Systems and methods for sensing drive current in a pixel

Abstract

A system and method for sensing drive current in a pixel. In some embodiments, the system includes: a first pixel, a second pixel, a differential sensing circuit, a reference current source, and a control circuit. The differential sensing circuit may have a first input, a second input, and an output. The first input is connected to a node at which a reference current generated by the reference current source is subtracted from a first pixel current, the first pixel current including a current generated by the first pixel. The second input may be configured to receive a second pixel current, the second pixel current including a current generated by the second pixel. The output may be configured to generate an output signal based on a difference between the current received at the first input and the current received at the second input.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority and the benefit of U.S. Provisional Application No. 62 / 887,395, filed on August 15, 2019, entitled "Fully Differential Front - End with Sensing of Adjacent Sub - pixels", the entire content of which is incorporated herein by reference. Technical Field

[0003] One or more aspects in accordance with embodiments of the present disclosure relate to displays, and more particularly to measuring pixel characteristics. Background Art

[0004] Video displays (such as those for computers or mobile devices) can have multiple pixels and multiple transistors in each pixel, where the multiple transistors include a driving transistor configured to control a driving current through a display element such as a light - emitting diode (LED) (e.g., an organic light - emitting diode (OLED)). Variations between the characteristics of the driving transistors of a display or changes over time in the characteristics of any one of the driving transistors, if not compensated, can degrade the quality of the image or video displayed by the display. To compensate for such variations or changes, it may be advantageous to measure the characteristics of the driving transistors.

[0005] Accordingly, there is a need for a system and method for measuring the characteristics of driving transistors in a display. Summary of the Invention

[0006] In accordance with an embodiment of the present disclosure, a system is provided, comprising: a first pixel; a second pixel; a differential sensing circuit; a reference current source; and a control circuit. The differential sensing circuit has a first input, a second input, and an output. The first input is connected to a node at which a reference current generated by the reference current source is subtracted from a first pixel current, the first pixel current including a current generated by the first pixel; the second input is configured to receive a second pixel current, the second pixel current including a current generated by the second pixel; the output is configured to generate an output signal based on a difference between the current received at the first input and the current received at the second input; and the control circuit is configured to: turn on the first pixel; turn off the second pixel; and cause the reference current source to generate a reference current.

[0007] In some embodiments: the system includes a display panel, the display panel including a first pixel and a second pixel, the first pixel being located in a first column of the display panel, the second pixel being located in a second column of the display panel, and the first pixel and the second pixel being adjacent and located in the same row of the display panel.

[0008] In some embodiments: The first pixel current further includes leakage currents from a plurality of pixels other than the first pixel in the first column, and the second pixel current includes leakage currents from a plurality of pixels other than the second pixel in the second column.

[0009] In some embodiments, the differential sensing circuit includes a low-pass current filter.

[0010] In some embodiments, the low-pass current filter includes a fully differential amplifier.

[0011] In some embodiments, the low-pass current filter further includes a common-mode feedback circuit having a bandwidth of at least 10 MHz.

[0012] In some embodiments, the differential sensing circuit further includes an integrator connected to the output of the low-pass current filter.

[0013] In some embodiments, the system further includes a driving circuit, wherein a first conductor of the display panel is connected to the first pixel, and the first conductor is configured to: transmit a first pixel current in a first state of the system, and transmit a current from the driving circuit to the first pixel in a second state of the system.

[0014] In some embodiments, the control circuit is configured to, in the second state: cause the low-pass current filter to operate in a reset state, and cause the driving circuit to drive the first conductor to a reference voltage.

[0015] According to an embodiment of the present disclosure, there is provided a method for sensing a current in a display, the display including: a first pixel; a second pixel; a differential sensing circuit; and a reference current source; the differential sensing circuit having a first input, a second input, and an output, the method including: feeding a difference between a first pixel current and a reference current generated by the reference current source to the first input, the first pixel current including a current generated by the first pixel; feeding a second pixel current to the second input, the second pixel current including a current generated by the second pixel; generating an output signal at the output based on a difference between the current received at the first input and the current received at the second input; turning on the first pixel; turning off the second pixel; and generating the reference current.

[0016] In some embodiments: The display includes a display panel, the display panel including a first pixel and a second pixel, the first pixel being located in a first column of the display panel, the second pixel being located in a second column of the display panel, and the first pixel and the second pixel being adjacent and located in the same row of the display panel.

[0017] In some embodiments: The first pixel current further includes leakage currents from a plurality of pixels other than the first pixel in the first column, and the second pixel current includes leakage currents from a plurality of pixels other than the second pixel in the second column.

[0018] In some embodiments, the differential sensing circuit includes a low-pass current filter.

[0019] In some embodiments, the low-pass current filter includes a fully differential amplifier.

[0020] In some embodiments, the low-pass current filter further includes a common-mode feedback circuit having a bandwidth of at least 10 MHz.

[0021] In some embodiments, the differential sensing circuit further includes an integrator connected to the output of the low-pass current filter.

[0022] In some embodiments, the display further includes a driving circuit, wherein a first conductor of the display panel is connected to the first pixel and is configured to: transmit a first pixel current in a first state of the display, and transmit a current from the driving circuit to the first pixel in a second state of the display.

[0023] In some embodiments, the method further includes: in the second state, operating the low-pass current filter in a reset state, and driving the first conductor to a reference voltage by the driving circuit.

[0024] According to an embodiment of the present disclosure, a system is provided, including: a first pixel; a second pixel; a differential sensing circuit; a reference current source; and a control means. The differential sensing circuit has a first input, a second input, and an output. The first input is connected to a node where a reference current generated by the reference current source is subtracted from a first pixel current, and the first pixel current includes a current generated by the first pixel. The second input is configured to receive a second pixel current, and the second pixel current includes a current generated by the second pixel. The output is configured to generate an output signal based on a difference between the current received at the first input and the current received at the second input. The control means is configured to: turn on the first pixel; turn off the second pixel; and cause the reference current source to generate a reference current.

[0025] In some embodiments: The system includes a display panel including a first pixel and a second pixel. The first pixel is located in a first column of the display panel, the second pixel is located in a second column of the display panel, the first pixel and the second pixel are adjacent, and are located in the same row of the display panel. Description of the Drawings

[0026] These and other features and advantages of the present disclosure will be appreciated and understood with reference to the specification, claims, and drawings, wherein:

[0027] Figure 1 is a scenario diagram according to an embodiment of the present disclosure;

[0028] Figure 2A is a schematic diagram of a display panel and a driving and sensing integrated circuit (IC) according to an embodiment of the present disclosure;

[0029] Figure 2B is a schematic diagram of a display panel and a driving and sensing integrated circuit according to an embodiment of the present disclosure;

[0030] Figure 2C is a schematic diagram of a display panel and a driving and sensing integrated circuit according to an embodiment of the present disclosure;

[0031] Figure 3A is a schematic diagram of the front end according to an embodiment of the present disclosure;

[0032] Figure 3B is a schematic diagram of the front end according to an embodiment of the present disclosure;

[0033] Figure 3C is a schematic diagram of the front end according to an embodiment of the present disclosure;

[0034] Figure 4 is a schematic diagram according to an embodiment of the present disclosure;

[0035] Figure 5A is a schematic diagram according to an embodiment of the present disclosure;

[0036] Figure 5B is a schematic diagram according to an embodiment of the present disclosure;

[0037] Figure 5C is a schematic diagram according to an embodiment of the present disclosure;

[0038] Figure 5D is a schematic diagram according to an embodiment of the present disclosure;

[0039] Figure 5E is a schematic diagram according to an embodiment of the present disclosure;

[0040] Figure 5F is a graph of a transfer function according to an embodiment of the present disclosure;

[0041] Figure 6 is a flowchart according to an embodiment of the present disclosure; and

[0042] Figure 7 is a timing diagram according to an embodiment of the present disclosure. Detailed Description

[0043] The following detailed description presented in conjunction with the accompanying drawings is intended as a description of exemplary embodiments of systems and methods for sensing drive current in a sensing pixel according to the present disclosure, and is not intended to represent the only forms in which the present disclosure may be constructed or utilized. This description sets forth the features of the present disclosure in connection with the illustrated embodiments. However, it is to be understood that the same or equivalent functions and structures may be implemented by different embodiments that are also intended to be included within the scope of the present disclosure. As denoted elsewhere herein, like reference numerals are intended to indicate like elements or features.

[0044] Referring to Figure 1 , in some embodiments, a display (e.g., a mobile device display) 105 may include a plurality of pixels arranged in rows and columns. Each pixel may be configured to produce light of one color (e.g., red, green, or blue), and may be part of a combined pixel that includes, for example, three such pixels and is configured to produce any color in a wide color gamut (in some contexts, what is referred to herein as a "pixel" is alternatively referred to as a "sub-pixel", and what is referred to herein as a "combined pixel" is alternatively referred to as a "pixel"). Each pixel may include a driving circuit, e.g., Figure 1 the 7-transistor 1-capacitor (7T1C) driving circuit shown on the left side of Figure 1 or the 4-transistor 1-capacitor (4T1C) driving circuit shown at the bottom of

[0045] The pixel drive and sense circuitry 145 (discussed further below in more detail) can be connected to drive sense conductor 135. The pixel drive and sense circuitry 145 can include a drive amplifier and sense circuitry configured to selectively connect to the drive sense conductor 135 one at a time. When current flows through drive transistor 110 and the lower transfer gate transistor 130 is off so that the drive sense conductor 135 is disconnected from the source node 140, current can flow through light emitting diode 120, causing it to emit light. When the lower transfer gate transistor 130 is on and the drive sense conductor 135 is driven to a voltage lower than the voltage of the cathode of light emitting diode 120, the light emitting diode 120 can be reverse biased, and any current flowing in the drive sense conductor 135 can flow to the pixel drive and sense circuitry 145, where the current can be sensed. The sensed current can be compared to a desired current (e.g., the current that an ideal or nominal transistor would drive at the same gate-source voltage), and in terms of how the sensed current differs from the ideal current, measures can be taken (e.g., the gate-source voltage can be adjusted) to compensate for the difference.

[0046] See Figure 2A , in some embodiments, for improved accuracy, the current of any pixel can be sensed in a different manner. For example, if Figure 2A the current driven by the drive transistor 110 of the left pixel (which can be referred to as the "odd" pixel) is to be sensed, it ("odd" pixel) can be turned on (by charging a capacitor of the odd pixel to turn on the drive transistor 110 of the odd pixel), while Figure 2A the drive transistor 110 of the right pixel (which can be referred to as the "even" pixel) can be turned off (by discharging a capacitor of the even pixel to turn off the drive transistor 110 of the even pixel), and the difference between two corresponding currents flowing out of two corresponding conductors (which can be referred to as "column conductors" 205) can be measured. Each of the column conductors 205 can be connected to all of the pixels in a column of the display; thus, even if all of the pixels other than the odd pixel whose characteristics are being determined are off, the total leakage current in the other pixels can be large. In terms of the leakage current in the adjacent column (containing the even pixels) being the same, when sensing the difference between the currents in the two column conductors 205, the effect of the leakage current on the current flowing into the column conductor connected to the odd pixel can be canceled out.

[0047] The SCAN1, SCAN2, and EMIT control lines can each occupy a separate line and can have different timings between the lines. As mentioned above, differential sensing can be used such that each operation can sense half of the pixels in a line. A set of identical gate control signals can be applied to the odd and even pixels such that there is no difference between the odd and even pixels. Each digital-to-analog converter (DAC) and associated driver amplifier 220 can be used both to drive the column conductors 205 to charge the capacitors of the pixels and to generate a reference current when the current driven by the drive transistor 110 is being sensed; this can be implemented using a multiplexer, as shown. Figure 1 The embodiment of Figure 1 does not include this feature but instead includes two separate digital-to-analog converters.

[0048] See Figure 2B , in some embodiments, when the circuit is in the drive mode, the gate of the drive transistor 110 of each pixel is at ELVSS and the source of the drive transistor 110 of each pixel is driven to ELVSS - VDRIVE such that

[0049] VGS = ELVSS - (ELVSS - VDRIVE) = VDRIVE.

[0050] The emission transistor of each pixel can remain off.

[0051] During this process, the corresponding VDRIVE can be stored across the pixel capacitor of each pixel. When sensing the odd pixels, the source of the drive transistor 110 of the even pixels can be driven to ELVSS such that they (the even pixels) will be turned off, as mentioned above.

[0052] See Figure 2C , in some embodiments, when the circuit is in the sense mode, the upper transfer gate transistor 125 ( Figure 1) is turned off, so that the gate of the drive transistor 110 is floating and the charge on the capacitor of each pixel is kept constant. The source of the drive transistor 110 of each pixel is driven (e.g., driven to VREF, which can be slightly less than ELVSS) so that each light emitting diode 120 is reverse biased and no current flows through the light emitting diode 120. The emission transistor of each pixel is turned on, and as a result of the light emitting diode 120 being reverse biased, any current driven by the driver transistor 110 of the pixel flows through the corresponding column conductor 205 to the sensing circuit. In this mode, the digital-to-analog converter and the driver amplifier 220 connected to the digital-to-analog converter can generate a reference current IREF. In some embodiments, the reference current IREF is generated by controlling the digital-to-analog converter and the driver amplifier 220 to generate a voltage ramp, which is applied to the capacitor to provide a current according to the following equation:

[0053] IREF = C dV / dt.

[0054] When sensing pixel current, various error sources may be relevant. For example, see Figure 3A , if a single-ended front end is used to sense the current, then the ground noise V g Can be coupled into the signal at the output of the amplifier:

[0055]

[0056] For display systems, C P Comparable C i much larger; therefore, the ground noise (V g ) can be very large at low frequencies.

[0057] See also Figure 3B , when the column capacitance (C P ) can be effective, but even with a mismatch between 1% and 5%, pseudo differential sensing may not be effective. In addition, common mode currents caused by noise may be excessive and may increase the dynamic range requirements of the front end.

[0058] See also Figure 3C , if a single-ended front end is used to sense the current, then the thermal noise V r Can be coupled into the signal at the output of the amplifier:

[0059]

[0060] The broadband thermal noise (which may be caused by the resistance of column conductor 205 (in Figure 3C The resistor Rp The effects of (modeling) generation can be reduced by using a front end configured as or including a low-pass filter, which can allow the sensed (DC) signal (I pixel ) to pass through. An example of such a low-pass filter (integrator) is shown in Figure 3C .

[0061] In operation, the front-end integrator can be reset prior to a sensing operation. Each sensing operation can be preceded by a driving operation, during which the driving amplifier 220 ( Figures 2A to 2C ) drives the column conductor 205 to a set voltage. Before the sensing operation begins, the voltage on the column conductor 205 can be restored to VREF. Another issue related to the Figure 3C circuit can be that the capacitance of the column conductor 205 to ground can be large, so the driving amplifier 220 (in the reset mode) may take a long time to bring the voltage of the column conductor 205 to VREF.

[0062] Figure 4 FIG. shows a differential sensing circuit 400, which has two inputs for sensing the difference between currents from a first pixel (e.g., Figures 2A to 2C an odd pixel of Figures 2A to 2C ) and a second pixel (e.g.,

[0063] an even pixel of Figure 4 ). The differential sensing circuit 400 has a two-stage architecture, where a low-pass current filter 405 (e.g., a first integrator, as shown) serves as the first stage, and an integrator 410 (e.g., a second integrator, as shown) serves as the second stage. The integrator 410 can be coupled to the low-pass current filter 405 through two mirror capacitors 425. Each of the low-pass current filter 405 and the integrator 410 can include a fully differential operational amplifier having a capacitor (or "feedback capacitor") in each feedback path. As mentioned above, this circuit can be used to perform differential sensing between two adjacent pixels (e.g., the red pixel and the green pixel in a combined pixel containing three pixels, namely the red pixel, the green pixel, and the blue pixel, or the green pixel and the blue pixel in the combined pixel). A wide-bandwidth common-mode feedback amplifier (CMFB) 415 (which can have an open-loop bandwidth between 10 MHz and 100 MHz) feeds back around the low-pass current filter 405. Figures 2A to 2CAs shown in these figures, a multiplexer is used to select at any time whether to drive amplifier 220 or differential sensing circuit 400 to be connected to column conductor 205).

[0064] In some embodiments, low-pass current filter 405 and integrator 410 can be fully differential. As used herein, a fully differential circuit is a circuit that does not compare a signal to ground (as opposed to a single-ended or pseudo-differential amplifier). Instead, each differential gain stage in a fully differential amplifier directly compares the two signals being processed to each other, for example.

[0065] Wide-bandwidth common-mode feedback amplifier 415 can calculate the common-mode output signal at the output of low-pass current filter 405 (e.g., it can calculate the average of the voltages at two output conductors using a resistor network), and feed it back to the common-mode input in low-pass current filter 405. The common-mode input can be, for example, (i) the gates of the current sources (or "tail current sources") connected to the two sources of the differential pair in low-pass current filter 405, or (ii) the nodes of two corresponding transistors in the load network of the differential pair in low-pass current filter 405.

[0066] In some embodiments, Figure 4 the performance of the circuit can be better than that of a pseudo-differential circuit (e.g., as Figure 3B shown in). This can be shown as follows.

[0067]

[0068] and

[0069]

[0070] Note

[0071] and refer to Figure 5B the circuit, it can be found that

[0072]

[0073] and

[0074]

[0075] Figure 5C shows a circuit that can be used to analyze Figure 4 low-pass current filter 405. In this circuit:[[]]

[0076]

[0077] Next

[0078]

[0079] See Figure 5D and note that the differential impedance is

[0080]

[0081] and the common - mode impedance is

[0082]

[0083] Use the following definitions:

[0084]

[0085]

[0086]

[0087] According to the previous equations:

[0088]

[0089]

[0090]

[0091]

[0092] See Figure 5E and the following can be approximate component values:

[0093] R1 → 9k

[0094] C P → 53pF

[0095] C i → 71fF

[0096] A → 10,000

[0097] For f << f 3dB and using the following assumptions:

[0098]

[0099] That is, and

[0100] R2 >> R1,

[0101] the following can be derived:

[0102]

[0103] and

[0104]

[0105] For f 3dB <<f<<f ug

[0106] where f ug ≡f 3dB ·A

[0107] (resistor)

[0108] And

[0109]

[0110] For higher frequencies, the following results are obtained:

[0111]

[0112] Figure 5F The resulting transfer function is plotted. At low frequencies, V out / V g ≈ΔC P / C P .

[0113] For frequencies less than f 3dB the differential impedance looking into the input terminals can be that of a large capacitor C i *A (the operational amplifier can make a relatively small capacitor C i appear larger, i.e., make it approximately C i *A). It may be advantageous to make the magnitude of this behavior significantly greater than the capacitance of the channel itself (i.e., make the impedance looking into the low-pass current filter significantly less than the impedance of the channel itself). In this case, most of the current driven by the drive transistor 110 flows into the low-pass current filter. For frequencies between f 3dB and f ug the differential impedance looking into the input terminals can have the characteristics of a resistor.

[0114] Figure 6 A flowchart showing a method for sensing using the circuit described herein is shown. First, at 605, the odd pixels are driven with a desired V gs for sensing, and the even pixels are driven with a V gs corresponding to black (with no emission from the light emitting diode 120). Then, at 610, the upper transfer gate transistors 125 of each pixel are turned off, and a V gsDrive two pixels to reset column conductor 205 (this driving step does not affect the charging on the capacitor of the pixel because the upper transfer gate transistor 125 of each pixel is turned off). Then, at 615, the circuit enters the sensing mode. During this step, the front end is in reset, that is, the switches (such as transistor switches) connected across the feedback capacitors of the low-pass current filter 405 and the integrator 410 are closed (such as the transistors are turned on), so that these capacitors become discharged and remain discharged during the reset. The circuit can be maintained in the reset mode until the voltages on the sensing front end and the column conductor 205 are balanced; the effect of this state can be to sample the front end offset. During the reset phase, the pixel current can be turned on or off (that is, the control signal EMIT_ENB can be high or low). Then, at 620, the front end is released from reset (such as the transistor connected across the feedback capacitor is turned off), and the integration of (the sensed current) begins. Finally, at 625, the output of the integrator 410 is sampled.

[0115] Figure 7 is a timing diagram showing the control signals for cycling through Figure 6 the states shown in Figure 6 The reference numerals of Figure 6 are repeated to show Figure 7 the correspondence between the steps of Figure 7Further features not shown may be present in some embodiments. For example, a wait state 705 (in which the low-pass current filter 405 is released from reset and allowed to settle, while the integrator 410 remains in the reset mode) may precede the integration state 620 (which may correspondingly start later). As another example, in some embodiments, the integration state is divided into two parts, in one of which the current from both odd and even pixels is cut off (by turning off the bottom transfer gate transistor 130 using the SCAN2_EN control signal), and in the other of which the even and odd pixels are turned on (by turning on the bottom transfer gate transistor 130 using the SCAN2_EN control signal). During the transition between these two parts, the connection polarity between the low-pass current filter 405 and the integrator 410 may be reversed, such that the output of the integrator, at the end of the second part, may be the difference between the current when the pixels are on and the current when the pixels are off (where the latter may include contributions not of interest (e.g., leakage current from other pixels which is different in even and odd pixels in terms of its effect)). Thus, operating in this mode can reduce errors caused by such currents that are not the current to be sensed (the current driven by the drive transistor 110 of the odd pixels). A hold state 710 (during which the low-pass current filter 405 is disconnected from the integrator 410) may also be present to reduce errors that may otherwise be introduced due to imperfect timing when the pixel current and the reference current are turned on. The SENSE_RESETB and SENSE_INTEG_EN signals may be used to control the reset state of the low-pass current filter 405 and the reset state of the integrator 410, respectively. If a wait state is used, the SENSE_INTEG_EN signal may remain low until the end of the wait state 705.

[0116] As used herein, the "input" of a circuit includes one or more conductors and may include further inputs. For example, a differential input may include a first conductor identified as a non-inverting input and a second conductor identified as an inverting input. Similarly, as used herein, the "output" of a circuit includes one or more conductors and may include further outputs. For example, a differential output may include a first conductor identified as a non-inverting output and a second conductor identified as an inverting output. As used herein, when a first component is described as being "selectively connected" to a second component, the first component is connected to the second component through a switch (e.g., a transistor switch) such that, depending on the state of the switch, the first component may be connected to the second component or disconnected from the second component.

[0117] Although the present disclosure provides examples of fully differential circuits in their application to sense pixel circuits, however, the present disclosure is not limited to such applications, and the systems and methods disclosed herein can be applied to other applications, such as, for example, in biomedical applications.

[0118] In some embodiments, various control signals and the control of circuits such as digital-to-analog converters can be performed by a processing circuit. The term "processing circuit" is used herein to mean any combination of hardware, firmware, and software that is used to process data or digital signals. Processing circuit hardware can include, for example, application-specific integrated circuits (ASICs), general-purpose or special-purpose central processing units (CPUs), digital signal processors (DSPs), graphics processing units (GPUs), and programmable logic devices such as field-programmable gate arrays (FPGAs). In a processing circuit, as used herein, each function is performed by hardware configured (i.e., hardwired) to perform that function or by more general hardware (such as a CPU) configured to run instructions stored in a non-transitory storage medium. The processing circuit can be fabricated on a single printed circuit board (PCB) or distributed across several interconnected PCBs. The processing circuit can contain other processing circuits; for example, the processing circuit can include two processing circuits, an FPGA and a CPU, interconnected on a PCB.

[0119] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed herein can be referred to as a second element, component, region, layer, or section without departing from the spirit and scope of the inventive concept.

[0120] For ease of description, in this document, spatial relative terms such as "below", "beneath", "lower", "under", "above", "upper", etc. may be used to describe the relationship of one element or feature shown in the drawings relative to another element or feature. It should be understood that such spatial relative terms are intended to encompass different orientations of the device in use or operation other than the orientation depicted in the drawings. For example, if the device in the drawings is flipped, the element described as "below", "beneath", or "under" other elements or features will then be oriented "above" the other elements or features. Thus, the example terms "below" and "beneath" can encompass both the above and below orientations. The device can be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative descriptors used in this document should be interpreted accordingly. Additionally, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can also be one or more intermediate layers.

[0121] The technical terms used in this document are only for describing specific embodiments and are not intended to limit the inventive concept. As used herein, terms such as "substantially", "about", and similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations in the measured or calculated values that would be recognized by a person of ordinary skill in the art. As used herein, the term "major part", when applied to a plurality of items, means at least half of the items.

[0122] As used herein, the singular form "a" is also intended to include the plural form, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of", when placed after a list of elements, modify the entire list of elements and not individual elements in the list. Further, when describing embodiments of the inventive concept, the use of "may" refers to "one or more embodiments of the present disclosure". Moreover, the term "exemplary" means an example or illustration. As used herein, the term "use" and its variants can be considered to be synonymous with the term "utilize" and its variants, respectively.

[0123] It will be understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it can be directly on, directly connected to, or directly coupled to the other element or layer, or one or more intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers.

[0124] Any numerical range recited herein is intended to include all sub-ranges having the same numerical precision within the recited range. For example, a range of “1.0 to 10.0” is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (including both), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lesser numerical limitations included therein, and any minimum numerical limitation recited in this specification is intended to include all greater numerical limitations included therein.

[0125] Although exemplary embodiments of systems and methods for sensing drive current in pixels have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. Accordingly, it will be understood that the systems and methods for sensing drive current in pixels constructed in accordance with the principles of the present disclosure may be embodied in ways other than those specifically described herein. The invention is also defined in the appended claims and their equivalents.

Claims

1. A system for sensing drive current in a pixel, comprising: A first pixel; A second pixel; A differential sensing circuit; A reference current source; And A control circuit, The differential sensing circuit has a first input, a second input, and an output, The first input is connected to a node at which a reference current generated by the reference current source is subtracted from a first pixel current, the first pixel current including a current generated by the first pixel; The second input is configured to receive a second pixel current, the second pixel current including a current generated by the second pixel; The output is configured to generate an output signal based on a difference between the current received at the first input and the current received at the second input; The control circuit is configured to: Turn on the first pixel; Turn off the second pixel; And Cause the reference current source to generate the reference current, Wherein the differential sensing circuit includes a low-pass current filter and a common-mode feedback circuit connected between an output and an input of the low-pass current filter, Wherein the input of the low-pass current filter is a common-mode input, and Wherein the common-mode feedback circuit is configured to calculate an average value of a voltage at the output of the low-pass current filter and provide the average value to the common-mode input of the low-pass current filter.

2. The system according to claim 1, wherein: The system includes a display panel, the display panel including the first pixel and the second pixel, The first pixel is located in a first column of the display panel, The second pixel is located in a second column of the display panel, and The first pixel and the second pixel are adjacent and located in the same row of the display panel.

3. The system according to claim 2, wherein: The first pixel current further includes leakage current from a plurality of pixels other than the first pixel in the first column, and The second pixel current includes leakage current from a plurality of pixels other than the second pixel in the second column.

4. The system according to claim 1, wherein the low-pass current filter includes a fully differential amplifier.

5. The system according to claim 4, wherein the common-mode feedback circuit has a bandwidth of at least 10 MHz.

6. The system according to claim 2, wherein the differential sensing circuit further includes an integrator connected to the output of the low-pass current filter.

7. The system according to claim 6, further including a driving circuit, Wherein a first conductor of the display panel is connected to the first pixel, the first conductor being configured to: Transfer the first pixel current in a first state of the system, and Transfer a current from the driving circuit to the first pixel in a second state of the system.

8. The system according to claim 7, wherein the control circuit is configured to, in the second state: Cause the low-pass current filter to operate in a reset state, and Cause the driving circuit to drive the first conductor to a reference voltage.

9. A method for sensing current in a display, the display comprising: a first pixel; a second pixel; a differential sensing circuit; and a reference current source; the differential sensing circuit having a first input, a second input, and an output, the method comprising: feeding the difference between a first pixel current, which includes a current generated by the first pixel, and a reference current generated by the reference current source to the first input; feeding a second pixel current, which includes a current generated by the second pixel, to the second input; generating an output signal at the output based on the difference between the current received at the first input and the current received at the second input; turning on the first pixel; turning off the second pixel; and generating the reference current, wherein the differential sensing circuit includes a low-pass current filter and a common-mode feedback circuit connected between an output and an input of the low-pass current filter, wherein the input of the low-pass current filter is a common-mode input, and the method further comprises: calculating an average value of a voltage at the output of the low-pass current filter; and providing the average value to the common-mode input of the low-pass current filter.

10. The method according to claim 9, wherein: the display includes a display panel, the display panel including the first pixel and the second pixel, the first pixel is located in a first column of the display panel, the second pixel is located in a second column of the display panel, and the first pixel and the second pixel are adjacent and located in the same row of the display panel.

11. The method according to claim 10, wherein: the first pixel current further includes leakage current from a plurality of pixels other than the first pixel in the first column, and the second pixel current includes leakage current from a plurality of pixels other than the second pixel in the second column.

12. The method according to claim 9, wherein the low-pass current filter includes a fully differential amplifier.

13. The method according to claim 9, wherein the common-mode feedback circuit has a bandwidth of at least 10 MHz.

14. The method according to claim 10, wherein the differential sensing circuit further includes an integrator connected to the output of the low-pass current filter.

15. The method according to claim 14, wherein the display further includes a driving circuit, wherein a first conductor of the display panel is connected to the first pixel, the first conductor being configured to: transfer the first pixel current in a first state of the display, and transfer a current from the driving circuit to the first pixel in a second state of the display.

16. The method according to claim 15, further comprising: In the second state, operating the low-pass current filter in a reset state, and driving the first conductor to a reference voltage by the driving circuit.

17. A system for sensing a driving current in a pixel, comprising: a first pixel; a second pixel; a differential sensing circuit; a reference current source; and means for control, The differential sensing circuit has a first input, a second input, and an output, The first input is connected to a node at which a reference current generated by the reference current source is subtracted from a first pixel current that includes a current generated by the first pixel; The second input is configured to receive a second pixel current that includes a current generated by the second pixel; The output is configured to generate an output signal based on a difference between the current received at the first input and the current received at the second input; The means for controlling is configured to: Turn on the first pixel; Turn off the second pixel; And Cause the reference current source to generate the reference current, Wherein the differential sensing circuit includes a low-pass current filter and a common-mode feedback circuit connected between an output and an input of the low-pass current filter, Wherein the input of the low-pass current filter is a common-mode input, and Wherein the common-mode feedback circuit is configured to calculate an average value of a voltage at the output of the low-pass current filter and provide the average value to the common-mode input of the low-pass current filter.

18. The system according to claim 17, wherein: The system includes a display panel that includes the first pixel and the second pixel, The first pixel is located in a first column of the display panel, The second pixel is located in a second column of the display panel, The first pixel and the second pixel are adjacent and located in the same row of the display panel.

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