5a, and a source connected to the drain of the transistor 6a. The transistor 9 a has a gate connected to the scanning line 3, a drain connected to the output of the comparison amplifier 10, and a source connected to one end of the image signal holding capacitor 7. Since the transistor 9a performs switching operation almost in voltage, the source and drain can be reversed.

  In this configuration example, the resistor 5a is used as the current detector 5, and the voltage value can be easily detected in proportion to the current flowing therethrough. Further, since it is possible to avoid making the resistor 5a in each pixel, there is a process advantage due to simplification of the configuration. Furthermore, at this time, it is also possible to prevent in principle the variation in the current value after the control due to the variation in the resistance value in each pixel. In some cases, the resistor 5a may be externally attached separately from the substrate on which the pixels are formed. In this sense, for example, a Hall element can be used instead of the resistor 5a.

  FIG. 3 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. 1, which is different from the configuration shown in FIG. In FIG. 3, the same reference numerals are given to the same components as those shown in the already described figures, and the description thereof is omitted.

  In this configuration example, the on-resistance of the n-channel transistor 5 b is used as the current detection unit 5. Therefore, in FIG. 3, the drain of the transistor 5b is connected to the power supply line 3, the source is connected to the drain of the transistor 8a and the non-inverting input terminal of the comparison amplifier 10, and the gate is connected to a voltage source (not shown). According to such a configuration, there is no need to form the resistor 5a as in the configuration shown in FIG. 2, and the configuration can be made of only an n-channel transistor. Therefore, it is possible to simplify the manufacturing process as an organic EL display device, and there are advantages in terms of manufacturing costs. Furthermore, at this time, it is also possible to prevent in principle the variation in the current value after the control due to the variation in the resistance value in each pixel.

  FIG. 4 is a block diagram showing the configuration of a specific pixel in an organic EL display device according to another embodiment of the present invention. Components identical to those already described in FIG. 4 are denoted by the same reference numerals and description thereof is omitted. In this embodiment, an organic EL element formed on the basis of a power source is used as the light emitting unit 4a. As a result, the current flowing through the light emitting unit 4a is in the current path of the light emitting unit 4a, the current control unit 6, the first switching unit 8, and the current detection unit 5.

  Also in this configuration, a negative feedback path is formed by the loop of the current detection unit 5, the comparison amplification unit 10, the second switching unit 9, the current control unit 6, the first switching unit 8, and the current detection unit 5, and the image signal line A voltage substantially equal to the image signal given to 2 is the output voltage of the current detector 5. Therefore, the current in the current detection unit 5 is a value that matches the image signal given to the image signal line 2, and the matching current flows to the light emitting unit 4 a via the first switching unit 8 and the current control unit 6. . Therefore, the variation of the current flowing through the light emitting unit 4a is eliminated in principle. Therefore, there is no luminance variation for each pixel.

  FIG. 5 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 5, the same reference numerals are given to the same components as in FIG. In this example, a resistor 5c is used for the current detection unit 5, and n-channel transistors 6b, 8b, and 9b are used for the current control unit 6, the first switching unit 8, and the second switching unit 9, respectively. As is well known, the transistors 6b, 8b, 9b can be thin film MOS transistors formed on a glass substrate. The transistors 6b, 8b, and 9b can be amorphous silicon transistors similarly to the transistors 6a, 8a, and 9a (FIG. 2 and the like).

  Supplementing the connection of the n-channel transistors 6b, 8b, and 9b is as follows. The transistor 6b has a drain connected to the cathode of the light emitting unit 4a and a source connected to the drain of the transistor 8b. The gate is connected to one end of the image signal holding capacitor 7. The transistor 8 b has a gate connected to the scanning line 3, a drain connected to the source of the transistor 6 b, and a source connected to the inverting input terminal of the comparison amplifier 10. The transistor 9 b has a gate connected to the scanning line 3, a drain connected to the output of the comparison amplification unit 10, and a source connected to one end of the image signal holding capacitor 7. Note that since the transistor 9b performs a switching operation substantially in voltage, the source and drain can be reversed.

  In this configuration example, similarly to the configuration example shown in FIG. 2, the resistor 5c is used as the current detection unit 5, and the voltage value can be easily detected in proportion to the current flowing therethrough. Further, since it is possible to avoid making the resistor 5c in each pixel, there is a process advantage due to the simplification of the configuration. Furthermore, at this time, it is also possible to prevent in principle the variation in the current value after the control due to the variation in the resistance value in each pixel. In some cases, the resistor 5c may be externally attached separately from the substrate on which the pixels are formed. In this sense, for example, a Hall element can be used instead of the resistor 5c.

  FIG. 6 is a block diagram showing a configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. In FIG. 6, the same components as those already described are denoted by the same reference numerals, and the description thereof is omitted. In this embodiment, unlike the embodiment shown in FIG. 1, the other end of the image signal holding capacitor 7a is connected to the power line 1 instead of the ground. There is no difference in operation as a pixel due to the difference between the capacitor 7 and the capacitor 7a.

  FIG. 7 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 7, the same components as those in FIG. In this example, a resistor 5a is used for the current detection unit 5, and p-channel transistors 6c, 8c, and 9c are used for the current control unit 6, the first switching unit 8, and the second switching unit 9, respectively. As is well known, the transistors 6c, 8c and 9c can be thin film MOS transistors formed on a glass substrate. Among them, an amorphous silicon transistor can be used.

  Supplementing the connection of the p-channel transistors 6c, 8c, and 9c is as follows. The transistor 6c has a drain connected to the anode of the light emitting unit 4 and a source connected to the drain of the transistor 8c. The gate is connected to one end of the image signal holding capacitor 7a. The transistor 8c has a gate connected to the scanning line 3, a source connected to one end of the resistor 5a, and a drain connected to the source of the transistor 6c. The transistor 9c has a gate connected to the scanning line 3, a source connected to the output of the comparison amplifier 10, and a drain connected to one end of the image signal holding capacitor 7a. Note that since the transistor 9c performs switching operation almost in voltage, the source and drain can be reversed.

  Also in this configuration example, the resistor 5a is used as the current detection unit 5 as in the configuration examples shown in FIGS. 2 and 5, and the voltage value can be easily detected in proportion to the current flowing therethrough. Further, since it is possible to avoid making the resistor 5a in each pixel, there is a process advantage due to simplification of the configuration. Furthermore, at this time, it is also possible to prevent in principle the variation in the current value after the control due to the variation in the resistance value in each pixel. In some cases, the resistor 5a may be externally attached separately from the substrate on which the pixels are formed. In this sense, for example, a Hall element may be used instead of the resistor 5a. In this configuration example, since the detection polarity of the resistor 5a as the current detection unit is not inverted, the input terminal of the comparison amplifier 10 is the same as that shown in FIG.

  FIG. 8 is a repetition of what has already been described, but the power supply line 1, image signal line 2, scanning line 3, and each pixel when the pixels having the configuration shown in FIG. 1 are arranged vertically and horizontally are arranged. It is a figure which shows a connection. In FIG. 8, the same reference numerals are given to the components already described. As shown in FIG. 8, the pixels 11, 12,... Are arranged in the horizontal (row) direction, and the pixels 11, 21,. From this figure, it can be easily understood that the current detection unit 5 and the comparison amplification unit 10 are not required for each pixel.

  FIG. 9 is a block diagram showing a configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. In FIG. 9, the same components as those already described are denoted by the same reference numerals, and the description thereof is omitted. In this embodiment, a first switching unit 80 having substantially the same function is used instead of the first switching unit 8 shown in FIG.

  The first switching unit 80 has the same function as the first switching unit 8 in FIG. 1 as a function of switching transmission / non-transmission between the current control unit 6 and the current detection unit 5. The difference is that the current input terminal of the current control unit 6 is connected to the power supply line 1 when the current control unit 6 and the current detection unit 5 are not transmitting. In this way, the current control unit 6 can always continue to flow current regardless of the switching position of the first switching unit 80, and the light emission of the light emitting unit 4 can be stably maintained until the next scan by the scanning line 3. can do.

  FIG. 10 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 10, the same components as those in FIG. 9 are denoted by the same reference numerals, and the description thereof is omitted. As illustrated in FIG. 10, a switch circuit including two n-channel transistors 801 and 802 is used as the first switching unit 80. Among these, the n-channel transistor 801 has the same connection and function as the n-channel transistor 8a shown in FIG.

  In the n-channel transistor 802, the drain is connected to the power supply line 1, the source is connected to the drain of the n-channel transistor 6a that is the current control unit, and the gate is connected to the second scanning line 3A having the opposite polarity to the scanning line 3. With the above configuration, one of the transistors 801 and 802 is turned on and the other is turned off by the scanning signal (pixel selection signal) supplied to the scanning lines 3 and 3A, so that the first switching as shown in FIG. The function of the unit 80 is realized.

  FIG. 11 is a block diagram showing a configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. Components identical to those already described in FIG. 11 are denoted by the same reference numerals, and will not be described unless added.

  In this embodiment, a first switching unit 80 having substantially the same function is used in place of the first switching unit 8 shown in FIG. In this respect, the modification of the embodiment shown in FIG. 9 to the embodiment shown in FIG. 1 is applied to the embodiment shown in FIG. However, in this embodiment, at one switching position of the first switching unit 80, the current control unit 6 is connected to the ground due to the current direction. In addition to the matters described in the embodiment shown in FIG. 4, there are effects unique to the embodiment shown in FIG. 9.

  FIG. 12 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 12, the same components as those in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 10, a switch circuit including two n-channel transistors 803 and 804 is used as the first switching unit 80. Among these, the n-channel transistor 803 has the same connection and function as the n-channel transistor 8b shown in FIG.

  In the n-channel transistor 804, the source is connected to the ground, the drain is connected to the source of the n-channel transistor 6b, which is a current control unit, and the gate is connected to the second scanning line 3A having the opposite polarity to the scanning line 3. With the above configuration, one of the transistors 803 and 804 is turned on and the other is turned off by the scanning signal (pixel selection signal) supplied to the scanning lines 3 and 3A, so that the first switching as shown in FIG. The function of the unit 80 is realized.

  FIG. 13 is a block diagram showing a configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. Components identical to those already described in FIG. 13 are denoted by the same reference numerals and description thereof is omitted. In this embodiment, a modification of the embodiment shown in FIG. 9 to the embodiment shown in FIG. 1 is applied to the embodiment shown in FIG. Since the operation and effect are obvious from the embodiment described above, they are omitted here.

  FIG. 14 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. In FIG. 14, the same reference numerals are given to the same components as those in FIG. 13, and the description thereof is omitted. As illustrated in FIG. 14, a switch circuit including two p-channel transistors 805 and 806 is used as the first switching unit 80. Among these, the p-channel transistor 805 has the same connection and function as the p-channel transistor 8c shown in FIG.

  In the p-channel transistor 806, the source is connected to the power supply line 1, the drain is connected to the source of the n-channel transistor 6 a that is a current control unit, and the gate is connected to the second scanning line 3 A having the opposite polarity to the scanning line 3. With the above configuration, one of the transistors 805 and 806 is turned on by the scanning signal (pixel selection signal) supplied to the scanning lines 3 and 3A, and the other is turned off, so that the first switching as shown in FIG. The function of the unit 80 is realized.

  FIG. 15 is a diagram showing connections between the power supply line 1, the image signal line 2, the scanning line 3, and the respective pixels when the pixels having the configuration shown in FIG. 9 are arranged vertically and horizontally. In FIG. 15, the components already described are given the same numbers. As shown in FIG. 15, the pixels 11A, 12A,... Are arranged in the horizontal (row) direction, and the pixels 11A, 21A,. From this figure, it can be easily understood that the current detection unit 5 and the comparison amplification unit 10 are not required for each pixel as in the embodiment shown in FIG.

  16, FIG. 18, and FIG. 20 are block diagrams each showing the configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. FIG. 17, FIG. 19, and FIG. FIG. 21 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. 16, FIG. 18, and FIG. In these drawings, the same components as those already described are denoted by the same reference numerals, and the description thereof is omitted.

  Each of the embodiments shown in FIGS. 16 to 21 is a further improvement of the embodiment shown in FIGS. 9 to 14. 16 corresponds to FIG. 9, FIG. 17, corresponding to FIG. 10, FIG.

  As shown in FIGS. 16, 18, and 20, a correction unit 90 is newly introduced, and this is inserted and connected between the scanning line 3 and the control input terminal of the current control unit 6. The purpose is to prevent noise from being generated at the control input terminal of the current control unit 6 due to switching by the second switching unit 9. The reason why noise is generated in the voltage of the control input terminal of the current control unit 6 due to the switching by the second switching unit 9 is that the voltage fluctuation of the scanning line 3 is controlled by the current control unit 6 of the second switching unit 9 due to parasitic capacitance or the like. This is considered to be transmitted to the input terminal) side.

  Therefore, by providing the correction unit 90, the voltage variation of the scanning line 3 can be intentionally transmitted to the control input terminal side of the current control unit 6 with reverse polarity. Thereby, the generated noise is canceled.

  As shown in FIGS. 17, 19, and 21, as a specific example of the correction unit 90, the gate of the n-channel transistors 901 and 902 or the p-channel transistor 903 and the source-drain common connection terminal can be used. These gates are connected to a second scanning line 3A having a polarity opposite to that of the scanning line 3.

  FIG. 22 is a diagram showing connections between the power supply line 1, the image signal line 2, the scanning line 3, and each pixel when the pixels having the configuration shown in FIG. 16 are arranged vertically and horizontally. In FIG. 22, the same reference numerals are given to components already described. As shown in FIG. 22, the pixels 11B, 12B,... Are arranged in the horizontal (row) direction, and the pixels 11B, 21B,. From this figure, it can be easily understood that the current detection unit 5 and the comparison amplification unit 10 are not required for each pixel as in the embodiment shown in FIGS.

  23, FIG. 25, and FIG. 27 are block diagrams each showing the configuration of a specific pixel in an organic EL display device according to still another embodiment of the present invention. FIG. 24, FIG. 26, and FIG. FIG. 28 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIGS. 23, 25, and 27. In these drawings, the same components as those already described are denoted by the same reference numerals, and the description thereof is omitted.

  These embodiments shown in FIGS. 23 to 28 are obtained by further improving the embodiments shown in FIGS. 16 to 21. FIG. 23 corresponds to FIG. 16, FIG. 24 corresponds to FIG.

  As shown in FIGS. 23, 25, and 27, a current mirror unit 70 (or 71) is newly introduced, and this is inserted and connected between the first switching unit 80 and the current detection unit 5. The purpose of this is to avoid disposing the current detection unit 5 directly on the output side of the first switching unit 80 and to prevent deterioration of the frequency characteristics at this part.

  As can be seen from the drawing, since the wiring corresponding to the reference numeral 2B is connected to each pixel and becomes long, the wiring capacity of this node may increase to some extent. If the current detection unit 5 made of, for example, a resistor is provided directly here, a delay depending on the CR product occurs. Therefore, such a delay can be prevented by outputting a current to the current detection unit 5 via the current mirror unit 70 (or 71).

  As shown in FIGS. 24, 26, and 28, as a specific example of the current mirror unit 70 (or 71), a circuit having a common base and emitter connection of each of the pnp transistors 701 and 702 or the npn transistors 711 and 712 is used. Can do. Here, the transistors 701 and 711 on the first switching unit 80 side operate as diodes with a common base and collector. Due to such a connection, the collector currents of the two transistors 701 and 702 (or 711 and 712) having the same base-emitter voltage are equal to each other, so that the current substantially equal to the output current from the first switching unit 80 is obtained. Is caused to flow through the resistor 5c (or 5a).

  FIG. 29 is a diagram showing connections between the power supply line 1, the image signal line 2, and the scanning line 3 and each pixel when the pixels having the configuration shown in FIG. 23 are used to arrange the pixels vertically and horizontally. In FIG. 29, the same reference numerals are given to components already described. As shown in FIG. 29, the pixels 11C, 12C,... Are arranged in the horizontal (row) direction, and the pixels 11C, 21C,. From this figure, it can be easily understood that the current detection unit 5 and the comparison amplification unit 10 are not required for each pixel, similarly to the embodiments shown in FIGS. 8, 15, and 22. The same applies to the current mirror unit 70.

1 is a block diagram showing a configuration of a specific pixel in an organic EL display device according to an embodiment of the present invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The circuit diagram which shows the example which applied the specific element to each block in embodiment different from the structure shown in FIG. 2 as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. FIG. 3 is a diagram showing connections between a power supply line 1, an image signal line 2, a scanning line 3 and each pixel when pixels are arranged vertically and horizontally using the pixels having the configuration shown in FIG. 1. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The figure which shows the connection of the power supply line 1, the image signal line 2, the scanning line 3, and each pixel at the time of arrange | positioning a pixel vertically and horizontally using the pixel which has the structure shown in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The figure which shows the connection of the power supply line 1, the image signal line 2, the scanning line 3, and each pixel at the time of pixel arrangement | positioning vertically and horizontally using the pixel which has the structure shown in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. The circuit diagram which shows the example which applied the specific element to each block in embodiment shown as a block diagram in FIG. The block diagram which shows the structure of the specific pixel in the organic electroluminescence display which concerns on another embodiment of this invention. FIG. 28 is a circuit diagram showing an example in which specific elements are applied to each block in the embodiment shown as a block diagram in FIG. 27. The figure which shows the connection of the power supply line 1, the image signal line 2, the scanning line 3, and each pixel at the time of pixel arrangement | positioning vertically and horizontally using the pixel which has the structure shown in FIG. The equivalent circuit diagram which shows the structure for every pixel of the organic electroluminescence display as a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power supply line, 2 ... Image signal line, 3 ... Scanning line, 3A ... 2nd scanning line (reverse polarity) 4, 4a ... Light emission part, 5 ... Current detection part, 5a ... Resistor, 5b ... N channel Transistors, 5c ... resistors, 6 ... current control unit, 6a ... n-channel transistor, 6b ... n-channel transistor, 6c ... p-channel transistor, 7, 7a ... image signal holding capacitor, 8 ... first switching unit, 8a ... n channel transistor, 8b... n channel transistor, 8c... p channel transistor, 9... second switching section, 9a... n channel transistor, 9b. 11B, 11C, 12, 12A, 12B, 12C, 21, 21A, 21B, 21C, 22, 22A, 22B, 22 ... Pixel, 70, 71 ... Current mirror part, 701, 702 ... pnp transistor, 711,712 ... npn transistor, 80 ... First switching part, 801,802,803,804 ... n channel transistor, 805,806 ... p channel Transistor 90... Corrector 901 902 n channel transistor 903 p channel transistor

Claims (14)

An organic EL display device in which a plurality of pixels are arranged in a matrix, a pixel is selected from the plurality of pixels according to a pixel selection signal, and the selected pixel is caused to emit light according to an image signal,
A light emitting unit;
A current control unit for controlling a current flowing through the light emitting unit;
A first switching unit that switches between transmission / non-transmission of current controlled by the current control unit according to the pixel selection signal;
A current detection unit that detects the value of the controlled current transmitted by the first switching unit as a voltage;
A comparison amplifier for comparing and amplifying the voltage value corresponding to the detected current and the voltage value corresponding to the image signal;
A second switching unit that switches between transmission and non-transmission of a voltage value that is a result of the comparison amplification in accordance with the pixel selection signal;
An image signal holding capacitor that is charged and discharged by the voltage value transmitted from the second switching unit;
The organic EL display device, wherein the current control unit controls the current flowing through the light emitting unit by a charging voltage of the image signal holding capacitor. The current detection unit is a resistor or a Hall element inserted and connected between a power source and the first switching unit;
The organic EL display device according to claim 1, wherein the light emitting unit is inserted and connected between the current control unit and ground.   2. The current detection unit detects a value of the controlled current as a voltage using an on-resistance of a thin film transistor inserted and connected between a power source and the first switching unit. The organic EL display device described. The current detection unit is a resistor or a Hall element inserted and connected between a ground and the first switching unit,
The organic EL display device according to claim 1, wherein the light emitting unit is inserted and connected between the current control unit and a power source. The light emitting unit, the current control unit, the first switching unit, the second switching unit, and the image signal holding capacitor are respectively provided in each of the plurality of pixels.
The comparison amplification unit and the current detection unit are provided in one set for each column of the matrix-like pixels,
The connection from the first switching unit to the current detection unit is made from all the pixels included in the column of pixels to which the current detection unit belongs,
2. The organic EL display according to claim 1, wherein the connection from the comparison amplification unit to the second switching unit is made for all pixels included in a column of pixels to which the comparison amplification unit belongs. apparatus.   The current control unit is an n-channel thin film transistor, outputs the current flowing through the light emitting unit as a drain / source current, and the current is controlled by a charging voltage of the image signal holding capacitor supplied to the gate. The organic EL display device according to claim 2.   The current control unit is a p-channel thin film transistor, outputs the current flowing through the light emitting unit as a source / drain current, and the current is controlled by a charging voltage of the image signal holding capacitor supplied to the gate. The organic EL display device according to claim 2.   The current control unit is an n-channel thin film transistor, outputs the current flowing through the light emitting unit as a drain / source current, and the current is controlled by a charging voltage of the image signal holding capacitor supplied to the gate. The organic EL display device according to claim 4.   2. The organic EL display device according to claim 1, wherein the current control unit is an amorphous silicon transistor.   2. The organic EL display device according to claim 1, wherein the first switching unit conducts the current to a power source or a ground when the current controlled by the current control unit is not transmitted.   When the first switching unit does not transmit the current controlled by the current control unit, the gate is a second pixel having a polarity opposite to that of the pixel selection signal as an element for conducting the current to a power source or a ground. The organic EL display device according to claim 10, further comprising a transistor to which a selection signal can be supplied.   2. The organic EL display according to claim 1, further comprising a correction unit that is connected to the output side of the second switching unit and removes noise generated by the second switching unit. apparatus.   The correction unit is a two-terminal element including a source / drain common connection terminal and a gate terminal, one of which is connected to the output side of the second switching unit, and the other is a second terminal having a polarity opposite to that of the pixel selection signal. 13. The organic EL display device according to claim 12, wherein the organic EL display device is a terminal to which a pixel selection signal can be supplied. A current mirror unit that is driven by the controlled current transmitted by the first switching unit and outputs a current having the same value as the current;
The organic EL display device according to claim 1, wherein the current detection unit detects a current value output from the current mirror unit as a voltage.

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