Electro-optical devices and electronic devices
By using an active matrix driving circuit in an OLED electro-optical device, the anode voltage is controlled by using the second and third transistors and capacitors, the problem of continuous power consumption in the voltage driving mode is solved, and the effect of reducing power consumption in an OLED electro-optical device is achieved. .
Patent Information
- Application Number
- CN201980077357.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-01-16
- Filing Date
- 2019-10-17
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2039-10-17
AI Technical Summary
In the voltage-driven mode, existing OLED electro-optical devices continue to consume power despite the black screen displaying the screen, because the continuous flow of current in the transistor needs to be maintained.
An active matrix driving circuit having a voltage applied to the light emitting element based on the image signal tone is adopted, including a first transistor for driving, a second transistor for setting the anode voltage, and a third transistor for maintaining the anode voltage, and a capacitor, by The pulse signal controls the conduction of the transistor to reduce power consumption.
It is realized that the voltage of the driving light emitting element is maintained without having to keep the transistor on, thereby reducing power consumption and flowing current only when required when writing a signal, reducing invalid power consumption.
Smart Images
Figure CN113168813B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an electro-optical device and an electronic device. Background Art
[0002] An electro-optical device using an element such as an organic light emitting diode (hereinafter referred to as "OLED") as a light emitting element is known. In the electro-optical device, a pixel circuit including a light emitting element, a transistor, etc. is provided corresponding to a pixel at each position where a scan line and a data line intersect. In the pixel circuit, when a data signal at a potential based on a tone level of a pixel is applied to a gate of the transistor, the transistor supplies a current based on a voltage across the gate and a source to the light emitting element, and the light emitting element emits light at a brightness based on the tone level.
[0003] The circuit described in Patent Document 1 has been proposed as an active type OLED driving circuit. The driving circuit includes a pixel circuit capable of operating in two modes, namely, a mode for current driving and a mode for voltage driving.
[0004] Prior art literature
[0005] Patent Literature
[0006] Patent Document 1: US 2011 / 0074758 A1 Summary of the invention
[0007] Technical issues
[0008] However, in Patent Document 1, when voltage driving is performed, in order to maintain the OLED anode voltage, it is necessary to keep current flowing in the transistor regardless of the display state in the screen. Therefore, there is a problem of continuous power consumption even when black is displayed on the entire screen, for example.
[0009] An object of the present technology is to provide an electro-optical device and an electronic device capable of solving such a problem.
[0010] Solution to the problem
[0011] The electro-optical device according to the present technology is an electro-optical device having an active matrix drive circuit for applying a voltage to a light emitting element based on a tone of an image signal, and the electro-optical device includes:
[0012] A first transistor for driving, wherein a source of the first transistor is connected to an anode of the light emitting element;
[0013] a second transistor for setting an anode voltage, the second transistor being connected between the anode and a power source and determining a voltage applied to the anode; and
[0014] The holding capacitor and the third transistor are connected to the anode and are used to hold the anode voltage during the light emission period. The present technology is also an electronic device including the above electro-optical device.
[0015] Advantageous Effects of the Invention
[0016] According to at least one embodiment, it is not necessary to keep the transistor turned on to maintain the voltage driving the light-emitting element, which makes it possible to reduce power consumption. In addition, the effects described here are not necessarily restrictive, and any one of the effects described in the present technology or effects different from them can be obtained. In addition, the content of the present technology should not be interpreted restrictively according to the effects shown in the following description. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 : is a block diagram showing an organic EL display device including an active matrix driving circuit to which the present technology can be applied.
[0018] Figure 2 is a block diagram showing the configuration of a pixel unit in an organic EL display device.
[0019] Figure 3 is a connection diagram showing the configuration of a conventional pixel circuit.
[0020] Figure 4 is a timing diagram showing the operation of a conventional pixel circuit.
[0021] Figure 5 is a connection diagram according to the first embodiment of the present technology.
[0022] Figure 6 is a timing chart showing the operation according to the first embodiment.
[0023] Figure 7 is a connection diagram according to a modification of the first embodiment.
[0024] Figure 8 is a timing chart showing the operation according to the modification of the first embodiment.
[0025] Fig. 9 is a connection diagram according to the second embodiment of the present technology.
[0026] Fig.10 is a timing chart showing the operation according to the second embodiment.
[0027] Fig.11 is a connection diagram according to a modification of the second embodiment.
[0028] Fig.12 is a timing chart showing the operation according to the modification of the second embodiment. DETAILED DESCRIPTION
[0029] The embodiments described below are preferred specific examples of the present technology, and various technically preferred limitations are applied thereto. However, the scope of the present technology is not limited to the embodiments unless otherwise specified in the following description.
[0030] Before describing the present technology, the configuration of a conventional display device (electro-optical device) disclosed in Patent Document 1 will be described. Figure 1 As shown, in an organic EL display device 10 including an active matrix driving circuit, a scanning line driving circuit 11, a direct current (DC) voltage supply unit 12, a data line (signal line) driving circuit 13, and a pixel unit 14 are formed on a semiconductor substrate (e.g., a silicon substrate). With respect to the pixel unit 14, a plurality of scanning lines extend from the scanning line driving circuit 11 in a horizontal direction, and a plurality of data lines extend from the data line driving circuit 13 in a vertical direction.
[0031] like Figure 2 As shown in the figure, a scan line driving circuit 11a for driving the transistor Tr1 of the pixel unit and a scan line driving circuit 11b for driving the transistor Tr2 of the pixel unit are provided. The pixel circuits connected to the data lines extending in the vertical direction and the scan lines extending in the horizontal direction are arranged in a matrix. The pixel circuits are arranged to correspond to the three primary colors of the pixel, as shown in R (red), G (green) and blue (B). These three pixels represent a single point of a color image.
[0032] Figure 3 A pixel circuit 14m of a single pixel is shown. The pixel circuit 14m is connected to a scan line Xm1 from a scan line drive circuit 11a, a scan line Xm2 from a scan line drive circuit 11b, and a data line Ym from a data line drive circuit 13. The anode of the OLED 15 is connected to the source of the drive transistor DrvTr through the source and drain of the transistor Tr4, and the drain of the drive transistor DrvTr is connected to the power line to which the DC voltage VCCP is being supplied. The DC voltage from the DC voltage supply unit 12b is supplied to the gate of the transistor Tr4. The source of the drive transistor DrvTr is written as the anode node Vanode. The OLED 15 is driven by the voltage at the anode node Vanode (the tone of the image signal).
[0033] The gate of the P-channel transistor Tr1 is connected to the scanning line Xm1, and the gate of the N-channel transistor Tr2 is connected to the scanning line Xm2. The respective sources and drains of the transistors Tr1 and Tr2 are connected to each other. The signal voltage Vsig is supplied to the common drain connection point via the data line Ym.
[0034] The common source connection point of the transistors Tr1 and Tr2 is connected to the gate of the drive transistor DrvTr. A capacitor Cs serving as a holding capacitor is inserted between a connection line connecting the common source connection point and the gate of the drive transistor DrvTr and a power supply line to which the DC voltage VSS is being supplied.
[0035] A power line supplied with a DC voltage VSS is connected to the drain of the transistor Tr3, and a source of the transistor Tr3 is connected to the source of the driving transistor DrvTr. A DC voltage from the DC voltage supply unit 12a is supplied to the gate of the transistor Tr3. The transistor Tr3 is an anode voltage setting transistor for determining a voltage applied to the anode. The capacitor Cs holds a signal voltage Vsig component between the gate of the driving transistor DrvTr and a power line supplied with VSS thereto.
[0036] Figure 4 1 is a timing diagram showing voltage driving of a conventional pixel circuit 14m. This circuit is a voltage driving circuit that controls the light emission brightness of the OLED 15 tone by tone by changing the voltage applied to the anode node Vanode according to the signal voltage Vsig. A method for determining the voltage applied to the anode node Vanode will be described below.
[0037] In a state where a DC voltage for turning on the transistor Tr3 is applied, the transistors Tr1 and Tr2 are turned on when writing a signal, and write the signal voltage Vsig. At this time, it is desirable that the gate voltage of the transistor Tr3 is set to the highest threshold voltage within the panel plane.
[0038] The transistor Tr3 continues to provide a constant current, and an equivalent current flows in the driving transistor DrvTr, so that the gate-source voltage Vgs_Drv of the driving transistor DrvTr becomes a voltage corresponding to the current. When the signal voltage Vsig is written to the gate, the source voltage (i.e., the anode node Vanode) is determined as follows. Vgs_Drv is the gate-source voltage of the driving transistor DrvTr.
[0039] Vsig-Vgs_Drv
[0040] The same DC voltage as the transistor Tr3 is also applied to the transistor Tr4, so the anode node Vanode is maintained at the voltage shown by the above equation. A current corresponding to the voltage of the anode node Vanode flows in the OLED 15, and the OLED emits light at a brightness corresponding to the signal voltage.
[0041] The N-channel transistor Tr3 is continuously turned on due to the DC voltage. This is necessary to maintain the Vanode for determining the light emission brightness of the OLED 15. However, in a conventional pixel circuit, there is a problem that the transistor Tr3 is continuously turned on, which means that power is continuously consumed regardless of the display state of the screen, even when black is displayed on the entire screen, for example.
[0042] The following will refer to Figure 5 A first embodiment of the present technology is described. A pixel unit according to the first embodiment is denoted by 141, and a pixel circuit is denoted by 141m. The pixel circuit 141m has a second holding capacitor Cs2 and a switching transistor Tr5 added thereto. Figure 3 The configuration in the above conventional configuration shown. The holding capacitor Cs2 is connected between the gate of the driving transistor DrvTr used as the first transistor and the drain of the switching transistor Tr5 used as the third transistor, and the source of the switching transistor Tr5 is connected to the source of the driving transistor DrvTr. However, with Figure 5 Different from the configuration shown, the switching transistor Tr5 may be connected to the gate side of the driving transistor DrvTr, and the holding capacitor Cs2 may be connected to the source side of the driving transistor DrvTr.
[0043] In addition, a pulse signal from the scanning circuit 21 is supplied to the gate of the transistor Tr3, which is connected between the anode node Vanode and the power supply and serves as a second transistor for anode voltage setting that determines the voltage applied to the anode, and a DC voltage is supplied to the gate of the transistor Tr4 from the DC voltage supply unit 22. A pulse signal from the scanning circuit 23 is supplied to the gate of the switching transistor Tr5 that has been added. The transistors Tr3 and Tr5 have the same conductivity type (N channel).
[0044] Figure 6 141m is a timing chart showing voltage driving of the pixel circuit 141m according to the first embodiment of the present technology. The transistor Tr4 is continuously turned on due to the DC voltage from the DC voltage supply unit 22. The transistors Tr1 and Tr2 are turned on when a signal is written.
[0045] In addition, when the signal is written and the light-emitting period before the signal is written is close to the end, the transistor Tr3 is turned on by the pulse signal from the scanning circuit 21. After the writing of the signal is completed, the transistor Tr5 is turned on while the transistor Tr3 is turned off. The voltage of the anode node Vanode is maintained by the holding capacitor Cs2. In other words, due to the pulse signal that is turned on when the signal supplied to the transistor Tr3 is written, the current flowing in the transistor Tr3 flows only in the pixel of the row where the signal is written. This makes it possible to reduce power compared to the configuration of applying a DC voltage to the transistor Tr3 in the conventional technology.
[0046] In addition, the phases of the pulses of the driving transistors Tr3 and Tr5 are inverted, and the influence of the charge injection to the anode node Vanode from the respective transistors can be eliminated. Therefore, the anode node Vanode can be accurately maintained at (Vsig-Vgs_Drv).
[0047] Figure 7 A configuration of a modification of the first embodiment is shown. The switching transistor Tr5 has been changed to a P-channel switching transistor Tr6. Figure 8 is a timing chart showing driving according to a varying voltage.
[0048] The transistor Tr3 and the switch transistor Tr6 have different conductivity types (N-channel and P-channel), so the transistor Tr3 can be turned from off to on and the switch transistor Tr6 can be turned from on to off using a pulse signal of the same polarity. Therefore, a shared scanning circuit 24 can be set for the transistor Tr3 and the switch transistor Tr6, which makes it possible to reduce the number of scanning circuits by one.
[0049] Will refer to Fig. 9 A second embodiment of the present technology is described. A pixel unit according to the second embodiment is denoted by 142, and a pixel circuit is denoted by 142m. The pixel circuit 142m has a structure in which a second holding capacitor Cs2 and a switching transistor Tr5 are added to the pixel unit. Figure 3 The source of the switching transistor Tr5 is connected to the source of the driving transistor DrvTr, and the second holding capacitor Cs2 is connected between the drain of the switching transistor Tr5 and the power supply line that supplies a fixed power supply (e.g., DC voltage VSS) thereto (power supply line). However, unlike Fig. 9 Depending on the configuration, the connection order of the switching transistor Tr5 and the holding capacitor Cs2 can be reversed.
[0050] Fig.10 142m is a timing diagram showing the voltage drive of the pixel circuit 142m according to the second embodiment of the present technology. This is similar to the timing diagram showing the operation according to the first embodiment. In other words, the transistor Tr4 is continuously turned on due to the DC voltage from the DC voltage supply unit 22. The transistors Tr1 and Tr2 are turned on when the signal is written. In addition, the inverted pulse signal is provided from the scanning circuits 21 and 23 to the transistor Tr3 and the switching transistor Tr5.
[0051] As in the first embodiment, in the second embodiment, the current flowing in the transistor Tr3 flows only in the pixel of the row in which the signal is written. This makes it possible to reduce power compared to the configuration in which a DC voltage is applied to the transistor Tr3 in the conventional technology. In addition, the phase of the pulses driving the transistors Tr3 and Tr5 is reversed, and the influence of the charge injection to the anode node Vanode from each transistor can be eliminated.
[0052] Fig.11 A configuration of a modification of the second embodiment is shown. The switching transistor Tr5 is changed to a switching transistor Tr6 having a conductivity type different from that of the transistor Tr3 (P channel). Fig.12 is a timing chart showing voltage driving.
[0053] The transistor Tr3 and the switch transistor Tr6 are N-channel and P-channel, respectively, so the transistor Tr3 can be turned from off to on, and the switch transistor Tr6 can be turned from on to off using a pulse signal of the same polarity. Therefore, a shared scanning circuit 24 can be set for the transistor Tr3 and the switch transistor Tr6, which makes it possible to reduce the number of scanning circuits by one.
[0054] Although the embodiments of the present technology have been specifically described above, the present technology is not limited to the above embodiments, and various modifications based on the technical spirit of the present technology are possible. For example, many variations such as those described below are possible. One or more forms of the variations described below can be selected and appropriately combined as needed. In addition, the configurations, methods, steps, shapes, materials, numerical values, etc. of the above embodiments can be combined with each other without departing from the spirit of the present technology.
[0055] For example, although transistors Tr1 and Tr2 are provided to apply a signal voltage to the gate of the driving transistor DrvTr, only one of these transistors may be provided. In addition, although the foregoing embodiment describes an OLED as a light-emitting element as an example of an electro-optical element, any element that emits light with a brightness based on current, such as an inorganic light-emitting diode, an LED (light-emitting diode), etc. may be used.
[0056] Next, an electronic device to which the electro-optical device according to the embodiment and the application example is applied will be described. The electro-optical device is suitable for a high-resolution display with a small pixel size. Therefore, the device can be applied to a display device such as a head-mounted display, smart glasses, a smart phone, an electronic viewfinder of a digital camera, etc. as an electronic device.
[0057] Furthermore, the present technology can also be configured as described below.
[0058] (1) An electro-optical device including an active matrix drive circuit that applies a voltage based on a tone of an image signal to a light emitting element, the device comprising:
[0059] a first transistor for driving, wherein a source of the first transistor is connected to an anode of the light emitting element;
[0060] a second transistor for setting an anode voltage, the second transistor being connected between the anode and a power source and determining a voltage applied to the anode; and
[0061] A holding capacitor and a third transistor are connected to the anode for holding the anode voltage during light emission.
[0062] (2) The electro-optical device according to (1), wherein the second transistor is turned on during signal writing, and then the third transistor is turned on to maintain the anode voltage.
[0063] (3) The electro-optical device according to (1) or (2), wherein the holding capacitor and the third transistor are connected between the gate and the source of the first transistor for driving.
[0064] (4) The electro-optical device according to any one of (1) to (3), wherein the holding capacitor and the third transistor are connected to a source of the first transistor for driving and a supply position of a DC potential.
[0065] (5) The electro-optical device according to any one of (1) to (4), wherein the second transistor and the third transistor have different conductivity types.
[0066] (6) The electro-optical device according to any one of (1) to (4), wherein the second transistor and the third transistor have the same conductivity type.
[0067] (7) An electronic device comprising the electro-optical device according to (1).
[0068] (8) The electronic device according to (7), wherein, in the electro-optical device, the second transistor is turned on during signal writing, and then the third transistor is turned on to maintain the anode potential.
[0069] Reference numerals list
[0070] 11a, 11b Scan line driving circuit
[0071] 13 Data line (signal line) driving circuit
[0072] 15 OLED
[0073] 21, 23 Scanning circuit
[0074] 22 DC voltage supply unit
[0075] DrvTr drive transistor.
Claims
1. An electro-optical device, comprising an active matrix driving circuit, the active matrix driving circuit applying a voltage based on a tone of an image signal to a light emitting element, the electro-optical device comprising: a first transistor for driving, wherein a source of the first transistor is connected to an anode of the light emitting element via a fourth transistor, and a drain of the first transistor is connected to a power supply line to which a DC voltage is supplied; a second transistor for setting an anode voltage, the second transistor being connected between the anode and a power source and determining a voltage applied to the anode; a first holding capacitor and a third transistor connected to the anode for holding the anode voltage during a light emitting period; a fifth transistor and a sixth transistor, a gate of the fifth transistor being connected to a first scan line of the active matrix drive circuit, and a gate of the sixth transistor being connected to a second scan line of the active matrix drive circuit, respective sources and drains of the fifth transistor and the sixth transistor being connected to each other, a signal voltage being supplied to a common drain connection point of the fifth transistor and the sixth transistor via a data line of the active matrix drive circuit, a common source connection point of the fifth transistor and the sixth transistor being connected to the gate of the first transistor, the fifth transistor being a P-channel transistor, and the sixth transistor being an N-channel transistor; as well as a second holding capacitor inserted between a connection line connecting the common source connection point and the gate of the first transistor and a supply position of a DC potential, wherein the third transistor is configured to be turned on during a period when the second transistor is in an off state and to be turned off during a period when the second transistor is in an on state, and the fourth transistor is configured to be turned on during a light emitting period and a signal writing period, The first holding capacitor and the third transistor are connected between the gate of the first transistor and the source of the first transistor, or the first holding capacitor and the third transistor are connected between the source of the first transistor and a supply position of the DC potential.
2. The electro-optical device according to claim 1, wherein: The second transistor is turned on during a signal writing period, and then the third transistor is turned on to maintain the anode voltage.
3. The electro-optical device according to claim 1, wherein: The second transistor and the third transistor have different conductivity types.
4. The electro-optical device according to claim 1, wherein: The second transistor and the third transistor have the same conductivity type.
5. An electronic device comprising the electro-optical device according to claim 1.
6. The electronic device according to claim 5, wherein: In the electro-optical device, the second transistor is turned on during a signal writing period, and then the third transistor is turned on to maintain the anode potential.