Driving circuit for light emitting diode display and light emitting diode display thereof

Abstract

The application discloses a driving circuit and a light-emitting diode display screen. The driving circuit is used for the light-emitting diode display screen and comprises a first current source and a second current source. The first current source is coupled to a current source end of the driving circuit and is used for outputting a first current to the light-emitting diode display screen through the current source end. The second current source is coupled to a current sinking end of the driving circuit and is used for receiving a second current from the light-emitting diode display screen through the current sinking end.

Description

TECHNICAL FIELD

[0001] The present application relates to a driving circuit for a display screen and the display screen thereof, in particular, to a driving circuit for a Light-Emitting Diode (LED) display screen and the related Light-Emitting Diode display screen. BACKGROUND

[0002] Light-Emitting Diodes (LEDs) are widely used in various display devices, such as television screens, computer monitors, outdoor signs, and portable systems, such as mobile phones, handheld game consoles, and the like. The display of a Light-Emitting Diode display screen is usually controlled and driven by a driving circuit, which can output data signals and scanning signals to control the Light-Emitting Diode pixels to emit light.

[0003] In recent years, there is a trend of large size and high resolution for Light-Emitting Diode display screens. Large size Light-Emitting Diode display screens are usually used in outdoor display devices, such as Public Information Displays (PIDs) or digital signage, and the like. Since outdoor display devices continuously send videos every day without interruption, power consumption becomes an important consideration for Light-Emitting Diode display screen products. Therefore, it is necessary to propose a new Light-Emitting Diode display screen structure that can be driven by lower power consumption. SUMMARY

[0004] Therefore, the main purpose of the present application is to propose a driving circuit structure for a Light-Emitting Diode (LED) display screen and the related Light-Emitting Diode display screen to solve the problem of power consumption.

[0005] An embodiment of the present application discloses a driving circuit for a Light-Emitting Diode (LED) display screen, which includes a first current source and a second current source. The first current source is coupled to a current source end of the driving circuit to output a first current to the Light-Emitting Diode display screen through the current source end. The second current source is coupled to a current sink end of the driving circuit to receive a second current from the Light-Emitting Diode display screen through the current sink end.

[0006] Another embodiment of the present application discloses a Light-Emitting Diode (LED) display screen, which includes a first Light-Emitting Diode and a second Light-Emitting Diode. The anode of the first Light-Emitting Diode is coupled to a first signal line, and the cathode of the first Light-Emitting Diode is coupled to a scanning line. The anode of the second Light-Emitting Diode is coupled to the scanning line, and the cathode of the second Light-Emitting Diode is coupled to a second signal line. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 FIG. 1 is a schematic diagram of a driving architecture for a passive matrix light emitting diode display panel.

[0008] Figure 2 FIG. 2 shows an architecture in which a select switch is coupled to a light emitting diode array on a display panel.

[0009] Figure 3 Figure 4 FIG. 3 is a schematic diagram of a display system.

[0010] Figure 5 FIG. 4 is a schematic diagram of a display system according to an embodiment of the present invention.

[0011] Figures 6 to 9 FIG. 5 is a schematic diagram of various pixel structure examples according to an embodiment of the present invention.

[0012] Figure 10 FIG. 6 is a schematic diagram of a display panel showing an image affected by coupling capacitance.

[0013] Figure 11 FIG. 7 is a schematic diagram of a display system according to an embodiment of the present invention.

[0014] Figure 12A Figure 12B FIG. 8 is a schematic diagram of structure examples of an upper data driving device and a lower data driving device.

[0015] In the drawings, the following reference numerals are used:

[0016] 100, C_G, C_B, C_R, C_R1, C_G1, current source

[0017] C_B1, C_R2, C_G2, C_B2, CU_R1,

[0018] CU_G1, CU_B1, CU_R2, CU_G2,

[0019] CU_B2, CD_R1, CD_G1, CD_B1,

[0020] CD_R2, CD_G2, CD_B2, 1202, 1222

[0021] LED1-LED4, LED_G, LED_B, light emitting diode

[0022] LED_R SW, SW_1-SW_N select switch VLED, -VLED power supply voltage Vds drain-to-source voltage Vf turn-on voltage I SW , I G , I B , I R , I current R​​SW Resistive 30, 40, 50, 110 display system

[0023] 300, 400, 500, 1000, 1100 display panel

[0024] 302, 402, 502, 503 data driving device 304, 404, 504, 1118 scan driving device R[1], G[1], B[1], R[2], G[2], B[2], signal line R[3], G[3], B[3], R[4], G[4], B[4]

[0025] S[1]~S[N] scan line SW_R1, SW_G1, SW_B1, SW_R2, control switch SW_G2, SW_B2, 1204, 1224 DRV1, DRV2, 1110 driving circuit GS1 gray scale value 1112 digital controller

[0026] 1114 upper data driving device 1116 lower data driving device 1120 memory

[0027] 1206, 1226 transistor 1208, 1228 operational amplifier NCS1 current source terminal NCS2 current sink terminal DETAILED DESCRIPTION

[0028] For a passive matrix light-emitting diode display panel (PM-LED panel), the driving circuit thereof has a constant current source for outputting current to drive light-emitting diodes (LEDs) on the display panel. Please refer to Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a driving architecture for a passive matrix light-emitting diode display panel, which includes a constant current source 100 connected to a plurality of light-emitting diodes (LED1-LED4), and each light-emitting diode LED1-LED4 is connected to a selection switch SW1-SW4, respectively. Under the control of the selection switches SW1-SW4, each light-emitting diode LED1-LED4 can be driven in time-sharing manner.

[0029] Figure 1 FIG. 2 shows a case where the constant current source is coupled to a column of light-emitting diodes, and each light-emitting diode is further coupled to a selection switch. Each selection switch can be coupled to a row of light-emitting diodes, as Figure 2 shown in the structure. Figure 2A selection switch SW is coupled to an array of light emitting diodes on a display panel. More specifically, the selection switch SW is coupled to M light emitting diode pixels, where each light emitting diode pixel includes a green light emitting diode LED G, a blue light emitting diode LED B, and a red light emitting diode LED R, which are driven by constant current sources C G, C B, and C R, respectively, which can receive a supply voltage V LED and provide a constant output current accordingly.

[0030] In order to reduce the overall power consumption of the light emitting diode driving system, the value of the supply voltage V LED is often required to be as small as possible. However, the supply voltage V LED must still be greater than a level that can allow the light emitting diode display panel to operate normally. As shown, the supply voltage V LED is equal to: Figure 2

[0031] V LED = V ds + V f + I SW × R SW ;

[0032] where V ds is the drain-to-source voltage of the transistors that implement the constant current sources C G, C B, and C R, V f is the forward voltage of each light emitting diode LED G, LED B, and LED R, I SW is the current flowing through the selection switch SW, and R SW is the on-resistance of the selection switch SW. Generally, the value of the drain-to-source voltage V ds should be large enough to provide sufficient headroom for the transistors of the constant current sources C G, C B, and C R to provide a constant current. That is, in order to output a constant current, the transistors must operate in the saturation region and avoid entering the linear region, so their drain-to-source voltage V ds needs to be greater than a certain level.

[0033] However, under the trend of large size and high resolution of display panels, the number of light emitting diode pixels coupled by a selection switch SW gradually increases (i.e., M increases), so that the current I SW through the selection switch SW rises, thereby increasing the required voltage value of the supply voltage V LED. Since the system power consumption is proportional to the size of the supply voltage V LED, the increased supply voltage V LED will result in an increase in power consumption, especially in the application of large size display panels.

[0034] Reference is made to Figure 3 , Figure 3 for a schematic diagram of a display system 30. As shown, Figure 3 ​As shown, the display system 30 includes a display panel 300, a data driving device 302 and a scan driving device 304. The display panel 300 includes an array of light emitting diodes, each of which is coupled to one of the signal lines R[1], G[1], B[1], R[2], G[2], B[2],... and one of the scan lines S[1] ~ S[N]. The signal lines R[1], G[1], B[1], R[2], G[2] and B[2] are coupled to current sources C_R1, C_G1, C_B1, C_R2, C_G2 and C_B2 in the data driving device 302, respectively; and the scan lines S[1] ~ S[N] are coupled to selection switches SW_1 ~ SW_N in the scan driving device 304, respectively.

[0035] The data driving device 302 is used to output display data signals to the light emitting diodes on the display panel 300. In this example, the current sources C_R1, C_G1, C_B1, C_R2, C_G2 and C_B2 in the data driving device 302 are used to output driving currents to drive the light emitting diodes on the display panel 300, which can emit light when receiving the driving currents. The current sources C_R1, C_G1, C_B1, C_R2, C_G2 and C_B2 are coupled to and controlled by control switches SW_R1, SW_G1, SW_B1, SW_R2, SW_G2 and SW_B2, respectively. In each display period, each control switch can be selectively controlled to be on or off, so as to determine whether the current source needs to output current to light up the selected light emitting diode in this display period. The on pulse length of the control switch can be used to determine the brightness of the selected light emitting diode. The light emitting diodes are scanned and selected row by row, as shown in FIG. 2. One row of light emitting diodes is coupled to one of the scan lines S[1] ~ S[N], and the corresponding selection switches SW_1 ~ SW_N are sequentially turned on to scan the light emitting diodes row by row. According to the control of the data driving device 302 and the scan driving device 304, each light emitting diode on the display panel 300 can display the desired brightness, thereby constructing the image to be displayed on each frame. Figure 3

[0036] Figure 3 FIG. 3 shows the case where the first row of light emitting diodes is scanned, in which the selection switch SW_1 is turned on and the other selection switches SW_2 ~ SW_N are turned off. In this case, the currents output by the current sources C_R1, C_G1, C_B1, C_R2, C_G2 and C_B2 will pass through the first row of light emitting diodes to drive the light emitting diodes to emit light. In this example, each pixel can be composed of a red light emitting diode, a green light emitting diode and a blue light emitting diode, but those skilled in the art should understand that the implementation of the light emitting diode pixel is not limited thereto. ​

[0037] It is worth noting that, Figure 3 The embodiments of the present application regarding the light emitting diode pixels are common-cathode structures, in which the cathodes of a row of light emitting diodes are commonly coupled to a scan line. In another embodiment, the light emitting diode pixels can also be connected as common-anode structures, in which the anodes of a row of light emitting diodes are commonly coupled to a scan line, as shown in Figure 4 .

[0038] More specifically, Figure 4 Another display system 40 is shown, which includes a display screen 400, a data driving device 402, and a scan driving device 404. The display screen 400 includes an array of light emitting diodes, which are connected in common-anode form. In detail, the cathode of each light emitting diode is coupled to a signal line, and the anode is coupled to a scan line. The corresponding selection switches SW_1-SW_N in the scan driving device 404 are sequentially turned on to scan the light emitting diodes row by row. The current sources C_R1, C_G1, C_B1, C_R2, C_G2, and C_B2 in the data driving device 402 can be used to provide a sinking current to the turned-on light emitting diodes in each display period, and the brightness of the light emitting diodes can be determined according to the turn-on pulses of the control switches SW_R1, SW_G1, SW_B1, SW_R2, SW_G2, and SW_B2 in the data driving device 402.

[0039] As mentioned above, as the number of light emitting diodes on the display screen increases, each selection switch is responsible for controlling more light emitting diodes, and the selection switch needs to pass more current, so that the power supply voltage received by the current source in the data driving device rises, thereby increasing the overall power consumption of the display system. To solve this problem, the present application proposes a hybrid structure for a light emitting diode display screen, in which common-cathode structures and common-anode structures coexist. For example, a scan line is coupled to the cathodes of some light emitting diodes and the anodes of some light emitting diodes, so that the power supply current and the sinking current can cancel each other out, thereby making the current passing through the selection switch equal to the difference between the power supply current and the sinking current, which is much smaller than Figure 3 or Figure 4 the current passing through the selection switch in the display screen structure, so that the voltage required by the current source can be reduced, thereby reducing the power consumption of the display system.

[0040] Please refer to Figure 5 , Figure 5 which is a schematic diagram of a display system 50 according to an embodiment of the present application. As shown in Figure 5As shown, the display system 50 includes a display panel 500, data drivers 502 and 503, and a scan driver 504. On the display panel 500, light emitting diodes coupled to signal lines R[l], G[l], B[l], R[2], G[2], and B[2] are connected in a common anode fashion, in which the anode of each light emitting diode is connected to a corresponding scan line and the cathode of each light emitting diode is connected to a corresponding signal line. Light emitting diodes coupled to signal lines R[3], G[3], B[3], R[4], G[4], and B[4] are connected in a common cathode fashion, in which the cathode of each light emitting diode is connected to a corresponding scan line and the anode of each light emitting diode is connected to a corresponding signal line.

[0041] For the light emitting diodes connected in the common cathode fashion, a source current can be received from one of the signal lines R[3], G[3], B[3], R[4], G[4], and B[4] by the data driver 502 for light emission; for the light emitting diodes connected in the common anode fashion, a sink current can be output to the data driver 503 by one of the signal lines R[l], G[l], B[l], R[2], G[2], and B[2] for light emission.

[0042] The data drivers 502 and 503 respectively include current sources for providing source currents and sink currents to drive the light emitting diodes on the display panel 500. In detail, the data driver 502 includes current sources CU_Rl, CU_Gl, CU_Bl, CU_R2, CU_G2, and CU_B2, which can be coupled to the display panel 500 through a plurality of current source terminals for outputting driving currents to the light emitting diodes on the display panel 500 through the current source terminals, respectively. Under the common cathode structure of the light emitting diode pixels, the current sources CU_Rl, CU_Gl, CU_Bl, CU_R2, CU_G2, and CU_B2 are coupled to the anodes of the light emitting diodes and the driving currents are output to the anodes of the light emitting diodes. The data driver 503 includes current sources CD_Rl, CD_Gl, CD_Bl, CD_R2, CD_G2, and CD_B2, which can be coupled to the display panel 500 through a plurality of current sink terminals for receiving sink currents from the light emitting diodes on the display panel 500 through the current sink terminals, respectively. Under the common anode structure of the light emitting diode pixels, the current sources CD_Rl, CD_Gl, CD_Bl, CD_R2, CD_G2, and CD_B2 are coupled to the cathodes of the light emitting diodes and the sink currents are from the cathodes of the light emitting diodes. The data drivers 502 and 503 can further include control switchers coupled to the current sources, which are similar to the embodiments of the control switchers described in Figure 3 and Figure 4 and will not be described in detail here.

[0043] The operation of the scan driving device 504 and the selection switches SW_1-SW_N is similar to the above embodiment, i.e., the selection switches SW_1-SW_N are sequentially turned on to scan the light emitting diodes on the display screen 500 row by row.

[0044] In Figure 5 the display screen 500 shown, the anodes of the light emitting diodes with common anode structure and the cathodes of the light emitting diodes with common cathode structure are coupled to the scan lines S[1]-S[N] and the selection switches SW_1-SW_N. More specifically, the anodes of the light emitting diodes with common anode structure and the cathodes of the light emitting diodes with common cathode structure in the same row are coupled to the same selection switch and are driven by the same scan signal. Therefore, the power supply current flowing through some light emitting diodes can flow to other light emitting diodes as a sinking current, which can greatly reduce the current flowing through the selection switches SW_1-SW_N in the scan driving device 504, thereby reducing the power supply voltage value for the current sources and the overall power consumption of the display system 50.

[0045] The common cathode and common anode structures can be arranged in any suitable manner. Please refer to Figure 6 , Figure 6 for more information. Figure 6 Fig. 1 is a schematic diagram of an embodiment of a pixel structure of the present application. As Figure 5 shown, the pixel can be a light emitting diode pixel on a light emitting diode display screen (such as the display screen 500 of Fig. 1) and includes a red light emitting diode LED_R, a green light emitting diode LED_G, and a blue light emitting diode LED_B, which are coupled to current sources C_R, C_G, and C_B in a data driving device through corresponding signal lines and are driven by the current sources C_R, C_G, and C_B, respectively. The current sources C_R, C_G, and C_B can receive a positive power supply voltage VLED or a negative power supply voltage -VLED, respectively, to output constant currents. When the light emitting diodes LED_R, LED_G, and LED_B emit light, the current sources C_R, C_G, and C_B can provide driving currents I R , I G , and I B for the light emitting diodes LED_R, LED_G, and LED_B, respectively. The light emitting diodes LED_R, LED_G, and LED_B are coupled to a selection switch SW in a scan driving device through the same scan line. In this example, the selection switch SW and the scan line are connected to the anode of the red light emitting diode LED_R, the cathode of the green light emitting diode LED_G, and the cathode of the blue light emitting diode LED_B.

[0046] As Figure 6As shown, the LED display screen can include M pixels in the same row and coupled to the same select switch SW, each of which has the same structure. In a display period, assuming that each LED in the row is lit by driving a corresponding current, the current I SW flowing through the select switch SW is equal to (I G + I B + I R ) x M. Note that the luminous efficiency of green LEDs and blue LEDs is generally greater than that of red LEDs, so more current is often required for a red LED to achieve the same brightness as a green or blue LED. In this case, the sum of the drive current I G for the green LED LED G and the drive current I B for the blue LED LED B minus the drive current I R for the red LED LED R can reach a very low value, so that the current flowing through the select switch SW is very small, and thus has a low voltage drop.

[0047] For comparison, please refer to Figure 6 and Figure 2 . In the pixel structure of Figure 2 , the LEDs LED R, LED G and LED B are connected in a common cathode manner, i.e., the cathodes of each LED LED R, LED G and LED B are commonly coupled to the select switch SW. In this case, when all the LEDs coupled to the select switch SW are turned on, the current I SW flowing through the select switch SW is equal to (I R + I G + I B ) x M. As the number of LED pixels coupled to the select switch SW increases (i.e., M increases), the current I SW also increases proportionally, thereby increasing the value requirement of the power supply voltage VLED and simultaneously increasing power consumption. In contrast, in the present application, the LED pixels can be connected in a structure as shown in Figure 6 , i.e., the cathode of the green LED LED G, the cathode of the blue LED LED B, and the anode of the red LED LED R are commonly coupled to the select switch SW. When all the LEDs coupled to the select switch SW are turned on, the current I SW flowing through the select switch SW is equal to (I G + I B - I R ) x M. In this case, the current I SWThe current I SW of the selection switch SW can be greatly reduced, and thus the cross voltage of the selection switch SW can be reduced. As a result, the values of the power supply voltages VLED and -VLED can be correspondingly reduced, and thus the power consumption of the display system can be reduced.

[0048] It is worth noting that, Figure 6 The pixel structure shown is only one of the many embodiments of the present application. Based on the combination of the common cathode structure and the common anode structure, there are many possible pixel structures that can make the current I SW of the selection switch SW drop. Figure 7 , Figure 8 and Figure 9 are shown as examples.

[0049] More specifically, Figure 7 A pixel structure is shown in which the cathode of the red light emitting diode LED_R, the anode of the green light emitting diode LED_G, and the anode of the blue light emitting diode LED_B in a pixel are coupled to the scan line and the selection switch SW. Assuming that the selection switch SW is coupled to M pixels, the current I SW of the selection switch SW is equal to (I R -I G -I B ) x M, and in the case that the currents of the light emitting diodes of different colors cancel each other out, the current I SW of the selection switch SW is a very small value.

[0050] Figure 8 A pixel structure is shown in which M pixels are arranged as shown in Figure 6 and N pixels are arranged as shown in Figure 7 . Through such an embodiment, if M and N are approximately equal, the current I SW of the selection switch SW will tend to be 0.

[0051] Figure 9 Another pixel structure is shown in which M pixels have the common cathode structure and N pixels have the common anode structure. Through such an embodiment, if M and N are approximately equal, the current I SW of the selection switch SW will also tend to be 0.

[0052] In addition to reducing the power consumption of the display system, the pixel structure of the present application also has the benefit of improving the image quality. Generally speaking, on a light emitting diode display screen, the light emitting diode array is controlled by the signal line and the scan line, and each light emitting diode includes a parasitic capacitance coupled between the corresponding signal line and the corresponding scan line. The parasitic capacitance will couple the driving signal on the signal line to the floating scan line, and the voltage change on the floating scan line will further be coupled back to the signal line, affecting the signal transition.

[0053] Please refer back to Figure 3 and Figure 4 . As shown in Figure 3 , when the selection switch SW_1 is turned on to scan the first row of LEDs, the other selection switches SW_2 ~ SW_N are turned off, leaving the other scan lines S[2] ~ S[N] floating. In this case, the rising pulse on the signal line will raise the voltage of the floating scan lines S[2] ~ S[N] through the coupling of the parasitic capacitance. Since a row of LEDs is commonly coupled to a scan line, the pulse signal on all the signal lines can provide coupling effect to raise the voltage of the floating scan lines S[2] ~ S[N]. The raised voltage on the floating scan lines S[2] ~ S[N] is coupled back to the signal line, increasing the transition speed of the pulse, thus affecting the pulse width and changing the brightness of the LEDs. Similarly, as shown in Figure 4 , when the selection switch SW_1 is turned on to scan the first row of LEDs, the other selection switches SW_2 ~ SW_N are turned off, leaving the other scan lines S[2] ~ S[N] floating. In this case, the falling pulse on the signal line will lower the voltage of the floating scan lines S[2] ~ S[N] through the coupling of the parasitic capacitance. Since a row of LEDs is commonly coupled to a scan line, the pulse signal on all the signal lines can provide coupling effect to lower the voltage of the floating scan lines S[2] ~ S[N]. The lowered voltage on the floating scan lines S[2] ~ S[N] is coupled back to the signal line, increasing the transition speed of the pulse, thus affecting the pulse width and changing the brightness of the LEDs. Under the trend of large size and high resolution of display screens, the number of LED pixels coupled to each scan line continues to increase, making the effect of coupling capacitance more serious, resulting in obvious inconsistency in the displayed image.

[0054] For example, please refer to Figure 10 , Figure 10 is a schematic diagram of the image displayed on a display screen 1000 affected by coupling capacitance. As shown in Figure 10 , the display screen 1000 can include two parts, where a first part (e.g. the left half) is controlled by a driving circuit DRV1 and a second part (e.g. the right half) is controlled by another driving circuit DRV2. In an embodiment, the display screen 1000 can be a split screen, where each part has its corresponding signal line and scan line driven by the respective driving circuit.

[0055] Assume that in an image frame, the first portion of display screen 1000 is intended to display the same grayscale, and a drive signal corresponding to a grayscale value GS1 is output to all signal lines coupled to driver circuit DRV1. In the same image frame, a portion of the second portion of display screen 1000 displays the same grayscale while the rest of the portion is black. Therefore, driver circuit DRV2 may output the drive signal corresponding to the same grayscale value GS1 to some signal lines, while not outputting the drive signal to other signal lines.

[0056] like Figure 10 As shown, although the left and right halves of the display screen 1000 are intended to display images of the same grayscale, they exhibit different brightness. In the left half controlled by the driving circuit DRV1, all light-emitting diodes are illuminated by the pulses of the driving signal, and the signal pulses on all signal lines can generate a strong ability to raise the voltage on the floating scan line. This rising voltage is then coupled back to the signal line to increase the rising speed of the signal pulse, thereby driving the light-emitting diodes to produce a higher brightness. In contrast, in the right half controlled by the driving circuit DRV2, the number of light-emitting diodes illuminated by the pulses of the driving signal is smaller, so the rising amplitude of the floating scan line is lower. Correspondingly, the amplitude of the increase in the signal pulse speed caused by its coupling effect is also smaller, thereby driving the light-emitting diodes in the right half to produce a lower brightness than the light-emitting diodes in the left half.

[0057] The combination of common cathode and common anode structures on the display helps solve the brightness difference problem caused by parasitic capacitance coupling. Figure 5 , the display screen 500 includes a structure in which common cathodes and common anodes of light-emitting diode pixels coexist. In the common cathode portion, the cathodes of the light-emitting diodes are commonly coupled to the scan lines, so that the signal pulses form a rising coupling effect on the floating scan lines S[2]~S[N]; in the common anode portion, the anodes of the light-emitting diodes are commonly coupled to the scan lines, so that the signal pulses form a falling coupling effect on the floating scan lines S[2]~S[N]. Since each scan line receives rising coupling and falling coupling at the same time, these two coupling effects can offset each other, so that the voltage change on the floating scan lines S[2]~S[N] is minimized. In this way, the impact of capacitive coupling on the transient behavior of the signal pulse can also be minimized, thereby improving the consistency of the displayed brightness and improving the image quality.

[0058] Please refer to Figure 11 , Figure 11 FIG. 1 is a schematic diagram of a display system 110 according to an embodiment of the present invention. Figure 11As shown, the display system 110 includes a display panel 1100 and a driving circuit 1110. The display panel 1100 can be a light emitting diode display panel composed of an array of light emitting diodes. The driving circuit 1110 can be used to control and drive the display panel 1100, and includes a digital controller 1112, an upper data driver 1114, a lower data driver 1116, and a scan driver 1118. A memory 1120 can be included in the driving circuit 1110 or independent of the driving circuit 1110, which is also shown in Figure 11 for convenience of explanation. The driving circuit 1110 can be implemented in an integrated circuit (IC), which can be included in a chip or a combination of chips.

[0059] In detail, on the display panel 1100, each light emitting diode is coupled to a signal line and a scan line. The light emitting diode can be coupled to the upper data driver 1114 and the lower data driver 1116 through the signal line, and coupled to the scan driver 1118 through the scan line. For a light emitting diode with a common cathode structure, the anode is coupled to the upper data driver 1114 through the signal line, and the cathode is coupled to the scan driver 1118 through the scan line. For a light emitting diode with a common anode structure, the cathode is coupled to the lower data driver 1116 through the signal line, and the anode is coupled to the scan driver 1118 through the scan line.

[0060] The scan driver 1118 sequentially scans the light emitting diodes on the display panel 1100 row by row, and the upper data driver 1114 and the lower data driver 1116 can provide a constant driving current to the scanned light emitting diodes. The scan driver 1118 can be composed of a plurality of selection switchers to achieve the scanning operation. The upper data driver 1114 includes a plurality of current sources to provide the power current required by the display panel 1100; the lower data driver 1116 includes a plurality of current sources to provide the sinking current required by the display panel 1100. The detailed operation of the upper data driver 1114, the lower data driver 1116, and the scan driver 1118 can refer to the description of the above paragraphs, which will not be repeated here.

[0061] The digital controller 1112 can be used to control the operations of the upper data driving device 1114, the lower data driving device 1116 and the scan driving device 1118. In one embodiment, the digital controller 1112 can be a timing controller used to control and synchronize the timing of the upper data driving device 1114, the lower data driving device 1116 and the scan driving device 1118. The digital controller 1112 is also coupled to a memory 1120, such as a Static Random Access Memory (SRAM), in which display data can be stored and then output to the upper data driving device 1114 or the lower data driving device 1116 at appropriate time points under the control of the digital controller 1112.

[0062] Referring to Figure 12A and 12B , Figure 12A and 12B are schematic diagrams showing the detailed structures of one channel of the upper data driving device 1114 and the lower data driving device 1116. Figure 12A The detailed structure of one channel of the upper data driving device 1114 is shown, which includes a current source 1202 and a control switcher 1204. In this example, the upper data driving device 1114 can be coupled to the display panel through a current source terminal NCS1, while the control switcher 1204 is coupled between the current source 1202 and the current source terminal NCS1.

[0063] In detail, the control switcher 1204 includes a transistor 1206 and an operational amplifier (op-amp) 1208. The transistor 1206 can be used as a switching component, while the op-amp 1208 is coupled between the gate terminal and the source terminal of the transistor 1206 to establish a feedback path. In order to control the current source 1202 to output a constant current, the output terminal of the current source 1202 should be locked at a constant voltage level, which can be achieved by the feedback-connected op-amp 1208. Therefore, by controlling the control switcher 1204, a current pulse with a constant current value I can be generated at the current source terminal NCS1 to be output to the display panel.

[0064] Similarly, Figure 12BThe detailed structure of one channel of the lower data driver 1116 is shown, which includes a current source 1222 and a control switcher 1224. In this example, the lower data driver 1116 can be coupled to the display panel through a current sink end NCS2, and the control switcher 1224 is coupled between the current source 1222 and the current sink end NCS2. Similarly, the control switcher 1224 includes a transistor 1226 and an operational amplifier 1228. The detailed operation of the control switcher 1224 is similar to the aforementioned control switcher 1204, in which a current pulse with a constant current value I output by the display panel can be generated at the current sink end NCS2 by controlling the control switcher 1224.

[0065] It is worth noting that, Figure 12A and 12B Only the structure of one channel of the upper data driver 1114 and the lower data driver 1116 is shown. In fact, the upper data driver 1114 and the lower data driver 1116 can include a large number of channels with the structure as shown in FIG. 12A and FIG. 12B to be coupled to a plurality of signal lines on the display panel. Figure 12A and 12B It is worth noting that,

[0066] It is also worth noting that the purpose of the present application is to propose a novel structure of display panel and driving circuit. Those skilled in the art can modify or change accordingly without being limited thereto. For example, the LED display panel structure of the present application is a mixed structure of common cathode and common anode, and the two embodiments can coexist by any and suitable means. As long as the display panel includes a first LED whose anode is connected to a signal line and whose cathode is connected to a scan line, and a second LED whose anode is connected to the same scan line and whose cathode is connected to another signal line, the related embodiments should belong to the scope of the present application. Correspondingly, the driving circuit of the present application has a source-end data driver and a sink-end data driver, wherein the source-end data driver includes one or more current sources for outputting current to the LED display panel, and the sink-end data driver includes one or more current sources for receiving current from the LED display panel.

[0067] The embodiments of the present application can be applied to various types of display panels that emit light by lighting LEDs, in particular, a passive matrix LED panel (PM-LED panel). Examples of such display panels include a mini-LED panel and a micro-LED panel, but are not limited thereto.

[0068] In summary, the present application proposes a novel structure of light emitting diode display screen, in which light emitting diodes with common cathode structure and light emitting diodes with common anode structure coexist on the display screen. The common cathode structure is that the anode of the light emitting diode is coupled to the signal line while the cathode of the light emitting diode is coupled to the scanning line. The common anode structure is that the anode of the light emitting diode is coupled to the scanning line while the cathode of the light emitting diode is coupled to the signal line. The driving circuit for driving the light emitting diode display screen includes an upper data driving device, a lower data driving device, and a scanning driving device. The upper data driving device (or power terminal data driving device) includes a current source for outputting current to the light emitting diode display screen; while the lower data driving device (or sinking terminal data driving device) includes a current source for receiving current from the light emitting diode display screen. The scanning driving device includes a selection switch for sequentially scanning the light emitting diodes row by row.

[0069] In the present application, a scanning line is coupled to the cathode of the light emitting diode with common cathode structure and the anode of the light emitting diode with common anode structure on the display screen. Therefore, the power supply current from the light emitting diode with common cathode structure and the sinking current flowing to the light emitting diode with common anode structure can offset each other, so as to minimize the cross voltage of the selection switch in the scanning driving device. The reduced cross voltage of the selection switch can reduce the value of the required power supply voltage, thereby reducing the power consumption of the display system. On the other hand, there is a parasitic capacitance coupling of the light emitting diode on the light emitting diode display screen. In the display screen structure in which the light emitting diode with common cathode structure and the light emitting diode with common anode structure coexist, the rising coupling effect generated by the light emitting diode with common cathode structure and the falling coupling effect generated by the light emitting diode with common anode structure can offset each other, so as to minimize the voltage variation on the floating scanning line caused by the capacitance coupling. In this way, the influence of the transient behavior of the signal pulse can also be minimized, thereby improving the consistency of the displayed brightness and improving the picture quality.

[0070] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A driving circuit for a light emitting diode display screen, characterized in that: The LED display screen has a plurality of LEDs, including a first LED and a second LED. The anode of the first LED is coupled to a first signal line, the cathode of the first LED is coupled to a scan line, the anode of the second LED is coupled to the scan line, and the cathode of the second LED is coupled to a second signal line. The first signal line is not physically connected to the cathode of any of the plurality of LEDs, and the second signal line is not physically connected to the anode of any of the plurality of LEDs. The driving circuit includes: a first current source coupled to the first signal line of the LED display screen, for outputting a first current to the LED display screen through the first signal line; and A second current source is coupled to the second signal line of the LED display screen and is used for receiving a second current from the LED display screen through the second signal line.

2. The driving circuit according to claim 1, wherein: The first current source is configured to be coupled to the anode of the first light emitting diode on the light emitting diode display screen, and the second current source is configured to be coupled to the cathode of the second light emitting diode on the light emitting diode display screen.

3. The driving circuit according to claim 1, wherein: The first current source is used to output the first current to the anode of the first light emitting diode, and the second current source is used to receive the second current from the cathode of the second light emitting diode.

4. The driving circuit according to claim 1, wherein: Also includes: a first control switch coupled between the first current source and the first signal line; as well as A second control switch is coupled between the second current source and the second signal line.

5. The driving circuit according to claim 1, wherein: Also includes: A selection switch is configured to be coupled to the cathode of the first LED on the LED display screen and the anode of the second LED on the LED display screen.

6. A light emitting diode display screen, characterized in that: A plurality of light emitting diodes are provided, the plurality of light emitting diodes comprising: A first light emitting diode, comprising: an anode coupled to a first signal line; and a cathode coupled to a scan line; and a second light emitting diode, comprising: an anode coupled to the scan line; and a cathode coupled to a second signal line; The first signal line is not physically connected to the cathode of any of the plurality of light-emitting diodes, and the second signal line is not physically connected to the anode of any of the plurality of light-emitting diodes.

7. The light emitting diode display screen according to claim 6, wherein: The first light emitting diode is used to receive a power current from a driving circuit through the first signal line, and the second light emitting diode is used to output a sink current to the driving circuit through the second signal line.

8. The light emitting diode display screen according to claim 7, wherein: The first light emitting diode and the second light emitting diode are used for receiving a scanning signal from the driving circuit through the scanning line.

9. The light emitting diode display screen according to claim 6, wherein: The first light emitting diode is a red light emitting diode of a pixel, the second light emitting diode is a green light emitting diode of the pixel, and the pixel further includes: A blue LED, including: an anode coupled to the scan line; and A cathode is coupled to a third signal line.

10. The light emitting diode display screen according to claim 6, wherein: The first light emitting diode is a green light emitting diode of a pixel, the second light emitting diode is a red light emitting diode of the pixel, and the pixel further includes: A blue LED, including: an anode coupled to a third signal line; and A cathode is coupled to the scan line.

Images