Pixel circuit and display panel

This application claims the priority benefit of Taiwan application serial no. 113149564, filed on Dec. 19, 2024. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

The invention relates to a pixel circuit and a display panel, and in particular to a pixel circuit and a display panel that may improve display quality.

In an electronic presentation system, the presentation content is displayed via a display panel, and the presenter may send a light signal to the display panel via a laser pen to guide the participants on the content to be explained.

In prior art, a display panel generally has a relatively low light reflectivity. Therefore, when a light signal is emitted to the display panel via the laser pen, the laser pen may not generate a clear light spot on the display panel, causing difficulty for the participants to watch.

The invention provides a pixel circuit and a display panel that may perform picture display and light signal detection.

A pixel circuit of the invention includes a driving circuit, a selection circuit, a light-emitting element, and a signal processor. The driving circuit is coupled to a power supply voltage and controlled by a data signal. The selection circuit is turned on or off according to a mode of the pixel circuit. The light-emitting element is coupled between the driving circuit and the selection circuit, and generates a sensing signal by sensing a luminance of a light signal in a light-sensing mode. The signal processor is coupled to the light-emitting element and generates light sensing information according to the sensing signal and a reference voltage.

A display panel of the invention includes a plurality of the pixel circuit above. The pixel circuits are arranged as a pixel array.

Based on the above, the pixel circuit of the invention may be operated in a display mode and a light-sensing mode. In the light-sensing mode, the light-emitting element generates a sensing signal by sensing the luminance of the light signal. The signal processor may generate light sensing information according to the sensing signal and a reference voltage. Thus, the display panel of the invention may receive a light signal to input information, and accordingly adjust the display luminance of the corresponding area to improve display quality.

FIG. 1 shows a schematic diagram of a pixel circuit of an embodiment of the invention.

FIG. 2 shows a schematic diagram of a pixel circuit of another embodiment of the invention.

FIG. 3 shows a schematic diagram of a pixel circuit of another embodiment of the invention.

FIG. 4 shows a schematic diagram of a display panel of an embodiment of the invention.

FIG. 5 A shows a schematic diagram of a display panel of an embodiment of the invention.

FIG. 5 B is an operation waveform diagram of a display panel of an embodiment of the invention.

FIG. 6 A and FIG. 6 B respectively show schematic diagrams of display panels of different embodiments of the invention.

FIG. 7 shows a schematic diagram of an application example of a display panel of an embodiment of the invention.

FIG. 8 A and FIG. 8 B show schematic diagrams of different application examples of a display panel of an embodiment of the invention.

FIG. 9 shows a schematic diagram of a display panel of another embodiment of the invention.

Referring to FIG. 1 , FIG. 1 shows a schematic diagram of a pixel circuit of an embodiment of the invention. A pixel circuit 100 includes a driving circuit 110 , a selection circuit 120 , a light-emitting element 130 , and a signal processor 140 . The driving circuit 110 is coupled to a power supply voltage ELVDD and controlled by a data signal DA 1 . The driving circuit 110 may receive the data signal DA 1 according to a scan signal, and turn the connection state between the light-emitting element 110 and the power supply voltage ELVDD on or off according to the data signal DA 1 .

The selection circuit 120 is coupled between the light-emitting element 130 and a reference ground voltage ELVSS. The selection circuit 120 turns the connection state between the light-emitting element 130 and the reference ground voltage ELVSS on or off according to the operation mode of the pixel circuit 100 . In particular, in the present embodiment, the operation mode of the pixel circuit 100 includes a light-sensing mode and a light-emitting mode. In the light-sensing mode, the selection circuit 120 may turn off the connection state between the light-emitting element 130 and the reference ground voltage ELVSS according to a selection signal SS 1 . In the light-emitting mode, the selection circuit 120 may turn on the connection state between the light-emitting element 130 and the reference ground voltage ELVSS according to the selection signal SS 1 .

The light-emitting element 130 is coupled between the driving circuit 110 and the selection circuit 120 . The light-emitting element 130 generates a display light beam in the display mode. The light-emitting element 130 is used to sense an external light signal in the light-sensing mode, and generate a sensing signal SLD according to the intensity of the sensed light signal.

The signal processor 140 is coupled to the light-emitting element 130 . The signal processor 140 generates light sensing information VSO according to the sensing signal SLD and a reference voltage VREF.

Referring to FIG. 2 below, FIG. 2 shows a schematic diagram of a pixel circuit of another embodiment of the invention. A pixel circuit 200 includes a driving circuit 210 , a selection circuit 220 , a light-emitting element 230 , a signal processor 240 , and a current-to-voltage converter 250 . In the present embodiment, the driving circuit 210 is coupled to the anode of the light-emitting element 230 . The driving circuit 210 includes switches SW 1 and SW 3 . The switches SW 1 and SW 3 are both transistor switches, wherein the switch SW 1 is coupled between the power supply voltage ELVDD and the light-emitting element 230 , and the control terminal of the switch SW 1 is coupled to one end of the switch SW 3 . Another end of the switch SW 3 receives the data signal DA 1 , and the control terminal of the switch SW 3 receives a scan signal GS 1 . The switch SW 3 may be turned on or off according to the scan signal GS 1 . When the switch SW 3 is turned on, the data signal DA 1 may be transmitted to the control terminal of the switch SW 1 via the switch SW 3 . In the light-emitting mode, the data signal DA 1 corresponds to the display grayscale value and controls the light-emitting element 230 to receive the corresponding driving current to generate the corresponding luminance. In the light-sensing mode, the data signal DA 1 may drive the switch SW 1 to be turned on and provide a current loop of the light-emitting element 230 .

The selection circuit 220 includes a switch SW 2 . The switch SW 2 may also be a transistor switch. The switch SW 2 is coupled between the light-emitting element 230 and the reference ground voltage ELVSS, and controlled by the selection signal SS 1 . The switch SW 2 may be turned on in the light-emitting mode and turned off in the light-sensing mode.

In the present embodiment, the light-emitting element 230 may be a micro light-emitting diode, and the maximum width thereof is between 1 micrometer and 50 micrometers. Micron-sized light-emitting diodes may be densely integrated into display pixels. In particular, the anode of the light-emitting element 230 is coupled to the switch SW 1 , and the cathode of the light-emitting element 230 is coupled to the switch SW 2 . In particular, in the light-emitting mode, via the turned-on switches SW 1 to SW 3 , the light-emitting element 230 may generate a display light beam based on the display grayscale value corresponding to the data signal DA 1 . In the light-sensing mode, the light-emitting element 230 may receive an external light signal and generate a sensing signal ILD by sensing the light intensity of the light signal. In the present embodiment, the sensing signal ILD may be a current signal.

The current-to-voltage converter 250 is coupled to the cathode of the light-emitting element 230 and also coupled to the reference ground terminal VSS. The current-to-voltage converter 250 may receive the sensing signal ILD as a current signal, and convert the sensing signal ILD into the sensing signal SLD as a voltage signal. The current-to-voltage converter 250 is a resistor RA. In particular, the sensing signal ILD flows through the resistor RA and generates the sensing signal SLD at a coupling node of the resistor RA and the light-emitting element 230 .

In the present embodiment, the reference ground voltages ELVSS and VSS may have the same or different voltage values.

In the present embodiment, the signal processor 240 is coupled to the cathode of the light-emitting element 230 to receive the sensing signal SLD. The signal processor 240 includes an operational amplifier OPA and a feedback circuit 241 . The positive input terminal of the operational amplifier OPA receives the sensing signal SLD; the negative input terminal of the operational amplifier OPA receives the reference voltage VREF generated by the feedback circuit 241 . In particular, the feedback circuit 241 includes resistors R 1 and R 2 coupled in series. The resistor R 1 is coupled between an input voltage VIN 1 and the negative input terminal of the operational amplifier OPA, and the resistor R 2 is coupled between the resistor R 1 and the output terminal of the operational amplifier OPA. The resistors R 1 and R 2 may generate the reference voltage VREF at the negative input terminal of the operational amplifier OPA according to the input voltage VIN and the output voltage of the operational amplifier OPA. The signal processor 240 is used for amplifying the sensing signal SLD to generate the light sensing information VSO.

Incidentally, the operational amplifier OPA receives a power supply voltage +VCC as a positive voltage and a power supply voltage −VCC as a negative voltage as the operating power supply. In the present embodiment, the voltage value of the light sensing information VSO may be between the power supply voltages +VCC and −VCC. In addition, the switches SW 1 to SW 3 in the present embodiment may be constructed using any different types of transistors without any specific limitation.

Referring to FIG. 3 below, FIG. 3 shows a schematic diagram of a pixel circuit of another embodiment of the invention. A pixel circuit 300 includes a driving circuit 310 , a selection circuit 320 , a light-emitting element 330 , and a signal processor 340 . In the present embodiment, the driving circuit 310 includes the switches SW 1 and SW 3 , and the selection circuit 320 includes the switch SW 2 . The driving circuit 310 , the selection circuit 320 , and the light-emitting element 330 have the same circuit configuration as the driving circuit 210 , the selection circuit 220 , and the light-emitting element 230 of the embodiment of FIG. 2 , and thus are not described again.

Different from the above embodiments, in the present embodiment, in the light-sensing mode, the light-emitting element 330 may generate the sensing signal SLD in the form of a voltage at the anode thereof by sensing the intensity of an external light signal. The signal processor 340 is coupled to the cathode of the light-emitting element 330 and receives the sensing signal SLD. The signal processor 340 includes a comparator CMP 1 and a reference voltage generator 341 . The negative input terminal of the comparator CMP 1 may be coupled to the cathode of the light-emitting element 330 and receive the sensing signal SLD; and the positive input terminal of the comparator CMP 1 may receive the reference voltage VREF. The reference voltage generator 341 receives a voltage VCC and is coupled to the output terminal of the comparator CMP 1 and the positive input terminal thereof. The reference voltage generator 341 generates the reference voltage VREF according to the voltage VCC and the output voltage of the comparator CMP.

The comparator CMP 1 may be implemented using an operational amplifier. The comparator CMP 1 receives the power supply voltage +VCC and the reference ground voltage VSS as the operating power supply. In particular, the reference ground voltage VSS may be a voltage of 0 volts. In the present embodiment, the signal processor 340 may generate the light sensing information VSO of logic value of 0 or 1, for example.

The reference voltage generator 341 includes resistors R 3 and R 4 . One end of the resistor R 3 receives the voltage VCC, and another end of the resistor R 3 is coupled to the positive input terminal of the comparator CMP 1 to generate the reference voltage VREF. The resistor R 4 is coupled between the resistor R 3 and the output terminal of the comparator CMP 1 . In the present embodiment, when the reference voltage VREF is greater than the sensing signal SLD, the signal processor 340 may generate the light sensing information VSO of logic value 1; correspondingly, when the reference voltage VREF is not greater than the sensing signal SLD, the signal processor 340 may generate the light sensing information VSO of logic value 0.

Referring to FIG. 4 below, FIG. 4 shows a schematic diagram of a display panel of an embodiment of the invention. A display panel 400 includes a plurality of pixel circuits 401 and 402 . In the present embodiment, the pixel circuits 401 and 402 are disposed on the same display column. The pixel circuit 401 includes a driving circuit 411 , a light-emitting element 413 , a selection circuit 412 , a signal processor 440 , and a current-to-voltage converter 450 . The pixel circuit 402 includes a driving circuit 421 , a light-emitting element 423 , a selection circuit 412 , a signal processor 440 , and a current-to-voltage converter 450 . In particular, the pixel circuits 401 and 402 share the same selection circuit 412 , signal processor 440 , and current-to-voltage converter 450 .

In the present embodiment, the driving circuit 411 includes switches SW 11 and SW 31 , and the driving circuit 421 includes switches SW 12 and SW 32 . The switches SW 31 and SW 32 are controlled by the scan signals GS 1 and GS 2 respectively. The scan signals GS 1 and GS 2 may be enabled in different first time interval and second time interval, respectively, and the data signals DA 1 and DA 2 may be transmitted to the light-emitting elements 413 and 423 in the first time interval and the second time interval, respectively. In the light-emitting mode, the shared selection circuit 412 may be turned on according to the selection signal SS in the first time interval and the second time interval. In this way, the light-emitting elements 413 and 423 may emit light according to the data signals DA 1 and DA 2 respectively in a time-sharing manner. In the light-sensing mode, the shared selection circuit 412 may be turned off according to the selection signal SS in the first time interval and the second time interval. The light-emitting element 413 may cooperate with the current-to-voltage converter 450 to generate a sensing signal SLD 1 in the first time interval according to the sensing light signal. The light-emitting element 423 may cooperate with the current-to-voltage converter 450 to generate another sensing signal SLD 2 in the second time interval according to the sensing light signal.

The signal processor 440 may receive the sensing signals SLD 1 and SLD 2 in a time-sharing manner, and perform a signal processing operation on the sensing signals SLD 1 and SLD 2 to generate the light signal sensing information VSO.

In the present embodiment, the circuit configuration and the operation details of the current-to-voltage converter 450 and the signal processor 440 are similar to those of the current-to-voltage converter 250 and the signal processor 240 of the above embodiments, and are not further described herein.

It is worth mentioning that, in the present embodiment, the display panel 400 may include a plurality of pixel circuits arranged in a pixel array. The two pixel circuits 401 and 402 shown in the figures are merely examples for illustration and are not intended to limit the scope of implementation of the invention. Moreover, the plurality of pixel circuits 401 and 402 in the same display column may be implemented by sharing the selection circuit 412 , the signal processor 440 , and the current-to-voltage converter 450 as shown in the figures to save circuit area. Or, in other embodiments of the invention, the method may be implemented by only sharing a portion of the selection circuit 412 , the signal processor 440 , and the current-voltage converter 450 , or not sharing the selection circuit 412 , the signal processor 440 , and the current-voltage converter 450 at all, and there are no specific restrictions.

Referring to FIG. 5 A below, FIG. 5 A shows a schematic diagram of a display panel of an embodiment of the invention. A display panel 500 includes a plurality of pixel circuits P 11 to P 22 and a controller 530 . The pixel circuits P 11 to P 22 are arranged in a pixel array, wherein the pixel circuits P 11 and P 21 are arranged in the same first display column, and the pixel circuits P 12 and P 22 are arranged in the same second display column; the pixel circuits P 11 and P 12 are arranged in the same first display row, and the pixel circuits P 21 and P 22 are arranged in the same second display row.

In the present embodiment, the pixel circuits P 11 and P 21 may share the same selection circuit 511 , current-to-voltage converter 512 , and signal processor 513 . The pixel circuits P 12 and P 22 may share the same selection circuit 521 , current-to-voltage converter 522 , and signal processor 523 . In addition, the pixel circuits P 11 and P 12 receive the same scan signal GS 1 , and the pixel circuits P 21 and P 22 receive the same scan signal GS 2 .

The controller 530 is coupled to the signal processors 513 and 523 and used for receiving light sensing information VSO 1 and VSO 2 generated by the signal processors 513 and 523 to obtain the position on the touch panel 500 irradiated by the external light signal. Correspondingly, the controller 510 may generate corresponding data signals DA 1 to DA 4 according to the light sensing information VSO 1 and VSO 2 , and transmit the data signals DA 1 to DA 4 to the pixel circuits P 11 to P 22 irradiated by the external light signal. In the display mode, the pixel circuits P 11 to P 22 irradiated by the external light signal are made to display at high luminance, for example, and the correspondingly illuminated light-emitting elements are adjusted.

For details of the operation of the display panel 500 , reference may be made to the operation waveform diagram of the display panel of the embodiment of the invention of FIG. 5 B . In FIG. 5 B , the scan signal GS 1 may be first enabled (pulled up to a relatively high voltage value) to drive the pixel circuits P 11 and P 12 to perform a data writing operation. At the same time, the data signal DA 1 may be written into the pixel circuits P 11 and P 12 . After the data writing operation of the pixel circuits P 11 and P 12 is completed, while the scan signal GS 1 is still enabled, the selection signal SS 1 may be enabled, and the switch in the selection circuit 511 shared by the pixel circuits P 11 and P 21 is turned off to enter the light-sensing mode. The current-to-voltage converter 512 and the signal processor 513 correspondingly execute related actions in the light-sensing mode.

Next, the scan signal GS 2 may be first enabled (pulled up to a relatively high voltage value) to drive the pixel circuits P 21 and P 22 to perform a data writing operation. At the same time, the data signal DA 2 may be written into the pixel circuits P 21 and P 22 . After the data writing operation of the pixel circuits P 21 and P 22 is completed, while the scan signal GS 2 is still enabled, the selection signal SS 2 may be enabled, and the switch in the selection circuit 521 shared by the pixel circuits P 21 and P 22 is turned off to enter the light-sensing mode. The current-to-voltage converter 522 and the signal processor 523 correspondingly execute related actions in the light-sensing mode.

Referring to FIG. 6 A and FIG. 6 B below, FIG. 6 A and FIG. 6 B respectively show schematic diagrams of display panels of different embodiments of the invention. In FIG. 6 A , a display panel 601 includes a plurality of pixel circuits P 11 to PNM. The pixel circuits P 11 to PNM are arranged into a pixel array. In particular, the pixel circuits P 11 to P 1 M receive the scan signal GS 1 , and the pixel circuits PN 1 to PNM receive the scan signal GS 2 . In the present embodiment, the pixel array may be divided into a plurality of pixel partitions GP 1 and GP 2 . The pixel circuits P 11 to PN 2 in the pixel partition GP 1 may share the same selection circuit SC 1 and signal processor 611 . Pixel circuits PN(M−1) to PNNM in the pixel partition GP 2 may share the same selection circuit SC 2 and signal processor 612 .

Each of the pixel circuits P 11 to PNM may be implemented by applying each of the pixel circuits of the above plurality of embodiments.

Incidentally, in the present embodiment, there is no specific limit on the number of pixel partitions divided in the display panel 601 , and there is also no specific limit on the number of pixel circuits in each of the pixel partitions. Designers may set the pixel partitions and the number of pixel circuits in each of the pixel partitions according to actual needs.

In FIG. 6 B , the display panel 601 includes the plurality of pixel circuits P 11 to PNM. The pixel circuits P 11 to PNM may be all of the pixel circuits on the display panel 601 , or pixel circuits in one pixel partition of the display panel 601 . The pixel circuits P 11 to PNM are arranged in an array, wherein the pixel circuits P 11 to P 1 M receive the same scan signal GS 1 , and the pixel circuits PN 1 to PNM receive the same scan signal GS 2 .

It is worth noting that, in the present embodiment, the display panel 602 further includes a multiplexer MUX. In particular, the pixel circuits P 11 to P 1 M of the present embodiment share a same signal processor 630 . The multiplexer MUX is coupled between the pixel circuits P 11 to P 1 M and the signal processor 630 . The multiplexer MUX may select each sensing signal generated by the pixel circuits P 11 to P 1 M in a time-sharing manner to transmit the sensing signal to the signal processor 630 , and enable the signal processor 630 to generate corresponding light sensing information in a time-sharing manner.

Referring to FIG. 7 below, FIG. 7 shows a schematic diagram of an application example of a display panel of an embodiment of the invention. In FIG. 7 , a laser device LSR may be used to generate a light signal, wherein the laser device LSR may be a laser pen having better collimation and emits the light signal to an area A 1 on a display panel 710 . On the display panel 710 , there are a plurality of pixel circuits R, G, B including light-emitting elements emitting red light, blue light, and green light to form a pixel array. During the light sensing period, the pixel circuits R, G, and B in the area A 1 sense the intensity of the light signal and may know the area A 1 irradiated by the light signal. Furthermore, in the light-emitting mode, the display panel 710 may make the pixel circuits R, G, and B in the area 710 emit light to act in correspondence to the light signal indication of the laser device LSR. In an embodiment not shown, it is not necessary for all the light-emitting elements in the pixel circuits R, G, and B to be used for light sensing and light emission at the same time. Any light-emitting element in the pixel circuits R, G, and B may be selected to be used for light sensing and light emission at the same time. It is particularly noted that the laser device LSR may be replaced by other elements that may generate a light signal, such as a light-emitting diode (LED) having more uniform light distribution, as long as these elements may generate enough light intensity to project onto the display panel and provide the desired light signals for sensing. The wavelength of the laser device may be shorter than that of the LED, and has a better reflection response.

Please refer to FIG. 8 A and FIG. 8 B below. FIG. 8 A and FIG. 8 B show schematic diagrams of different application examples of the display panel of an embodiment of the invention. In FIG. 8 A , a display panel 810 may generate a corresponding luminance display in the area A 1 corresponding to the position of the laser device LSR projecting the light signal. In FIG. 8 B , when the intensity of the light signal projected by the laser device LSR is increased, the display panel 810 may expand the light-emitting area A 1 to the area A 2 in response to the intensity of the light signal. In other words, in an embodiment of the invention, the display panel 810 may increase or decrease the area providing high-luminance display according to the intensity of the light signal projected by the laser device LSR to enhance the interactive experience between the user and the display panel 810 .

Referring to FIG. 9 , FIG. 9 shows a schematic diagram of a display panel of another embodiment of the invention. A display panel 910 may include a photodiode S in addition to the pixel circuits R, G, B of light-emitting elements for emitting red light, blue light, and green light. The photodiode S may be a PN-type photodiode or a PIN-type photodiode. Thereby, the density of the light signal sensing elements per unit area in the display panel 910 may be increased to improve the sensitivity of light signal sensing.

Based on the above, the pixel circuit of the invention senses an external light signal via a light-emitting element in a light-sensing mode to generate light sensing information. Furthermore, in the light-emitting mode, the pixel circuit may emit light according to the light sensing information. In this way, the user may interact with the display panel by emitting a light signal to the display panel, thereby effectively improving the working performance of the display panel.