JP4009077B2 - Current drive - Google Patents

Description

となる。
【００９１】
第２の帰還電流用伝送路６９４の抵抗の影響を受けるので、第２の帰還電流Ｉ２４の大きさは、第３の参照電流Ｉ２３よりも小さい。同様に、第１の帰還電流用伝送路６９２の抵抗の影響を受けるので、第１の帰還電流Ｉ２５の大きさは、第２の帰還電流Ｉ２４よりも小さい。ここで、ｄ１＝Ｉ２０−Ｉ２１、ｄ２＝Ｉ２１−Ｉ２２、ｄ３＝Ｉ２３−Ｉ２４、ｄ４＝Ｉ２４−Ｉ２５とする。
【００９２】
第２の参照電流用伝送路６９３と、第２の帰還電流用伝送路６９４との抵抗値が等しいとすると、これらの伝送路の抵抗の影響は等しいので、ｄ２＝ｄ３が成り立つ。したがって、第２の平均電流Ｉ４２は、

となる。
【００９３】
また、第１の参照電流用伝送路６９１と、第１の帰還電流用伝送路６９２との抵抗値が等しいとすると、これらの伝送路の抵抗の影響は等しいので、ｄ１＝ｄ４が成り立つ。したがって、第１の平均電流Ｉ４１は、

となる。
【００９４】
このように、Ｉ４１＝Ｉ４２＝Ｉ４３が成り立つので、第１〜第３の電流駆動回路６０２，６３２，６６２に入力される電流の大きさは等しい。このため、階調データが同一であれば、第１〜第３の集積回路６００，６３０，６６０のいずれが駆動しても発光素子の輝度に差は生じないので、表示パネル１４０に表示むらが生じない。
【００９５】
なお、本実施形態では、３個の集積回路を接続した場合について説明したが、同様に、３個よりも多くの集積回路をカスケード接続してもよい。このように、本実施形態によると、多数の集積回路を用いることが容易にできるので、表示むらを生じさせることなく、大型の表示パネルを駆動することができる。
【００９６】
また、以上の実施形態において、表示パネルの発光素子は、電流駆動型のものであればよく、例えば発光ダイオードであってもよい。
【００９７】
【発明の効果】
以上のように本発明によると、電流駆動型の発光素子を用いた表示装置の表示むらを低減することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る電流駆動装置を備えた表示装置の構成の例を示す回路図である。
【図２】図１の電流駆動装置における各電流の大きさを示す説明図である。
【図３】（ａ）本発明の第２の実施形態に係る電流駆動装置の構成の例を示す回路図である。
（ｂ）図３（ａ）の電流駆動装置における各電流の大きさの関係を示す説明図である。
【図４】図３（ａ）の電流演算手段の具体的な例を示した回路図である。
【図５】本発明の第３の実施形態に係る電流駆動装置の構成の例を示す回路図である。
【図６】図５の定電圧電流演算手段の具体的な例を示した回路図である。
【図７】本発明の第４の実施形態に係る電流駆動装置の構成の例を示す回路図である。
【図８】図７の電流駆動装置における各電流の大きさの関係を示す説明図である。
【図９】従来の電流駆動装置を備えた表示装置の構成の例を示す回路図である。
【図１０】（ａ）伝送路に接続されたトランジスタの動作を示すグラフである。
（ｂ）図９の回路における電流の大きさの関係を示す説明図である。
【符号の説明】
１００，２００，４００，６００ 第１の集積回路
１０２，６０２ 第１の電流駆動回路
１１０，２１０ カレントミラー回路
１１１，６０８ 基準電流源
１５０，２５０，６３０ 第２の集積回路
１５２，６３２ 第２の電流駆動回路
１６０ カレントミラー部
１９１ 参照電流用伝送路
１９２ 帰還電流用伝送路
１９３，１９４ 伝送路（外部抵抗）
２３０ 電流演算手段
４３０ 定電圧電流演算手段
６０４ 第１の電流演算手段
６１０ 第１のカレントミラー部
６２０ 第２のカレントミラー部
６３４ 第２の電流演算手段
６４０ 第３のカレントミラー部
６５０ 第４のカレントミラー部
６６０ 第３の集積回路
６６２ 第３の電流駆動回路
６６４ 第３の電流演算手段
６７０ 第５のカレントミラー部
６８０ 第６のカレントミラー部
６９１ 第１の参照電流用伝送路
６９２ 第１の帰還電流用伝送路
６９３ 第２の参照電流用伝送路
６９４ 第２の帰還電流用伝送路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current drive device for driving a current drive type element.
[0002]
[Prior art]
In recent years, flat panel displays have been reduced in size, thickness, and weight. In particular, display devices that use light-emitting elements such as organic EL (electro-luminescent) elements and light-emitting diodes that emit light do not require a backlight device, so they are thinner and lighter than display devices that use liquid crystals. Is possible.
[0003]
Light-emitting elements such as organic EL elements and light-emitting diodes vary in luminance depending on the amount of current applied, and a current driving device including a constant current source is required to drive these elements. The current driving device includes a plurality of constant current sources, and changes the number of operating constant current sources to change the magnitude of the output current in accordance with gradation data representing the luminance that the light emitting element should have. Then, it becomes possible to perform display with luminance according to the gradation data.
[0004]
Such a current driving device is integrated in a single semiconductor integrated circuit when the display device is small. However, when the panel size of the display device is increased and the number of pixels is increased, a plurality of integrated circuits are required. It becomes.
[0005]
FIG. 9 is a circuit diagram showing an example of the configuration of a display device including a conventional current driving device. The current driver of FIG. 9 includes first and second integrated circuits 900 and 950. In addition to the current driving device, the display device in FIG. 9 includes a display panel 940 in which organic EL elements as light emitting elements are arranged in a matrix, and a scanning line driving circuit 942 that controls the scanning lines of the display panel 940. I have. The first and second integrated circuits 900 and 950 drive the display panel 940.
[0006]
The first integrated circuit 900 includes a current driving circuit 902, a reference current source 911, and p-type transistors 912, 913, and 914. The p-type transistors 912 to 914 have substantially the same shape and size, and constitute a current mirror circuit. The second integrated circuit 950 includes a current driving circuit 952, n-type transistors 961 and 962, and p-type transistors 963 and 965. The n-type transistors 961 and 962 have substantially the same shape and size, and constitute a current mirror circuit. The p-type transistors 963 and 965 have substantially the same shape and size, and also constitute a current mirror circuit.
[0007]
The current drive circuits 902 and 952 receive the drain currents of the p-type transistors 914 and 965, respectively, and output a current corresponding to the gradation data of each pixel to the display panel 940. Although shown in a simplified manner in FIG. 9, the current driving circuits 902 and 952 usually have several hundred output terminals. The number of output terminals is determined by the number of pixels of the display panel and the number of terminals that can be mounted on the integrated circuit package.
[0008]
Next, the operation of the current driver shown in FIG. 9 will be described. Based on the reference current I 0 output from the reference current source 911 in the current driver 900, the current mirror circuit composed of the p-type transistors 912 to 914 generates the current I 1 and outputs it to the current driver circuit 902. Since the p-type transistors 912 and 914 have the same shape and size, the current I1 is equal to the reference current I0.
[0009]
Gradation data corresponding to each pixel is input to the current driving circuit 902, and the current driving circuit 902 outputs a current weighted according to the gradation data based on the current I1. The current output from the current driving circuit 902 is given to each light emitting element on the line selected by the scanning line driving circuit 942 of the display panel 940, and each light emitting element emits light.
[0010]
When the size of the display panel 940 is relatively small, only the integrated circuit 900 can be driven. However, when the size of the display panel 940 increases and the number of pixels increases, it is necessary to operate a plurality of integrated circuits 900 and the like in parallel.
[0011]
In this case, if different current sources are used in each integrated circuit, the luminance of the light emitting element differs for each connected integrated circuit, and display unevenness may occur. This is because there are variations in characteristics that occur during manufacturing between integrated circuits, and therefore the magnitudes of the reference currents output from the respective current sources are not uniform.
[0012]
In the conventional current driver of FIG. 9, the reference current I2 is supplied from the first integrated circuit 900 to the second integrated circuit 950 in order to prevent display unevenness. In FIG. 9, the p-type transistor 913 outputs a reference current I2 to the second integrated circuit 950 through the transmission line 991. In the second integrated circuit 950, the gate and drain of the n-type transistor 961 are connected, and the reference current I2 flows from the drain to the source of the n-type transistor 961.
[0013]
The transmission line 991 has a wiring resistance. When the first and second integrated circuits 900 and 950 are, for example, mounted on a COG (chip on glass), the connection resistance at the pad is also included in the wiring resistance.
[0014]
FIG. 10A is a graph showing the operation of the transistors 913 and 961 connected to the transmission line 991. In FIG. 10A, the vertical axis indicates the reference current I2 flowing through the transistors 913 and 961. The horizontal axis represents the drain voltage VD1 of this transistor for the p-type transistor 913 and the drain voltage VD2 of this transistor for the n-type transistor 961.
[0015]
Although the p-type transistor 913 is designed to operate in the saturation region, the saturation current is not always constant because of the influence of the channel length modulation effect of the transistor. That is, the saturation current decreases as the drain voltage VD1 increases.
[0016]
If there is no wiring resistance in the transmission line 991, the voltages VD1 and VD2 match. At this time, in FIG. 10A, the intersection A between the graph of the p-type transistor 913 and the graph of the n-type transistor 961 indicates the values of the drain voltages VD1 and VD2 and the reference current I2 of these two transistors. Yes. In this case, the value of the reference current I2 is equal to the reference current I0.
[0017]
Next, considering the wiring resistance of the transmission line 991, a voltage drop occurs due to the wiring resistance, so that VD1> VD2. At this time, in FIG. 10A, the reference current I2 decreases, and the operating point of the p-type transistor 913 moves from point A to point B. That is, in this case, the reference current I2 is smaller than the reference current I0.
[0018]
FIG. 10B is an explanatory diagram showing a relationship of current magnitudes in the circuit of FIG. Based on the reference current I2 input to the second integrated circuit 950, the current mirror circuit composed of the n-type transistors 961 and 962 generates a current I3. Based on the current I 3, the current mirror circuit composed of the p-type transistors 963 and 965 generates the current I 4 and outputs it to the current drive circuit 952. The current I4 generated based on the reference current I2 in this way is smaller than the current I1 input to the current drive circuit 902.
[0019]
Therefore, even when the luminance of the light emitting elements should be the same, the current output from the current drive circuit 952 that operates based on the current I4 is the current output from the current drive circuit 902 that operates based on the current I1. Smaller than. Therefore, when the wiring resistance of the transmission line 991 cannot be ignored, the luminance of the light emitting element is different for each connected integrated circuit even in the current driver of FIG. 9, and display unevenness occurs in a block shape.
[0020]
[Problems to be solved by the invention]
As described above, in the conventional current driver, the value of the reference current cannot be accurately transmitted between the integrated circuits due to the resistance of the transmission path between the integrated circuits. For this reason, when a plurality of integrated circuits drive a display panel, the same gradation data is given, and the luminance varies among the integrated circuits to be driven among the light emitting elements that should have the same luminance, and the display unevenness is in a block shape. There was a problem that occurred. When the number of pixels is large and a large number of integrated circuits are required, errors in the value of the reference current transmitted between the integrated circuits accumulate, so that there is a problem that even larger display unevenness occurs.
[0021]
An object of the present invention is to reduce display unevenness of a display device using a current-driven light-emitting element.
[0022]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the means of the invention of claim 1 includes a first integrated circuit and a second integrated circuit as a current driver, and the first integrated circuit uses a reference current as a reference current. In response to the current mirror circuit that generates a reference current and outputs the reference current to the second integrated circuit via a reference current transmission line, and a feedback current output from the second integrated circuit, a current-driven element A first current driving circuit that generates and outputs a current for driving the first current driving circuit, and the second integrated circuit generates the feedback current according to the reference current and provides a transmission path for the feedback current. Output to the first integrated circuit, and generate a drive circuit current according to the reference current, and output the current mirror unit, and the resistance value of the feedback current transmission line equal A second current driving circuit that receives the driving circuit current as an input via an external resistor having a resistance value, and generates and outputs a current for driving a current driving type element based on the driving circuit current; It is what has.
[0023]
According to the first aspect of the present invention, the resistance value of the feedback current transmission line that feeds back current from the second integrated circuit to the first current driving circuit of the first integrated circuit, and the second integrated circuit The resistance value of the current path applied to the current drive circuit equally Therefore, the currents supplied to the first and second current drive circuits can be made equal. For this reason, between the elements that should have the same luminance, the luminance is different for each integrated circuit to be driven, and display unevenness can be prevented.
[0024]
According to a second aspect of the present invention, the current driving device includes a first integrated circuit and a second integrated circuit, wherein the first integrated circuit generates a reference current according to a reference current, Output to the second integrated circuit via a current transmission line and the reference current equal A current mirror circuit that generates and outputs current, and the reference current output by the current mirror circuit. equal A current calculation means for obtaining and outputting an average current having a magnitude obtained by averaging the current and the feedback current output from the second integrated circuit; and a current for driving a current-driven element based on the average current. A first current driving circuit that generates and outputs the first current driving circuit, wherein the second integrated circuit generates the feedback current in accordance with the reference current, and the first current drive circuit via the feedback current transmission line. Output current to the integrated circuit, and generate current for driving circuit according to the reference current, and generate current for driving current-driven elements based on the current mirror section for output and the current for driving circuit. And a second current driving circuit that outputs the current.
[0025]
According to the invention of claim 2, the reference current is equal An average current of the current and the feedback current from the second integrated circuit to the first integrated circuit is obtained and applied to the first current driver circuit of the first integrated circuit. The magnitude of the average current is equal to the current given to the second current drive circuit. equal Therefore, the currents applied to the first and second current drive circuits are equal, and display unevenness can be prevented.
[0026]
According to a third aspect of the present invention, the current driving device includes a first integrated circuit and a second integrated circuit, wherein the first integrated circuit generates a reference current according to a reference current, Output to the second integrated circuit via a current transmission line and the reference current equal A current mirror circuit that generates and outputs current, and the reference current output by the current mirror circuit. equal An average current having a magnitude obtained by averaging the current and the feedback current output from the second integrated circuit is obtained and output, and the voltage at the input is calculated. Constant Constant voltage current calculating means for maintaining the current driving circuit, and a current driving circuit for generating and outputting a current for driving the current driving type element based on the average current, and the second integrated circuit includes: A current mirror unit that generates the feedback current according to a reference current, outputs the feedback current to the first integrated circuit via a feedback current transmission line, and generates and outputs a drive circuit current according to the reference current And a current drive circuit that generates and outputs a current for driving a current-driven element based on the drive circuit current.
[0027]
According to the invention of claim 3, the voltage at the input of the constant voltage current calculating means is Constant Therefore, the average current can be accurately obtained, and display unevenness is hardly caused.
[0028]
According to a fourth aspect of the present invention, the current driver includes first, second, and third integrated circuits, and the first integrated circuit generates a first reference current according to a reference current, Output to the second integrated circuit via the first reference current transmission line and the reference current equal A first current mirror unit that generates and outputs a current, and a first feedback current output by the second integrated circuit; equal A second current mirror that generates and outputs a current, and the reference current equal Current and the first feedback current equal First current calculation means for obtaining and outputting a first average current having a magnitude obtained by averaging the current, and generating and outputting a current for driving a current-driven element based on the first average current And the second integrated circuit generates a second reference current in response to the first reference current, and passes through a second reference current transmission line. Output to the third integrated circuit and to the first reference current. equal A third current mirror unit that generates and outputs a current; and a first feedback current transmission line that generates the first feedback current according to a second feedback current output from the third integrated circuit. And output to the first integrated circuit via the second feedback current. equal A fourth current mirror unit for generating and outputting a current, and the first reference current equal Current and the second feedback current equal A second current calculating means for obtaining and outputting a second average current having a magnitude obtained by averaging the current, and generating and outputting a current for driving a current-driven element based on the second average current; The third integrated circuit generates a third reference current in response to the second reference current and uses the second reference current as a second reference current. equal A fifth current mirror section for generating and outputting a current; and generating the second feedback current in accordance with the third reference current, and the second integration through the second feedback current transmission line. Output to the circuit and to the third reference current equal A sixth current mirror section for generating and outputting a current, and the second reference current equal Current and the third reference current equal Third current calculation means for obtaining and outputting a third average current having a magnitude obtained by averaging the current, and generating and outputting a current for driving a current-driven element based on the third average current And a third current driving circuit.
[0029]
According to the fourth aspect of the present invention, even when three or more integrated circuits are used, the currents supplied to the current driving circuits in the integrated circuits can be made equal. Therefore, display unevenness can be prevented even in a display device using a large screen with a large number of pixels.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0031]
(First embodiment)
FIG. 1 is a circuit diagram showing an example of the configuration of a display device including a current driving device according to the first embodiment of the present invention. The current driving device in FIG. 1 includes a first integrated circuit 100 and a second integrated circuit 150. The display device of FIG. 1 includes a display panel 140 and a scanning line driving circuit 142 in addition to the current driving device.
[0032]
The first integrated circuit 100 includes a first current driving circuit 102, a current mirror circuit 110, and a reference current source 111. The second integrated circuit 150 includes a second current drive circuit 152 and a current mirror unit 160. The current mirror circuit 110 includes p-type transistors 112 and 113. The current mirror unit 160 includes n-type transistors 161 and 162 and p-type transistors 163, 164 and 165.
[0033]
In the display panel 140, light emitting elements are arranged in a matrix. The light emitting element is, for example, an organic EL element. Each light emitting element forms a pixel of the display panel 140.
[0034]
To the current driver circuit 102, gradation data corresponding to each pixel of the display panel 140 and a feedback current I5 output from the second integrated circuit 150 are input. The current drive circuit 102 obtains a current weighted according to the gradation data for each light emitting element connected to the line, based on the feedback current I5, and outputs it.
[0035]
The current drive circuit 152 is supplied with gradation data corresponding to each pixel of the display panel 140 and a drive circuit current I6. The current driving circuit 152 calculates and outputs a current weighted according to the gradation data for each light emitting element of one line connected to the current driving circuit 152 based on the current I6.
[0036]
The display panel 140 is driven using a display driving method called line sequential. That is, the scanning line driving circuit 142 normally drives the lines in the order from the uppermost line to the lowermost line. In the case of the display panel 140 of FIG. 1, the potential of the non-display line is at the power supply level. The scan line driver circuit 142 performs line selection by reducing the potential of a line to be displayed.
[0037]
When the scanning line driving circuit 142 selects a line, the current driving circuits 102 and 152 output a current corresponding to the gradation data from each terminal to each pixel of the line. A current flows forward in each light emitting element on the selected line, and the luminance of the light emitting element varies according to the magnitude of the flowing current. When the display of one line is performed for a certain period, the scanning line driving circuit 142 selects the next line, and the current driving devices 102 and 152 output a current according to the gradation data of each pixel of the line. Thereafter, display is similarly performed line by line, and when the display of one frame is completed, the operation of starting display again from the upper end line is repeated.
[0038]
The reference current source 111 has one end connected to the drain of the p-type transistor 112 and the other end grounded. The source of the p-type transistor 112 is connected to the power supply, and the gate is connected to the gate of the p-type transistor 113. The source of the p-type transistor 113 is connected to the power supply, and the drain is connected to the drain of the n-type transistor 161 via the reference current transmission line 191. The gate and drain of the p-type transistor 112 are connected. The p-type transistors 112 and 113 are substantially the same in shape and size. Thus, the p-type transistors 112 and 113 constitute a current mirror circuit 110. The reference current source 111 passes the reference current I0 between the source and drain of the p-type transistor 112.
[0039]
In the current mirror unit 160, the sources of the n-type transistors 161 and 162 are grounded, the gate of the n-type transistor 161 is connected to the gate of the n-type transistor 162, and the drain of the n-type transistor 162 is connected to the drain of the p-type transistor 163. Has been. The gate and drain of the n-type transistor 161 are connected, and the n-type transistors 161 and 162 constitute a current mirror circuit.
[0040]
The sources of the p-type transistors 163 to 165 are connected to the power supply, and the gate of the p-type transistor 163 is connected to the gates of the p-type transistors 164 and 165. The drain of the p-type transistor 164 is connected to the current driving circuit 102 via the feedback current transmission path 192. The drain of the p-type transistor 165 is connected to the current drive circuit 152 via transmission lines 193 and 194 as external resistors. The gate and drain of the p-type transistor 163 are connected, and the p-type transistors 163 to 165 constitute a current mirror circuit. Here, the n-type transistors 161 and 162 have substantially the same shape and size, and the p-type transistors 163 to 165 have substantially the same shape and size.
[0041]
In the circuit as described above, the current mirror circuit 110 constituted by the p-type transistors 112 and 113 generates the reference current I2 according to the reference current I0, and the second integrated circuit via the reference current transmission line 191. This is output to 150 n-type transistors 161. At this time, as described with reference to FIG. 10A, the magnitude of the reference current I2 is affected by the resistance of the reference current transmission path 191 and is smaller than the reference current I0.
[0042]
The n-type transistor 162 causes a current I3 substantially equal to the reference current I2 to flow from the drain of the n-type transistor 162. The p-type transistor 164 generates a feedback current I5 according to the current I3 and outputs it to the current drive circuit 102. The p-type transistor 165 generates a drive circuit current I6 according to the current I3 and outputs the drive circuit current I6 to the current drive circuit 152 via the transmission lines 193 and 194.
[0043]
Here, if the feedback current transmission line 192 is on the same wiring board as the reference current transmission line 191, and the length and width are the same wiring as the reference current transmission line 191, the feedback current transmission line 192 is provided. The resistance values of the path 192 and the reference current transmission path 191 are substantially the same. In this case, if ΔI = I0−I2, the feedback current I5 is smaller than the reference current I2 by ΔI due to the resistance of the feedback current transmission path 192, so that I5 = I0−2ΔI. The current drive circuit 102 operates based on this feedback current I5.
[0044]
On the other hand, in the second integrated circuit 150 at the subsequent stage, the current driving circuit 152 operates based on the current I6. If the drain current of the p-type transistor 165 is directly input to the current drive circuit 152, a current substantially equal to the reference current I2 is supplied to the current drive circuit 152. Then, the current output from the current driving circuit 152 is larger than the current output from the current driving circuit 102, and display unevenness occurs on the display panel.
[0045]
Therefore, the drain of the p-type transistor 165 is connected to the current drive circuit 152 via the transmission lines 193 and 194. Here, the sum of the resistance values of the transmission lines 193 and 194 is made substantially equal to the resistance value of the feedback current transmission line 192. For example, the resistance values of the transmission lines 193 and 194 may both be set to ½ of the resistance value of the feedback current transmission line 192.
[0046]
Then, the resistance value between the p-type transistor 165 and the current drive circuit 152 becomes substantially equal to the resistance value between the p-type transistor 164 and the current drive circuit 102, so that the current I 6 supplied to the current drive circuit 152 and The feedback current I5 given to the current drive circuit 102 is substantially equal. Therefore, display unevenness can be prevented from occurring on the display panel.
[0047]
FIG. 2 is an explanatory diagram showing the magnitude of each current in the current driver of FIG. Since the current I6 given to the current drive circuit 152 passes through the transmission lines 193 and 194, it has a value substantially equal to the feedback current I5, not the reference current I2.
[0048]
Instead of the transmission lines 193 and 194, a resistor having a resistance value substantially equal to the feedback current transmission line 192 may be used as the external resistance.
[0049]
The first integrated circuit 100 may not include the reference current source 111 and may input / output a reference current to / from a reference current source outside the first integrated circuit 100. In this case, the current mirror circuit 110 composed of the p-type transistors 112 and 113 may be configured to output a reference current according to the reference current.
[0050]
(Second Embodiment)
FIG. 3A is a circuit diagram showing an example of the configuration of the current driver according to the second embodiment of the present invention. The current driving device shown in FIG. 3A includes a first integrated circuit 200 and a second integrated circuit 250. The first integrated circuit 200 includes a current mirror circuit 210 in place of the current mirror circuit 110 in the first integrated circuit 100 of FIG. The second integrated circuit 250 is the same as the second integrated circuit 150 of FIG. 1 except that the drain current of the p-type transistor 165 is directly input to the second current driver circuit 152. The same constituent elements as those of the current driving device of FIG.
[0051]
In FIG. 3A, a current mirror circuit 210 is obtained by further adding a p-type transistor 114 in the current mirror circuit 110. The source of the p-type transistor 114 is connected to the power supply, and the gate is connected to the gate of the p-type transistor 112. The p-type transistor 114 outputs the drain current I1 to the current calculation unit 230. The shapes and sizes of the p-type transistors 112 and 114 are substantially the same. Thus, since the p-type transistors 112 to 114 constitute the current mirror circuit 210, the current I1 is substantially equal to the reference current I0.
[0052]
The p-type transistor 164 outputs a feedback current I 7 from the drain, and supplies this to the current calculation means 230 via the feedback current transmission path 192. The p-type transistor 165 outputs the drive circuit current I 4 from the drain and directly supplies it to the current drive circuit 152. The current calculation means 230 obtains an average current I8 having a magnitude obtained by averaging the input current I1 and the feedback current I7, and outputs the average current I8 to the first current drive circuit 102.
[0053]
Since it is affected by the resistance of the reference current transmission line 191, the reference current I2 and the current I3 are smaller than the reference current I0 by ΔI. Further, since it is affected by the resistance of the feedback current transmission line 192, the feedback current I7 output from the p-type transistor 164 is smaller by ΔI than the current I3. The value of the current I4 is substantially equal to the reference current I2 and the current I3.
[0054]
FIG. 3B is an explanatory diagram showing the relationship between the magnitudes of the currents in the current driver of FIG. The average current I8 given to the current drive circuit 102 is a value obtained by averaging the current I1 and the feedback current I7, which is substantially equal to the reference current I2. Further, the current I4 given to the current driving circuit 152 is substantially equal to the reference current I2.
[0055]
Thus, since the average current I8 applied to the current drive circuit 102 and the current I4 applied to the current drive circuit 152 become equal, the luminance of the display panel varies between the integrated circuits that drive the light emitting elements. Can be prevented.
[0056]
FIG. 4 is a circuit diagram showing a specific example of the current calculation means 230 in FIG. In FIG. 4, the current calculation means 230 includes n-type transistors 231 and 232 and p-type transistors 233 and 234.
[0057]
The n-type transistor 231 has a gate and a drain connected, a source is grounded, and operates as an active resistance element. A current I1 and a feedback current I7 are input to the drain of the n-type transistor 231, and a current obtained by adding the current I1 and the feedback current I7 flows between the drain and the source of the transistor. The gate of the n-type transistor 232 is connected to the gate of the n-type transistor 231, and the source of the n-type transistor 232 is grounded. The n-type transistors 231 and 232 form a current mirror circuit.
[0058]
The sources of the p-type transistors 233 and 234 are connected to the power supply, the gate of the p-type transistor 233 is connected to the gate of the p-type transistor 234, and the drain of the p-type transistor 233 is connected to the drain of the n-type transistor 232. The gate and drain of the p-type transistor 233 are connected, and the p-type transistors 233 and 234 constitute a current mirror circuit.
[0059]
The W / L of the n-type transistor 231 (ratio of the channel width W and the channel length L of the transistor) and the W / L of the n-type transistor 232 have a 2: 1 relationship. For this reason, the current mirror circuit formed by the n-type transistors 231 and 232 averages the current that is half the current obtained by adding the current I1 and the feedback current I7, that is, the current I1 and the feedback current I7. Current is passed between the drain and source of n-type transistor 232. Further, the shapes and sizes of the p-type transistors 233 and 234 are substantially the same. For this reason, the current mirror circuit formed by the p-type transistors 233 and 234 outputs an average current I 8 having substantially the same magnitude as the drain current of the n-type transistor 232 to the current driving circuit 102.
[0060]
4 can output the average current I8 obtained by averaging the current I1 and the feedback current I7.
[0061]
(Third embodiment)
FIG. 5 is a circuit diagram showing an example of the configuration of the current driver according to the third embodiment of the present invention. The current driver of FIG. 5 includes a first integrated circuit 400 and a second integrated circuit 250. The first integrated circuit 400 includes a constant voltage current calculation unit 430 in place of the current calculation unit 230 in the first integrated circuit 200 of FIG. The same components as those of the current driver of FIG. 3A are denoted by the same reference numerals, and description thereof is omitted.
[0062]
The constant voltage current calculation means 430 obtains an average current I10 having a magnitude obtained by averaging the current I1 and the feedback current I7, and outputs the average current I10 to the first current drive circuit 102. However, the constant voltage / current calculation means 430 is configured to keep the voltage at its input substantially constant.
[0063]
4 adds the current I1 in the first integrated circuit 200 and the feedback current I7 from the second integrated circuit to the n-type transistor 231 that operates as an active resistance element. A voltage drop occurs. The magnitude of this voltage drop varies depending on the amount of current flowing. For this reason, the drain voltages of the p-type transistors 114 and 164 fluctuate, and the current I1 and the feedback current I7 may fluctuate due to the fluctuation.
[0064]
Therefore, the constant voltage current calculation means 430 keeps the voltage of the terminal to which the current is input at a constant value. Then, by adding the current, it is possible to prevent the drain voltage of the p-type transistors 114 and 164 from greatly fluctuating, and thus it is possible to reduce an error in obtaining the average current.
[0065]
FIG. 6 is a circuit diagram showing a specific example of the constant voltage current calculation means 430 of FIG. In FIG. 6, the constant voltage current calculation means 430 includes a differential amplifier circuit 435, a resistor 436, a reference voltage source 437, an inverting amplifier 438, an n-type transistor 442, and p-type transistors 443 and 444. Yes.
[0066]
The inverting input terminal of the differential amplifier circuit 435 is connected to the drain of the p-type transistor 114 and the drain of the p-type transistor 164. The resistor 436 is connected between the inverting input terminal and the output terminal of the differential amplifier circuit 435. One end of a reference voltage source 437 is connected to the non-inverting input terminal of the differential amplifier circuit 435. The other end of the reference voltage source 437 is grounded. The output terminal of the differential amplifier circuit 435 is connected to the gate of the n-type transistor 442 via the inverting amplifier 438.
[0067]
The source of the n-type transistor 442 is grounded, and the drain is connected to the drain of the p-type transistor 443. The sources of the p-type transistors 443 and 444 are connected to the power supply, and the gate of the p-type transistor 443 is connected to the gate of the p-type transistor 444. The gate and the drain of the p-type transistor 443 are connected, and the p-type transistors 443 and 444 constitute a current mirror circuit.
[0068]
The differential amplifier circuit 435 is an operational amplifier, for example, and is negatively fed back via a resistor 436. For this reason, there is an imaginary short between the inverting input terminal and the non-inverting input terminal, and both terminals have the same potential. Therefore, the inverting input terminal is also equal to the voltage of the reference voltage source.
[0069]
Both the current I1 and the feedback current I7 input to the constant voltage current calculation unit 430 flow through the resistor 436. When the sum of these currents is I9, the voltage output from the reference voltage source 437 is VP, and the resistance value of the resistor 436 is RF, the output voltage VO of the differential amplifier circuit 435 is VP−I9 × RF. . The inverting amplifier 438 outputs a voltage I9 × RF + VK obtained by inverting the output voltage VO (the voltage VK is a constant value). Therefore, if the resistance value RF and the voltage VK are set to appropriate values, the n-type transistor 442 , A drain current substantially equal to the current I9 flows.
[0070]
The W / L of the p-type transistor 443 and the W / L of the p-type transistor 444 have a 2: 1 relationship. For this reason, the current mirror circuit formed by the p-type transistors 443 and 444 outputs a current I10 having a magnitude half that of the drain current of the n-type transistor 442 to the current driving circuit 102. The current I10 is an average current of the current I1 and the feedback current I7.
[0071]
As described above, when the constant voltage / current calculation unit 430 of FIG. 6 is used, the terminal voltage of the inverting input terminal of the differential amplifier circuit 435 is held at a constant value, so that the drain voltages of the p-type transistors 114 and 164 are large. It can be prevented from fluctuating. For this reason, the average current I10 can be obtained more accurately.
[0072]
(Fourth embodiment)
In the first to third embodiments, the current driving device including two integrated circuits has been described. In the fourth embodiment, the current driving device including three cascaded integrated circuits. Will be described.
[0073]
FIG. 7 is a circuit diagram showing an example of the configuration of the current driver according to the fourth embodiment of the present invention. The current driver of FIG. 7 includes a first integrated circuit 600, a second integrated circuit 630, and a third integrated circuit 660. The first to third integrated circuits 600, 630, and 660 are all configured similarly.
[0074]
The first integrated circuit 600 includes a first current driving circuit 602, a first current calculation unit 604, a first current mirror unit 610, and a second current mirror unit 620. The second integrated circuit 630 includes a second current driving circuit 632, a second current calculation means 634, a third current mirror unit 640, and a fourth current mirror unit 650. The third integrated circuit 660 includes a third current drive circuit 662, third current calculation means 664, a fifth current mirror unit 670, and a sixth current mirror unit 680.
[0075]
The first current mirror unit 610 includes n-type transistors 611 and 612 and p-type transistors 613, 614 and 615. The reference current I20 is input from the reference current source 608 to the drain of the n-type transistor 611 in the first current mirror unit 610. The configuration of the first current mirror unit 610 is the same as that of the current mirror unit 160 of FIG.
[0076]
That is, the sources of the n-type transistors 611 and 612 are grounded, the gate of the n-type transistor 611 is connected to the gate of the n-type transistor 612, and the drain of the n-type transistor 612 is connected to the drain of the p-type transistor 613. The gate and drain of the n-type transistor 611 are connected, and the n-type transistors 611 and 612 constitute a current mirror circuit.
[0077]
The sources of the p-type transistors 613 to 615 are connected to the power supply, and the gate of the p-type transistor 613 is connected to the gates of the p-type transistors 614 and 615. The drain of the p-type transistor 614 is connected to the third current mirror circuit 640 via the first reference current transmission line 691. The drain of the p-type transistor 615 is connected to the current calculation means 604. The gate and the drain of the p-type transistor 613 are connected, and the p-type transistors 613 to 615 constitute a current mirror circuit. Here, the n-type transistors 611 and 612 have substantially the same shape and size, and the p-type transistors 613 to 615 have substantially the same shape and size.
[0078]
The first current mirror unit 610 generates the first reference current I21 according to the reference current I20, and the third current mirror unit of the second integrated circuit 630 via the first reference current transmission path 691. Output to 640. Further, the first current mirror unit 610 generates a current I31 that is substantially equal to the reference current I20 and outputs the current I31 to the first current calculation unit 604.
[0079]
Since the internal configuration of the second current mirror unit 620 is the same as that of the first current mirror unit 610, detailed description thereof is omitted. The second current mirror unit 620 generates a current I32 that is substantially equal to the first feedback current I25 output from the fourth current mirror unit 650 of the second integrated circuit 630, and supplies the current I32 to the first current calculation unit 604. Output.
[0080]
The first current calculation means 604 is the same as the current calculation means 230 shown in FIG. 4, for example, and obtains a first average current I41 having a magnitude obtained by averaging the current I31 and the current I32 to obtain the first current Output to the drive circuit 602. The first current drive circuit 602 is the same as the current drive circuit 102 of FIG. The first current driving circuit 602 generates a current for driving the current-driven light emitting element of the display panel 140 based on the first average current I41 and the gradation data corresponding to each pixel of the display panel 140. Output.
[0081]
In the second integrated circuit 630, the internal configurations of the third and fourth current mirror units 640 and 650 are the same as those of the first and second current mirror units 610 and 620, respectively. To do.
[0082]
The third current mirror unit 640 generates the second reference current I22 according to the first reference current I21, and the fifth current mirror unit 640 uses the second reference current transmission path 693 to generate the fifth reference current I22. Output to the current mirror unit 670. The third current mirror unit 640 generates a current I33 that is substantially equal to the first reference current I21 and outputs the current I33 to the second current calculation unit 634.
[0083]
The fourth current mirror unit 650 generates a first feedback current I25 according to the second feedback current I24 output from the sixth current mirror unit 680 of the third integrated circuit 660, and the first feedback current This is output to the second current mirror unit 620 of the first integrated circuit 600 through the transmission line 692. The fourth current mirror unit 650 generates a current I34 that is substantially equal to the second feedback current I24 and outputs the current I34 to the second current calculation unit 634.
[0084]
The second current calculation means 634 is, for example, the same as the current calculation means 230 of FIG. 4, and obtains a second average current I42 having a magnitude obtained by averaging the current I33 and the current I34 to obtain the second current Output to the drive circuit 632. The second current drive circuit 632 is similar to the current drive circuit 102 of FIG. The second current driving circuit 632 generates a current for driving the current-driven light emitting element of the display panel 140 based on the second average current I42 and the gradation data corresponding to each pixel of the display panel 140. Output.
[0085]
In the third integrated circuit 660, the internal configurations of the fifth and sixth current mirror units 670 and 680 are the same as those of the first and second current mirror units 610 and 620, respectively. To do.
[0086]
The fifth current mirror unit 670 generates a third reference current I23 according to the second reference current I22 and outputs the third reference current I23 to the sixth current mirror unit 680. Further, the fifth current mirror unit 670 generates a current I35 substantially equal to the second reference current I22 and outputs the current I35 to the third current calculation unit 664.
[0087]
The sixth current mirror unit 680 generates a second feedback current I24 according to the third reference current I23, and the fourth current mirror unit 680 includes a fourth feedback current transmission path 694 through the fourth feedback circuit 694 of the second integrated circuit 630. Output to the current mirror unit 650. The sixth current mirror unit 680 generates a current I36 substantially equal to the third reference current I23 and outputs the current I36 to the third current calculation unit 664.
[0088]
The third current calculation means 664 is, for example, the same as the current calculation means 230 of FIG. 4, and obtains a third average current I43 having a magnitude obtained by averaging the current I35 and the current I36 to obtain the third current Output to the drive circuit 662. The third current drive circuit 662 is the same as the current drive circuit 102 of FIG. The third current driving circuit 662 generates a current for driving the current-driven light emitting element of the display panel 140 based on the third average current I43 and the gradation data corresponding to each pixel of the display panel 140. Output.
[0089]
FIG. 8 is an explanatory diagram showing the relationship between the magnitudes of the currents in the current driving device of FIG. Similar to the current driver of FIG. 1, the first reference current I21 is smaller in magnitude than the reference current I20 because it is affected by the resistance of the first reference current transmission line 691. Similarly, since it is affected by the resistance of the second reference current transmission line 693, the magnitude of the second reference current I22 is smaller than the first reference current I21.
[0090]
Since the third reference current I23 is input from the fifth current mirror unit 670 to the sixth current mirror unit 680 without passing through the transmission line, the magnitude thereof is equal to the second reference current I22. Therefore, the third average current I43 is

It becomes.
[0091]
Since the second feedback current transmission line 694 is affected by the resistance, the magnitude of the second feedback current I24 is smaller than that of the third reference current I23. Similarly, since it is affected by the resistance of the first feedback current transmission line 692, the magnitude of the first feedback current I25 is smaller than the second feedback current I24. Here, d1 = I20−I21, d2 = I21−I22, d3 = I23−I24, and d4 = I24−I25.
[0092]
If the resistance values of the second reference current transmission line 693 and the second feedback current transmission line 694 are equal, d2 = d3 holds because the influence of the resistance of these transmission lines is the same. Therefore, the second average current I42 is

It becomes.
[0093]
Further, assuming that the resistance values of the first reference current transmission line 691 and the first feedback current transmission line 692 are equal, the influences of the resistances of these transmission lines are equal, so that d1 = d4 holds. Therefore, the first average current I41 is

It becomes.
[0094]
Thus, since I41 = I42 = I43 is established, the magnitudes of the currents input to the first to third current driving circuits 602, 632, 662 are equal. For this reason, if the grayscale data is the same, there is no difference in luminance of the light emitting element even when any of the first to third integrated circuits 600, 630, and 660 is driven, and thus display unevenness is displayed on the display panel 140. Does not occur.
[0095]
In the present embodiment, the case where three integrated circuits are connected has been described. Similarly, more than three integrated circuits may be cascade-connected. As described above, according to the present embodiment, since a large number of integrated circuits can be easily used, a large display panel can be driven without causing display unevenness.
[0096]
In the above embodiment, the light emitting element of the display panel may be a current driven type, for example, a light emitting diode.
[0097]
【The invention's effect】
As described above, according to the present invention, display unevenness of a display device using a current-driven light emitting element can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an example of a configuration of a display device including a current driving device according to a first embodiment of the present invention.
2 is an explanatory diagram showing the magnitude of each current in the current driver of FIG. 1; FIG.
FIG. 3A is a circuit diagram showing an example of a configuration of a current driver according to a second embodiment of the present invention.
(B) It is explanatory drawing which shows the relationship of the magnitude | size of each electric current in the current drive device of Fig.3 (a).
FIG. 4 is a circuit diagram showing a specific example of the current calculation means of FIG.
FIG. 5 is a circuit diagram showing an example of a configuration of a current driver according to a third embodiment of the present invention.
6 is a circuit diagram showing a specific example of the constant voltage current calculation means of FIG. 5. FIG.
FIG. 7 is a circuit diagram showing an example of a configuration of a current driver according to a fourth embodiment of the present invention.
FIG. 8 is an explanatory diagram showing the relationship between the magnitudes of the currents in the current driver of FIG.
FIG. 9 is a circuit diagram illustrating an example of a configuration of a display device including a conventional current driving device.
FIG. 10A is a graph showing the operation of a transistor connected to a transmission line.
(B) It is explanatory drawing which shows the relationship of the magnitude | size of the electric current in the circuit of FIG.
[Explanation of symbols]
100, 200, 400, 600 First integrated circuit
102,602 first current drive circuit
110, 210 Current mirror circuit
111,608 reference current source
150, 250, 630 second integrated circuit
152,632 Second current driving circuit
160 Current mirror section
191 Reference current transmission line
192 Return current transmission line
193,194 Transmission path (external resistance)
230 Current calculation means
430 Constant voltage current calculation means
604 First current calculation means
610 First current mirror section
620 Second current mirror section
634 Second current calculation means
640 Third current mirror section
650 Fourth current mirror section
660 Third integrated circuit
662 Third current drive circuit
664 Third current calculation means
670 Fifth current mirror section
680 Sixth current mirror section
691 First reference current transmission line
692 First feedback current transmission line
693 Second reference current transmission line
694 Second feedback current transmission line

Claims (4)

A first integrated circuit;
A second integrated circuit,
The first integrated circuit includes:
A current mirror circuit that generates a reference current according to a reference current and outputs the reference current to the second integrated circuit via a reference current transmission line;
A first current driving circuit that generates and outputs a current for driving a current-driven element based on a feedback current output from the second integrated circuit,
The second integrated circuit includes:
A current mirror that generates the feedback current according to the reference current, outputs the feedback current to the first integrated circuit via the feedback current transmission line, and generates and outputs a drive circuit current according to the reference current And
The drive circuit current is input through an external resistor having a resistance value equal to the resistance value of the feedback current transmission line, and a current for driving a current drive type element is generated based on the drive circuit current. And a second current driving circuit for outputting the current driving device. A first integrated circuit;
A second integrated circuit,
The first integrated circuit includes:
A current mirror circuit that generates a reference current according to a reference current, outputs the reference current to the second integrated circuit via a reference current transmission line, and generates and outputs a current equal to the reference current;
Current calculation means for obtaining and outputting an average current of a magnitude obtained by averaging the current equal to the reference current output from the current mirror circuit and the feedback current output from the second integrated circuit;
A first current driving circuit that generates and outputs a current for driving a current-driven element based on the average current;
The second integrated circuit includes:
A current mirror that generates the feedback current according to the reference current, outputs the feedback current to the first integrated circuit via the feedback current transmission line, and generates and outputs a drive circuit current according to the reference current And
And a second current driving circuit that generates and outputs a current for driving a current-driven element based on the driving circuit current. A first integrated circuit;
A second integrated circuit,
The first integrated circuit includes:
A current mirror circuit that generates a reference current according to a reference current, outputs the reference current to the second integrated circuit via a reference current transmission line, and generates and outputs a current equal to the reference current;
An average current having a magnitude obtained by averaging the current equal to the reference current output from the current mirror circuit and the feedback current output from the second integrated circuit is obtained and output, and the voltage at the input is kept constant . Constant voltage and current calculation means to maintain,
A current driving circuit that generates and outputs a current for driving a current-driven element based on the average current;
The second integrated circuit includes:
A current mirror that generates the feedback current according to the reference current, outputs the feedback current to the first integrated circuit via the feedback current transmission line, and generates and outputs a drive circuit current according to the reference current And
And a current driving circuit that generates and outputs a current for driving a current-driven element based on the driving circuit current. Comprising first, second and third integrated circuits;
The first integrated circuit includes:
A first reference current is generated in accordance with a reference current and output to the second integrated circuit via a first reference current transmission line, and a current equal to the reference current is generated and output. Current mirror part of
A second current mirror unit that generates and outputs a current equal to the first feedback current output by the second integrated circuit;
A first current calculating means obtains and outputs the first average current magnitude averaged a current equal to the current equal to the first feedback current to said reference current,
And a first current driving circuit that generates and outputs a current for driving a current-driven element based on the first average current,
The second integrated circuit includes:
A second reference current is generated according to the first reference current, and is output to a third integrated circuit via a second reference current transmission line, and a current equal to the first reference current is generated. And outputting a third current mirror unit,
The first feedback current is generated according to the second feedback current output from the third integrated circuit, and is output to the first integrated circuit via the first feedback current transmission line. A fourth current mirror unit that generates and outputs a current equal to the second feedback current;
A second current calculation means obtains and outputs a second average current magnitude averaged a current equal to said first of said equal current to the reference current a second feedback current,
And a second current driving circuit that generates and outputs a current for driving a current-driven element based on the second average current,
The third integrated circuit includes:
A fifth current mirror unit that generates a third reference current according to the second reference current and generates and outputs a current equal to the second reference current;
The second feedback current is generated according to the third reference current, and is output to the second integrated circuit via the second feedback current transmission line, and is equal to the third reference current. A sixth current mirror unit for generating and outputting
A third current calculation means obtains and outputs a third average current magnitude averaged a current equal to the second of said equal current to the reference current third reference current,
And a third current driving circuit that generates and outputs a current for driving a current-driven element based on the third average current.

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