JP4754541B2 - Current drive - Google Patents

Description

  The present invention relates to a current drive device, and more particularly to a technology of a current drive device suitable as a display driver such as an organic EL (Electro Luminescence) panel.

  In recent years, flat panel displays such as organic EL panels have been increased in size, definition, thickness, weight, and cost. In general, an active matrix method is preferably used as a driving method for a large and high-definition display panel. Hereinafter, a display driver for a conventional active matrix display panel will be described.

  FIG. 20 is a circuit diagram showing a configuration of a display panel and a conventional current driving device which is a display driver connected to the display panel. Here, the display panel is an organic EL panel.

  As shown in the figure, the conventional current driving device has a plurality of pixel circuits 1005a1, 1005a2,..., 1005an (hereinafter referred to as pixel circuit 1005a when called without distinction). ), And 1001an (hereinafter referred to as current supply unit 1001a when not distinguished from each other), and current supply units 1001a, 1001a1, 1001a2,. And a reference current supply unit (bias circuit) 1101 for supplying a reference current. In the present specification, the “reference current” represents a current having a predetermined value flowing from the reference current source, and also represents a current transmitted from the reference current source by the current mirror circuit.

  In the case where the size of the display panel is large, such as a television display device, a large number of current supply units 1001 a are provided on a plurality of semiconductor chips 1105. These semiconductor chips 1105 are often arranged in the frame portion of the display panel.

  Each of the pixel circuits 1005a1, 1005a2,..., 1005an includes a p-channel first TFT (Thin-Film-Transistor) 1104 connected to the current supply unit 1001a via a signal line, a first TFT 1104, The pixel includes a second TFT 1102 constituting a current mirror circuit and an organic EL element 1103 that emits light in accordance with a current supplied from the second TFT 1102.

  The reference current supply unit 1101 is connected to a p-channel first MISFET 1108 having a power supply voltage supplied to one end thereof, a resistor 1107 for generating a reference current, a first MISFET 1108, and a current A p-channel type second MISFET 1109 constituting a mirror circuit and an n-channel type current input MISFET 1110 connected to the second MISFET 1109 and transmitting a reference current to the current supply unit 1001a are provided.

  When each of the current supply units 1001a controls m-bit gradation, the current sources 1112-1, 1112-2,..., 1112-m arranged in parallel to the output unit connected to the pixel circuit 1005a. (M is a positive integer) and switches 1115-1, 1115-2,..., 1115-m that control currents flowing through the current sources 1112-1, 1112-2,. And have. Here, each of the current sources 1112-1, 1112-2,..., 1112-m is configured by a current input MISFET 1110 and an n-channel MISFET constituting a current mirror circuit. In addition, each of the switches 1151-1, 115-2,..., 1115-m performs a switching operation independently based on the display data.

  FIG. 23 is a diagram showing a circuit arrangement and a circuit configuration of a current supply unit in a conventional current driving device. Here, an example of a current supply unit for 64 gradations, in each of which six current sources are provided, is shown. The current sources 1112-1, 1112-2,..., 1112-6 are provided with one, two,. These MISFETs are arranged as shown in the upper diagram of FIG. 23 in plan view, and adjacent MISFETs are connected to be connected to the same output unit.

  With the above configuration, the current supply unit 1001a substantially operates as a current addition type D / A converter, receives display data as a digital signal, and generates a current corresponding to the display data as an analog signal. It pulls in from the output part.

  As is well known, the organic EL element exhibits rectification like a diode and changes its luminance in accordance with the amount of current that is energized. In the pixel circuit 1005a, the amount of current supplied to the organic EL element 1103 changes according to the amount of current flowing through the TFT 1104. Therefore, the organic EL element 1103 is current-driven by the current supply unit 1001a and changes its luminance.

As described above, the current driving device drives the plurality of pixel circuits 1005a in the display panel based on the display data to realize gradation display (for example, Japanese Patent Laid-Open Nos. 11-88072 and 11- No. 340765).
JP 2000-276108 A

  However, in the display device having the above-described configuration, image display disturbance such as display unevenness may be observed during image display. There are several possible causes for this.

  First, display disturbance due to charge injection from the display panel or instantaneous bias voltage fluctuation, so-called crosstalk, can be considered. This will be described below.

  FIG. 21A is a diagram showing an example of monochrome display on the display panel, and FIG. 21B is a pixel circuit arranged on the XXIb-XXIb line of the display panel shown in FIG. The circuit diagram which shows the conventional electric current supply part, (c) is a graph which shows the operating point of TFT at the time of black display, (d) is a graph which shows the operating point of TFT at the time of white display . FIG. 22A is a diagram showing an example of black and white display on the display panel, as in FIG. 21A, and FIG. 22B is a diagram showing pixel circuits arranged on the XXIIb-XXIIb line of the display panel. The circuit diagram which shows the conventional electric current supply part connected to the pixel circuit, (c) is a graph figure which shows the operating point of TFT at the time of switching from black display time to white display, (d) is continuous It is a graph showing the operating point of the TFT when performing white display.

  As shown in FIG. 21B, when black display is performed in the conventional display device, the switches 1111-1, 115-2,..., 1115-m in the current supply unit 1001a are all off, and white When the display is performed, all the switches 1115-1, 1115-2, ..., 1115-m in the current supply unit 1001a are turned on.

  At this time, the stray capacitance 1220a1 generated in the pixel circuit 1005a1 that performs black display and the signal line connected thereto is charged by the power supply, and the gate voltages of the first TFT 1104 and the second TFT 1102 rise to, for example, about 4V. . As shown in FIG. 21C, the operating point of the first TFT 1104 and the second TFT 1102 at this time is an intersection of the IV characteristic curve of the current supply unit 1001a and the IV characteristic curve of the TFT.

  On the other hand, when white is displayed, charge is drawn to the current supply portion 1001an side, so that the charge held in the stray capacitance 1220an generated in the pixel circuit 1005an or a signal line connected thereto is larger than that in black display. Less. Therefore, the gate voltages of the first TFT 1104 and the second TFT 1102 are about 2 V, for example, and as shown in FIG. 21D, the operating points of the first TFT 1104 and the second TFT 1102 are higher than in the case of black display. Is also on the low voltage side. The operating point voltages of these TFTs vary depending on the on-resistance of the TFT and the magnitude of the current drawn by the current supply unit 1001a.

  FIG. 22B shows the pixel circuit and the current supply unit when the black display is switched to the white display, and the pixel circuit and the current supply unit when the white display continues. When the black display is switched to the white display, all of the switches 1115-1, 1115-2, ..., 1115-6 of the current supply unit 1001a1 are turned on, and the maximum amount of current flows from the panel side. Thereby, the organic EL element 1103 in the pixel circuit 1005a1 emits light with the maximum luminance.

  At this time, the electric charge accumulated in the floating capacitance 1220a1 is injected into the current supply unit 1001a1 through the signal line.

  When the amount of injected charge is relatively small, the charge passes through the current sources 1112-1, 1112-2, ..., 1112-6 to the ground. However, since the pixel circuit 1005a1 displayed black just before, the stray capacitance 1220a1 is charged to near the power supply voltage. Therefore, at the moment when the current supply unit 1001a1 and the pixel circuit 1005a1 are electrically connected, a voltage close to the power supply voltage is applied to each drain of the current sources 1112-1, 1112-2,. The potential of the bias line 1050 is temporarily pushed up through the parasitic capacitance Cgd existing between the drains. A waveform 1051 shown in FIG. 22B represents a voltage fluctuation generated in the bias line 1050.

  Since the gate electrode of the current source in the other current supply unit 1001a is also connected to the bias line 1050, when a voltage change like the waveform 1051 occurs in the bias line 1050, the amount of current flowing through the current supply unit 1001a is temporarily To be more. As a result, as indicated by a dotted line in FIG. 22D, the current supply unit 1001an is temporarily in an excessive drive state.

  When the voltage variation of the bias line 1050 converges within the display data writing period, the current supply unit 1001a returns to a predetermined driving state, and normal display is performed. However, when the voltage variation does not converge within the display data writing period, the pixel circuit 1005a continues to be in an excessive drive state until the next frame, so that a crosstalk display in which a bright line is visually recognized occurs.

  On the other hand, on the bias line 1050 in the case of switching from white display to black display, a temporary voltage drop occurs contrary to the above. As a result, a crosstalk display in which a dark line with reduced brightness is visually recognized occurs.

  By the way, the stray capacitance 1220a is several pF to several tens of pF in the case of a small panel for mobile phone use, but may be 100 pF or more in the case of a large panel. Therefore, when the display panel is enlarged, the crosstalk display becomes more prominent. In particular, a current driving device for an organic EL panel drives a pixel circuit with a very small current of about several tens of nA, and thus easily causes a crosstalk display.

  Note that the image display may be disturbed for reasons other than the above-described crosstalk.

  In recent years, the display panel has become larger in screen, and accordingly, the length of the driver LSI for the display device (length in the long side direction) has reached 10 mm to 20 mm. In such a case, in the semiconductor chip provided with the conventional current driving device, there is a possibility that the output voltage varies between the output terminals separated from each other, and the image quality is deteriorated, for example, a bright and dark part is generated in the display image.

  The inventor of the present application investigated the cause of the variation in output voltage between the output terminals of the display device driver LSI (semiconductor chip). As a result, the current distributed to the MISFET constituting the current source 1112 (see FIG. 20) on the semiconductor chip It turned out that there was variation. In the first place, the current mirror circuit is based on the premise that the diffusion conditions of the transistors constituting the current mirror circuit are equal, and that there is no significant difference in threshold value Vt and carrier mobility. In addition, the current is distributed according to the size ratio of the transistors. However, when the length of the chip of the driver LSI for display device is as long as 10 mm to 20 mm, it is considered difficult to uniformly diffuse the impurities contained in the transistor. In addition, if the positions of the transistors are different, display variations such as etching variations may occur depending on the manufacturing process. As a result, the threshold value of the transistor serving as the current mirror varies. If the threshold value of the transistor varies, an error occurs in the output current when the same gate voltage is applied. Usually, the variation in diffusion has a gradual inclination with respect to the wafer surface. For this reason, even when uniform display is performed with constant display data, a bright to dark gradation occurs on the display panel.

  Further, as described above, a display device having a large-screen display panel uses a plurality of semiconductor chips provided with a current driving device including a current supply unit. In such a case, the current values output from the current driving devices on different semiconductor chips vary. In display devices, manufacturing conditions such as diffusion conditions of semiconductor chips arranged adjacent to each other are often different. Accordingly, the deviation in the characteristics of the MISFETs constituting the current source of the current supply unit 1001a1 is increased, and the display unevenness is easily visually recognized for each semiconductor chip.

  As described above, the variation in the output units of the current supply unit 1001a and the variation in the characteristics of the semiconductor chips also disturb the image display similarly to the crosstalk.

  An object of the present invention is to provide a current driving device capable of suppressing disturbance of image display by solving any of the various problems described above.

  A first current driving device of the present invention is a current driving device provided on a semiconductor chip, and is a first conductivity type first device that transmits the reference current from a reference current source for supplying a reference current. MISFET, the first MISFET and a current mirror circuit, and a first conductivity type current distribution MISFET for flowing the reference current, and a second conductivity type current connected to the current distribution MISFET. A plurality of current supply units each including an input MISFET, a current source MISFET constituting the current mirror circuit and the current input MISFET, and an output terminal for outputting a current corresponding to display data; A current transmission MISFET constituting a current mirror circuit with the current source MISFET and the current input MISFET, and the semiconductor chip. Of the distance from the current transmitting MISFET is provided on the following areas 200 [mu] m, and a reference current output terminal for outputting a current transmitted from the current transmitting MISFET.

  Thus, when a large-screen display panel is driven by arranging a plurality of semiconductor chips provided with the current driving device of the present invention, a current with a small error can be transmitted as a reference current to the next-stage semiconductor chip. Compared with a circuit, variation in output current for each semiconductor chip can be reduced. As a result, a large-screen or high-definition display device in which display unevenness and display disturbance are suppressed can be realized.

  If the reference current output terminal is provided on a region of the semiconductor chip within a distance of 100 μm from the current transmission MISFET, an error in the current transmitted to the next semiconductor chip can be further reduced. More preferable.

  The reference current source is outside the semiconductor chip, and is connected to the reference current source on a region of the semiconductor chip having a distance of 200 μm or less from the current input MISFET, and is connected to the current input MISFET. Since the first reference current input terminal for transmitting the current is further provided, when the semiconductor chips are cascade-connected, the reference current output from the preceding semiconductor chip can be used for current input with a small error. Can be transmitted to MISFET. Therefore, when used in a display device, display unevenness generated for each semiconductor chip can be reduced.

  A first reference current input terminal connected to the drain of the first MISFET and provided on a region of the semiconductor chip having a distance of 200 μm or less from the current input MISFET; and a drain of the first MISFET An input-side current mirror circuit composed of a second conductivity type MISFET, and an input-side current mirror circuit connected to the input-side current mirror circuit, on a region of the semiconductor chip having a distance of 200 μm or less from the current input MISFET An output-side current mirror circuit which is provided on the current transmission path from the current transmission MISFET to the reference current output terminal and which is configured by a MISFET of the first conductivity type. And driving the pixel circuit on the display panel by arranging a single semiconductor chip. Therefore, the manufacturing cost of the display device can be reduced as compared with the case where a plurality of types of semiconductor chips are used.

  When a plurality of pairs of the current distribution MISFETs and the current input MISFETs are provided for the semiconductor chip, the number of gate electrodes of the current source MISFETs connected to one current input MISFET is larger than that of the conventional one. Therefore, the change in the gate potential of the current source MISFET can be quickly converged. Therefore, by using the current driving device of the present invention, it is possible to suppress display unevenness for each semiconductor chip and simultaneously suppress crosstalk display.

  In the case of further comprising connection switching means for switching the current distribution MISFET between the current distribution MISFET and the current input MISFET so that the current distribution MISFET is connected to a different current input MISFET every predetermined period. Since the variation in characteristics of the current distribution MISFETs can be averaged, a display device in which display unevenness is further suppressed can be realized.

  On the semiconductor chip, a plurality of MISFET regions in which the current source MISFETs are collectively provided are arranged in a row, and each of the plurality of current supply units is arranged in at least two of the MISFET regions. By having the MISFET, the characteristic variation of the current source MISFET can be averaged, so that display unevenness is hardly visible and a display device with high display quality can be realized.

  The gate electrode of the current distribution MISFET is commonly connected to a bias line, and a resistance element is further provided between the gate electrodes of the current distribution MISFETs adjacent to each other on the bias line. As a result, the gate voltage applied to the current distribution MISFET can be tilted in accordance with the variation in threshold value of the current distribution MISFET. As a result, variation in the reference current distributed to each current supply unit can be reduced. Can do.

  The second current driver of the present invention comprises a first conductivity type first MISFET through which a reference current flows during driving, the first MISFET and a current mirror circuit, and a first current for flowing the reference current. A first conductivity type MISFET, a second conductivity type first MISFET whose drain is connected to the first current distribution MISFET, a first current input MISFET and a current A second-conductivity-type current source MISFET constituting a mirror circuit, and a switch connected to each of the current source MISFETs for switching on or off the current flowing through the current source MISFET according to display data; A plurality of current supply units connected to the switch and having an output terminal for outputting a current corresponding to the display data to the display panel; In the current driving device provided on the semiconductor chip, a plurality of pairs of the first current distribution MISFET and the first current input MISFET are provided for the semiconductor chip. And a bias line commonly connected to the gate electrode of one MISFET and the gate electrode of the first current distribution MISFET.

  As a result, the number of gate electrodes of the current source MISFET connected to one first current input MISFET can be reduced as compared with the prior art, so that the change in the gate potential of the current source MISFET can be quickly converged. It becomes possible. Therefore, according to the current driving device of the present invention, the occurrence of crosstalk display can be suppressed, so that a display device having a large screen or a high-definition display panel can be realized.

  Since the gate electrodes of all the current source MISFETs and all the first current input MISFETs in the plurality of current supply units are connected to each other, the gate potential applied to the current source MISFETs can be reduced. Since the inclination can be made in accordance with the variation in the threshold value, the variation in the output current for each output terminal can be suppressed.

  Each of the plurality of current supply units is interposed between the switch and the output terminal, and is turned on when a voltage lower than the power supply voltage of the display panel is applied to the gate electrode during driving. When the current driving device of the present invention is used for a display device, if the first cascode MISFET is an n-channel type, a current source is supplied from the display panel at the time of display switching. It is possible to prevent a high voltage from being applied to the MISFET for use. Therefore, occurrence of crosstalk display can be suppressed.

  The switch is also a second cascode MISFET that forms a cascode connection with the current source MISFET and is controlled to be turned on or off depending on whether a predetermined voltage is applied to the gate electrode during driving. When the output terminal is connected to the display panel, the second cascode MISFET can limit the high voltage applied from the display panel, so that the occurrence of crosstalk display can be suppressed. In particular, when the switch is a MISFET for voltage limitation, the circuit area can be reduced as compared with the case where a MISFET for voltage limitation is separately provided.

  Switching between the first current distribution MISFET and the first current input MISFET so that the first current distribution MISFET is connected to a different current input MISFET every arbitrary period. By further providing the connection switching means, the reference current distributed by the current distribution MISFET is shuffled and output, so that the characteristic variation of the current distribution MISFET can be averaged.

  In particular, the connection switching means preferably includes a first bias current switching switch and a second bias current switching switch.

  On the semiconductor chip, a first terminal temporarily connected to the first bias current changeover switch during driving and a second terminal temporarily connected to the second bias current changeover switch during driving. The terminal is further provided, so that when the display panel is driven by arranging a plurality of semiconductor chips, the current distributed by the current distribution MISFET is passed through the first terminal and the second terminal. It can also be switched to output from the output terminal of the adjacent semiconductor chip. For this reason, not only in the semiconductor chip but also in the output current of the current driving device provided on the semiconductor chips adjacent to each other can be averaged.

  The second current driving device of the present invention includes a first conductive type dummy current distribution MISFET constituting a current mirror circuit with the first MISFET and the first current distribution MISFET, and the dummy current distribution. And a dummy connection switching means for temporarily connecting the current MISFET and the current input MISFET, for example, to sequentially switch the current distribution MISFETs connected between the adjacent current input MISFETs. Since it can be controlled, the output current from the output terminal can be made uniform relatively easily.

  On the semiconductor chip, a plurality of MISFET regions in which the current source MISFETs are collectively provided are arranged in a row, and each of the plurality of current supply units is arranged in at least two of the MISFET regions. By having the MISFET, the characteristic variation of the current distribution MISFET and the current source MISFET can be averaged, so that an error in the output current between the output terminals can be reduced. In particular, it is not necessary to provide a new element and the wiring structure may be arbitrarily changed, so that an increase in circuit area can be suppressed.

  By further including a resistance element provided between the gate electrodes of the current distribution MISFETs that are adjacent to each other on the bias line, the gate voltage applied to the current distribution MISFET is set to the threshold value of the current distribution MISFET. It can be tilted according to the variation of

  The third current driver of the present invention includes a first conductivity type first current input MISFET in which a first reference current flows during driving, and a first conductivity type second MISFET in which a second reference current flows during driving. Current input MISFET, the first current input MISFET and the first conductivity type current source MISFET constituting the current mirror circuit, and the current source MISFET, respectively. A switch for switching on or off the current flowing through the current source MISFET, and a second current input MISFET and a current mirror circuit that are provided between the current source MISFET and the switch, respectively. A cascode MISFET of one conductivity type, and an output terminal connected to the switch for outputting a current corresponding to the display data. And a plurality of current supply portion that is provided on the semiconductor chip.

  As a result, the output current from the output terminal becomes an average value of the current that should flow through the current source MISFET and the current that should flow through the cascode MISFET, and thus the characteristic variation of the current source MISFET and the characteristic variation of the cascode MISFET cancel each other. As a result, variation in output current from the output terminal can be reduced.

  A fourth current driver of the present invention is a current driver provided on a semiconductor chip, and includes a first reference current input terminal for inputting a first reference current, and the first reference current input terminal for a first period. A first current input MISFET of the first conductivity type to which a current flowing through the first reference current input terminal is transmitted, and a first current input MISFET and a current mirror circuit constituting the first current input MISFET in the first period. A current source MISFET of one conductivity type, a plurality of current supply units having an output terminal for outputting a current corresponding to display data, the first current input MISFET and the current in the first period; A first current transfer MISFET of the first conductivity type that forms a current mirror circuit with the source MISFET, and a first reference current to which a current flowing through the first current transfer MISFET is transmitted during the first period A second reference current input terminal for inputting a second reference current, a current flowing through the second reference current input terminal during a second period, and the current source MISFET, A first conductivity type second current input MISFET constituting a current mirror circuit, and a first conductivity type second current transmission MISFET constituting a current mirror circuit with the current source MISFET in the second period. A second reference current output terminal to which a current flowing through the second current transmission MISFET is transmitted during the second period, the first reference current input terminal, the first current input MISFET, A first switch provided on the current transmission path between the first current transmission MISFET and the second switch provided on the current transmission path between the first reference current output terminal When A third switch provided on a current transmission path between the second reference current input terminal and the second current input MISFET; the second current transmission MISFET; and the second reference current. And a fourth switch provided on a current transmission path to the output terminal.

  Thus, when the first reference current is driven by turning on both the first and second switches in the first period and turning off the third and fourth switches in the second period. And the case of driving with the second reference current. As a result, variation in output current from the current supply unit is suppressed, and uniform display is possible.

  The first display device of the present invention includes a display panel provided with a pixel circuit having a light-emitting element whose luminance changes in accordance with the amount of supplied current, and a plurality of semiconductor chips arranged in a row. Provided with a current driving device for supplying a driving current to the pixel circuit, wherein each of the plurality of semiconductor chips is provided at an end for inputting a reference current A semiconductor chip adjacent to each other among the plurality of semiconductor chips, having a reference current input terminal and a reference current output terminal provided at an end for outputting a reference current for a next-stage semiconductor chip The reference current input terminal and the reference current output terminal are provided to face each other.

  As a result, the reference current transmission path can be made shortest between the semiconductor chips provided with the current driving device, so that variations in the output current for each semiconductor chip can be reduced as compared with the prior art.

  A second display device of the present invention includes a display panel provided with a pixel circuit having a light-emitting element whose luminance changes in accordance with the amount of supplied current, and a driving current supplied to each of the pixel circuits. A display device including a plurality of semiconductor chips provided with a current driving device, wherein the current driving device includes a first conductivity type first MISFET through which a reference current flows during driving, and the first MISFET. And a plurality of first conductivity type current distribution MISFETs for supplying the reference current and a plurality of second conductivity type MISFETs each having a drain connected to each of the plurality of current distribution MISFETs. The current input MISFET, the second conductivity type current source MISFET constituting the current mirror circuit and the current input MISFET, and the drive current corresponding to the display data are displayed on the screen. And a plurality of current supply section and an output terminal for outputting the circuit.

  As a result, fluctuations in the gate potential of the current source MISFET can be quickly converged, so that occurrence of crosstalk display can be suppressed and uniform display can be realized.

According to a third display device of the present invention, there is provided a display panel provided with a pixel circuit having a light emitting element whose luminance changes in accordance with the amount of supplied current, and for supplying a driving current to each of the pixel circuits. A display device including a plurality of semiconductor chips provided with a current driving device, wherein the current driving device includes a first conductivity type first current input MISFET through which a first reference current flows during driving, A first conductivity type second current input MISFET in which a second reference current flows during driving; a first conductivity type current source MISFET that forms a current mirror circuit with the first current input MISFET; A switch connected to each of the current source MISFETs for switching on or off a current flowing through the current source MISFET according to display data; and the current source MI A cascode MISFET of the first conductivity type that is provided between the FET and the switch and constitutes a current mirror circuit with the second current input MISFET, and a drive current corresponding to the display data connected to the switch And a plurality of current supply units having output terminals for outputting to the pixel circuit.

  As a result, the output current from the output terminal is an average value of the current that should flow through the current source MISFET and the current that should flow through the cascode MISFET, and thus the characteristic variation of the current source MISFET and the characteristic variation of the cascode MISFET are offset. As a result, variation in output current from the output terminal can be reduced.

  On the semiconductor chip, a first reference current input terminal for inputting the first reference current, a first reference current output terminal for outputting the first reference current, and the second A second reference current input terminal for inputting a second reference current, and a second reference current output terminal for outputting the second reference current. The first reference current output The terminal is connected to the first reference current input terminal of the adjacent semiconductor chip, and the second reference current output terminal is connected to the second reference current input terminal of the adjacent semiconductor chip. The variation in the output current from the terminals in the same semiconductor chip is reduced, and the variation in the output current between the semiconductor chips is also reduced, so that uniform display can be performed over the entire display panel.

  According to the current driver of the present invention, by providing a plurality of current distribution MISFETs and current input MISFETs per semiconductor chip for distributing the reference current, the output impedance at the gate of the MISFET constituting the current supply unit is relatively Therefore, when used in a display device, fluctuations in the gate potential of the MISFET due to current flowing from the display panel can be suppressed. As a result, occurrence of crosstalk in the display device can be suppressed.

(First embodiment)
FIG. 1 is a circuit diagram showing a connection portion of two chips provided with a current driving device according to a first embodiment of the present invention.

  The display device of this embodiment includes a display panel provided with a pixel circuit (not shown) having an organic EL element, and a current driving device for supplying a driving current to the pixel circuit via a signal line. Yes. The current driving device is used as a source driver of a current driving display device such as an organic EL display device, similarly to the current driving device shown in FIG. In the display device of the present embodiment, a plurality of semiconductor chips provided with integrated current driving devices are arranged on the frame portion of the display panel. In FIG. 1, two semiconductor chips connected to each other are shown as a first semiconductor chip 20 and a second semiconductor chip 22, respectively.

  In the display device of the present embodiment, the first semiconductor chip 20 includes a current supply unit 40 for supplying a drive current to each of a plurality of pixel circuits (not shown) provided on the display panel, and a current A reference current supply unit for supplying a reference current to the supply unit 40, an n-channel first current transfer MISFET 7, and a reference current output terminal 9 connected to the first current transfer MISFET 7 are provided. ing. The reference current output terminal 9 is provided at a position facing the second semiconductor chip 22 in the first semiconductor chip 20. Although a large number (for example, 528) of current supply units 40 are actually provided, only one is shown in FIG.

  The reference current supply unit is connected to the first MISFET 1 having a power supply voltage supplied to one end thereof, the reference current source 4 for generating a reference current, and the first MISFET 1 A p-channel type second MISFET (current distribution MISFET) 2 constituting the current mirror circuit and an n-channel type current input connected to the second MISFET 2 for transmitting a reference current to the current supply unit 40 MISFET3.

The current supply unit 40 includes current sources 5-1, 5-2,..., 5-m (m is a positive integer) and a switch for turning on or off the current flowing through each current source. is doing. Each of the current sources 5-1, 5-2,..., 5-m includes a current input MISFET 3 and a first current transmission MISFET 7 and a MISFET (current source MISFET) that forms a current mirror circuit. For example, the current source 5-1 is one MISFET, the current source 5-2 is two MISFETs connected in parallel to each other, and the current source 5-m is 2 ^m-1 connected in parallel to each other. It is composed of a number of MISFETs. The current supply unit 40 is a so-called current addition type D / A converter, and each switch is turned on or off according to display data to enable display of 2 ^m gradations.

  The second semiconductor chip 22 includes a reference current input terminal 11 connected to the reference current output terminal 9, a p-channel type third MISFET 13 connected to the reference current input terminal 11, and a cascode to the third MISFET 13. A p-channel fourth MISFET 15 having a gate electrode connected to the reference current input terminal 11, a third MISFET 13 and a p-channel fifth MISFET 17 constituting a current mirror circuit, and a fifth MISFET 17 A p-channel sixth MISFET 19 that forms a current mirror circuit with the fourth MISFET 15 and an n-channel seventh MISFET 23 (first semiconductor chip) that receives a reference current flowing through the sixth MISFET 19. 20 equivalent to the current input MISFET in FIG. A current supply unit 41 for supplying a drive current to each of a plurality of pixel circuits (not shown) provided above, and an n-channel type second for transmitting a reference current to the next-stage semiconductor chip And a current transmission MISFET 27. A reference current output terminal (not shown) connected to the second current transmission MISFET 27 is also provided on the second semiconductor chip 22.

  The reference current input terminal 11 is provided in the vicinity of the position facing the first semiconductor chip in the second semiconductor chip 22, and is disposed so as to be particularly close to the reference current output terminal 9.

  In the second semiconductor chip 22, the third MISFET 13, the fourth MISFET 15, the fifth MISFET 17, the sixth MISFET 19, and the seventh MISFET 23 receive the reference current output terminal 9 from the first semiconductor chip 20. It functions as a reference current supply unit for transmitting the reference current transmitted via the current supply unit 41 to the current supply unit 41.

  The current supply unit 41 includes current sources 25-1, 25-2,..., 25-m, and a switch for turning on or off the current flowing through each current source. Like the current sources 5-1, 5-2,..., 5-m, the current sources 25-1, 25-2,..., 25-m respectively include the seventh MISFET 23 and the second current transmission MISFET 27. And a MISFET constituting a current mirror circuit.

  Although only two semiconductor chips are shown in FIG. 1, a chip having the same configuration as the second semiconductor chip 22 may be further arranged according to the size of the display panel. In a normal display device, semiconductor chips provided with a current supply unit are often arranged in a line. In this case, a reference current is output from a reference current output terminal 9 provided near the end of each semiconductor chip. A reference current is transmitted in cascade to the input terminal 11.

  The semiconductor chip of the present embodiment having the above-described configuration is characterized in that the reference current supply unit of the second semiconductor chip 22 is disposed in the vicinity of the reference current input terminal 11 and the first semiconductor chip 20. The current transmission MISFET 7 is disposed in the vicinity of the reference current output terminal 9. Here, the distance between the reference current supply unit including the seventh MISFET 23 and the reference current input terminal 11 and the distance between the current transmission MISFET 7 and the reference current output terminal 9 are subject to variations in electrical characteristics due to impurity diffusion or the like. As long as it does not cause a problem. This distance varies depending on manufacturing conditions and processes, but it is acceptable if it is 200 μm or less, and generally it is particularly preferable if it is 100 μm or less.

  As a result, the output current of the current transmitting MISFET 7 of the semiconductor chips adjacent to each other can be distributed as the reference current for the second semiconductor chip 22, so that the output current (drive current of the pixel circuit) for each semiconductor chip The variation can be reduced as compared with the conventional case. As a result, a display device that performs more uniform display can be realized.

  In addition, in the display device according to the present embodiment, the reference current supply unit and the reference current input terminal 11 of the semiconductor chip are arranged in the vicinity of the position facing the preceding semiconductor chip in the semiconductor chip to transmit current. The MISFET for reference and the reference current output terminal 9 are arranged in the vicinity of the position facing the semiconductor chip at the next stage in the semiconductor chip.

  Thereby, since the distance between the reference current output terminal 9 and the reference current input terminal 11 is shortened, it is possible to further suppress the variation of the current output from the current supply unit for each semiconductor chip. However, since the effect of suppressing the variation among the semiconductor chips is smaller than the effect obtained by providing the input / output terminal of the reference current in the vicinity of the MISFET that transmits the reference current, the reference current output terminal 9 and the reference current input are not necessarily provided. The terminal 11 may not be provided at the end of the semiconductor chip.

  In a single semiconductor chip, the reference current supply unit (or MISFET) is arranged at the center of the chip depending on the position of the current supply unit rather than the end of the chip as in the present embodiment. The characteristic variation is reduced. Therefore, also in this method, it is preferable to provide the reference current output terminal 9 and the reference current input terminal 11 close to the reference current supply unit.

  As described above, by using the semiconductor chip of this embodiment, it is possible to suppress variation in characteristics between semiconductor chips, so that a display device in which occurrence of display unevenness and the like is reduced can be realized.

  Note that a current mirror circuit formed of a p-channel type MISFET may be provided between the first current transmission MISFET 7 and the reference current output terminal 9.

  FIG. 2 is a circuit diagram showing a connection portion between two chips provided with an example of the current driving device according to the first embodiment.

  In the example shown in the figure, in the first semiconductor chip 20, a p-channel type third MISFET 7 connected between the first current transmission MISFET 7 and the reference current output terminal 9 is connected to the first current transmission MISFET 7. Current transmission MISFET 10, third current transmission MISFET 10 and p-channel type fourth current transmission MISFET 12 constituting a current mirror circuit are provided.

Further, the reference current supply unit of the second semiconductor chip 22 has a configuration in which all the conductivity types of the MISFETs constituting the reference current supply unit of FIG. 1 are replaced. That is, the second semiconductor chip 22 is cascode-connected to the n-channel eighth MISFET 33 connected to the reference current input terminal 11 and the eighth MISFET 33, and the gate electrode is connected to the reference current input terminal 11. The n-channel ninth MISFET 35, the eighth MISFET 33, the n-channel tenth MISFET 37 constituting the current mirror circuit, and the tenth MISFET 37 are cascode-connected to the ninth MISFET 35 and the current mirror circuit. An n-channel eleventh MISFET 39 and a p-channel twelfth MISFET 43 receiving a reference current flowing through the tenth MISFET 37 are provided. In such a configuration, the distance between each of the first current transfer MISFET 7, the third current transfer MISFET 10, and the fourth current transfer MISFET 12 and the reference current output terminal 9 of the first semiconductor chip 20 is 200 μm. The distance between the three MISFETs of the first current transmission MISFET 7, the third current transmission MISFET 10, and the fourth current transmission MISFET 12 is also 200 μm or less. The reference current output terminal 9, the eighth MISFET 33, and the ninth MISFET 35 of the first semiconductor chip 20 are located in the vicinity of 200 μm or less from the reference current input terminal 11 of the second semiconductor chip 22 and the first current transmission MISFET 7. The distances from the tenth MISFET 37, the eleventh MISFET 39 and the twelfth MISFET 43 are each 200 μm or less, and the distances between the MISFETs are also 200 μm or less. In addition, since the reference current input terminal 11 of the second semiconductor chip 22 and the reference current output terminal 9 of the first semiconductor chip 20 are arranged so as to be close to each other, the output current for each semiconductor chip is not changed. The variation of the can be reduced.

  The first semiconductor chip 20 and the second semiconductor chip 22 shown in FIGS. 1 and 2 are slightly different in the configuration of the reference current supply unit. On the other hand, in the semiconductor chip used for the display device, the reference current supply unit may have the same configuration.

  FIG. 3 is a circuit diagram showing a connection portion between two chips provided with a current driver according to a modification of the first embodiment. In the modification of the first embodiment shown in the figure, a first reference current input terminal 11a1 and a second reference current input terminal 11b1 are provided near the end of the first semiconductor chip 20. The configuration of the reference current supply unit is the same as the reference current supply unit of the second semiconductor chip 22 shown in FIG. 2, but is connected to the first reference current input terminal 11a1 and the second reference current input terminal 11b1. Is different.

  That is, the first semiconductor chip 20 of the present modification is cascode-connected to the n-channel type eighth MISFET 33a1 connected to the second reference current input terminal 11b1 and the eighth MISFET 33a1, and the gate electrode is the first. The n-channel ninth MISFET 35a1 connected to one reference current input terminal 11a1, the eighth MISFET 33a1, the n-channel tenth MISFET 37a1 constituting the current mirror circuit, and the tenth MISFET 37a1 are cascode-connected. The ninth MISFET 35a1 and an n-channel eleventh MISFET 39a1 constituting a current mirror circuit, and a p-channel first MISFET 1 receiving a reference current flowing through the tenth MISFET 37a1 are provided. The gate electrodes of the first MISFET 1 and the second MISFET 2, the drain of the first MISFET 1, and the drain of the tenth MISFET 37a1 are connected to the first reference current input terminal 11a1.

  In this modification, the configuration of the first semiconductor chip 20 and the second semiconductor chip 22 is the same. However, in the first semiconductor chip 20, the first reference current input terminal 11a1 is connected to the grounded resistor 16 (or reference current source), whereas the second reference current input terminal 11b1 is grounded. In the second semiconductor chip 22, the first reference current input terminal 11 a 2 is in an open state, and the second reference current input terminal 11 b 2 is connected to the reference current output terminal 9 of the first semiconductor chip 20.

  If the semiconductor chip of this modification is used, the display panel can be driven by only one type of chip, so that the manufacturing cost of the display device can be reduced.

  In the example of the semiconductor chip or current driving device described above, the MISFETs constituting the current sources 5-1, 5-2,..., 5-m are n-channel type. Even if it replaces, it can be operated similarly. In this case, the conductivity types of the MISFET and the current transmission MISFET constituting the reference current supply unit may be switched.

  When a plurality of semiconductor chips according to this modification are cascade-connected, a resistor having the same resistance value as that of the resistor 16 may be connected to the reference current output terminal of the final semiconductor chip.

  In the current driver of this embodiment, the value of the current output from the reference current output terminal 9 of the first semiconductor chip 20 does not necessarily have to be equal to the value of the reference current flowing through the reference current source 4. The current output from the reference current output terminal 9 is a reference current for the second semiconductor chip 22 (referred to as a second reference current). A current mirror circuit having an appropriate mirror ratio is used as the reference current input terminal 11. If provided between the seventh MISFET 23 and the MISFET in the current source constituting the current supply unit 40 and the MISFET in the current source constituting the current supply unit 41, the same current can be supplied.

(Second Embodiment)
FIG. 4 is a circuit diagram showing a current driver according to the second embodiment of the present invention. The current driving device of this embodiment is characterized in that, in addition to the conventional current driving device shown in FIG. 21, a current distribution MISFET 55 and a current input MISFET 57 for transmitting a reference current to each of the current supply units 59 are provided. It is a point. Here, “current supply unit 59” means each of current supply units 59-1 to m shown in FIG. 4, and “current distribution MISFET 55” means each of current distribution MISFETs 55-1 to 55-m. "Current input MISFET 57" means each of the current input MISFETs 57-1 to 57-m.

  As shown in FIG. 4, the current driver according to the present embodiment includes a p-channel first MISFET 53, a reference current source 58 connected to the first MISFET 53, for generating a reference current, and a first MISFET 53 and a current mirror circuit, and p-channel type current distribution MISFETs 55-1, 55-2,..., 55-n for distributing a reference current, and current distribution MISFETs 55-1, 55-2,. , 55-n and n-channel current input MISFETs 57-1, 57-2,..., 57-n, and current input MISFETs 57-1, 57-2,. , 59-n for supplying a reference current to the pixel circuit and supplying a drive current to a pixel circuit (not shown). Here, n is the number of outputs per semiconductor chip. The gate electrode of the first MISFET 53 and the gate electrodes of the current distribution MISFETs 55-1, 55-2,..., 55-n are connected to a common bias line 56.

  Further, the configuration of each of the current supply units 59-1, 59-2,..., 59-n is substantially the same as the current supply unit 40 (see FIG. 1) described in the first embodiment. For example, the current supply unit 59-1 includes m current sources composed of MISFETs 57-1 constituting a current mirror circuit and a current input MISFET 57-1, and a switch for turning on or off the current flowing through the current source (FIG. Not shown). However, among the MISFETs constituting the current source, the gate electrodes of the MISFETs connected to different output terminals may not be connected as shown in FIG. 4, but may be connected to each other as described later. Good.

When this current supply unit 59 has m current sources, 2 ^m gradation display is possible. Although not shown in the example shown in FIG. 4, each of the current supply units 59 has a current source for 6 bits and is composed of 63 MISFETs having the same size. In FIG. 4, one set of the current supply unit 59 and the current input MISFET is shown as the current supply unit 51. Here, the “current supply unit 51” means each of the current supply units 51-1 to 51-m.

  In the current driving device of the present embodiment, the current distribution MISFET 55 and the current input MISFET 57 for distributing the reference current are provided for each current supply unit 59. Therefore, when the display device switches from black display to white display. Even if current flows from the panel side, the operation of the current source in the current supply unit 59 is less affected. That is, in the current driver of this embodiment, the gate of the MISFET connected to one set of the current distribution MISFET 55 and the current input MISFET 57 is provided by providing the current distribution MISFET 55 and the current input MISFET 57 for each current supply unit. The number of electrodes is reduced compared to the conventional one. For this reason, since the capacity of the bias wiring connecting the gate electrode of the current input MISFET 57 and the gate electrode of the MISFET constituting the current source of the current supply unit 59 is reduced, the MISFET constituting the current source in the current supply unit 59 is reduced. It is easy to absorb the fluctuation of the potential of the gate electrode. As a result, fluctuations in the output of the current supply unit 59 are suppressed.

  For the same reason, even when switching from white display to black display, the current distribution MISFET 55 is not affected, and a constant current can be distributed to the current supply unit 59 at all times.

  Therefore, if the current driver of this embodiment is used, the fluctuation of the gate potential of the current source MISFET in the current supply unit 59 quickly converges within the display data writing period, thereby suppressing the occurrence of crosstalk. A current-driven display device with little display disturbance can be realized.

  Further, by providing the semiconductor chip provided with the current driving device of this embodiment with the input terminal and the output terminal of the reference current described in the first embodiment, a display device that further suppresses display disturbance and display unevenness. Can be realized.

  FIG. 5 is a diagram showing the semiconductor chip of this embodiment when the input terminal and the output terminal for the reference current are provided at the end of the chip.

  Each of the first semiconductor chip 70 and the second semiconductor chip 72 shown in FIG. 5 is provided with the current driving device of this embodiment described above. The first semiconductor chip 70 includes a current distribution MISFET 55 and a first MISFET 53, a p-channel type current transmission MISFET 61 that forms a current mirror circuit, and a reference current output terminal 9 connected to the current transmission MISFET 61. And are provided.

  On the other hand, the second semiconductor chip 72 includes a reference current input terminal 11 connected to the reference current output terminal 9, an n-channel type eighth MISFET 33 connected to the reference current input terminal 11, and an eighth MISFET 33. N-channel ninth MISFET 35 having a gate electrode connected to the reference current input terminal 11, an eighth MISFET 33, an n-channel tenth MISFET 37 constituting a current mirror circuit, and a tenth An n-channel eleventh MISFET 39 that is cascode-connected to the MISFET 37 and forms a current mirror circuit with the ninth MISFET 35, a p-channel twelfth MISFET 43 that receives a reference current flowing through the tenth MISFET 37, and a reference current An output terminal 9 (not shown) is provided. Here, the same member name and the same code | symbol are attached | subjected to the same member as 1st Embodiment shown in FIG.

  Further, the reference current output terminal 9 is disposed near the end portions of the first semiconductor chip 70 and the second semiconductor chip 72, for example. Further, the distance between the reference current output terminal 9 and the current transmission MISFET 61 is about 100 μm or less. The reference current input terminal 11 is disposed, for example, in the vicinity of the end of the second semiconductor chip 72 and is provided so as to face the reference current output terminal 9 of the first semiconductor chip 70. The distance between the reference current input terminal 11 and the MISFET constituting the reference current supply unit such as the twelfth MISFET 43 is about 100 μm or less.

  The reference current generated in the reference current source 58 and the first MISFET 53 is transmitted to the current transmission MISFET 61 through the current mirror and output from the reference current output terminal 9. Next, the reference current is input to the reference current input terminal 11 and is input to the twelfth MISFET 43 via the eighth MISFET 33, the ninth MISFET 35, the tenth MISFET 37, and the eleventh MISFET 39. The reference current is provided on the second semiconductor chip 72 and is transmitted to the MISFET 43 (not shown) for current transmission that forms a current mirror circuit with the twelfth MISFET 43. The reference current transmitted to the current transmission MISFET is further transmitted to the next-stage semiconductor chip via a reference current output terminal 9 (not shown).

  With the configuration as described above, a reference current with a small error is transmitted from the reference current output terminal 9 close to the reference current input terminal 11, so that the occurrence of crosstalk is suppressed and current drive is performed in the same semiconductor chip. Variations in output current for each semiconductor chip provided with the device can be kept small.

  Therefore, by adopting the reference current input / output configuration as described above, it becomes possible to realize image display with less unevenness, and to realize a large screen and high-definition organic EL display panel, LED display panel, and the like. It becomes possible.

  Although not shown, the reference current supply unit having the same configuration as the example shown in FIG. 3 can have only one type of semiconductor chip used for the display device, and can reduce the manufacturing cost. .

  In the current driver of this embodiment, FIG. 4 shows an example in which the current distribution MISFET 55 and the current input MISFET 57 are provided for each current supply unit 59, but one set is provided for two or more current supply units 59. The current distribution MISFET 55 and the current input MISFET 57 may be provided. In this case, it is sufficient that there are two or more pairs of the current distribution MISFET 55 and the current input MISFET 57 per semiconductor chip. The effect of suppressing crosstalk increases as the number of current distribution MISFETs 55 increases. However, in an actual circuit, it is preferable to design in consideration of the balance between circuit area and performance.

  FIG. 6 is a circuit diagram showing a modified example of the current driver of the present embodiment. In the semiconductor chip, the threshold voltage Vt of the MISFET arranged in the direction from the reference current input terminal to the reference current output terminal (longitudinal direction of the chip) is close to, for example, the input terminal due to factors such as an impurity concentration gradient. The slope is high on the side and low on the side close to the output terminal.

  Therefore, as shown in FIG. 6, in the current driving device of the present embodiment, among the MISFETs constituting the current sources in the current supply units 59-1 to 59-m, the gate electrodes of the MISFETs connected to different output terminals, The gate electrodes of the current input MISFET 57 may be connected to each other. In this case, since a voltage with a gradient applied to the gate electrode of each MISFET in accordance with the gradient of the threshold value of each MISFET can be applied, variation in the current output from the current supply unit 59 can be reduced. . In the case of this modification, the current input MISFET 57 and the MISFET in the current supply unit 59 and the n-channel type current transmission MISFET 66 constituting the current mirror circuit, and the reference current output terminal 9 connected to the current transmission MISFET 66 are used. Are connected to the next-stage semiconductor chip. At this time, if the current transmission MISFET 66 and the reference current output terminal 9 are arranged in the vicinity of the end portion of the semiconductor chip as in the example of FIG. 3, variations in output current for each semiconductor chip can be reduced.

(Third embodiment)
FIG. 7 is a circuit diagram showing a current driving device according to the third embodiment of the present invention. FIGS. 8A and 8B show the current supply unit 51 in the current driving device of this embodiment. It is a circuit diagram which expands and shows an example of composition.

  As shown in FIG. 7, the current drive device according to the present embodiment includes a plurality of current distribution MISFETs, similarly to the current drive device according to the second embodiment. However, the following points are the characteristics of the current driving device of the present embodiment, which are different from the current driving device of the second embodiment.

  First, the first feature of the current driver of the present embodiment is that an n-channel cascode MISFET 77 that is cascode-connected to an n-channel MISFET serving as a current source in the current supply unit 59 is provided. Here, the configuration of the current supply unit 59 is shown in a simplified manner in FIG. 7, but actually, it is as shown in FIG. 8 (a) or (b).

  In the example shown in FIG. 8 (a), one cascode is supplied to each of the m-bit current sources 60-1, 60-2,... 60-m via the switches 64-1, 64-2,. A MISFET 77 is provided. The gate voltage Vclp of the cascode MISFET 77 is set to a value lower than the power supply voltage (for example, about 3 V) of the display panel. Further, the threshold voltage of the cascode MISFET 77 is equal to or lower than the gate voltage Vclp, and the cascode MISFET 77 is in an on state throughout the driving.

  As a result, the cascode MISFET 77 functions as a clamp circuit, and limits the current flowing from the panel side when the switches 64-1, 64-2,..., 64-m are switched from the non-conductive state to the conductive state all at once. Can do. In particular, since the gate voltage Vclp is set to a value lower than the power supply voltage of the display panel, even when a high voltage is instantaneously applied to the output terminal 68 from the display panel side, the current sources 60-1 and 60 −2,..., 60-m, the voltage applied to the drains of the MISFETs can be set to the gate voltage Vclp or less. Therefore, since the gate potential of the MISFET constituting the current sources 60-1, 60-2,... 60-m is less susceptible to fluctuations caused by the current flowing from the display panel, the current driver according to the present embodiment performs crosstalk display. Occurrence is suppressed and uniform display is realized.

  As the current control means, instead of the cascode MISFET 77, a resistance element such as a polysilicon resistance, a diffusion resistance, or a well resistance may be provided. In a semiconductor integrated circuit, a current limiting resistor for preventing inflow of charges from the outside is generally arranged to protect the internal circuit from electrostatic breakdown. Here, the resistor plays a role of limiting the inflow of charges from the display panel and removing a high-frequency component. Since the high-frequency component is removed, the parasitic capacitance between the gate and the drain of the MISFET that is the current source can be reduced, so that the fluctuation of the gate potential due to the charge flowing from the panel can be suppressed.

Further, the current supply unit in the current driver of the present embodiment may have a configuration as shown in FIG. In this example, cascode MISFETs 77-1, 77-2,... Instead of switches (corresponding to switches 64-1 to m in FIG. 8A) for controlling the amount of current flowing through the current supply unit 59. 77-m is provided. Then, each of the cascode MISFETs 77-1, 77-2,..., 77-m is turned on when a gate voltage Vclp lower than the power supply voltage of the display panel is applied. Note that the cascode MISFETs 77-1, 77-2,..., 77-m of this embodiment also serve as output control switches of the current supply unit 59, and thus are controlled to be turned on or off according to display data.

  Accordingly, the cascode MISFETs 77-1, 77-2,..., 77-m serve to prevent a large current from flowing suddenly to the current source of the current supply unit 59 when switching from black display to white display. . Further, according to this configuration, the circuit area can be reduced as compared with the embodiment shown in FIG. 8A. Therefore, the current driver of this embodiment is required to reduce the area of the driver LSI. It is preferably used for a display device.

  Next, the second feature of the current driver of the present embodiment is that the current distribution MISFET 55 is cascode-connected between the p-channel type current distribution MISFET 55 and the current input MISFET 57 and is the same as the current distribution MISFET 55. A conductive type second current distribution MISFET 73 is provided. For this reason, the current driver of the present embodiment is cascode-connected to the p-channel 13th MISFET 71 provided between the drain of the first MISFET 53 and the reference current source 58, and the current transmission MISFET 61, 13 MISFETs 71 and a p-channel type fourth current transmission MISFET 75 constituting a current mirror circuit. The gate electrodes of the second current distribution MISFET 73 are connected to a common bias line, and form a current mirror circuit with the thirteenth MISFET 71 and the fourth current transmission MISFET 75. Here, the “second current distribution MISFET 73” is an expression when the second current distribution MISFETs 73-1 to 73-m are not distinguished from each other.

  With such a configuration, in the current driving device of the present embodiment, it is possible to suppress and stabilize the fluctuation of the reference current transmitted to the current sources 60-1 to 60-m of the current supply unit 59 via the current input MISFET 57. it can. Therefore, the display quality of the current drive type display device can be further improved by using the current drive device of this embodiment.

  Next, as described in the first embodiment, the third feature of the current driver of the present embodiment is that the reference current output terminal 9 and the reference current input terminal 11 are provided near the end of the semiconductor chip. In addition, n-channel type current transmission MISFETs 79 and 81, which mutually constitute a current mirror circuit, are also provided in the vicinity of the end of the semiconductor chip. Further, in the example shown in FIG. 7, the reference current source 58 is outside the first semiconductor chip 70, and a reference current input terminal is provided between the reference current source 58 and the drain of the thirteenth MISFET 71. In this case, the first semiconductor chip 70 and the second semiconductor chip 72 can have the same configuration.

  As a result, variations in output current between the semiconductor chips can be suppressed, and the driver of the display device can be configured with a single type of semiconductor chip.

  In the current driving device of the present embodiment, the example having the above three features has been described. However, even when only one of the features or a combination of any two features is used, compared to the conventional case. More uniform display.

  In the current drive device of this embodiment, the conductivity type of the MISFET included in the current supply unit 59 may be a p-channel type, and the current supply unit 59 side may have a higher potential than the display panel. In that case, all the conductivity types of the MISFETs constituting the current driving device may be reversed. The same applies to the following embodiments.

(Fourth embodiment)
FIG. 9 is a circuit diagram showing a current driver according to the fourth embodiment of the present invention.

  As shown in the figure, the current driving device of this embodiment is the current driving device of the second embodiment, in which the reference current distributed by the current mirror circuit composed of the current distribution MISFET 55 is arbitrarily switched. It is characterized in that it is output from the output terminal of the current supply unit 59 (shuffled). Therefore, in the current driving device of the present embodiment, the circuit configuration inside the current supply units 51-1 to 51-n is the same as that of the second embodiment.

  In the example of the current drive device of this embodiment shown in FIG. 9, a current distribution MISFET 55 is provided for each current supply unit 59, and between the drain of the current distribution MISFET 55 and the drain of the current input MISFET 57. A first bias current changeover switch 91 and a second bias current changeover switch 92 are provided. For example, a first bias current changeover switch 91-1 and a second bias current changeover switch 92-1 are provided between the current distribution MISFET 55-1 and the current input MISFET 57-1 and the current distribution MISFET 55-2. A first bias current changeover switch 91-2 and a second bias current changeover switch 92-2 are provided between the current input MISFET 57-2.

  With this configuration, the reference current distributed by each of the current distribution MISFETs 55-1 to 55-n can be output from the output terminal of the current supply unit 59 that is different every arbitrary period. The switching timing of the connection between the first bias current changeover switch 91 and the second bias current changeover switch 92 can be arbitrarily set, for example, every n lines (n is a positive integer) or every frame.

  FIGS. 10A to 10C are circuit diagrams illustrating an example of an output current switching method in the current driving device of the present embodiment. FIGS. 11A to 11C are diagrams illustrating the current of the present embodiment. FIG. 6 is a circuit diagram showing another example of an output current switching method in the drive device.

  FIGS. 10A to 10C show a method of switching the connection between the current distribution MISFET 55 and the current supply unit 51 located on both sides when one current distribution MISFET 55 is viewed. Here, when the connection is switched between the adjacent current distribution MISFETs 55, the dummy is placed next to the current distribution MISFET 55-1 and next to the current distribution MISFET 55-n with the current distribution MISFETs 55-1 to 55-n interposed therebetween. Current distribution MISFETs 95 and 99 may be provided. At this time, dummy bias current change-over switches 96, 97, 100, and 101 are also provided.

  The present system will be described by taking the current distribution MISFET 55-1 as an example. Here, an example is shown in which connection switching is performed for each horizontal scanning period.

  First, during the first horizontal scanning period, as shown in FIG. 10A, the current distribution MISFET 55-1 is connected to the current supply unit 51-1, as usual.

  In the next horizontal scanning period, as shown in FIG. 10B, the current distribution MISFET 55-1 is connected to the current supply unit 51-2.

  Further, in the next horizontal scanning period, as shown in FIG. 10C, the current distribution MISFET 55-1 is connected to the dummy wiring. Although only the current distribution MISFET 55-1 has been described here, the connection of other current distribution MISFETs 55 is similarly switched.

  As described above, since the relationship between the current distribution MISFET 55 and the output current can be switched in three ways, variations in the characteristics of the current distribution MISFET 55 can be offset. For this reason, if the current drive device of this embodiment is used, a current drive type display device in which display flickering is suppressed can be realized. In the example shown in FIG. 10, the connection switching patterns are three patterns shown in (a) to (c), but may be more than this, or only two patterns shown in (b) and (c). But you can.

  Moreover, the current drive device of this embodiment can also take the switching system as shown to Fig.11 (a)-(c).

  That is, in the first horizontal scanning period, as shown in FIG. 11A, the current distribution MISFET 55-1 is connected to the current supply unit 51-3.

  In the next horizontal scanning period, as shown in FIG. 11B, the current distribution MISFET 55-1 is connected to the current supply unit 51-2.

  Further, in the next horizontal scanning period, as shown in FIG. 11C, the current distribution MISFET 55-1 is connected to the dummy bias current changeover switch 97b. Even with such a switching method, the error in the output current from the current supply unit 59 is apparently offset.

  In the current driver of the present embodiment, the connection switching method of the current distribution MISFET 55 is not limited to the above-described method, and the current supply unit 51 to which each of the current distribution MISFETs 55-1 to 55-n is connected is arbitrarily switched. be able to. However, it is more preferable to connect the current distribution MISFET 55 to the second bias current changeover switch 92 located as close as possible because the wiring can be shortened and simplified. Therefore, it is most preferable to switch the connection between the current distribution MISFETs 55 adjacent to each other.

  In the current driver of this embodiment, the bias current changeover switches 91 and 92 for switching the connection between the output terminals are provided between the current distribution MISFET 55 and the current input MISFET 57, but the current supply unit 59. -1 may be provided between the drain of the n-channel MISFET constituting -1 and the switch 64 (see FIG. 8), respectively.

  Further, in the current driver shown in FIGS. 9 to 11, the switch (or switching terminal) is used as the connection switching means between the current distribution MISFET 55 and the current input MISFET 57, but other switching means may be provided. Good.

  In the current driver of the present embodiment, when the circuit area is limited, the current distribution MISFET 55 and the current input MISFET 57 may be provided at a rate of one for each of the plurality of current supply units 59.

-Modification of the fourth embodiment-
FIG. 12 is a circuit diagram showing a current driver and a semiconductor chip according to a modification of the fourth embodiment of the present invention.

  The current driver of this modification has a configuration substantially similar to that of the current driver shown in FIG. However, in the first semiconductor chip 70, the first terminal 160 connected to the first bias current changeover switch 91-n and the second terminal connected to the second bias current changeover switch 92-n. The difference from the fourth embodiment is that 162 is provided. Further, in the second semiconductor chip 72, in addition to the first terminal 160 and the second terminal 162, a third terminal 164 connected to the first bias current changeover switch 91-1, and a second bias. A fourth terminal 166 connected to the current changeover switch 92-1 is further provided.

  As a result, when a plurality of semiconductor chips provided with the current driving device of the present modification are arranged, the current distribution MISFET 55 and the current input MISFET provided not only in the same semiconductor chip but also on adjacent semiconductor chips. The connection can be switched between and. In the example shown in FIG. 12, the first terminal 160 is connected to the first bias current changeover switch 91-n, and the second terminal 162 is connected to the second bias current changeover switch 92-n. However, the first terminal 160 and the second terminal 162 may be designed to be connected to the first bias current changeover switch 91 and the second bias current changeover switch 92 that are located farther from each other.

  By driving the current driving device of this modification as described above, not only variations in output current from the output terminals in the semiconductor chip are reduced, but also variations in output current between the semiconductor chips are reduced. Is possible.

(Fifth embodiment)
FIG. 13 is a diagram showing a configuration of a current supply unit in the first specific example of the current driver according to the fifth embodiment of the present invention.

  In the current driving devices according to the first to fourth embodiments of the present invention, the MISFETs constituting the current supply units 59-1, 59-2,..., 59-3 are as shown in the layout diagram on the upper side of FIG. In many cases, the current supply units are arranged together. In the following description, among the regions where these MISFETs are provided, the regions where the MISFETs constituting the current supply unit 59-1 are arranged are the first MISFET region 76-1, the current supply unit 59-2. A region in which the MISFET constituting the MISFET is arranged is called a second MISFET region 76-2, and a region in which the MISFET constituting the current supply unit 59-3 is arranged is called a third MISFET region 76-3. And Note that the first to third MISFET regions are referred to as MISFET regions 76 when called without distinction. Although not shown in FIG. 14, 16 and 32 MISFETs of the same size are further provided in the MISFET region 76, respectively.

  The current driving device of this specific example is characterized in that, in the current driving device having such a circuit arrangement, one current supply unit 59 is composed of MISFETs provided in different MISFET regions 76.

  The MISFET constituting the current supply unit 59 has characteristic variations due to the difference in position in the semiconductor chip, the manufacturing process, and the like. In particular, the characteristic variation between MISFETs in different MISFET regions is relatively large. Therefore, in the current driver of this specific example, the output current is shuffled between the adjacent output terminals or between the output terminals separated from each other, thereby averaging the characteristic variation of the MISFETs constituting the current supply unit 59. Therefore, it is possible to suppress variations in output current for each output terminal. Therefore, by using the current driving device of this specific example for a display device, display unevenness can be suppressed and display image quality can be improved.

  In the current driver of this example, one current supply unit 59 may be configured by combining MISFETs in an arbitrary MISFET region 76 in the semiconductor chip, but as shown in FIG. 13, they are adjacent to each other. Combining MISFETs in the MISFET region is particularly preferable because wiring becomes easy. However, in order to make the output current more uniform, it is necessary to combine MISFETs in the MISFET regions that are separated from each other. In practice, the design is performed in consideration of the balance between the ease of wiring and the effect of reducing variations. In any case, at the time of circuit design, the MISFET in which MISFET region is connected to which output terminal of which current supply unit 59 may be determined using a random number or the like.

  FIG. 14 is a diagram illustrating a configuration of a current supply unit in the second specific example of the current driver according to the fifth embodiment.

  In the current driving device of the first specific example, the arrangement of MISFETs serving as current sources corresponding to the bits in each MISFET region 76 is fixed (see FIG. 13).

  On the other hand, in the current driver of this specific example, as shown in the layout diagram on the upper side of FIG. 14, the gate electrodes of arbitrary MISFETs provided in the MISFET region 76 are connected to each other and the current of the current supply unit 59 is obtained. Constitutes the source. In other words, in the current driver of this specific example, the selection of the MISFET constituting the current source is randomly changed for each output terminal.

  Even in the MISFETs provided in the same MISFET region 76, variation in characteristics is observed depending on the position. Therefore, as in this example, the current supply unit is selected by MISFETs randomly selected from the MISFETs provided in each MISFET region 76. By configuring 59, it becomes possible to make the variation in output current more uniform and to be suppressed than in the first specific example. Thus, by using the current driving device of this example for a display device, it is possible to suppress display unevenness and improve display image quality. Further, since the area for providing the switch is not necessary, the circuit area can be reduced as compared with the fourth embodiment.

  The circuit arrangement and wiring structure of the current driver according to the first and second specific examples of the present embodiment are not limited to those of the first to fourth embodiments, but also in the conventional current driver shown in FIG. Even if applied, the same effect can be obtained. Further, if the wiring structure of this embodiment is applied to the fourth embodiment, the current error due to the output terminal can be remarkably reduced.

(Sixth embodiment)
FIG. 15 is a circuit diagram showing a current driver according to the sixth embodiment of the present invention.

  As shown in the figure, the current driver of this embodiment is similar to the second current driver shown in FIG. 4 except that a resistor 62 is provided between the gate electrodes of the current distributing MISFETs 55 on the bias line 56 and adjacent to each other. Is provided. Here, the “resistor 62” is an expression when the resistors 62-1, 62-2,..., 62- (n−1) in FIG. A current source or wiring (not shown) for creating a potential gradient is connected to the reference current output terminal side of the bias line 56 shown in FIG.

  In the current driving device of the present embodiment, the provision of the resistor 62 reduces the output current error between the output terminals. This will be described below.

  The current mirror circuit is based on the premise that the diffusion conditions of the transistors constituting the current mirror circuit are equal, and that there is no significant difference in threshold value Vt and carrier mobility. However, when the chip length of the driver LSI for display device is as long as 10 mm to 20 mm, it becomes difficult to uniformly diffuse the impurities contained in the transistor. As a result, the threshold value of the transistor serving as the current mirror varies, and as a result, the output voltage varies. Usually, the variation in diffusion has a gradual inclination with respect to the wafer surface. For this reason, for example, the threshold voltage Vt of the current distribution MISFET 55 becomes lower in the direction from the current distribution MISFET 55-1 to the current distribution MISFET 55-n.

  In the current driver of this embodiment, since the resistor 62 is provided on the bias line 56, the gate voltage applied to the current distribution MISFETs 55-1 to 55-n is inclined according to the gradient of the threshold value Vt. As a result, the value of the current flowing through the current distribution MISFET 55 can be made substantially constant.

  Therefore, according to the current drive device of this embodiment, it is possible to suppress variations in output current from the current supply unit 59 in the semiconductor chip and improve the image quality of the display device.

  Note that the current driver of this embodiment employs the reference current input / output terminal configuration described in the first embodiment and the configuration described in the fourth and fifth embodiments. Also good.

(Seventh embodiment)
FIG. 16 is a circuit diagram showing a current driver according to the seventh embodiment of the present invention.

  As shown in the figure, the current driver of this embodiment includes the same MISFET as each of the MISFETs constituting the current source of the current supply unit 59 in addition to the conventional current driver as shown in FIG. A cascode MISFET 80 which is of a conductive type and forms a cascode connection with the MISFET is provided. The configuration of the current supply unit 59 shown in FIG. 16 seems to be similar to the configuration of the current supply unit 59 shown in FIG. 7, but the cascode MISFET 80 is provided for each MISFET constituting the current source. And an output terminal (not shown) are provided with a switch 64 for gradation control of the output current, and the gate electrode of each cascode MISFET 80 is the gate of the second current input MISFET 105. The difference is that the electrodes are connected in common. The drain and gate electrodes of the second current input MISFET 105 are connected to each other and set so that a reference current flows. The cascode MISFET 80 forms a current mirror circuit with the second current input MISFET 105. For example, a second current distribution MISFET (not shown) for distributing a reference current is connected to the drain of the second current input MISFET 105.

  Therefore, in each of the current supply units 59 described in the present embodiment, a bias voltage is received from both directions from the current input MISFET 57 side and from the second current input MISFET 105 side.

  With this configuration, the output current of the current supply unit 59 should flow when the cascode MISFET 80 and the current that should flow through the MISFET (current source MISFET) constituting the current source when the cascode MISFET 80 is not connected are provided alone. The current is averaged. The gate voltages equal to each other are applied to all the current source MISFETs, and the gate voltages equal to each other are also applied to all the cascode MISFETs 80. The threshold values of the current source MISFET and the cascode MISFET 80 are set on the semiconductor chip. Depending on the position, gradients in opposite directions change from the right to the left in FIG. Therefore, by averaging the current that should flow through the current source MISFET and the current that should flow through the cascode MISFET 80, variations in the output current for each output terminal are averaged and made uniform. Therefore, by using the current drive device of this embodiment, a high-definition display device in which display unevenness is suppressed can be realized.

  In FIG. 16, a pair of a current input MISFET 57 and a current distribution MISFET (first MISFET) 55, and a second current input MISFET 105 and a second current distribution MISFET pair per semiconductor chip. Although the example provided is shown, you may combine with the structure demonstrated with the current drive device of 2nd Embodiment.

  FIG. 17 is a circuit diagram showing the current driver when the current driver according to this embodiment is combined with the second embodiment. In the current drive device, a plurality of pairs of a current input MISFET 57 and a current distribution MISFET 55 are provided.

  In this case, it is preferable to provide a plurality of pairs of the second current input MISFET 105 and the second current distribution MISFET 55b per semiconductor chip. In particular, if the number of pairs of the current input MISFET 57 and the current distribution MISFET 55 and the number of pairs of the second current input MISFET 105 and the second current distribution MISFET 55b are made equal, the variation of the output current for each terminal is more effective. This is particularly preferable. The gate electrode of the second current distribution MISFET 55b is connected to the common bias line 56b. With such a configuration, occurrence of crosstalk display can be suppressed when the current driver of this embodiment is used in a display device.

  In addition, when taking this structure, it is also possible to combine with the structure demonstrated in 4th, 5th embodiment. For example, the current driving device shown in FIG. 17 includes a connection switching unit 130a provided between the current distribution MISFET 55 and the current input MISFET 57, a second current distribution MISFET 55b, and a second current input MISFET 105. It further includes connection switching means 130b provided therebetween. Then, the connection switching unit 130a connects the current distribution MISFET 55 to a different current input MISFET 57 for each arbitrarily set period. Similarly, the connection switching unit 130b connects the second current distribution MISFET 55b to a different second current input MISFET 105 for each arbitrarily set period. Thereby, the output current from the current supply unit 59 can be made more uniform.

  Further, the configuration of the current driving device of the present embodiment may be combined with the configuration described in the first embodiment.

  FIG. 18 is a circuit diagram showing the current driver when the current driver according to the present embodiment has the terminal structure described in the first embodiment. As shown in the figure, in the current driver of the present embodiment, the first reference current input terminal 124 and the first reference current input terminal 124 and the first current input terminal 124 are within a range of 200 μm or less, preferably 100 μm or less, of the semiconductor chip. One reference current output terminal 126 is provided, and the second reference current input terminal 128 and the second reference current output terminal 130 are within a range of 200 μm or less, preferably 100 μm or less, from the second current input MISFET 105. What is necessary is just to provide. When a plurality of semiconductor chips provided with current driving devices are arranged in the frame portion of the display panel, the first reference current output terminal 126 and the first reference current input terminal 124 of the second semiconductor chip 122 at the next stage are arranged. And the second reference current output terminal 130 and the second reference current input terminal 128 of the second semiconductor chip 122 may be connected. As a result, variations in output current between semiconductor chips can be suppressed.

(Eighth embodiment)
FIG. 19 is a circuit diagram showing a semiconductor chip on which a current driver according to the eighth embodiment of the present invention is formed. In the current driving device shown in the figure, the configuration of the current supply unit 40 is the same as that of the current supply unit 40 shown in FIG. 2, and the other configuration will be described below.

  A feature of the semiconductor chip of the present embodiment is that the direction in which the reference current flows is switched at every arbitrary time interval when the semiconductor chip is arranged in a line on the periphery of the display panel, for example.

  As shown in FIG. 19, the current driver according to the present embodiment includes a first reference current input terminal 146 connected to a reference current source 151 for flowing a first reference current, and a MISFET constituting the current source 5. And the current mirror circuit, the gate electrode and the drain are connected to each other, the first current input MISFET 3a to which the first reference current is transmitted, the MISFET constituting the current source 5 and the first current input A first current transmission MISFET 7b that forms a current mirror circuit with the MISFET 3a, a first reference current output terminal 150 to which an output current from the first current transmission MISFET 7b is transmitted, a second reference current source 153, Alternatively, the second reference current input terminal 148 for inputting the second reference current output from the semiconductor chip at the next stage and the MI constituting the current source 5 A second current input MISFET 36 having a gate and drain connected to the FET and a current mirror circuit, and a second current input MISFET and a MISFET constituting the current source 5 to form a current mirror circuit. The second current transmission MISFET 7a, the second reference current output terminal 144 to which the output current from the second current transmission MISFET 7a is transmitted, the switch SW1 connected to the second reference current output terminal 144, the first A switch SW2 connected to the first reference current input terminal 146, a switch SW3 connected to the second reference current input terminal 148, and a switch SW4 connected to the first reference current output terminal 150. . In addition, current transmission on the current transmission path between the first reference current input terminal 146 and the first current input MISFET 3a and between the second reference current output terminal 144 and the second current transmission MISFET 7a. A reference current changeover switch 154 is provided on the path, and on the current transmission path between the second reference current input terminal 148 and the second current input MISFET 3b, and between the first reference current output terminal 150 and the first reference current output terminal 150. A reference current switch 156 is provided on the current transmission path to the one current transmission MISFET 7b.

  Further, the distance between the first reference current input terminal 146 and the first current input MISFET 3a is preferably 200 μm or less, more preferably 100 μm or less, and the first reference current output terminal 150 and the first current input terminal 146 are not more than 100 μm. The distance from the current transmission MISFET 7b is also preferably 200 μm or less, more preferably 100 μm or less. Similarly, the distance between the second reference current input terminal 148 and the second current input MISFET 3b is preferably 200 μm or less, more preferably 100 μm or less, and the second reference current output terminal 144 The distance from the second current transmission MISFET 7a is also preferably 200 μm or less, and more preferably 100 μm or less.

  Thereby, when the semiconductor chips of this embodiment are cascade-connected, it is possible to reduce variations in output current (drive current of the pixel circuit) for each semiconductor chip.

  In the display device, when the first semiconductor chip 140 and the second semiconductor chip are disposed adjacent to each other, the first reference current output terminal 150 and the second semiconductor chip 142 of the first semiconductor chip 140 are arranged. The first reference current input terminal 146 is connected to each other, and the second reference current output terminal 148 of the first semiconductor chip 140 and the second reference current input terminal 144 of the second semiconductor chip 142 are connected to each other. Has been.

  In the current driver of this embodiment, the switch SW1 and the switch SW3 operate in synchronization with each other, and the switch SW2 and the switch SW4 operate in synchronization with each other. In addition, the operations of the switches SW1 and SW3 are controlled so that the operations of the switches SW2 and SW4 are turned on or off. During the operation of the current driver of the present embodiment, as will be described below, the first period in which the first reference current is transmitted to the plurality of semiconductor chips and the second reference current in the plurality of semiconductor chips. And the second period transmitted to are alternately repeated.

  First, in the first period, as shown in FIG. 19, the switches SW2 and SW4 are turned on, the switches SW1 and SW3 are turned off, and the reference current switch 154 is connected to the first reference current input terminal 146 and the first switch. The current transmission path between the first current input MISFET 3a is made conductive, and the current transmission path between the second reference current output terminal 144 and the second current transmission MISFET 7b is cut off. At the same time, the reference current switch 156 conducts the current transfer path between the first reference current output terminal 150 and the first current transfer MISFET 7b, and the second reference current input terminal 148 and the second reference current input terminal 148 The current transmission path between the current input MISFET 3b is cut off. By such control, the first reference current is transmitted to the plurality of semiconductor chips via the first reference current input terminal 146 and the first reference current output terminal 150.

  Next, in the second period, the switches SW2 and SW4 are turned off, the switches SW1 and SW3 are turned on, and the reference current switch 154 includes the first reference current input terminal 146 and the first current input MISFET 3a. Is interrupted, and the current transfer path between the second reference current output terminal 144 and the second current transfer MISFET 7b is made conductive. At the same time, the reference current switch 156 cuts off the current transmission path between the first reference current output terminal 150 and the first current transmission MISFET 7b, and the second reference current input terminal 148 and the second reference current input terminal 148 The current transmission path between the current input MISFET 3b is made conductive. By such control, the second reference current supplied from the second reference current source 153 is supplied to a plurality of semiconductor chips via the second reference current input terminal 148 and the second reference current output terminal 144. It is transmitted.

  When driving a large-screen display panel, it is necessary to arrange a large number of semiconductor chips provided with a current driving device, but in a conventional current driving device that supplies a reference current from only one side, the first-stage semiconductor chip An error is likely to occur between the reference current supplied to the semiconductor chip and the reference current transmitted to the final semiconductor chip. In contrast, in the current driving device of the present embodiment, the reference currents from the two types of reference current sources are alternately transmitted every arbitrary period, so that variations in the output current from the output terminals are averaged. Therefore, by using the current driver of this embodiment, it is possible to realize a display device in which the display is uniform even when the size of the display panel is increased.

  In FIG. 19, the configuration of the current supply unit 40 is the same as that of the first embodiment. However, the configuration is the same as that of the current supply units of other embodiments as long as the direction in which the reference current flows can be switched. You may take

  Further, a current transmission path between the first reference current input terminal 146 and the first current input MISFET 3a, and a current transmission path between the second reference current output terminal 144 and the second current transmission MISFET 7b. However, each current transmission path may be provided separately. In this case, a reference current switch is not required. Similarly, a current transmission path between the first reference current output terminal 150 and the first current transmission MISFET 7b, and between the second reference current input terminal 148 and the second current input MISFET 3b. The current transmission path may be provided separately.

It is a circuit diagram which shows the connection part of two chips | tips in which the current drive device which concerns on the 1st Embodiment of this invention was provided. It is a circuit diagram which shows the connection part of two chips | tips in which the example of the current drive device which concerns on 1st Embodiment was provided. It is a circuit diagram which shows the connection part of two chips | tips in which the current drive device which concerns on the modification of 1st Embodiment was provided. It is a circuit diagram which shows the current drive device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the semiconductor chip which concerns on 2nd Embodiment at the time of providing the input terminal and output terminal of a reference current in the edge part of a chip | tip. It is a circuit diagram which shows the modification of the current drive device which concerns on 2nd Embodiment. It is a circuit diagram which shows the current drive device which concerns on the 3rd Embodiment of this invention. (A), (b) is a circuit diagram which expands and shows the structural example of the current supply unit 51 among the current drive devices of 3rd Embodiment. It is a circuit diagram which shows the current drive device which concerns on the 4th Embodiment of this invention. (A)-(c) is a circuit diagram which shows an example of the switching method of an output current in the current drive device of 4th Embodiment. (A)-(c) is a circuit diagram which shows another example of the switching method of an output current in the current drive device of 4th Embodiment. It is a circuit diagram which shows the current drive device and semiconductor chip which concern on the modification of the 4th Embodiment of this invention. It is a figure which shows the structure of a current supply part in the 1st specific example of the current drive device which concerns on the 5th Embodiment of this invention. It is a figure which shows the structure of a current supply part in the 2nd specific example of the current drive device which concerns on 5th Embodiment. It is a circuit diagram which shows the current drive device which concerns on the 6th Embodiment of this invention. It is a circuit diagram which shows the current drive device which concerns on the 7th Embodiment of this invention. It is a circuit diagram which shows the current drive device which concerns on the 1st modification of 7th Embodiment. It is a circuit diagram which shows the current drive device which concerns on the 2nd modification of 7th Embodiment. It is a circuit diagram which shows the semiconductor chip with which the current drive device which concerns on the 8th Embodiment of this invention was formed. It is a circuit diagram which shows the structure of the conventional current drive device which is a display panel and the display driver connected to the display panel. (A) is a figure which shows the example of the monochrome display in a display panel, (b) is the pixel circuit arrange | positioned on the XXIb-XXIb line | wire of the display panel shown to (a), and the conventional circuit connected to this pixel circuit The circuit diagram which shows a current supply part, (c) is a graph which shows the operating point of TFT at the time of black display, (d) is a graph which shows the operating point of TFT at the time of white display. (A) is a figure which shows the example of the monochrome display in a display panel, (b) is the pixel circuit arrange | positioned on the XXIIb-XXIIb line | wire of the display panel shown to (a), and the electric current supply connected to this pixel circuit (C) is a graph showing the operating point of the TFT when switching from black display to white display, and (d) is a graph of the TFT when continuously displaying white. It is a graph which shows an operating point. It is a figure which shows the circuit arrangement | positioning and circuit structure of a current supply part among the conventional current drive devices.

Explanation of symbols

1, 53 First MISFET
2 Second MISFET
3 MISFET for current input
4,58 Reference current source
5, 5-1 to m, 25, 25-1 to m, 60 Current source
7 MISFET for first current transmission
9 Reference current output terminal
10 Third MISFET for current transmission
11 Reference current input terminal
11a First reference current input terminal
11b Second reference current input terminal
12 MISFET for fourth current transmission
13 Third MISFET
15 4th MISFET
16 resistance
17 Fifth MISFET
19 Sixth MISFET
20 First semiconductor chip
22 Second semiconductor chip
23 Seventh MISFET
27 Second MISFET for current transmission
33, 33a Eighth MISFET
35, 35a Ninth MISFET
37, 37a Tenth MISFET
39, 39a Eleventh MISFET
40, 41, 59, 59-1 to n Current supply unit
43 12th MISFET
51, 51-1 to n Current supply unit
55, 55-1 to MISFET for current distribution
56 Bias line
57, 57-1-n MISFET for current input
61, 66, 79, 81 MISFET for current transmission
62 Resistance
64 switches
68 Output terminal
70 First semiconductor chip
71 13th MISFET
72 Second semiconductor chip
73 Second MISFET for current distribution
75 Fourth MISFET for current transmission
76 MISFET region
76-1 First MISFET region
76-2 Second MISFET region
76-3 Third MISFET region
77, 77-1 to 80, cascode MISFET
91 1st bias current changeover switch
92 Second bias current selector switch
95, 95a, 95b, 99 MISFET for dummy current distribution
96, 96a, 96b Dummy bias current selector switch
97, 97a, 97b, 100, 101 Dummy bias current selector switch
105 MISFET for second current input

Claims (11)

A first MISFET of a first conductivity type in which a reference current flows during driving;
A first current distribution MISFET of a first conductivity type configured to form a current mirror circuit with the first MISFET and to pass the reference current;
A second conductivity type first current input MISFET having a drain connected to the first current distribution MISFET;
A current flowing through the current source MISFET according to display data, connected to the first current input MISFET, the second conductivity type current source MISFET constituting the current mirror circuit, and the current source MISFET. A plurality of current supply units connected to the switch and having an output terminal for outputting a current corresponding to the display data to the display panel. A current driving device provided;
A plurality of pairs of the first current distribution MISFET and the first current input MISFET are provided for the semiconductor chip,
A bias line connected in common to the gate electrode of the first MISFET and the gate electrode of the first current distribution MISFET ;
The current driving device, wherein the gate electrodes of all of the current source MISFETs and all of the first current input MISFETs in the plurality of current supply units are connected to each other . The current driver according to claim 1 ,
Each of the plurality of current supply units is interposed between the switch and the output terminal, and is turned on when a voltage lower than the power supply voltage of the display panel is applied to the gate electrode during driving. A current driving device having the first cascode MISFET. The current driver according to claim 1 ,
The switch is a second cascode MISFET that forms a cascode connection with the current source MISFET and is controlled to be turned on or off depending on whether or not a predetermined voltage is applied to the gate electrode during driving. apparatus. In the current drive device according to any one of claims 1 to 3 ,
A second MISFET of a first conductivity type connected to the first MISFET and through which the reference current flows during driving;
A first conductivity type second MISFET provided between the first current distribution MISFET and the first current input MISFET and having gate electrodes connected in common to the gate electrode of the second MISFET. A current driving device further comprising a current distribution MISFET. In the current drive device according to any one of claims 1 to 4 ,
Switching between the first current distribution MISFET and the first current input MISFET so that the first current distribution MISFET is connected to a different current input MISFET every arbitrary period. A current driving device further comprising connection switching means. The current driver according to claim 5 , wherein
The connection switching means is
A first bias current selector switch;
A current driving device having a second bias current changeover switch. The current driver according to claim 5 or 6 ,
A first conductivity type dummy current distribution MISFET constituting a current mirror circuit with the first MISFET and the first current distribution MISFET;
A current driving device further comprising dummy connection switching means for temporarily connecting the dummy current distribution MISFET and the current input MISFET. The current driver according to claim 6 ,
On the semiconductor chip,
A first terminal temporarily connected to the first bias current changeover switch during driving;
And a second terminal that is temporarily connected to the second bias current changeover switch during driving. In the current drive device according to any one of claims 1 to 8 ,
On the semiconductor chip, a plurality of MISFET regions in which the current source MISFETs are collectively provided are arranged in a row,
Each of the plurality of current supply units includes a MISFET disposed in at least two of the MISFET regions. In the current drive device according to any one of claims 1 to 9 ,
A current driving apparatus further comprising a resistance element provided between the gate electrodes of the first current distribution MISFETs adjacent to each other on the bias line. In the current drive device according to any one of claims 1 to 10 ,
A plurality of first conductivity type third current distribution MISFETs for transmitting the reference current during driving;
A plurality of second current input MISFETs of a second conductivity type, each having a gate electrode and a drain connected to each of the plurality of third current distribution MISFETs;
The second MISFET for current input and a current mirror circuit are configured, and a third cascode MISFET of a second conductivity type provided between each of the current source MISFETs and the switch is further provided. Current drive.

Images