On-chip open circuit, short circuit and LED voltage detection method for micro LED or micro OLED

Abstract

The invention relates to an on-chip open circuit, short circuit and LED voltage detection method for a micro LED or a micro OLED. A micro light emitting diode micro LED display includes a plurality of rows of light emitting diode LEDs, each of the LEDs in a row including a channel, where each channel includes: a feedback path configured to feed an anode voltage of each LED to an input of a voltage comparator; a column driver including a digital-to-analog converter (DAC) and the voltage comparator, where the DAC is configured to receive a plurality of voltage inputs from the resistor ladder and to provide a corresponding plurality of voltage outputs to the inputs of the voltage comparator, and wherein the voltage comparator is configured to continuously compare individual voltage outputs of the plurality of voltage outputs received from the DAC with the anode voltage of each LED; and a data latch configured to store a comparison result from the voltage comparator.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to the design of micro light emitting diode (micro-LED) displays, and in particular to on-chip components of micro-LED display panels and methods thereof for detecting open-circuit, short-circuit, and LED anode voltage of micro-LED display panels. BACKGROUND

[0002] Micro-LED displays are widely used in augmented / mixed reality (AR / MR), virtual reality (VR), large video displays, TVs and monitors, automotive displays, mobile phones, smart watches and wearable devices, tablet computers, laptop computers, and other applications. The technology for manufacturing micro-LED displays continues to rapidly develop. For example, the demand for micro-LED displays with smaller pixels closer together for higher image quality promotes further miniaturization and integration of micro-LEDs in display devices.

[0003] Micro-LED screens are composed of LED lights of micron size. These lights are used to directly produce color pixels. By having thousands or more LED lights, high-quality images and videos can be displayed without the need for a backlight.

[0004] As the size of the LED is reduced to the pm level, the LED fabrication process becomes increasingly challenging. LED manufacturers face the problem of low quantum efficiency (or luminance efficiency versus driving current) and luminance uniformity of micro-LEDs on display panels.

[0005] In addition, Mura or visual non-uniformity on the display panel can also cause problems Mura of micro-LED display panels. Mura can cause an unpleasant feeling (e.g., nausea), and therefore Mura inspection is performed during display quality testing.

[0006] Therefore, there is a need for devices and methods for detecting errors in open-circuit, short-circuit, and LED anode voltage. SUMMARY

[0007] One embodiment of the present disclosure provides a micro light emitting diode (micro-LED) display comprising: a resistor ladder; a plurality of rows of light emitting diodes (LEDs), each LED in a row including a channel, wherein each channel includes: a feedback path configured to feed an anode voltage of each LED to an input of a voltage comparator; a column driver including a digital-to-analog converter (DAC) and the voltage comparator, wherein the DAC is configured to receive a plurality of voltage inputs from the resistor ladder and provide a corresponding plurality of voltage outputs to the input of the voltage comparator, and wherein the voltage comparator is configured to continuously compare individual voltage outputs of the plurality of voltage outputs received from the DAC to the anode voltage of each LED; a data latch configured to store comparison results from the voltage comparator, wherein each comparison result corresponds to a voltage output of the plurality of voltage outputs received from the DAC; and an LED detection module configured to determine whether the micro-LED display is operable based on the comparison results.

[0008] Another embodiment of the present disclosure provides a method of detecting an anode voltage of a micro light emitting diode (micro-LED) display including a plurality of rows of light emitting diodes (LEDs), wherein each LED in a row includes a channel, the method comprising: enabling the row of LEDs; feeding an anode voltage of an LED to an input of a voltage comparator; selecting one voltage from a plurality of voltages and outputting the one voltage to a voltage comparator; outputting a corresponding plurality of voltage outputs to a voltage comparator with a DAC; comparing the anode voltage to the selected one voltage; capturing a 1-bit comparison result for all channels of the micro-LED display with a data latch; and determining whether the micro-LED display is operable based on the comparison result. BRIEF DESCRIPTION OF DRAWINGS

[0009] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0010] Figure 1 is an example micro light emitting diode (micro-LED) display system according to the present technology;

[0011] Figure 2 is an example portion of a micro-LED display system according to the present technology;

[0012] Figures 3A to 3B is an example micro-LED display system according to the present technology Figure 2 is an example condition of an LED of a micro-LED display system of

[0013] Figure 3CExample comparative results of LED detection modules according to the present technology are shown;

[0014] Figures 4A to 4B Example pixel circuit of a micro-LED display system according to the present technology is shown; Figure 2

[0015] Figure 5 Another method of detecting short, open and / or anode voltage of LEDs of a micro-LED display system according to the present technology is shown;

[0016] Figure 6 Another method of detecting short, open and / or anode voltage of LEDs of a micro-LED display system according to the present technology is shown;

[0017] Figure 7 Another method of detecting short, open and / or anode voltage of LEDs of a micro-LED display system according to the present technology is shown; and

[0018] Figure 8 Another method of detecting short, open and / or anode voltage of LEDs of a micro-LED display system according to the present technology is shown.

[0019] Throughout the drawings, like reference characters indicate corresponding components throughout the several views. Those of ordinary skill in the art will realize that elements in the figures are illustrated for simplicity and clarity and that the drawing can not be to scale. For example, the dimensions of some of the elements in each of the figures can be exaggerated relative to other elements to help improve understanding of various embodiments of the present application. Also, common and well-understood elements that are useful but not necessary for an enabling understanding of the application are often omitted to promote clarity and conciseness. DETAILED DESCRIPTION

[0020] Micro-LED display panels and associated methods to detect open / short of micro-LEDs and anode voltage with minimal additional hardware are disclosed herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the technology described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring aspects of the specific aspects.

[0021] ​References throughout this specification to "one example" or "an example" mean that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present technology. The appearances of the phrase "in one example" or "in an example" in various places in the specification are not necessarily all referring to the same example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more examples.

[0022] Spatially relative terms such as "beneath", "below", "lower", "bottom", "above", "upper" and the like can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 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 one or more intervening layers can also be present.

[0023] In light of the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications can be made without departing from the disclosure. Additionally, although a variety of advantages and features have been mentioned, it is not necessarily every embodiment that will exhibit such advantages and / or features. Thus, the disclosure can encompass other embodiments that do not exhibit one or more of the advantages and / or features. In the description of the methods, the steps can include more, fewer, or other steps. Additionally, steps can be performed in any suitable order. Accordingly, this disclosure can encompass other embodiments that are not expressly disclosed herein. In the context of this disclosure, the terms "about", "approximately", and the like mean + / - 5% of the stated value.

[0024] Throughout this specification, several technical terms are used. Such terms are presented herein with their ordinary meanings unless otherwise specifically defined herein or the context of their use clearly dictates otherwise. It should be noted that in this document, element names and symbols can be used interchangeably (e.g., Si and silicon); however, both have the same meaning.

[0025] In short, disclosed herein are on-chip components of micro-LED display panels, and related methods for determining whether a micro-LED display panel is operational. Also disclosed herein are on-chip silicon backplanes configured to detect open-circuit, short-circuit, and anode voltage of micro-LEDs, which can help LED manufacturers diagnose their LED fabrication issues and are desirable. On-chip micro-LED anode voltage detection can also be used to collect Mura (process-induced non-uniformity) data of micro-LED display panels without the need for optical equipment. This Mura data can be used by an on-chip de-Mura module to correct or at least minimize Mura.

[0026] In some embodiments, the resistor ladder can output a plurality of voltage inputs to a digital-to-analog converter (DAC). The DAC, in turn, can output a plurality of voltage outputs corresponding to these voltage inputs to a voltage comparator. Similarly, the feedback path can feed the anode voltage into each of the plurality of LEDs on the micro-LED display panel. The anode voltage can then also be output to the voltage comparator. The voltage comparator sequentially compares the voltage outputs from the DAC with the anode voltage of the LEDs, stores the comparison results to a data latch, and then transfers these data results to the LED detection module. In some embodiments, the LED detection module accumulates the comparison results as 5-bit data results. In other embodiments, the LED detection module serially shifts previously stored results to the next bit position before storing a new result (i.e., a new comparison data). In this way, the LED detection module can determine whether the micro-LED display panel is operational based on the comparison results.

[0027] Figure 1 is an example micro light emitting diode (micro-LED) display system 200 according to the present technology. The micro-LED display 200 includes a frame buffer 220, a bit plane generator 225, a micro-LED display panel 230, a timing controller 207, and a word line gate driver 235. The micro-LED display panel 230 includes an N x M array of pixels 204[0][0]... 204[N-l][M-l]. In the illustrated example, indices n, m correspond to a row and a column of pixel circuits in the array of pixel circuits. For an array of pixel circuits N x M, the indices are for index n ranging from 0 to N-l, and for index m ranging from 0 to M-l.

[0028] Each column 204[0][m]... 204[N-l][m] of pixels 204 includes a corresponding data line 226[m] (also referred to herein as a bit line). Each row 204[n][0]... 204[n][M-l] of pixels 204 includes a corresponding scan line 240[n] (also referred to herein as a word line).

[0029] The timing controller 207 is configured to transmit control signals (CS) to the frame buffer 220, the bit plane generator 225, and the word line gate driver 235. The frame buffer 220 receives and stores display data.

[0030] In a display operation, the frame buffer 220 then transmits the display data 205[0]...205[M-l] row by row to the bit plane generator 225. In some embodiments, the display data for each pixel is an 8-bit binary number; however, it will be appreciated that the display data can be a 10-bit binary number or any other suitable bit width binary number. The frame buffer 220 can be a static random access memory (SRAM), a dynamic random access memory (DRAM), or other type of storage element. The frame buffer 220 can transmit data representing all pixels 204[0][0]...204[N-l][M-l] in the complete display panel 230.

[0031] The bit plane generator 225 converts the display data into an image signal or a video signal that can be displayed on a monitor, screen, or other display. The bit plane generator 225 receives the display data 205[0]...205[M-l] from the frame buffer 220. The display data 205[0]...205[M-l] is a gray scale level for each pixel on the display panel 230. The gray scale level instructs the bit plane generator 225 to adjust the luminance of one or more LEDs of each pixel 204 in the display panel 230. The bit plane generator 225 is configured to generate bit planes. All bit planes generated in a period of one frame form a pulse width modulation (PWM) of all pixels 204 on the display panel 230.

[0032] Conventionally, each micro-LED in the micro-LED display 200 requires an optimal current to be driven to achieve maximum (quantum) efficiency. The display 200 includes a constant current source to generate the optimal current, and then uses a PWM (e.g., the GPWM signals generated by the bit plane generator 225) to control the brightness of the 8-bit gray scale of the display data 205[0]...205[M-l].

[0033] To display an image or a video, the bit plane generator 225 sequentially reads out all data rows (e.g., 1024 rows) from the frame buffer 220 and switches all bit lines 226[0]...226[M-l] to sequentially write bit plane data onto each row of the pixel array. Conventionally, due to the impedance of the bit lines 226[0]...226[M-l], there is not enough time to switch the bit lines 226[0]...226[M-l] fast enough to accommodate 10-bit dimming after adjusting the luminance of the 8-bit gray scale with the bit plane generator 225. This becomes more difficult for higher resolution and higher frame rate displays. Switching the bit lines 226[0]...226[M-l] also consumes a significant amount of power.

[0034] In operation, frame buffer 220 provides display data to bit plane generator 225. Word lines 240[0]...240[N-l] select a row of pixels 204[0][0]...204[N-l][M-l] for writing by bit lines 226[0]...226[M-l]. In some embodiments, bit plane generator 225 outputs a binary 8-bit gray scale pulse width modulation (GPWM) signal for each pixel on micro LED display panel 230 through multiple bit planes. In this way, each pixel 204 of micro LED display panel 230 is turned on or off according to its value on the bit plane, and the 8-bit gray scale luminance of each pixel is adjusted.

[0035] The complete display operation is as follows. Timing controller 207 controls the overall display operation of display system 200. Timing controller can also control when and what data is to be written into pixel circuit 204. Timing controller 207 outputs control signals CS (row address, row address enable, clock) to word line gate driver 235, which turns on (or enables) a row of pixel circuits 204[n][0]...204[n][M-l] via scan lines (or word lines) 240[0]...240[N-l] for writing display data on data lines 226[0]...226[M-l]. At the same time, timing controller 207 also outputs control signals CS (clock, output enable) to bit plane generator 225 (or source driver if display panel 230 is analogically driven) to output display data to data lines 226[0]...226[M-l]. The gray scale (or display data) on data lines 226[0]...226[M-l] is written into pixel circuits 204[0][0]...204[N-l][M-l] selected by scan lines 240[0]...240[N-l]. After completing writing bit plane data to the selected row of pixel circuits 204[0][0]...204[N-l][M-l] and before removing the bit plane data on data lines 226[0]...226[M-l], gate driver 235 turns off (or disables) the row of pixel circuits 204[0][0]...204[N-l][M-l]. The operation is repeated for the next row of pixel circuits until the last row of pixel circuits of display panel 230.

[0036] Figure 2 is an example portion of a micro LED display system 300 according to the present technology. In some embodiments, micro LED display system 300 (also referred to herein as a micro LED display panel) includes a resistor ladder 305, a plurality of rows of LEDs (e.g., micro LEDs) 310, a plurality of columns of LEDs (e.g., micro LEDs) 315, and a plurality of pixel circuits 320. In some embodiments, micro LED display system 300 is a micro LED display panel that is analogically driven. Figure 1) and an LED detection module 330 configured to determine whether the micro LED display panel 300 is operable based on the comparison results as described herein. Figure 2 Only a portion of micro LED display panel 300 is shown, including a close-up view of a single channel (channel m) of a row of LEDs. Also shown are frame buffer 325, output latch 335, and serial bus 340.

[0037] In some embodiments, the resistor ladder 305 is configured to output multiple voltage inputs to the DAC 320. In some embodiments, the resistor ladder is configured to sweep the multiple voltage inputs sequentially, i.e., from the lowest voltage to the highest voltage. In some embodiments, the resistor ladder 305 is configured to output 16 voltage inputs (v_0 to v_15) in increments determined by the value of the resistance of the resistor ladder 305.

[0038] Each LED in the row of LEDs belongs to a specific column of LEDs (also referred to as a "channel," ranging from channel 0, ..., channel m, ..., channel M). Each channel (channel 0 to channel M) may include a feedback path (e.g., Figures 3A to 3B ), column driver (or source driver) 310, digital-to-analog converter (DAC) 320, voltage comparator 345, and data latch 315, as shown and described in detail in FIG.

[0039] In some embodiments, the feedback path includes transistor M7 and outputs a signal v_fdback[m]. The feedback path can feed the anode voltage to the LED. In some embodiments, the fed-back anode voltage is then transmitted to a voltage comparator 345A, as shown by the dashed arrow at element 1A.

[0040] In some embodiments, DAC 320 is a 4-bit DAC decoder. In some embodiments, DAC 320 is a digital-to-analog converter configured to convert a binary number into an equivalent analog output signal proportional to the value of the binary number. In some embodiments, DAC 320 receives a plurality of sequential voltage inputs (v_0 to v_15) from resistor ladder 305—binary number sel[3:0] (arrow 1C). Depending on the value of sel[3:0], the DAC selects a voltage from v_0 to v_15 and outputs the voltage output to voltage comparator 345A (arrow 1B). In some embodiments, the plurality of voltage outputs is 16 voltage outputs corresponding to the 16 voltage inputs (v_0 to v_15) from resistor ladder 305.

[0041] In some embodiments, voltage comparator 345A receives the feedback anode voltage of the LED (arrow 1A) and one voltage output from DAC 320 (arrow IB). Voltage comparator 345A can then compare the anode voltage to the selected one voltage output from DAC 320 to produce a comparison result. In some embodiments, each comparison result corresponds to a voltage output of the plurality of voltage outputs received from DAC 320. Voltage comparator 345A can then transmit these comparison results to data latch 315 (arrow 2). In some embodiments, the comparison results are 1-bit. In such embodiments, each bit of the comparison result corresponds to an individual comparison between one of the 16 output voltages of DAC 320 and the feedback anode voltage of the LED.

[0042] In some embodiments, data latch 315 receives and stores the comparison results. In some embodiments, detection module 330 is the module labeled “Method 1”. In some embodiments, detection module 330 is module “Method 2”. Although module “Method 1” is illustrated as receiving the comparison results from data latch 315, it should be understood that in some embodiments, module “Method 2” receives the comparison results from data latch 315.

[0043] In Method 1, all 16 comparison results are added together as one number using an adder. Thus, the result of Method 1 at the end is a 5-bit comparison result.

[0044] In Method 2, each bit in 16-bit latch 315 stores one comparison result. Since 16 different voltages (v_0, v_1,... v_15) are compared by the resistor ladder, 16 comparisons can be performed. In some embodiments, one comparison will result in a 1-bit result. Thus, at the end of Method 2, there are 16 comparisons which result in a 16-bit comparison result. In some embodiments, the comparison result is first stored at bit 0 of the 16-bit latch. The comparison result can then be shifted serially to LED detection module 330 (arrow 3).

[0045] The comparison results (as Figure 3C shown and explained in detail in Method 1 and Method 2) can be used to determine whether a micro-LED display is operable. It should be understood by one of skill in the art that module “Method 1” and module “Method 2” are alternatives, and not both operating on a single micro-LED display panel 300 at the same time.

[0046] In operation, the feedback path is configured to feed the anode voltage to the LEDs in the LED row, as shown by the dashed arrow at 1A of Figure 2 In some embodiments, the feedback path is configured to feed the anode voltage to the LEDs in the LED row, as shown by the dashed arrow at 1A of Figures 3A to 3BIn more detail, in some embodiments, the DAC 320 is configured to receive a plurality of voltage inputs from the resistor ladder 305 and select one voltage from the 16 voltages from the resistor ladder 305 according to the value of sel[3:0] and then output to the voltage comparator 345A (as shown by the dashed arrow at 1C and IB in Figure 2 In some embodiments, the voltage comparator 345A is configured to continuously compare the individual voltage outputs received from the DAC with the anode voltage of the LED. The data latch 315 can then store the comparison results from the voltage comparator 345A. In some embodiments, the input to the DAC is sel[3:0] and the output of the DAC is a voltage selected from v_0,..., v_15 according to the value of sel[3:0].

[0047] In some embodiments, this process is repeated for each LED in the row until comparison results are obtained for all voltage outputs (v_0...v_15) from the DAC 320. The processed results can then be transferred into the frame buffer 325. This can be repeated for each LED row in the micro-LED display panel.

[0048] After completing the LED detection for all LED rows on the micro-LED display panel, the comparison results can be transmitted off-chip through the serial bus 340 for the next stage of the LED diagnostic process.

[0049] Figures 3A to 3B is an example condition of an LED of a micro-LED display system according to the present technology. Figure 2 In some embodiments, the comparison results are used to detect faults or conditions of the micro-LED display panel. Example faults / conditions include open circuits (as shown in Figure 3A and described in Figure 3C short circuits (as shown in Figure 3B and described in Figure 3C and / or voltage “bubbles” (as shown in Figure 3C and described in). In some embodiments, one or more of these faults / conditions in the comparison results declare the micro-LED display as inoperable. For example, if a short circuit is detected, the micro-LED display panel can be declared as inoperable.

[0050] Figure 3A is an example of an open circuit according to the present technology. As illustrated in Figure 3A , the LED is open (as indicated by the “X”). Thus, a high voltage (close to VDDLED) will be fed back to the voltage comparator (e.g. voltage comparator 345A). Thus, the comparison results will all be “1”, as shown in Figure 3Cas shown in FIG. 6. In some embodiments, the open circuit comparison results will cause the micro-LED display panel to be declared inoperable.

[0051] Figure 3B is an example of a short circuit according to the present technology. If the LED is shorted, a low voltage (close to VSSLED) will be fed back to the voltage comparator (e.g., voltage comparator 345A). Thus, the comparison results will all be “0”, as shown in FIG. 7. In some embodiments, the short circuit comparison results will cause the micro-LED display panel to be declared inoperable. Figure 3C

[0052] Figure 3C Example comparison results for an LED detection module according to the present technology are shown. In some embodiments, the comparison results are 16-bit comparison results.

[0053] Comparison results for an “unexpected situation with a bubble” are also illustrated. A bubble occurs when the voltage is unexpectedly high or unexpectedly low when compared to one or more of the 16 voltage outputs from a DAC (e.g., DAC 320). When the module “Method 2” (as shown in FIG. 6) is implemented into a micro-LED display panel, a bubble can be detected. This type of scenario is referred to as a “bubble” because once the comparison value “0” switches to a comparison value “1”, the comparison value is expected to remain at “1” as the voltage from the resistor ladder 305 and DAC 320 decreases. In the bubble situation, the comparison results can show this bubble because the shifter is able to shift the previously stored result to the next bit location before storing the new result. Thus, this scenario can result in unexpected “1”s or “0”s in the comparison results. Figure 2 The bubble in FIG. 8 is the voltage at bit 4 of the comparison results for an unexpected situation. The bubble is circled in FIG. 8. In some embodiments, the bubble can only be detected when compared to the expected results (also shown in FIG. 8). The expected results show the LED voltage (v_led) between v_9 and v_10 of the voltage outputs. By comparing the expected results to the unexpected situation, the bubble can be detected. Figure 3C Figure 3C Figure 3C The bubble in FIG. 8 is the voltage at bit 4 of the comparison results for an unexpected situation. The bubble is circled in FIG. 8. In some embodiments, the bubble can only be detected when compared to the expected results (also shown in FIG. 8). The expected results show the LED voltage (v_led) between v_9 and v_10 of the voltage outputs. By comparing the expected results to the unexpected situation, the bubble can be detected.

[0054] In some embodiments, the micro-LED display is declared inoperable when the comparison results indicate a bubble. The bubble can indicate that the voltage comparator (e.g., voltage comparator 345A) is malfunctioning. In some embodiments, the bubble indicates an unexpected event. In some embodiments, the micro-LED display is declared inoperable when the comparison results indicate a short circuit. In some embodiments, the micro-LED display is declared inoperable when the comparison results indicate an open circuit. In some embodiments, the micro-LED display is declared operable when the comparison results correspond to the expected results. ​​​

[0055] In some embodiments, a bubble can be detected only when the method 2 module (as shown in Figure 2 ) is implemented. In method 2, the comparison results are shifted to the next bit position of the 16-bit latch (as shown in Figure 2 ). Thus, all 16 comparison results can be saved in the 16-bit latch with the information in Figure 3C . As such, a bubble can be observed. If a bubble is observed, all 16 comparison results can be unreliable because the bubble indicates that the voltage comparator is not functioning properly. In contrast, when the method 1 module is used, the adder adds all 16 comparison results to 5-bit data (from 0 to 16). Thus, in method 1, a bubble cannot be detected.

[0056] Figures 4A to 4B is an example pixel circuit of a micro-LED display system according to the Figure 2 technology. As shown, in some embodiments, each pixel circuit includes an LED, a pulse width modulation (PWM) signal, and a feedback path 410. In some embodiments, the feedback path 410 includes a transistor. The feedback path 410 can allow a voltage to be fed back to the LED and then transmitted to a voltage comparator (e.g., voltage comparator 345A). In this regard, an open circuit, a short circuit, or anode voltage of the LED can be detected with minimal additional hardware.

[0057] Figure 5 is a method 500 of detecting short circuits, open circuits, and / or anode voltage of LEDs of a micro-LED display system according to the technology. In some embodiments, the method 500 can be performed with a micro-LED display panel (e.g., micro-LED display panel 300) including multiple rows of LEDs (as shown in Figure 1 ) and an LED detection module (e.g., LED detector module 330). In some embodiments, each LED of the row of LEDs includes a channel (e.g., channel 0, channel m, channel M). Each channel can include a feedback path (e.g., feedback path 410), a column driver (e.g., column driver 310) including a DAC (e.g., DAC 320) that includes a resistor ladder (e.g., resistor ladder 305) and a MUX, a voltage comparator (e.g., voltage comparator 345A), and a data latch (e.g., data latch 315). In different embodiments, the method can include additional steps or can be performed with fewer steps than shown in the flowchart.

[0058] In block 505, a row of LEDs is enabled. For each channel (and thus each LED) of the row of LEDs, blocks 510-535 are performed.

[0059] In block 510, the anode voltage is fed back to the input of the voltage comparator.

[0060] In block 515, the MUX selects one voltage from v_0 to v_15 and outputs to the voltage comparator.

[0061] In block 520, the LED anode voltage is selected by the MUX.

[0062] In block 525, the 1-bit comparison result of all channels is captured or held by the latch. In some embodiments, this produces the comparison result. In some embodiments, the comparison result is a 16-bit data comparison result for the 16 voltage outputs of the DAC.

[0063] In block 530, the comparison result is serially shifted to the LED detection module. In some embodiments, the data latch is a 16-bit data latch.

[0064] In decision block 535, it is determined whether sel[3:0] is equal to 15. If it is determined that sel[3:0] is equal to 15, then the method proceeds to block 540.

[0065] In decision block 540, it is determined whether this is the last row of LEDs. If it is determined that this is the last row, then the method proceeds to block 545.

[0066] Returning to decision block 535, if sel[3:0] is not equal to 15, then the method returns to block 515. Meanwhile, sel[3:0] is increased by 1 to select another voltage.

[0067] Returning to decision block 540, if it is determined that it is not the last row of LEDs, then the method returns to block 505 for the next row.

[0068] In block 545, the method ends.

[0069] Figure 6 is another method of detecting short, open, and / or anode voltage of a micro-LED display system according to the present technology. In some embodiments, method 600 can utilize a resistor ladder (e.g., resistor ladder 305), a plurality of rows of LEDs (e.g., rows of LEDs 310), a plurality of columns of LEDs (e.g., columns of LEDs 315), a plurality of voltage comparators (e.g., voltage comparators 320), a plurality of multiplexers (e.g., multiplexers 325), a plurality of latches (e.g., latches 330), and / or a plurality of shift registers (e.g., shift registers 335). Figure 1A micro-LED display panel (e.g., micro-LED display panel 300) such as that shown in FIG. 3 can be used to perform the method 500. In some embodiments, each LED in the row of LEDs includes a channel (e.g., channel 0, …, channel m, …, channel M). Each channel can include a feedback path (e.g., feedback path 410), a column driver (e.g., column driver 310) including a DAC (e.g., DAC 320), a voltage comparator (e.g., voltage comparator 345A), and a data latch (e.g., data latch 315).

[0070] In some embodiments, the method 600 occurs after the method 500. In different embodiments, the method 600 can include additional steps or can be performed with fewer steps than shown in the flowchart.

[0071] In block 605, the comparison result is communicated to the LED detection module.

[0072] In block 610, the LED detection module accumulates the comparison result into a 5-bit comparison result. In some embodiments, the LED detection module includes an adder.

[0073] In block 615, a value of the anode voltage of the LED is determined.

[0074] Figure 7 is another method of detecting short circuits, open circuits, and / or anode voltages of LEDs of a micro-LED display system according to the present technology. In some embodiments, the LED detection module includes a shifter (e.g., module “Method 2”). In some embodiments, the method 700 can utilize a micro-LED display panel (e.g., micro-LED display panel 300) including a resistor ladder (e.g., resistor ladder 305), a plurality of rows of LEDs (e.g., rows 0, …, row m, …, row M) as shown in FIG. 3, and an LED detection module (e.g., LED detector module 330). Figure 1 A micro-LED display panel (e.g., micro-LED display panel 300) such as that shown in FIG. 3 can be used to perform the method 500. In some embodiments, each LED in the row of LEDs includes a channel (e.g., channel 0, …, channel m, …, channel M). Each channel can include a feedback path (e.g., feedback path 410), a column driver (e.g., column driver 310) including a DAC (e.g., DAC 320), a voltage comparator (e.g., voltage comparator 345A), and a data latch (e.g., data latch 315). In such embodiments, the shifter can shift a previously stored result to the next bit position before storing a new comparison result.

[0075] In some embodiments, the method 700 occurs after the method 500. In different embodiments, the method 700 can include additional steps or can be performed with fewer steps than shown in the flowchart.

[0076] In block 705, the comparison result is communicated to the LED detection module.

[0077] In block 710, the LED detection module shifts the previously stored comparison result to the next bit position before (or as) the new comparison result is communicated. In some embodiments, the LED detection module includes a shifter.

[0078] In block 715, the value of the anode voltage of the LED is determined and / or it is determined whether the comparison result is valid, as shown and explained in Figures 3A to 3C .

[0079] Figure 8 is another method of detecting short circuits, open circuits, and / or anode voltages of LEDs of a micro-LED display system according to the present technology. In some embodiments, the method 800 can be performed with a micro-LED display panel (such as the micro-LED display panel 300) that includes a resistor ladder (such as the resistor ladder 305), multiple rows of LEDs (as shown in Figure 1 ), and an LED detection module (such as the LED detector module 330). In some embodiments, each LED of the row of LEDs includes a channel (such as channel 0, channel m, channel M). Each channel can include a feedback path (such as the feedback path 410), a column driver (such as the column driver 310) that includes a DAC (such as the DAC 320), a voltage comparator (such as the voltage comparator 345A), and a data latch (such as the data latch 315).

[0080] In some embodiments, the method 800 occurs after the method 600 or the method 700.

[0081] In decision block 805, it is determined whether the comparison result indicates a short circuit. In some embodiments, as shown in Figure 3C , a short circuit is indicated when all 16 bits of the comparison result are at “0”. If it is determined that there is no short circuit, the method proceeds to block 810.

[0082] In decision block 810, it is determined whether the comparison result indicates an open circuit. In some embodiments, as shown in Figure 3C , an open circuit is indicated when all 16 bits of the comparison result are at “1”. If it is determined that there is no open circuit, the method proceeds to block 815.

[0083] In decision block 815, it is determined whether the comparison result indicates a bubble (or voltage bubble). In some embodiments, as shown in Figure 3CAs shown in the middle, when the bit unexpectedly is at "0" or "1", it indicates a voltage bubble. If it is determined that there is no voltage bubble, the method proceeds to block 820.

[0084] In decision block 820, it is determined whether the comparison result matches the expected result. In Figure 3C An example expected result is shown in the middle, which shows the LED voltage between v_9 and v_10. If it is determined that the comparison result matches the expected result, the method proceeds to block 830.

[0085] In block 830, the micro LED display panel is declared operable.

[0086] Returning to decision block 805, if the comparison result indicates a short, the method proceeds to block 825.

[0087] In block 825, the micro LED display panel is declared inoperable.

[0088] Returning to decision block 810, if the comparison result indicates an open, the method proceeds to block 825.

[0089] In block 825, the micro LED display panel is declared inoperable.

[0090] Returning to decision block 815, if the comparison result indicates a voltage bubble, the method proceeds to block 825.

[0091] In block 825, the micro LED display panel is declared inoperable.

[0092] Returning to decision block 820, if the comparison result does not match the expected result, the method proceeds to block 825.

[0093] In block 825, the micro LED display panel is declared inoperable.

[0094] It should be understood that all methods 500, 600, 700, and 800 should be interpreted as merely representative. In some embodiments, the process blocks of all methods 500, 600, 700, and 800 can be executed simultaneously, sequentially, in different orders, or even omitted, without departing from the scope of the present disclosure.

Claims

1. A micro light emitting diode display comprising: resistor ladder; A plurality of rows of light emitting diodes, each of the light emitting diodes in a row comprising a channel, wherein each channel comprises: a feedback path configured to feed the anode voltage of each light emitting diode to an input of a voltage comparator; a column driver comprising a digital-to-analog converter and the voltage comparator, wherein the digital-to-analog converter is configured to receive a plurality of voltage inputs from the resistor ladder and provide a corresponding plurality of voltage outputs to the input of the voltage comparator, and wherein the voltage comparator is configured to sequentially compare individual ones of the plurality of voltage outputs received from the digital-to-analog converter with the anode voltage of each light emitting diode; a data latch configured to store comparison results from the voltage comparator, wherein each comparison result corresponds to a voltage output from the plurality of voltage outputs received from the digital-to-analog converter; as well as A light emitting diode detection module is configured to determine whether the micro light emitting diode display is operable based on the comparison result. The micro light emitting diode display according to claim 1 , wherein the comparison result is 16-bit data.

3. The micro light emitting diode display of claim 2, wherein the data latch is a 16-bit data latch.

4. The micro light emitting diode display according to claim 2, wherein the light emitting diode detection module comprises: A shifter is configured to shift a previously stored comparison result to a next bit position before a new comparison result is stored by the data latch. 5 . The micro light emitting diode display of claim 4 , wherein when the comparison result indicates bubbles, the micro light emitting diode display is declared inoperable.

6. The micro light emitting diode display according to claim 2, wherein the light emitting diode detection module comprises: An adder is configured to accumulate the comparison result of each light emitting diode into a 5-bit data result.

7. The micro light emitting diode display of claim 2, wherein the plurality of voltage outputs is 16 output voltages.

8. The micro light emitting diode display of claim 2, wherein the D / A converter is a 4-bit D / A converter.

9. The micro light emitting diode display of claim 1, wherein when the comparison result indicates a short circuit, the micro light emitting diode display is declared inoperable.

10. The micro light emitting diode display of claim 1, wherein the micro light emitting diode display is declared operational when the comparison result corresponds to an expected result.

11. The micro light emitting diode display of claim 1, wherein when the comparison result indicates an open circuit, the micro light emitting diode display is declared inoperable.

12. A method for detecting an anode voltage of a micro light emitting diode display comprising a plurality of rows of light emitting diodes, wherein each light emitting diode in a row comprises a channel, the method comprising: enabling the row of light emitting diodes; Feeding the anode voltage of the light emitting diode to the input of the voltage comparator; selecting one voltage from a plurality of voltages and outputting the one voltage to a voltage comparator; Utilizing a digital / analog converter to output corresponding multiple voltage outputs to a voltage comparator; comparing the anode voltage to the selected one of the voltages; capturing 1-bit comparison results of all channels of the micro light emitting diode display using a data latch; and It is determined whether the micro light emitting diode display is operable based on the comparison result.

13. The method of claim 12, wherein determining whether the micro light emitting diode display is operable comprises: The comparison results of each LED are added together to form a 5-bit data result.

14. The method of claim 12, wherein when the comparison result indicates a short circuit, the micro light emitting diode display is declared inoperable.

15. The method of claim 12, wherein the micro light emitting diode display is declared operational when the comparison result corresponds to an expected result.

16. The method of claim 12, wherein when the comparison result indicates an open circuit, the micro light emitting diode display is inoperable.

17. The method of claim 12, wherein determining whether the micro light emitting diode display is operable comprises: Before a new comparison result is stored by the data latch, the previously stored comparison result is shifted to the next bit position.

18. The method of claim 17, wherein when the comparison result indicates air bubbles, the micro light emitting diode display is declared inoperable.

19. The method according to claim 12, further comprising: After the comparison result is transmitted to the light emitting diode detection module for each row of light emitting diodes, the comparison result is transmitted to a serial bus.

20. The method according to claim 12, wherein the comparison result is 16-bit data.

Images