Display device

Abstract

The present invention provides a display device, comprising a pixel circuit. The pixel circuit comprises a first sub-pixel circuit and a second sub-pixel circuit. The first sub-pixel circuit comprises a first driving transistor, a second driving transistor and a first light-emitting unit. The first light-emitting unit is electrically connected to the first driving transistor and the second driving transistor. The second sub-pixel circuit comprises a third driving transistor and a second light-emitting unit. The second light-emitting unit is electrically connected to the third driving transistor. The voltage level of the first gate terminal of the first driving transistor of the first sub-pixel circuit is associated with the voltage level of the second gate terminal of the third driving transistor of the second sub-pixel circuit.

Description

Technical Field

[0001] The present invention relates to a device, and more particularly, to a display device having a compensation circuit for a color shift problem. Background Art

[0002] A light-emitting device (LED) display device includes a plurality of pixels, and each of the pixels may include three sub-pixels of a red LED, a green LED, and a blue LED. The red LED, the green LED, and the blue LED are driven by different drive currents, respectively. In an LED display device, the grayscale of the light emitted from the LED is controlled by the drive current. However, the color shift problem may arise due to the change in the drive current. Taking the green LED as an example, when the drive current of the green LED increases, the color of the green light may shift so that the color of the green light becomes light blue. On the contrary, when the drive current of the green LED decreases, the color of the green light may also shift so that the color of the green light becomes light red.

[0003] In the prior art, in order to solve the color shift problem, a data processing circuit outside the LED panel is used to process the display data in advance, and then the display data is input to the LED panel to drive the pixels. However, this may reduce the range of grayscale control or reduce the accuracy of grayscale control of the relevant primary colors. Summary of the invention

[0004] The present invention is directed to a display device including a compensation circuit for the color shift problem.

[0005] In an embodiment of the present invention, a display device includes a pixel circuit. The pixel circuit includes a first sub-pixel circuit and a second sub-pixel circuit. The first sub-pixel circuit includes a first driving transistor, a second driving transistor and a first light-emitting unit. The first light-emitting unit is electrically connected to the first driving transistor and the second driving transistor. The second sub-pixel circuit includes a third driving transistor and a second light-emitting unit. The second light-emitting unit is electrically connected to the third driving transistor. The voltage level of the first gate terminal of the first driving transistor of the first sub-pixel circuit is associated with the voltage level of the second gate terminal of the third driving transistor of the second sub-pixel circuit.

[0006] In order to make the foregoing content easier to understand, several embodiments of the drawings are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure.

[0008] Figure 1is a schematic diagram showing a display device according to an embodiment of the present invention;

[0009] Figure 2 is a schematic diagram showing the relationship between the driving current and the gray scale of a green LED according to an embodiment of the present invention;

[0010] Figure 3 is a schematic diagram showing the relationship between the current density and the wavelength of a green LED according to an embodiment of the present invention;

[0011] Figure 4 is a chromaticity diagram showing the position of a color point corresponding to light emitted from a light emitting unit according to an embodiment of the present invention;

[0012] Figure 5 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0013] Figure 6 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0014] Figure 7 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0015] Figure 8 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0016] Fig. 9 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0017] Fig.10 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention;

[0018] Fig.11 is a schematic diagram showing the relationship between the driving current and the gray scale of a green LED according to another embodiment of the present invention;

[0019] Fig.12 is a schematic diagram showing the relationship between the current density and the wavelength of a green LED according to another embodiment of the present invention;

[0020] Fig.13 is a chromaticity diagram illustrating a position of a color point corresponding to light emitted from a light emitting unit according to another embodiment of the present invention.

[0021] Description of Figure Numbers

[0022] 10: display device;

[0023] 100, 200, 300, 400, 500, 600, 700: circuit;

[0024] 110: first sub-pixel circuit;

[0025] 120: a second sub-pixel circuit;

[0026] 130: a third sub-pixel circuit;

[0027] 140_1: first light emitting unit;

[0028] 140_2: second light emitting unit;

[0029] 140_3: third light emitting unit;

[0030] 150: compensation circuit;

[0031] A1, A2, B1, B2, C1, C2: color points;

[0032] DATA_B, DATA_BC, DATA_G, DATA_GC, DATA_R: data lines;

[0033] G1, G2, G3, G4, G5: gate terminals;

[0034] I1, I2, I3, I4, I5, I6: current;

[0035] P1, P2, P3: sub-pixels;

[0036] SCAN: scan line;

[0037] Tcb, Tcg, Tcg1, Tcg2, Tdb, Tdg, Tdr: driving transistors;

[0038] Tsb, Tsbc, Tsg, Tsgc, Tsr: switching circuit;

[0039] VDD: first system voltage;

[0040] VDD2: second system voltage;

[0041] VSS: Third system voltage. DETAILED DESCRIPTION

[0042] The following embodiments are provided to describe the present disclosure in detail, but the present disclosure is not limited to the embodiments provided, and the embodiments provided may be appropriately combined. The terms "coupling / coupled" or "connecting / connected" used in this specification (including claims) of the present application may refer to any direct or indirect connection method. For example, "a first transistor is connected to a second transistor" should be interpreted as "a first transistor is directly connected to a second transistor" or "a first transistor is indirectly connected to a second transistor via other devices or connecting members". The term "signal" may refer to current, voltage, charge, temperature, data, electromagnetic waves, or any one or more signals. In addition, the term "and / or" may refer to "at least one of". For example, "a first signal and / or a second signal" should be interpreted as "at least one of a first signal and a second signal".

[0043] Figure 1 1 is a schematic diagram showing a display device according to an embodiment of the present invention. The display device 10 may include a pixel circuit 100. The pixel circuit 100 may include a plurality of sub-pixels. For simplicity, Figure 1 The pixel circuit 100 is shown to include only three sub-pixels P1, P2, and P3, but the present invention is not limited thereto. Figure 1 , the pixel circuit 100 of the present embodiment includes a first sub-pixel circuit 110, a second sub-pixel circuit 120 and a third sub-pixel circuit 130. In the present embodiment, the first sub-pixel circuit 110 is disposed in the first sub-pixel P1 and the first sub-pixel P1 can display red, the second sub-pixel circuit 120 is disposed in the second sub-pixel P2 and the second sub-pixel P2 can display green, and the third sub-pixel circuit 130 is disposed in the third sub-pixel P3 and the third sub-pixel P3 can display blue, but the present invention is not limited thereto. The display device 10 can be an OLED display device, a small LED display device, a micro LED display device, a quantum dot LED display device, an LCD display device, a spliced ​​display device or a foldable display device.

[0044] The first sub-pixel circuit 110 includes two driving transistors Tcg and Tdr (a first driving transistor and a second driving transistor) and a first light emitting unit 140_1. The first driving transistor Tcg is electrically connected in parallel with the second driving transistor Tdr. The first driving transistor Tcg may have a first channel width and a first channel length, the second driving transistor Tdr may have a second channel width and a second channel length, and the third driving transistor Tdg may have a third channel width and a third channel length. In some embodiments, the channel width to length ratio (W / L) of the first driving transistor Tcg may be set to be smaller than the channel width to length ratio of the second driving transistor Tdr. That is, the ratio of the first channel width to the first channel length is smaller than the ratio of the second channel width to the second channel length. In some embodiments, the channel width to length ratio (W / L) of the first driving transistor Tcg may be set to be smaller than the channel width to length ratio of the third driving transistor Tdg. That is, the ratio of the first channel width to the first channel length is smaller than the ratio of the third channel width to the third channel length. One end of the first light-emitting unit 140_1 is electrically connected to two driving transistors Tcg and Tdr, and the other end of the first light-emitting unit 140_1 is electrically connected to the third system voltage VSS. The second sub-pixel circuit 120 includes a third driving transistor Tdg and a second light-emitting unit 140_2. The second light-emitting unit 140_2 is electrically connected to the third driving transistor Tdg. The third sub-pixel circuit 130 includes a driving transistor Tdb and a third light-emitting unit 140_3. The third light-emitting unit 140_3 is electrically connected to the driving transistor Tdb. In the present embodiment, the first sub-pixel circuit 110 includes a compensation circuit for the color shift problem. For example, the first driving transistor Tcg can act as a compensation circuit to compensate for the color shift of green light. The voltage level of the first gate terminal G1 of the first driving transistor Tcg (one of the two driving transistors) of the first sub-pixel circuit 110 can be associated with the voltage level of the second gate terminal G2 of the third driving transistor Tdg of the second sub-pixel circuit 120. This means that the voltage level of the first gate terminal G1 of the first driving transistor Tcg can be changed or adjusted according to the voltage level of the second gate terminal G2 of the third driving transistor Tdg. Alternatively, the voltage level of the second gate terminal G2 of the third driving transistor Tdg can be changed or adjusted according to the voltage level of the first gate terminal G1 of the first driving transistor Tcg. The change or adjustment of the voltage level of the first gate terminal G1 or the second gate terminal G2 can be performed by circuit design or by a lookup table. The lookup table can be made, for example, according to the desired color compensation and the desired compensation current I1 generated by the first driving transistor Tcg, but the present invention is not limited thereto.According to some embodiments, the lookup table can be made by the following parameters, which include the channel W / L ratio of the first driving transistor Tcg and the third driving transistor Tdg, the voltage applied to the first gate terminal G1 and the second gate terminal G2, the voltage applied to the source terminal of the first driving transistor Tcg and the voltage applied to the source terminal of the third driving transistor Tdg, or a combination thereof.

[0045] like Figure 1 As shown in , in the present embodiment, the first gate terminal G1 may be electrically connected to the second gate terminal G2. In this case, the voltage level of the first gate terminal G1 may be adjusted to be associated with the voltage level of the second gate terminal G2 through circuit design. For example, the voltage level of the first gate terminal G1 may be the same as the voltage level of the second gate terminal G2. Specifically, the first sub-pixel circuit 110 further includes a third switch circuit Tsr. The first end (e.g., source end) of the first driving transistor Tcg is electrically connected to the first system voltage VDD, and the second end (e.g., drain end) of the first driving transistor Tcg is electrically connected to the first light-emitting unit 140_1. The first system voltage VDD may be a common power supply of a high voltage. In the present embodiment, the first light-emitting unit 140_1 may include a light-emitting diode (e.g., a red LED) for emitting red light, and the second end of the first driving transistor Tcg is electrically connected to the anode end of the light-emitting diode. The first gate terminal G1 of the first driving transistor Tcg is electrically connected to the second gate terminal G2 of the third driving transistor Tdg. A first terminal of the second driving transistor Tdr is electrically connected to the first system voltage VDD, and a second terminal of the second driving transistor Tdr is electrically connected to the first light emitting unit 140_1. A fourth gate terminal G4 of the second driving transistor Tdr is electrically connected to the third switching circuit Tsr. A first terminal of the third switching circuit Tsr is electrically connected to the fourth gate terminal G4 of the second driving transistor Tdr, and a second terminal of the third switching circuit Tsr is electrically connected to the first data line DATA_R. A control terminal of the third switching circuit Tsr is electrically connected to the scan line SCAN.

[0046] On the other hand, the second sub-pixel circuit 120 further includes a second switch circuit Tsg. A first end of the third drive transistor Tdg is electrically connected to the first system voltage VDD, and a second end of the third drive transistor Tdg is electrically connected to the second light-emitting unit 140_2. In the present embodiment, the second light-emitting unit 140_2 may include a light-emitting diode (e.g., a green LED) for emitting green light, and a second end of the third drive transistor Tdg is electrically connected to an anode end of the light-emitting diode. A second gate end G2 of the third drive transistor Tdg is electrically connected to the second switch circuit Tsg. A first end of the second switch circuit Tsg is electrically connected to a second gate end G2 of the third drive transistor Tdg, and a second end of the second switch circuit Tsg is electrically connected to a second data line DATA_G. A control end of the second switch circuit Tsg is electrically connected to a scan line SCAN.

[0047] In the present embodiment, the first driving transistor Tcg is electrically connected in parallel with the second driving transistor Tdr in the first sub-pixel circuit 110. When the scan line SCAN turns on the second switch circuit Tsg, the data voltage applied to the second data line DATA_G turns on the first driving transistor Tcg and the third driving transistor Tdg. Therefore, the third driving transistor Tdg outputs a driving current I2 to drive the green LED 140_2 to emit green light. On the other hand, the first driving transistor Tcg outputs a compensation current I1 to drive the red LED 140_1. According to some embodiments, the driving current may be controlled by the driving transistor. For example, the ratio of the first channel width to the first channel length of the first driving transistor Tcg may be made smaller than the ratio of the third channel width to the third channel length of the third driving transistor Tdg. Therefore, the first driving transistor Tcg may generate a first driving current I1 to drive the red LED 140_1, the third driving transistor Tdg may generate a second driving current I2 to drive the green LED 140_2, and the first driving current I1 may be made smaller than the second driving current I2. Therefore, due to the smaller first driving current I1, the red LED 140_1 is slightly lit until red light is emitted to compensate for the color shift of the green light. In some embodiments, the first driving transistor Tcg can drive the first color light emitting unit (LED 140_1) using a specified amount of compensation current I1 to compensate for the color shift of the second color light emitting unit (LED 140_2).

[0048] In addition, the third sub-pixel circuit 130 further includes a switch circuit Tsb. The first end of the driving transistor Tdb is electrically connected to the first system voltage VDD, and the second end of the driving transistor Tdb is electrically connected to the third light-emitting unit 140_3. In the present embodiment, the third light-emitting unit 140_3 may include a light-emitting diode for emitting blue light (e.g., a blue LED), and the second end of the driving transistor Tdb is electrically connected to the anode end of the light-emitting diode. The third gate terminal G3 of the driving transistor Tdb is electrically connected to the switch circuit Tsb. The first end of the switch circuit Tsb is electrically connected to the third gate terminal G3 of the driving transistor Tdb, and the second end of the switch circuit Tsb is electrically connected to the third data line DATA_B. The control end of the switch circuit Tsb is electrically connected to the scan line SCAN.

[0049] In this embodiment, the LED may include, for example, an organic light emitting diode (OLED), a small LED, a micro LED or a quantum dot light emitting diode (such as QLED, QDLED), a fluorescent material, a phosphor or other suitable materials, or any arrangement and combination thereof, but the present invention is not limited thereto.

[0050] Figure 2 is a schematic diagram showing the relationship between the driving current and the gray scale of the green LED according to the embodiment of the present invention. Figure 3 is a schematic diagram showing the relationship between the current density and the wavelength of a green LED according to an embodiment of the present invention. Figure 4 : is a chromaticity diagram showing the position of a color point corresponding to light emitted from a light emitting unit according to an embodiment of the present invention.

[0051] See also Figures 1 to 4 As the driving current I2 of the green LED 140_2 increases, the color point A1 may shift to the color point B1, and thus the color point A1 has a low grayscale and the color point B1 has a high grayscale. Therefore, the color of the green light emitted from the light emitting unit becomes as follows: Figure 4 That is, since the driving current I2 of the green LED 140_2 increases, a color shift problem occurs.

[0052] In order to solve the color shift problem, a driving transistor Tcg is added to the first sub-pixel circuit 110 to act as a compensation circuit. The driving transistor Tcg automatically lights up the red LED 140_1 using a specified amount of compensation current I1 to compensate for the color shift of the green light and keep the wavelength of the green light the same as the dominant wavelength of 520 nanometers (nm). The value of the compensation current I1 increases as the grayscale increases, and the maximum value is located in the high grayscale. In this embodiment, the target hue is, for example, a green hue corresponding to the dominant wavelength of 520 nanometers, such as Figure 3As shown in . The channel width and length ratio of the driving transistor Tcg can be set to control the wavelength of the green light emitted from the light emitting unit to remain the same as the main wavelength. Therefore, the color point B1 can be changed to the color point C1 after compensation, and the wavelength of the green light of the color point A1 and the color point C1 is consistent with the main wavelength.

[0053] In an embodiment, the first sub-pixel circuit 110 may display green, the second sub-pixel circuit 120 may display blue, and the third sub-pixel circuit 130 may display red. In this case, the driving transistor Tcg may automatically light up the green LED of the first sub-pixel circuit 110 to compensate for the color shift of the blue light.

[0054] Figure 5 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Figure 1 and Figure 5 The circuit 200 of this embodiment is Figure 1 , and the main difference therebetween is, for example, that the first end of the first driving transistor Tcg is electrically connected to the second system voltage VDD2. The second system voltage VDD2 may be different from the first system voltage VDD. That is, the first driving transistor Tcg and the second driving transistor Tdr of the first sub-pixel circuit 110 are connected to different system voltages VDD and VDD2. According to some embodiments, the second system voltage VDD2 may be less than the first system voltage VDD. Therefore, the driving current I1 may be adjusted to be less than the driving current I2. Therefore, the driving current I1 used for compensation will not be too large, and the main wavelength or color in the second sub-pixel 120 may be maintained.

[0055] In the present embodiment, the second system voltage VDD2 and the channel width to length ratio of the driving transistor Tcg may be set to control the wavelength of the green light emitted from the light emitting unit to remain the same as the main wavelength.

[0056] Figure 6 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Figure 1 and Figure 6 The circuit 300 of this embodiment is Figure 1 The circuit 100 depicted in FIG. 300 is similar to the circuit 100 depicted in FIG. 300 , and the main difference therebetween is that, for example, the first sub-pixel circuit 110 of the circuit 300 further includes a first switching circuit Tsgc.

[0057] Specifically, a first terminal of the first driving transistor Tcg is electrically connected to the first system voltage VDD, and a second terminal of the first driving transistor Tcg is electrically connected to the first light emitting unit 140_1. A first gate terminal G1 of the first driving transistor Tcg is electrically connected to the first switching circuit Tsgc. A first terminal of the second driving transistor Tdr is electrically connected to the first system voltage VDD, and a second terminal of the second driving transistor Tdr is electrically connected to the first light emitting unit 140_1. A fourth gate terminal G4 of the second driving transistor Tdr is electrically connected to the third switching circuit Tsr.

[0058] A first end of the third switch circuit Tsr is electrically connected to a first gate terminal G1 of the second drive transistor Tdr, and a second end of the third switch circuit Tsr is electrically connected to a first data line DATA_R. A control end of the third switch circuit Tsr is electrically connected to a scan line SCAN. A first end of the first switch circuit Tsgc is electrically connected to a third data line DATA_GC, and a second end of the first switch circuit Tsgc is electrically connected to a first gate terminal G1 of the first drive transistor Tcg. A control end of the first switch circuit Tsgc is electrically connected to a scan line SCAN.

[0059] On the other hand, a first end of the third driving transistor Tdg is electrically connected to the first system voltage VDD, and a second end of the third driving transistor Tdg is electrically connected to the second light emitting unit 140_2. A second gate end G2 of the third driving transistor Tdg is electrically connected to the second switch circuit Tsg. A first end of the second switch circuit Tsg is electrically connected to the second gate end G2 of the third driving transistor Tdg, and a second end of the second switch circuit Tsg is electrically connected to the second data line DATA_G. A control end of the second switch circuit Tsg is electrically connected to the scan line SCAN.

[0060] like Figure 6As shown in FIG. 1 , the first gate terminal G1 of the driving transistor Tcg is electrically connected to the first switching circuit Tsgc, and the second gate terminal G2 of the driving transistor Tdg is electrically connected to the second switching circuit Tsg. The first switching circuit Tsgc and the second switching circuit Tsg are respectively connected to two independent data lines DATA_GC and DATA_G. The two data lines DATA_GC and DATA_G respectively provide two associated data voltages to the first gate terminal G1 of the driving transistor Tcg and the second gate terminal G2 of the driving transistor Tdg. This means that the data voltage provided by the data line DATA_G can be changed or adjusted according to the data voltage provided by the data line DATA_GC. Alternatively, the data voltage provided by the data line DATA_GC can be changed or adjusted according to the data voltage provided by the data line DATA_G. The change or adjustment of the data voltage provided by the data line DATA_G or the data line DATA_GC can be performed by circuit design or by a lookup table. The lookup table can be made, for example, according to the desired color compensation and the desired compensation current I1 generated by the first driving transistor Tcg, but the present invention is not limited thereto. Therefore, the voltage level of the first gate terminal G1 of the driving transistor Tcg of the first sub-pixel circuit 110 is associated with the voltage level of the second gate terminal G2 of the driving transistor Tdg of the second sub-pixel circuit 120. The data voltage provided by the data line DATA_G may be a data voltage for driving the green LED 140_2 to emit green light. The data voltage provided by the data line DATA_GC may be a data voltage for driving the red LED 140_1 to emit red light and for compensating for the color shift of green light and associated with the data voltage provided by the data line DATA_G. The red LED 140_1 and the green LED 140_2 emit different colors and may have different electro-optical characteristics. Therefore, by sharing the same data line DATA_G (in the absence of the data line DATA_GC) to drive two LEDs of different colors, the compensation current I1 may not be accurately controlled. In this embodiment, an independent data line DATA_GC is used to drive the red LED 140 for compensation, and the compensation current I1 may be more accurately controlled.

[0061] In this embodiment, the data voltage provided by the data line DATA_GC and the channel width to length ratio of the driving transistor Tcg may be set to control the wavelength of the green light emitted from the light emitting unit to remain the same as the main wavelength.

[0062] Figure 7 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Figure 1 and Figure 7 , the circuit 400 of this embodiment is Figure 1, and the main difference therebetween is that, for example, the sub-pixel circuit 120 of the circuit 400 further includes a driving transistor Tcb, and the gate terminal G5 is electrically connected to the gate terminal G3, so that the voltage level of the gate terminal G5 is the same as the voltage level of the gate terminal G3. For example, the driving transistor Tcb can act as a compensation circuit to compensate for the color shift of blue light. The driving transistor Tcb automatically lights up the green LED 140_2 using a specified amount of compensation current I4 to compensate for the color shift of blue light.

[0063] In this embodiment, the channel width and length ratio of the driving transistor Tcb can be set to control the wavelength of the blue light emitted from the light emitting unit to remain the same as the main wavelength of the blue light (eg, 450 nm). The driving transistor Tdb outputs a driving current I3 to drive the blue LED 140_3 to emit blue light.

[0064] Figure 8 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Figure 7 and Figure 8 The circuit 500 of this embodiment is Figure 7 , and the main difference therebetween is that, for example, the first terminals of the driving transistors Tcg and Tcb are electrically connected to the second system voltage VDD2. In this embodiment, the second system voltage VDD2 and the channel width to length ratio of the driving transistors Tcg and Tcb can be set to control the wavelength of the blue light emitted from the light emitting unit to remain the same as the main wavelength of the blue light.

[0065] Fig. 9 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Figure 6 and Fig. 9 The circuit 600 of this embodiment is Figure 6 3 is similar to the circuit 300 depicted in , and the main difference therebetween is that, for example, the sub-pixel circuit 120 of the circuit 600 further includes a driving transistor Tcb and a switching circuit Tsbc for compensating for the color shift of blue light.

[0066] Specifically, a first end of the switch circuit Tsbc is electrically connected to the data line DATA_BC, and a second end of the switch circuit Tsbc is electrically connected to the fifth gate terminal G5 of the driving transistor Tcb. A control end of the switch circuit Tsbc is electrically connected to the scan line SCAN. A first end of the switch circuit Tsb is electrically connected to the gate terminal G3 of the driving transistor Tdb, and a second end of the switch circuit Tsb is electrically connected to the data line DATA_B. A control end of the switch circuit Tsb is electrically connected to the scan line SCAN.

[0067] The switch circuit Tsbc and the switch circuit Tsb are connected to two data lines DATA_BC and DATA_B, respectively. The two data lines DATA_BC and DATA_B provide two associated data voltages to the gate terminal G5 of the driving transistor Tcb and the gate terminal G3 of the driving transistor Tdb, respectively. Therefore, the voltage level of the gate terminal G5 of the driving transistor Tcb of the sub-pixel circuit 120 is associated with the voltage level of the gate terminal G3 of the driving transistor Tdb of the sub-pixel circuit 130. The data voltage provided by the data line DATA_B may be a data voltage for driving the blue LED 140_3 to emit blue light. The data voltage provided by the data line DATA_BC may be a data voltage for compensating for the color shift of blue light and associated with the data voltage provided by the data line DATA_B.

[0068] In this embodiment, the data voltage provided by the data line DATA_BC and the channel width to length ratio of the driving transistor Tcb may be set to control the wavelength of the blue light emitted from the light emitting unit to remain the same as the main wavelength of the blue light.

[0069] exist Figures 7 to 9 In the embodiment of Figures 1 to 6 Circuit operation for compensating for the color shift of blue light is fully taught, suggested, and implemented in the embodiments shown in , and therefore no further description is provided here.

[0070] Fig.10 2 is a schematic diagram showing a circuit for driving a light emitting unit according to another embodiment of the present invention. Fig.10 , the circuit 700 of the present embodiment includes a sub-pixel circuit 110, a sub-pixel circuit 120 and a sub-pixel circuit 130 that display red, green and blue respectively, but the present invention is not limited thereto. The sub-pixel circuit 130 includes a driving transistor Tdb, a switching circuit Tsb and a compensation circuit 150. The compensation circuit 150 is configured for the color shift problem and includes two driving transistors Tcg1 and Tcg2. In the present embodiment, the sub-pixel circuit 120 displays green and acts as the second sub-pixel circuit as mentioned above, and the sub-pixel circuit 130 displays blue and acts as the first sub-pixel circuit as mentioned above. The first sub-pixel circuit 130 includes a compensation circuit for compensating for the color shift problem of the green LED 140_2 in the second sub-pixel circuit 120.

[0071] Specifically, see Fig.10, a first end of the first driving transistor Tcg1 is electrically connected to the second system voltage VDD2, and a second end of the first driving transistor Tcg1 is electrically connected to the fourth driving transistor Tcg2. A first gate terminal G1 of the first driving transistor Tcg1 is electrically connected to a second gate terminal G2 of the third driving transistor Tdg. A first end of the second driving transistor Tdb is electrically connected to the first system voltage VDD, and a second end of the second driving transistor Tdb is electrically connected to the third light emitting unit 140_3. A third gate terminal G3 of the second driving transistor Tdb is electrically connected to a third switching circuit Tsb. A first end of the fourth driving transistor Tcg2 is electrically connected to a second end of the first driving transistor Tcg1, and a second end of the fourth driving transistor Tcg2 is electrically connected to the third light emitting unit 140_3. A first gate terminal G1 of the fourth driving transistor Tcg2 is electrically connected to a second gate terminal G2 of the third driving transistor Tdg. A first end of the third switching circuit Tsb is electrically connected to a third gate terminal G3 of the second driving transistor Tdb, and a second end of the third switching circuit Tsb is electrically connected to a third data line DATA_B. A control end of the third switching circuit Tsb is electrically connected to a scan line SCAN. The first system voltage VDD and the second system voltage VDD2 may be different, for example, the second system voltage VDD2 may be less than the first system voltage VDD. Therefore, the driving current I6 may be adjusted to be less than the driving current I5. Therefore, the driving current I6 used for compensation will not be too large, and the main wavelength or color in the second sub-pixel 120 may be maintained.

[0072] On the other hand, a first end of the third driving transistor Tdg of the sub-pixel circuit 120 (second sub-pixel circuit) is electrically connected to the first system voltage VDD, and a second end of the third driving transistor Tdg is electrically connected to the second light emitting unit 140_2. A second gate end G2 of the third driving transistor Tdg is electrically connected to the second switch circuit Tsg. A first end of the second switch circuit Tsg is electrically connected to a second gate end G2 of the third driving transistor Tdg, and a second end of the second switch circuit Tsg is electrically connected to the second data line DATA_G. A control end of the second switch circuit Tsg is electrically connected to a scan line SCAN.

[0073] In the present embodiment, the voltage level of the first gate terminal G1 of the driving transistor Tcg1 is associated with the voltage level of the second gate terminal G2 of the driving transistor Tdg. The first gate terminal G1 is electrically connected to the second gate terminal G2 so that the voltage level of the first gate terminal G1 is the same as the voltage level of the second gate terminal G2. In addition, the first gate terminals G1 of the driving transistors Tcg1 and Tcg2 are electrically connected to the second gate terminal G2 of the driving transistor Tdg so that the voltage level of the first gate terminals G1 of the driving transistors Tcg1 and Tcg2 is the same as the voltage level of the second gate terminal G2 of the driving transistor Tdg.

[0074] The first driving transistor Tcg1 and the fourth driving transistor Tcg2 are different types of transistors, and the first driving transistor Tcg1 and the second driving transistor Tdb are the same type of transistors. For example, the first driving transistor Tcg1 and the second driving transistor Tdb may be p-type transistors, and the fourth driving transistor Tcg2 may be an n-type transistor.

[0075] Fig.11 FIG. 4 is a schematic diagram showing the relationship between the driving current and the gray scale of a green LED according to another embodiment of the present invention. Fig.12 FIG. 4 is a schematic diagram showing the relationship between the current density and the wavelength of a green LED according to another embodiment of the present invention. Fig.13 is a chromaticity diagram illustrating a position of a color point corresponding to light emitted from a light emitting unit according to another embodiment of the present invention.

[0076] See also Figures 10 to 13 As the driving current I5 of the green LED 140_2 decreases, the color point A2 may shift to the color point B2, and thus the color point A2 has a high grayscale and the color point B2 has a low grayscale. Therefore, the color of the green light emitted from the light emitting unit becomes as follows: Fig.13 That is, since the driving current I5 of the green LED 140_2 is reduced, a color shift problem occurs.

[0077] In order to solve the color shift problem, the driving transistor Tcg1 and the driving transistor Tcg2 are added to the sub-pixel circuit 130 to act as a compensation circuit. The driving transistor Tcg1 and the driving transistor Tcg2 automatically light up the blue LED 140_3 using a specified amount of compensation current I6 to compensate for the color shift of the green light and keep the wavelength of the green light the same as the main wavelength of 520 nanometers. For the compensation current I6, the maximum value is located in the middle grayscale and the minimum value is located in the highest grayscale. In the lowest grayscale, the compensation current I6 is also the minimum value for controlling the blue LED 140_3 not to emit light. In this embodiment, the target hue is, for example, a green hue corresponding to a main wavelength of 520 nanometers, such as Fig.12 As shown in . The channel width to length ratio of the driving transistor Tcg1 and the driving transistor Tcg2 can be set separately to control the wavelength of the green light emitted from the light emitting unit to remain the same as the main wavelength. Therefore, the color point B2 can be changed to the color point C2 after compensation, and the wavelength of the green light of the color point A2 and the color point C2 is consistent with the main wavelength.

[0078] In summary, in an embodiment of the present invention, in order to solve the color shift problem, a driving transistor is added to at least one of the sub-pixel circuits to act as a compensation circuit. The added driving transistor can drive the light-emitting unit of the first color using a specified amount of compensation current to compensate for the color shift of the light-emitting unit of the second color. The system voltage, the data voltage, and the channel width to length ratio of the added driving transistor can be set to control the wavelength of the light to remain the same as the main wavelength. Therefore, after compensation, the color shift problem of the light is solved.

[0079] It will be apparent to those skilled in the art that various modifications and variations may be made to the disclosed embodiments without departing from the scope or spirit of the present disclosure. In view of the foregoing, it is intended that the present disclosure encompass modifications and variations as long as the modifications and variations fall within the scope of the appended claims and their equivalents.

Claims

1. A display device, comprising a pixel circuit, wherein the pixel circuit comprises: A first sub-pixel circuit includes a first driving transistor, a second driving transistor, and a first light emitting unit electrically connected to the first driving transistor and the second driving transistor; as well as a second sub-pixel circuit including a third driving transistor and a second light emitting unit electrically connected to the third driving transistor, wherein a voltage level of a first gate terminal of a first driving transistor of the first sub-pixel circuit is associated with a voltage level of a second gate terminal of the third driving transistor of the second sub-pixel circuit, The first sub-pixel circuit further includes a third switch circuit. A first terminal of the first driving transistor is electrically connected to a first system voltage, and a second terminal of the first driving transistor is electrically connected to the first light emitting unit; A first terminal of the second driving transistor is electrically connected to the first system voltage, a second terminal of the second driving transistor is electrically connected to the first light emitting unit, and a fourth gate terminal of the second driving transistor is electrically connected to the third switching circuit; and A first terminal of the third switch circuit is electrically connected to the fourth gate terminal of the second driving transistor, a second terminal of the third switch circuit is electrically connected to the first data line, and a control terminal of the third switch circuit is electrically connected to the scan line. 2 . The display device according to claim 1 , wherein the first gate terminal is electrically connected to the second gate terminal.

3. The display device according to claim 1, wherein the first sub-pixel circuit comprises a first switch circuit electrically connected to the first gate terminal; The second sub-pixel circuit includes a second switch circuit electrically connected to the second gate terminal; and The first switch circuit and the second switch circuit are connected to two data lines, respectively.

4. The display device according to claim 1, wherein the first driving transistor has a first channel width and a first channel length, the third driving transistor has a third channel width and a third channel length, and a ratio of the first channel width to the first channel length is smaller than a ratio of the third channel width to the third channel length. 5 . The display device according to claim 1 , wherein the first sub-pixel and the second sub-pixel display different colors. 6 . The display device according to claim 5 , wherein the first sub-pixel circuit is disposed in a first sub-pixel, the second sub-pixel circuit is disposed in a second sub-pixel, the first sub-pixel displays red, and the second sub-pixel displays green. 7 . The display device according to claim 5 , wherein the first sub-pixel circuit is disposed in a first sub-pixel, the second sub-pixel circuit is disposed in a second sub-pixel, the first sub-pixel displays green, and the second sub-pixel displays blue.

8. The display device according to claim 1, wherein the second sub-pixel circuit further comprises a second switch circuit, A first terminal of the third driving transistor is electrically connected to the first system voltage, a second terminal of the third driving transistor is electrically connected to the second light emitting unit, and the second gate terminal of the third driving transistor is electrically connected to the second switching circuit; and A first terminal of the second switch circuit is electrically connected to the second gate terminal of the third driving transistor, a second terminal of the second switch circuit is electrically connected to the second data line, and a control terminal of the second switch circuit is electrically connected to the scan line.

9. The display device according to claim 1, wherein the first sub-pixel circuit further comprises a first switch circuit and a third switch circuit, A first terminal of the first driving transistor is electrically connected to a first system voltage, a second terminal of the first driving transistor is electrically connected to the first light emitting unit, and the first gate terminal of the first driving transistor is electrically connected to the first switching circuit; A first terminal of the second driving transistor is electrically connected to the first system voltage, a second terminal of the second driving transistor is electrically connected to the first light emitting unit, and a fourth gate terminal of the second driving transistor is electrically connected to the third switching circuit; A first terminal of the third switch circuit is electrically connected to the fourth gate terminal of the second driving transistor, a second terminal of the third switch circuit is electrically connected to the first data line, and a control terminal of the third switch circuit is electrically connected to the scan line; and A first end of the first switch circuit is electrically connected to the third data line, a second end of the first switch circuit is electrically connected to the first gate end of the first driving transistor, and a control end of the first switch circuit is electrically connected to the scan line. 10 . The display device according to claim 1 , wherein the first sub-pixel circuit comprises a third switch circuit electrically connected to a first data line, and the second sub-pixel circuit comprises a second switch circuit electrically connected to a second data line. 11 . The display device according to claim 1 , wherein the first driving transistor generates a first driving current, the third driving transistor generates a third driving current, and the first driving current is smaller than the third driving current.

12. A display device, comprising a pixel circuit, wherein the pixel circuit comprises: A first sub-pixel circuit includes a first driving transistor, a second driving transistor, and a first light emitting unit electrically connected to the first driving transistor and the second driving transistor; as well as a second sub-pixel circuit including a third driving transistor and a second light emitting unit electrically connected to the third driving transistor, wherein a voltage level of a first gate terminal of a first driving transistor of the first sub-pixel circuit is associated with a voltage level of a second gate terminal of the third driving transistor of the second sub-pixel circuit, The first sub-pixel circuit further includes a third switch circuit. A first terminal of the first driving transistor is electrically connected to a second system voltage, and a second terminal of the first driving transistor is electrically connected to the first light emitting unit; The first terminal of the second driving transistor is electrically connected to a first system voltage, the second terminal of the second driving transistor is electrically connected to the first light emitting unit, the fourth gate terminal of the second driving transistor is electrically connected to the third switching circuit, and the first system voltage is different from the second system voltage; and A first terminal of the third switch circuit is electrically connected to the fourth gate terminal of the second driving transistor, a second terminal of the third switch circuit is electrically connected to the first data line, and a control terminal of the third switch circuit is electrically connected to the scan line. 13 . The display device according to claim 12 , wherein the first gate terminal is electrically connected to the second gate terminal.

14. The display device according to claim 12, wherein the first driving transistor has a first channel width and a first channel length, the third driving transistor has a third channel width and a third channel length, and a ratio of the first channel width to the first channel length is smaller than a ratio of the third channel width to the third channel length.

15. The display device according to claim 12, wherein the second sub-pixel circuit further comprises a second switch circuit, A first terminal of the third driving transistor is electrically connected to the first system voltage, a second terminal of the third driving transistor is electrically connected to the second light emitting unit, and the second gate terminal of the third driving transistor is electrically connected to the second switching circuit; and A first terminal of the second switch circuit is electrically connected to the second gate terminal of the third driving transistor, a second terminal of the second switch circuit is electrically connected to the second data line, and a control terminal of the second switch circuit is electrically connected to the scan line. 16 . The display device according to claim 12 , wherein the first driving transistor generates a first driving current, the third driving transistor generates a third driving current, and the first driving current is smaller than the third driving current. 17 . The display device according to claim 12 , wherein the first sub-pixel and the second sub-pixel display different colors. 18 . The display device according to claim 17 , wherein the first sub-pixel circuit is disposed in a first sub-pixel, the second sub-pixel circuit is disposed in a second sub-pixel, the first sub-pixel displays red, and the second sub-pixel displays green. 19 . The display device according to claim 17 , wherein the first sub-pixel circuit is disposed in a first sub-pixel, the second sub-pixel circuit is disposed in a second sub-pixel, the first sub-pixel displays green, and the second sub-pixel displays blue.

20. The display device according to claim 12, wherein the first sub-pixel circuit further comprises a fourth driving transistor, The second terminal of the first driving transistor is electrically connected to the fourth driving transistor, and the first gate terminal of the first driving transistor is electrically connected to the second gate terminal of the third driving transistor; The second terminal of the second driving transistor is electrically connected to the first light emitting unit, and the third gate terminal of the second driving transistor is electrically connected to the third switch circuit; The first terminal of the fourth driving transistor is electrically connected to the second terminal of the first driving transistor, the second terminal of the fourth driving transistor is electrically connected to the first light emitting unit, and the first gate terminal of the fourth driving transistor is electrically connected to the second gate terminal of the third driving transistor; and A first terminal of the third switch circuit is electrically connected to the third gate terminal of the second driving transistor, a second terminal of the third switch circuit is electrically connected to the first data line, and a control terminal of the third switch circuit is electrically connected to the scan line.

Images