This application claims priority under 35 USC § 119 to Korean Patent Application No. 10-2020-0097951, filed on Aug. 5, 2020 in the Korean Intellectual Property Office (KIPO), the disclosure of which is incorporated herein by reference in its entirety.
Embodiments of the present inventive concept relate to a display device, and more particularly to a display panel of an organic light emitting diode (OLED) display device, and the OLED display device.
Reduction of power consumption may be desirable in an organic light emitting diode (OLED) display device employed in a portable device such as a smartphone and a tablet computer. Recently, in order to reduce the power consumption of the OLED display device, a low frequency driving technique which decreases a driving frequency when displaying a still image has been developed. For example, when performing low frequency driving, the OLED display device may not drive a display panel at least one frame, and the display panel may display an image based on stored data voltages, thereby reducing power consumption of the OLED display device.
However, while the display panel displays an image based on the stored data voltages, the stored data voltages may be distorted by leakage currents in pixels of the display panel, and thus an image quality of the OLED display device may be degraded. Further, when a driving frequency for the display panel is changed from a previous driving frequency to a current driving frequency, luminance of the display panel driven at the current driving frequency may be different from luminance of the display panel driven at the previous driving frequency, and this luminance difference may be perceived by a user as a defect.
Some embodiments provide a display panel of an organic light emitting diode (OLED) display device capable of reducing luminance difference when a driving frequency is changed.
Some embodiments provide an OLED display device capable of reducing luminance difference when a driving frequency is changed.
According to embodiments, there is provided a display panel of an OLED display device including a first pixel configured to emit first color light, a second pixel configured to emit second color light, and a third pixel configured to emit third color light. Each of the first, second and third pixels includes at least two transistors, at least one capacitor and an organic light emitting diode. At least two transistors or at least one capacitor included in the third pixel has a size different from a size of a corresponding one of at least two transistors and at least one capacitor included in the first pixel or the second pixel.
In embodiments, the size of the at least one of the at least two transistors and the at least one capacitor included in the third pixel may be determined such that a data voltage range for the third pixel is adjusted close to a data voltage range for the first pixel or the second pixel.
In embodiments, the at least one of the at least two transistors may be implemented with a p-type metal-oxide-semiconductor (PMOS) transistor, and another one of the at least two transistors may be implemented with an n-type metal-oxide-semiconductor (NMOS) transistor.
In embodiments, the first pixel may be a red pixel that emits red light, the second pixel may be a green pixel that emits green light, and the third pixel may be a blue pixel that emits blue light.
In embodiments, each of the red, green and blue pixels may include a storage capacitor including a first electrode coupled to a first power supply voltage line and a second electrode coupled to a gate node, a boost capacitor including a first electrode coupled to the gate node, and a second electrode coupled to a gate writing signal line, a first transistor including a gate electrode coupled to the gate node, a second transistor configured to transfer a data voltage to a source of the first transistor in response to a gate writing signal of the gate writing signal line, a third transistor configured to diode-connect the first transistor in response to a gate compensation signal of a gate compensation signal line, a fourth transistor configured to apply an initialization voltage to the gate node in response to a gate initialization signal, a fifth transistor configured to couple the first power supply voltage line and the source of the first transistor in response to an emission signal, a sixth transistor configured to couple a drain of the first transistor and an anode of the organic light emitting diode in response to the emission signal, and a seventh transistor configured to apply an anode initialization voltage to the anode of the organic light emitting diode in response to the gate compensation signal. The organic light emitting diode may include the anode and a cathode coupled to a second power supply voltage line.
In embodiments, the boost capacitor included in the blue pixel may have a capacitance lower than a capacitance of the boost capacitor included in the red pixel or the green pixel.
In embodiments, each of the red, green and blue pixels may further include a parasitic capacitor, and the parasitic capacitor included in the blue pixel may have a size different from a size of the parasitic capacitor included in the red pixel or the green pixel.
In embodiments, each of the red, green and blue pixels may further include a negative parasitic boost capacitor between the gate compensation signal line and the gate electrode of the first transistor, and the negative parasitic boost capacitor included in the blue pixel may have a capacitance higher than a capacitance of the negative parasitic boost capacitor included in the red pixel or the green pixel.
In embodiments, a width of the gate compensation signal line in the blue pixel may be greater than a width of the gate compensation signal line in the red pixel or the green pixel.
In embodiments, an area of the gate electrode of the first transistor in the blue pixel may be greater than an area of the gate electrode of the first transistor in the red pixel or the green pixel.
In embodiments, a ratio of a channel width to a channel length of the first transistor in the blue pixel may be greater than a ratio of a channel width to a channel length of the first transistor in the red pixel or the green pixel.
In embodiments, the channel width of the first transistor in the blue pixel may be greater than the channel width of the first transistor in the red pixel or the green pixel.
In embodiments, the channel length of the first transistor in the blue pixel may be less than the channel length of the first transistor in the red pixel or the green pixel.
In embodiments, the storage capacitor included in the blue pixel may have a capacitance higher than a capacitance of the storage capacitor included in the red pixel or the green pixel.
In embodiments, the first, second, fifth and sixth transistors may be implemented with PMOS transistors, and the third and fourth transistors may be implemented with NMOS transistors.
In embodiments, the seventh transistor may be implemented with a PMOS transistor.
In embodiments, the seventh transistor may be implemented with an NMOS transistor.
In embodiments, each of the red, green and blue pixels may include a storage capacitor including a first electrode coupled to a first power supply voltage line and a second electrode coupled to a gate node, a first transistor including a gate electrode coupled to the gate node, a second transistor configured to transfer a data voltage to a source of the first transistor in response to a gate writing signal of a gate writing signal line, a third transistor configured to diode-connect the first transistor in response to a gate compensation signal of a gate compensation signal line, a fourth transistor configured to apply an initialization voltage to the gate node in response to a gate initialization signal, a fifth transistor configured to couple the first power supply voltage line and the source of the first transistor in response to an emission signal, a sixth transistor configured to couple a drain of the first transistor and an anode of the organic light emitting diode in response to the emission signal, and a seventh transistor configured to apply an anode initialization voltage to the anode of the organic light emitting diode in response to the gate compensation signal. The organic light emitting diode may include the anode and a cathode coupled to a second power supply voltage line.
In embodiments, each of the red, green and blue pixels may further include a parasitic boost capacitor between the gate writing signal line and the gate electrode of the first transistor, and a negative parasitic boost capacitor between the gate compensation signal line and the gate electrode of the first transistor. At least one of the parasitic boost capacitor, the negative parasitic boost capacitor, the first transistor and the storage capacitor included in the blue pixel may have a size different from a size of a corresponding one of the parasitic boost capacitor, the negative parasitic boost capacitor, the first transistor and the storage capacitor included in the red pixel or the green pixel.
In embodiments, each of the red, green and blue pixels may include a storage capacitor including a first electrode coupled to a first power supply voltage line, and a second electrode coupled to a gate node, a first transistor including a gate electrode coupled to the gate node, a second transistor configured to transfer a data voltage to a source of the first transistor in response to a gate writing signal of a gate writing signal line, a third transistor configured to diode-connect the first transistor in response to a gate compensation signal of a gate compensation signal line, a fourth transistor configured to apply an initialization voltage to the gate node in response to a gate initialization signal, a fifth transistor configured to couple the first power supply voltage line and the source of the first transistor in response to an emission signal having a low level, a sixth transistor configured to couple a drain of the first transistor and an anode of the organic light emitting diode in response to the emission signal having the low level, and a seventh transistor configured to apply an anode initialization voltage to the anode of the organic light emitting diode in response to the emission signal having a high level. The organic light emitting diode may include the anode and a cathode coupled to a second power supply voltage line.
In embodiments, each of the red, green and blue pixels may include a storage capacitor including a first electrode coupled to a first power supply voltage line, and a second electrode coupled to a gate node, a first transistor including a gate electrode coupled to the gate node, a second transistor configured to transfer a data voltage to a source of the first transistor in response to a gate writing signal of a gate writing signal line, a third transistor configured to diode-connect the first transistor in response to a gate compensation signal of a gate compensation signal line, a fourth transistor configured to apply an initialization voltage to the gate node in response to a gate initialization signal, a fifth transistor configured to couple the first power supply voltage line and the source of the first transistor in response to an emission signal, a sixth transistor configured to couple a drain of the first transistor and an anode of the organic light emitting diode in response to the emission signal, and a seventh transistor configured to apply an anode initialization voltage to the anode of the organic light emitting diode in response to the gate writing signal for a next pixel row. The organic light emitting diode may include the anode and a cathode coupled to a second power supply voltage line.
In embodiments, the first, second, fifth and sixth transistors may be implemented with PMOS transistors, and the third and fourth transistors may be implemented with NMOS transistors.
In embodiments, the seventh transistor may be implemented with a PMOS transistor.
In embodiments, the seventh transistor may be implemented with an NMOS transistor.
According to embodiments, there is provided an OLED display device including a display panel including a first pixel configured to emit first color light, a second pixel configured to emit second color light, and a third pixel configured to emit third color light, a data driver configured to provide data voltages to the first, second and third pixels, a scan driver configured to provide a gate writing signal, a gate compensation signal and a gate initialization signal to the first, second and third pixels, an emission driver configured to provide an emission signal to the first, second and third pixels, and a controller configured to control the data driver, the scan driver and the emission driver. Each of the first, second and third pixels includes at least two transistors, at least one capacitor and an organic light emitting diode. At least one of at least two transistors or at least one capacitor included in the third pixel has a size different from a size of a corresponding one of at least two transistors or the at least one capacitor included in the first pixel or the second pixel.
As described above, in a display panel of an OLED display device and the OLED display device according to embodiments, each of first, second and third pixels may include at least two transistors, at least one capacitor and an organic light emitting diode. At least one of at least two transistors and at least one capacitor included in the third pixel may have a size different from a size of a corresponding one of at least two transistors and at least one capacitor included in the first pixel or the second pixel. Accordingly, when a driving frequency for the display panel is changed, a difference between luminance of the display panel driven at a previous driving frequency and luminance of the display panel driven at a current driving frequency may be reduced, and the luminance difference may not be perceived by a user.
Illustrative, non-limiting embodiments will be more clearly understood from the following detailed description in conjunction with the accompanying drawings.
Hereinafter, embodiments of the present inventive concept will be explained in detail with reference to the accompanying drawings.
Referring to
In some embodiments, as illustrated in
Each of the red, green and blue pixels may include at least two transistors, at least one capacitor and an organic light emitting diode. For example, as illustrated in
In some embodiments, each of the red, green and blue pixels RPX, GPX and BPX may be a hybrid oxide polycrystalline (HOP) pixel suitable for low frequency driving for reducing power consumption. In the HOP pixel, one of the at least two transistors may be implemented with a p-type metal-oxide-semiconductor (PMOS) transistor, and another of the at least two transistors may be implemented with an n-type metal-oxide-semiconductor (NMOS) transistor. For example, as illustrated in
The OLED display device including the display panel 100 according to embodiments may perform low frequency driving. Thus, the display panel 100 may be driven at a normal driving frequency (e.g., about 60 Hz), or may be driven at a low frequency lower than the normal driving frequency. For example, the display panel 100 may be driven at the normal driving frequency when displaying a moving image and may be driven at the low frequency when displaying a still image. To drive the display panel 100 at the low frequency, the OLED display device may drive the display panel 100 in at least one frame period of a plurality of consecutive frame periods and may not drive the display panel 100 in the remaining frame periods of the plurality of consecutive frame periods.
For example, as illustrated in
In a conventional OLED display device that performs the low frequency driving, in a case where a display panel of the conventional OLED display device is driven at the normal driving frequency NDF, as represented by a luminance graph 210 in
However, in the display panel 100 according to embodiments, since at least one transistor (e.g., TN3 and TN4 in
Further, in the display panel 100 according to embodiments, to further reduce the difference between the luminance of the display panel 100 in the non-driven frame period (e.g., FP2 and FP4) and the luminance of the display panel 100 in the driven frame period (e.g., FP1 and FP3), and to reduce a difference between the luminance 210 of the display panel 100 driven at the normal driving frequency NDF and the luminance 230 of the display panel 100 driven at the low frequency LF, a self bias operation that applies a self bias SELF_BIAS to each of the red, green and blue pixels RPX, GPX and BPX may be performed in the non-driven frame period (e.g., FP2 and FP4). For example, in a case where the display panel 100 is driven at the normal driving frequency NDF of about 60 Hz, the OLED display device may apply an initialization bias VINT_BIAS using an initialization voltage (e.g., an initialization voltage VINT in
Even if the self bias operation using the self bias SELF_BIAS is performed in the non-driven frame period (e.g., FP2 and FP4), in a case where the initialization voltage of the initialization bias VINT_BIAS and the data voltage of the self bias SELF_BIAS have a great difference, or in a case where the initialization voltage is excessively lower than the data voltage, the difference between the luminance 210 of the display panel 100 driven at the normal driving frequency NDF and the luminance 230 of the display panel 100 driven at the low frequency LF may be perceived by a user.
However, in the display panel 100 according to embodiments, the red pixel RPX, the green pixel GPX and the blue pixel BPX may be designed differently such that at least one of the at least two transistors, the at least one capacitor and a parasitic capacitor included in the blue pixel BPX may have a size different from a size of a corresponding one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the red pixel RPX or the green pixel GPX. The size of the at least one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the blue pixel BPX may be determined such that a data voltage range for the blue pixel BPX may be adjusted similar to a data voltage range for the red pixel RPX or the green pixel GPX. For example, the size of the at least one of the at least two transistors, the at least one capacitor and/or the parasitic capacitor included in the blue pixel BPX may be determined such that a data voltage range for the blue pixel BPX may have a value between that of the red pixel RPX and the green pixel GPX.
For example, as illustrated in
However, in the display panel 100 according to embodiments, the blue pixel BPX may be designed differently from the red pixel RPX and/or the green pixel GPX such that at least one of the at least two transistors, the at least one capacitors and the parasitic capacitor included in the blue pixel BPX may have a size different from a size of a corresponding one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the red pixel RPX or the green pixel GPX. Accordingly, the data voltage range 330 for the blue pixel BPX may be changed to a data voltage range 350, and the initial voltage VINT corresponding to the data voltage range 330 may be increased to an initial voltage VINT′ corresponding to the data voltage range 350. For example, with respect to the blue pixel BPX, the 0-gray voltage BVO of about 6.5 V may be changed to a 0-gray voltage BVO′ of about 7 V, the 255-gray voltage BV255 of about 2 V may be changed to a 255-gray voltage BV255′ of about 3 V, and the data voltage range 330 from about 2 V to about 6.5 V may be changed to the data voltage range 350 from about 3 V to about 7 V. In this case, the initial voltage VINT of about −3.5 V corresponding to the data voltage range 330 from about 2 V to about 6.5 V may be increased to the initial voltage VINT′ of about −2.5 V corresponding to the data voltage range 350 from about 3 V to about 7 V. Accordingly, a difference between the initialization voltage VINT′ of the initialization bias VINT_BIAS and the data voltage of the self bias SELF_BIAS may be reduced, the difference between the luminance 210 of the display panel 100 driven at the normal driving frequency NDF and the luminance 230 of the display panel 100 driven at the low frequency LF may be reduced, and thus the luminance difference when the driving frequency is changed may not be perceived by the user.
Although
As described above, in the display panel 100 according to embodiments, in each of the red, green and blue pixels RPX, GPX and BPX, at least one transistor may be implemented with the PMOS transistor, and at least one another transistor may be implemented with the NMOS transistor. Accordingly, the leakage current in each of the red, green and blue pixels RPX, GPX and BPX at the low frequency driving may be reduced, and a luminance change within each frame period may be reduced. Further, in the display panel 100 according to embodiments, the red pixel RPX, the green pixel GPX and the blue pixel BPX may be differently designed such that at least one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the blue pixel BPX may have a size different from a size of a corresponding one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the red pixel RPX or the green pixel GPX. Thus, the data voltage range 350 for the blue pixel BPX may be similar to the data voltage range 310 for the red pixel RPX and the data voltage range 320 for the green pixel GPX, and the initial voltage VINT′ may be increased. Accordingly, when a driving frequency for the display panel 100 is changed, a difference between luminance of the display panel 100 driven at a previous driving frequency (e.g., the normal driving frequency NDF) and luminance of the display panel 100 driven at a current driving frequency (e.g., the low frequency LF) may be reduced, and the luminance difference may not be perceived by the user.
Referring to
Each of the red, green and blue pixels RPX1, GPX1 and BPX1 may include a storage capacitor Cst, a boost capacitor Cbst1 or Cbst2, a first transistor TP1, a second transistor TP2, a third transistor TN3, a fourth transistor TN4, a fifth transistor TP5, a sixth transistor TP6, a seventh transistor TN7 and an organic light emitting diode EL.
The storage capacitor Cst may store a data voltage RVDAT, GVDAT and BVDAT′ or a compensated data voltage where a threshold voltage of the first transistor TP1 is subtracted from the data voltage RVDAT, GVDAT and BVDAT′ transferred through the second transistor TP2 and the (diode-connected) first transistor TP1 from a data line DL1 and DL2. In some embodiments, the storage capacitor Cst may include a first electrode coupled to a first power supply voltage line ELVDDL through which a first power supply voltage ELVDD is transferred, and a second electrode coupled to a gate node NG1 and NG2 of the first transistor TP1.
The boost capacitor Cbst1 and Cbst2 may change a voltage of the gate node NG1 and NG2 when a gate writing signal GW is changed. For example, when the gate writing signal GW is increased from a low level to a high level, the boost capacitor Cbst1 and Cbst2 may increase the voltage of the gate node NG1 and NG2. In some embodiments, the boost capacitor Cbst1 and Cbst2 may include a first electrode coupled to the gate node NG1 and NG2, and a second electrode coupled to a gate writing signal line GWL through which the gate writing signal GW is transferred.
The first transistor TP1 may generate a driving current based on the voltage of the gate node NG1 and NG2, or a voltage of the second electrode of the storage capacitor Cst. The first transistor TP1 may be referred to as a driving transistor for driving the organic light emitting diode EL. In some embodiments, the first transistor TP1 may include a gate electrode coupled to the gate node NG1 and NG2, a first terminal (e.g., a source) coupled to a second terminal of the fifth transistor TP5, and a second terminal (e.g., a drain) coupled to a first terminal of the sixth transistor TP6.
The second transistor TP2 may transfer the data voltage RVDAT, GVDAT and BVDAT′ to the source of the first transistor TP1 in response to the gate writing signal GW of the gate writing signal line GWL. The second transistor TP2 may be referred to as a switching transistor or a scan transistor for transferring the data voltage RVDAT, GVDAT and BVDAT′ of the data line DL1 and DL2 to the first electrode of the first transistor TP1.
For example, the second transistor TP2 of the red pixel RPX1 may transfer the data voltage RVDAT for the red pixel RPX1 to the source of the first transistor TP1 of the red pixel RPX1, the second transistor TP2 of the green pixel GPX1 may transfer the data voltage GVDAT for the green pixel GPX1 to the source of the first transistor TP1 of the green pixel GPX1, and the second transistor TP2 of the blue pixel BPX1 may transfer the data voltage BVDAT′ for the blue pixel BPX1 to the source of the first transistor TP1 of the blue pixel BPX1. In some embodiments, the second transistor TP2 may include a gate electrode coupled to the gate writing signal line GWL through which the gate writing signal GW is transferred, a first terminal coupled to the data line DL1 or DL2, and a second terminal coupled to the source of the first transistor TP1.
The third transistor TN3 may diode-connect the first transistor TP1 in response to a gate compensation signal GC of a gate compensation signal line GCL. The third transistor TN3 may be referred to as a threshold voltage compensating transistor for compensating the threshold voltage of the first transistor TP1. While the gate writing signal GW and the gate compensation signal GC are applied, the data voltage RVDAT, GVDAT and BVDAT′ transferred by the second transistor TP2 may be transferred to the storage capacitor Cst through the first transistor TP1 that is diode-connected by the third transistor TN3, and thus the voltage where the threshold voltage of the first transistor TP1 is subtracted from the data voltage RVDAT, GVDAT and BVDAT′ may be stored in the storage capacitor Cst. In some embodiments, the third transistor TN3 may include a gate electrode coupled to the gate compensation signal line GCL through which the gate compensation signal GC is transferred, a first terminal coupled to the drain of the first transistor TP1, and a second terminal coupled to the gate node NG1 or NG2.
The fourth transistor TN4 may apply an initialization voltage VINT to the gate node NG1 and NG2 in response to a gate initialization signal GI. The fourth transistor TN4 may be referred to as a gate initializing transistor for initializing the gate node NG1 and NG2, or the first transistor TP1 and the storage capacitor Cst. While the gate initialization signal GI is applied, the fourth transistor TN4 may apply the initialization voltage VINT to the gate node NG1 and NG2, and the first transistor TP1 and the storage capacitor Cst may be initialized due to the initialization voltage VINT applied to the gate node NG1 and NG2. In some embodiments, the fourth transistor TN4 may include a gate electrode receiving the gate initialization signal GI, a first terminal receiving the initialization voltage VINT, and a second terminal coupled to the gate node NG1 or NG2.
The fifth transistor TP5 may couple the first power supply voltage line ELVDDL through which the first power supply voltage ELVDD is transferred and the source of the first transistor TP1 in response to an emission signal EM, and the sixth transistor TP6 may couple the drain of the first transistor TP1 and an anode of the organic light emitting diode EL in response to the emission signal EM. The fifth and sixth transistors TP5 and TP6 may be referred to as emission transistors for allowing the organic light emitting diode EL to emit light. While the emission signal EM is applied, the fifth and sixth transistors TP5 and TP6 may be turned on to form a path of the driving current from the first power supply voltage line ELVDDL through which the first power supply voltage ELVDD is transferred to a second power supply voltage line ELVSSL through which a second power supply voltage ELVSS is transferred. In some embodiments, the fifth transistor TP5 may include a gate electrode receiving the emission signal EM, a first terminal coupled to the first power supply voltage line ELVDDL through which the first power supply voltage ELVDD is transferred, and a second terminal coupled to the source of the first transistor TP1, and the sixth transistor TP6 may include a gate electrode receiving the emission signal EM, a first terminal coupled to the drain of the first transistor TP1, and a second terminal coupled to the anode of the organic light emitting diode EL.
The seventh transistor TN7 may apply an anode initialization voltage AVINT to the anode of the organic light emitting diode EL in response to the gate compensation signal GC. According to embodiments, the anode initialization voltage AVINT may be substantially the same as the initialization voltage VINT or may be different from the initialization voltage VINT. The seventh transistor TN7 may be referred to as a diode initializing transistor for initializing the organic light emitting diode EL. While the gate compensation signal GC is applied, the seventh transistor TN7 may initialize the organic light emitting diode EL by using the anode initialization voltage AVINT. In some embodiments, the seventh transistor TN7 may include a gate electrode coupled to the gate compensation signal line GCL through which the gate compensation signal GC is transferred, a first terminal receiving the anode initialization voltage AVINT, and a second terminal coupled to the anode of the organic light emitting diode EL.
The organic light emitting diode EL may emit light based on the driving current generated by the first transistor TP1. While the emission signal EM is applied, the driving current generated by the first transistor TP1 may be provided to the organic light emitting diode EL, and the organic light emitting diode EL may emit light based on the driving current. In some embodiments, the organic light emitting diode EL may include the anode coupled to the second terminal of the sixth transistor TP6, and a cathode coupled to the second power supply voltage line ELVSSL through which the second power supply voltage ELVSS is transferred.
In some embodiments, in each of the red, green and blue pixels RPX1, GPX1 and BPX1, a negative parasitic boost capacitor Nbst may be formed between the gate compensation signal line GCL and the gate node NG1 and NG2, or the gate electrode of the first transistor TP1. When the gate compensation signal GC of the gate compensation signal line GCL is changed, the voltage of the gate node NG1 and NG2 may be changed by the negative parasitic boost capacitor Nbst. For example, when the gate compensation signal GC is decreased from a high level to a low level, the voltage of the gate node NG1 and NG2 may be decreased by the negative parasitic boost capacitor Nbst. However, the decrease of the voltage of the gate node NG1 and NG2 by the negative parasitic boost capacitor Nbst may be compensated by the boost capacitor Cbst1 and Cbst2.
In some embodiments, as illustrated in
In the display panel according to some embodiments, the boost capacitor Cbst2 included in the blue pixel BPX1 may have a capacitance lower than a capacitance of the boost capacitor Cbst1 included in the red/green pixel RPX1/GPX1. For example, the boost capacitor Cbst1 of the red/green pixel RPX1/GPX1 may have a capacitance of about 7 fF, the boost capacitor Cbst2 of the blue pixel BPX1 may have a capacitance of about 5 fF, but the capacitances of the boost capacitors Cbst1 and Cbst2 are not limited thereto. Thus, a second boost amount (or a second increase amount) of the voltage of the gate node NG2 caused by the boost capacitor Cbst2 in the blue pixel BPX1 may be reduced compared with a first boost amount (or a first increase amount) of the voltage of the gate node NG1 caused by the boost capacitor Cbst1 in the red/green pixel RPX1/GPX1. Accordingly, the data voltage BVDAT′ for the blue pixel BPX1 may be determined or set by considering a difference between the first boost amount and the second boost amount. For example, the data voltage BVDAT′ for the blue pixel BPX1 may be determined or set by adding a boost voltage difference DVCBST corresponding to the difference between the first boost amount and the second boost amount to a conventional data voltage BVDAT in a case where the blue pixel BPX1 is designed substantially identically to the red/green pixel RPX1/GPX1. Accordingly, as illustrated in
Hereinafter, an example of an operation of each of the red, green and blue pixels RPX1, GPX1 and BPX1 will be described below with reference to
Referring to
In the initialization period PINI, as illustrated in
In the data writing period PDW, as illustrated in
In some embodiments, the boost capacitor Cbst2 included in the blue pixel BPX1 may have a capacitance lower than a capacitance of the boost capacitor Cbst1 included in the red/green pixel RPX1/GPX1. Thus, at a rising edge GW_RE of the gate writing signal GW, a second boost amount VCBST2 of the voltage V_NG2 of the gate node NG2 caused by the boost capacitor Cbst2 in the blue pixel BPX1 may be reduced compared with a first boost amount VCBST1 of the voltage V_NG1 of the gate node NG1 caused by the boost capacitor Cbst1 in the red/green pixel RPX1/GPX1. Accordingly, the data voltage BVDAT′ for the blue pixel BPX1 may be determined or set by adding a boost voltage difference DVCBST corresponding to a difference between the first boost amount VCBST1 and the second boost amount VCBST2 to a conventional data voltage BVDAT for the blue pixel BPX1.
For example, as illustrated in
At a falling edge GC_FE of the gate compensation signal GC, in each of the red, green and blue pixels RPX1, GPX1 and BPX1, by the negative parasitic boost capacitor Nbst, the voltage V_NG1 and V_NG2 of the gate node NG1 and NG2 may be decreased by the first boost amount VCBST1. For example, at the falling edge GC_FE of the gate compensation signal GC, in the red pixel RPX1, the voltage V_NG1 of the gate node NG1 may be decreased by the first boost amount VCBST1 and may become the voltage RVDAT-VTH where the threshold voltage VTH is subtracted from the data voltage RVDAT. Further, at the falling edge GC_FE of the gate compensation signal GC, in the blue pixel BPX1, the voltage V_NG2 of the gate node NG2 may be decreased by the first boost amount VCBST1 and may become the voltage BVDAT−VTH where the threshold voltage VTH is subtracted from the conventional data voltage BVDAT.
In the emission period PEM, the organic light emitting diode EL may emit light. In the emission period PEM, the gate initialization signal GI, the gate writing signal GW and the gate compensation signal GC have the off levels, and the emission signal EM may have the on level. As illustrated in
Referring to
In the display panel according to embodiments, the negative parasitic boost capacitor Nbst2 included in the blue pixel BPX2 may have a capacitance higher than a capacitance of the negative parasitic boost capacitor Nbst1 included in the red/green pixel RPX2/GPX2. For example, the negative parasitic boost capacitor Nbst1 included in the red/green pixel RPX2/GPX2 may have a capacitance of about 3 fF, the negative parasitic boost capacitor Nbst2 included in the blue pixel BPX2 may have a capacitance of about 4 fF, but the capacitances of the negative parasitic boost capacitors Nbst1 and Nbst2 are not limited thereto. Thus, (an absolute value of) a second negative boost amount (or a second decrease amount) of a voltage of the gate node NG2 caused by the negative parasitic boost capacitor Nbst2 in the blue pixel BPX2 may be increased compared with (an absolute value of) a first negative boost amount (or a first decrease amount) of a voltage of the gate node NG1 caused by the negative parasitic boost capacitor Nbst1 in the red/green pixel RPX2/GPX2. Accordingly, the data voltage BVDAT′ for the blue pixel BPX2 may be determined or set by considering a difference between the first negative boost amount and the second negative boost amount. For example, the data voltage BVDAT′ for the blue pixel BPX2 may be determined or set by adding a negative boost voltage difference DVNBST corresponding to the difference between the first negative boost amount and the second negative boost amount to a conventional data voltage BVDAT in a case where the blue pixel BPX2 is designed substantially identically to the red/green pixel RPX2/GPX2. Accordingly, as illustrated in
For example, as illustrated in
At a falling edge GC_FE of a gate compensation signal GC, in the red pixel RPX2, the voltage V_NG1 of the gate node NG1 may be decreased by the first negative boost amount VNBST1 (corresponding to the boost amount VCBST) by the negative parasitic boost capacitor Nbst1 and may become the voltage RVDAT-VTH where the threshold voltage VTH is subtracted from the data voltage RVDAT. Further, at the falling edge GC_FE of the gate compensation signal GC, in the blue pixel BPX2, the voltage V_NG2 of the gate node NG2 may be decreased by the second negative boost amount VNBST2 by the negative parasitic boost capacitor Nbst2 and may become the voltage BVDAT−VTH where the threshold voltage VTH is subtracted from the conventional data voltage BVDAT.
In some embodiments, a width of the gate compensation signal line GCL in the blue pixel BPX2 may be greater than a width of the gate compensation signal line GCL in the red/green pixel RPX2/GPX2 such that the negative parasitic boost capacitor Nbst2 included in the blue pixel BPX2 may have a capacitance higher than a capacitance of the negative parasitic boost capacitor Nbst1 included in the red/green pixel RPX2/GPX2. In other embodiments, an area of an electrode of the gate node NG2, or a gate electrode of the first transistor TP1 in the blue pixel BPX2 may be greater than an area of the gate node NG1, or a gate electrode of the first transistor TP1 in the red/green pixel RPX2/GPX2 such that the negative parasitic boost capacitor Nbst2 included in the blue pixel BPX2 may have a capacitance higher than a capacitance of the negative parasitic boost capacitor Nbst1 included in the red/green pixel RPX2/GPX2. In still other embodiments, the width of the gate compensation signal line GCL in the blue pixel BPX2 may be greater than the width of the gate compensation signal line GCL in the red/green pixel RPX2/GPX2, and the area of the gate electrode of the first transistor TP1 in the blue pixel BPX2 may be greater than the area of the gate electrode of the first transistor TP1 in the red/green pixel RPX2/GPX2.
Referring to
In the display panel according to embodiments, a ratio of a channel width to a channel length of the first transistor TP12 in the blue pixel BPX3 may be greater than a ratio of a channel width to a channel length of the first transistor TP11 in the red/green pixel RPX3/GPX3. Thus, a driving characteristic of the first transistor TP12 of the blue pixel BPX3 may be different from the first transistor TP11 of the red pixel RPX3 and the green pixel GPX3. Accordingly, as illustrated in
In some embodiments, the channel width of the first transistor TP12 in the blue pixel BPX3 may be greater than the channel width of the first transistor TP11 in the red/green pixel RPX3/GPX3 such that the ratio of the channel width to the channel length of the first transistor TP12 in the blue pixel BPX3 may be greater than the ratio of the channel width to the channel length of the first transistor TP11 in the red/green pixel RPX3/GPX3. In other embodiments, the channel length of the first transistor TP12 in the blue pixel BPX3 may be less than the channel length of the first transistor in the red/green pixel RPX3/GPX3 such that the ratio of the channel width to the channel length of the first transistor TP12 in the blue pixel BPX3 may be greater than the ratio of the channel width to the channel length of the first transistor TP11 in the red/green pixel RPX3/GPX3. In still other embodiments, the channel width of the first transistor TP12 in the blue pixel BPX3 may be greater than the channel width of the first transistor TP11 in the red/green pixel RPX3/GPX3, and the channel length of the first transistor TP12 in the blue pixel BPX3 may be less than the channel length of the first transistor in the red/green pixel RPX3/GPX3.
Referring to
In the display panel according to embodiments, the storage capacitor Cst2 included in the blue pixel BPX4 may have a capacitance higher than a capacitance of the storage capacitor Cst1 included in the red/green pixel RPX4/GPX4. Thus, similarly to a difference between the red/green pixel RPX1/GPX1 and the blue pixel BPX1 described in
Referring to
In the display panel according to embodiments, a size of at least one of the parasitic boost capacitor PCbst2, the negative parasitic boost capacitor Nbst2, the first transistor TP12 and the storage capacitor Cst2 included in the blue pixel BPX5 may be different from a size of a corresponding one of the parasitic boost capacitor PCbst1, the negative parasitic boost capacitor Nbst1, the first transistor TP11 and the storage capacitor Cst1 included in the red/green pixel RPX5/GPX5. In some embodiments, the parasitic boost capacitor PCbst2 included in the blue pixel BPX5 may have a capacitance lower than a capacitance of the parasitic boost capacitor PCbst1 included in the red/green pixel RPX5/GPX5. In other embodiments, the negative parasitic boost capacitor Nbst2 included in the blue pixel BPX5 may have a capacitance higher than a capacitance of the negative parasitic boost capacitor Nbst1 included in the red/green pixel RPX5/GPX5. In still other embodiments, a ratio of a channel width to a channel length of the first transistor TP12 in the blue pixel BPX5 may be greater than a ratio of a channel width to a channel length of the first transistor TP11 in the red/green pixel RPX5/GPX5. In still other embodiments, the storage capacitor Cst2 included in the blue pixel BPX5 may have a capacitance higher than a capacitance of the storage capacitor Cst1 included in the red/green pixel RPX5/GPX5. Accordingly, as illustrated in
Referring to
The fifth and sixth transistors TP5 and TP6 may be turned on in response to the emission signal EM having a low level, and the seventh transistor TN7′ may be turned on in response to the emission signal EM having a high level. For example, as illustrated in
Further, in the display panel according to embodiments, a size of at least one of the parasitic boost capacitor PCbst2, the negative parasitic boost capacitor Nbst2, the first transistor TP12 and the storage capacitor Cst2 included in the blue pixel BPX6 may be different from a size of a corresponding one of the parasitic boost capacitor PCbst1, the negative parasitic boost capacitor Nbst1, the first transistor TP11 and the storage capacitor Cst1 included in the red/green pixel RPX6/GPX6. Accordingly, a difference between luminance of the display panel driven at a normal driving frequency and luminance of the display panel driven at a low frequency may be reduced, and thus the luminance difference when a driving frequency for the display panel is changed may not be perceived by a user.
Referring to
The seventh transistor TP7 may apply an anode initialization voltage AVINT to an anode of the organic light emitting diode EL in response to a gate writing signal NGW for a next pixel row. For example, as illustrated in
In some embodiments, as illustrated in
Further, in the display panel according to embodiments, a size of at least one of the parasitic boost capacitor PCbst2, the negative parasitic boost capacitor Nbst2, the first transistor TP12 and the storage capacitor Cst2 included in the blue pixel BPX7 may be different from a size of a corresponding one of the parasitic boost capacitor PCbst1, the negative parasitic boost capacitor Nbst1, the first transistor TP11 and the storage capacitor Cst1 included in the red/green pixel RPX7/GPX7. Accordingly, a difference between luminance of the display panel driven at a normal driving frequency and luminance of the display panel driven at a low frequency may be reduced, and thus the luminance difference when a driving frequency for the display panel is changed may not be perceived by a user.
Referring to
According to embodiments, the display panel 410 may include red, green and blue pixels RPX1, GPX1 and BPX1 illustrated in
The data driver 420 may provide the data voltages VDAT to the red, green and blue pixels RPX, GPX and BPX in response to a data control signal DCTRL and output image data ODAT received from the controller 450. In some embodiments, the data control signal DCTRL may include, but not limited to, an output data enable signal, a horizontal start signal and a load signal. The data driver 420 may receive, as the output image data ODAT, frame data at a driving frequency DF from the controller 450. In some embodiments, the data driver 420 and the controller 450 may be implemented with a signal integrated circuit, and the signal integrated circuit may be referred to as a timing controller embedded data driver (TED). In other embodiments, the data driver 420 and the controller 450 may be implemented with separate integrated circuits.
The scan driver 430 may provide the gate initialization signal GI, the gate writing signal GW and the gate compensation signal GC to the red, green and blue pixels RPX, GPX and BPX in response to a scan control signal SCTRL received from the controller 450. In some embodiments, the scan control signal SCTRL may include, but not limited to, a scan start signal and a scan clock signal. In some embodiments, the scan driver 430 may sequentially provide each of the gate initialization signal GI, the gate writing signal GW and the gate compensation signal GC to the red, green and blue pixels RPX, GPX and BPX on a pixel row basis. In some embodiments, the scan driver 430 may be integrated or formed in a peripheral portion of the display panel 410. In other embodiments, the scan driver 430 may be implemented with at least one integrated circuit.
The emission driver 440 may provide the emission signal EM to the red, green and blue pixels RPX, GPX and BPX in response to an emission control signal EMCTRL received from the controller 450. In some embodiments, the emission control signal EMCTRL may include, but not limited to, an emission start signal and an emission clock signal. In some embodiments, the emission driver 440 may sequentially provide the emission signal EM to the red, green and blue pixels RPX, GPX and BPX on a pixel row basis. In some embodiments, the emission driver 440 may be integrated or formed in the peripheral portion of the display panel 410. In other embodiments, the emission driver 440 may be implemented with at least one integrated circuit.
The controller 450 (e.g., a timing controller (TCON)) may receive input image data IDAT and a control signal CTRL from an external host processor (e.g., an application processor (AP), a graphic processing unit (GPU) or a graphic card). In some embodiments, the control signal CTRL may include, but not limited to, a vertical synchronization signal, a horizontal synchronization signal, an input data enable signal, a master clock signal, etc.
The controller 450 may generate the output image data ODAT, the data control signal DCTRL, the scan control signal SCTRL and the emission control signal EMCTRL based on the input image data IDAT and the control signal CTRL. The controller 450 may control an operation of the data driver 420 by providing the output image data ODAT and the data control signal DCTRL to the data driver 420, may control an operation of the scan driver 430 by providing the scan control signal SCTRL to the scan driver 430, and may control an operation of the emission driver 440 by providing the emission control signal EMCTRL to the emission driver 440.
In some embodiments, the controller 450 of the OLED display device 400 may change the driving frequency DF for the display panel 410 by analyzing the input image data IDAT. For example, the OLED display device 400 may drive the display panel 410 at a normal driving frequency or an input frame frequency IFF (e.g., about 60 Hz) of the input image data IDAT when the input image data IDAT represent a moving image and may drive the display panel 410 at a low frequency lower than the normal driving frequency or the input frame frequency IFF when the input image data IDAT represent a still image. In an embodiment, although the controller 450 receives the input image data IDAT at the fixed input frame frequency IFF (e.g., about 60 Hz), the controller 450 may provide the output image data ODAT at the driving frequency in a wide driving frequency range (e.g., from about 1 Hz to about 60 Hz) to the data driver 420. For example, as illustrated in
Further, although
As described above, the driving frequency DF of the display panel 410 may be changed. However, in the OLED display device 400 according to embodiments, at least one of the at least two transistors, the at least one capacitor and a parasitic capacitor included in the blue pixel BPX may have a size different from a size of a corresponding one of the at least two transistors, the at least one capacitor and the parasitic capacitor included in the red pixel RPX or the green pixel GPX. Accordingly, a difference between luminance of the display panel 410 driven at the normal driving frequency and luminance of the display panel driven 410 at the low frequency may be reduced, and thus the luminance difference when the driving frequency DF for the display panel 410 is changed may not be perceived by a user.
Referring to
The processor 1110 may perform various computing functions or tasks. The processor 1110 may be an application processor (AP), a micro processor, a central processing unit (CPU), etc. The processor 1110 may be coupled to other components via an address bus, a control bus, a data bus, etc. Further, in some embodiments, the processor 1110 may be further coupled to an extended bus such as a peripheral component interconnection (PCI) bus.
The memory device 1120 may store data for operations of the electronic device 1100. For example, the memory device 1120 may include at least one non-volatile memory device such as an erasable programmable read-only memory (EPROM) device, an electrically erasable programmable read-only memory (EEPROM) device, a flash memory device, a phase change random access memory (PRAM) device, a resistance random access memory (RRAM) device, a nano floating gate memory (NFGM) device, a polymer random access memory (PoRAM) device, a magnetic random access memory (MRAM) device, a ferroelectric random access memory (FRAM) device, etc, and/or at least one volatile memory device such as a dynamic random access memory (DRAM) device, a static random access memory (SRAM) device, a mobile dynamic random access memory (mobile DRAM) device, etc.
The storage device 1130 may be a solid state drive (SSD) device, a hard disk drive (HDD) device, a CD-ROM device, etc. The I/O device 1140 may be an input device such as a keyboard, a keypad, a mouse, a touch screen, etc, and an output device such as a printer, a speaker, etc. The power supply 1150 may supply power for operations of the electronic device 1100. The OLED display device 1160 may be coupled to other components through the buses or other communication links.
In the OLED display device 1160, each of first, second and third pixels may include at least two transistors, at least one capacitor and an organic light emitting diode. At least one of the at least two transistors, the at least one capacitor and a parasitic capacitor included in the third pixel (e.g., a blue pixel) may have a size different from a size of a corresponding one of the at least two transistor and the at least one capacitor included in the first pixel (e.g., a red pixel) or the second pixel (e.g., a green pixel). Accordingly, when a driving frequency for a display panel is changed, a difference between luminance of the display panel driven at a previous driving frequency and luminance of the display panel driven at a current driving frequency may be reduced, and the luminance difference may not be perceived by a user.
The inventive concepts may be applied to any OLED display device 1160, and any electronic device 1100 including the OLED display device 1160. For example, the inventive concepts may be applied to a mobile phone, a smart phone, a wearable electronic device, a tablet computer, a television (TV), a digital TV, a 3D TV, a personal computer (PC), a home appliance, a laptop computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital camera, a music player, a portable game console, a navigation device, etc.
The foregoing is illustrative of embodiments and is not to be construed as limiting thereof. Although a few embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of the present inventive concept. Accordingly, all such modifications are intended to be included within the scope of the present inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various embodiments and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims.
Number | Date | Country | Kind |
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10-2020-0097951 | Aug 2020 | KR | national |