Micro LED Power Considering Outlier Pixel Dynamic Resistance

Abstract

Described herein are systems, devices, methods, and computer-readable media for reducing the number of undriven or under-driven uLEDs of a uLED die. The methods include, by a controller of a micro light emitting diode (uLED) die, measuring the dynamic series resistance (R d ) or forward voltage (V f ) by the controller; d or V f Based on the maximum current level (I PWM_MAX ) PWM_0 ) and causing the uLED driver to supply current at the selected current level by the controller.

Description

[Technical field]

[0001] Claiming priority This application claims the benefit of priority to U.S. Patent Application No. 17 / 123,021, filed December 15, 2020, which is incorporated by reference in its entirety herein.

[0002] Technical Field The present disclosure relates to light emitting devices and light emitting device control systems configured to reduce or eliminate dark aberrations experienced due to abnormally high dynamic series resistance in light emitting diodes (LEDs). [Background technology]

[0003] In some applications, such as home or commercial lighting, the user experience in terms of the visual effect of the lighting is very important. Automotive lighting is another application where the user experience is very important. If the dynamic series resistance of a light emitting diode (LED) is high, the forward voltage of the LED may be higher than the supply voltage and the LED will likely not perform as expected. Such an LED may appear as a black or dark spot in the illuminated LED. [Brief description of the drawings]

[0004] The figures show various views of a device, system, or method including a control system that can vary the light emitted from one or more light emitting diodes (LEDs), according to some embodiments. The terms "front," "rear," "top," "side," and other directional terms are used merely for convenience in describing the devices and systems and other elements, and should not be construed as limiting in any way.

[0005] [Figure 1] FIG. 1 illustrates, by way of example, a logical block diagram of an embodiment of a system for driving a die containing a matrix of micro LEDs (uLEDs).

[0006] [Diagram 2] FIG. 1 illustrates, by way of example, a perspective view of an embodiment of a uLED die including undriven and / or underdriven uLEDs.

[0007] [Diagram 3] FIG. 13 illustrates, by way of example, a diagram of an embodiment of a graph of driver circuit efficiency versus relative dynamic series resistance of an outlier uLED.

[0008] [Figure 4] FIG. 1 illustrates, by way of example, a conceptual block diagram of an embodiment of a package including a matrix of uLEDs and corresponding driver circuitry.

[0009] [Diagram 5] FIG. 2 shows, by way of example, a circuit diagram of an embodiment of a uLED pixel (uLED driver circuit and corresponding uLED).

[0010] [Figure 6] FIG. 13 shows, by way of example, a logic circuit diagram of an embodiment of a system that takes into account outlier pixel dynamic series resistance (Rd) for driving a matrix of uLEDs.

[0011] [Figure 7] FIG. 13 shows a graph of an embodiment of Rd distribution for multiple uLED matrix dies as an example.

[0012] [Figure 8] FIG. 2 shows, by way of example, a circuit diagram of an embodiment of a uLED pixel.

[0013] [Figure 9] FIG. 13 shows by way of example a diagram of an embodiment of a system for analyzing uLED Rd of a uLED die.

[0014] [Figure 10]FIG. 13 shows an example current vs. voltage graph of a uLED with an outlier Rd and a uLED with a lower Rd.

[0015] [Figure 11] FIG. 13 shows an example graph of peak driver current (%) versus dynamic series resistance of a uLED.

[0016] [Figure 12] FIG. 13 shows an example graph of relative dynamic resistance of a uLED with an outlier Rd versus VLED.

[0017] [Figure 13] FIG. 13 shows, by way of example, a diagram of an embodiment of a method for driving a uLED matrix die.

[0018] [Figure 14] FIG. 14 illustrates in more detail an embodiment of a chip-level implementation of a system supporting functionality such as that described in relation to FIGS. 6-13.

[0019] [Figure 15] FIG. 1 illustrates, by way of example, a logical block diagram of a system including circuitry that may be included in a uLED package.

[0020] [Figure 16] FIG. 1 illustrates, by way of example, a block diagram of an embodiment of a machine (eg, a computer system) for implementing one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Compact pixelated LEDs, such as an array of micro LEDs on a uLED die (sometimes denoted as "uLEDs"), can include a large monolithic die area. uLED arrays can be used for automotive lighting, such as headlights, tail lights, parking lights, fog lights, direction lights, etc. Such applications are merely examples, and many other applications of uLED arrays are possible.

[0022] A uLED array can include uLED dies hybridized with driver electronics for control of individual pixel brightness. The driver electronics can be fabricated, for example, using complementary metal-oxide semiconductor (CMOS) materials or processes, or other semiconductor manufacturing processes.

[0023] In some embodiments, the driver electronics (uLED driver) can implement a linear driving scheme. A linear driving scheme is one practical solution for such control electronics, especially for large uLED array configurations. However, special care is required in a linear driving scheme, such as providing both a stable uLED current supply and acceptable heat dissipation to control the voltage supply to the driver electronics. To help ensure that more uLED drivers operate above their matching voltage (a voltage that provides sufficient power to the corresponding uLEDs being driven by the driver), the voltage supply to the driver electronics is generally limited to the highest forward voltage (V f ) However, such settings are not temperature or energy efficient.

[0024] The advantage of monolithic uLED chips is that they provide a large forward voltage (V f ) with a narrow dispersion (e.g., standard deviation <100 millivolts). f ) uniformity is, for example, the relationship between the supplied voltage and the forward voltage (V f) to reduce heat loss. f ) is excessively high (e.g., more than 20%, 25%, or a percentage more or less than the average forward voltage (V f ), there may still be a small but relevant set of outlier uLEDs.

[0025] One solution to provide sufficient supply voltage is to select the highest V for all uLEDs on the die, including the outliers. f This involves providing a larger (or equal) supply voltage. Using this solution, all uLEDs, including outliers, will be driven properly. However, the heat losses will increase (up to prohibitive levels in some practical cases) since the voltage drop across the driver electronics will increase on average.

[0026] Another solution does not include consideration of outlier uLEDs. Skipping such outliers allows the supply voltage to be kept low, thereby allowing for a narrow forward voltage (V f ) variance. In this solution, we take advantage of the V f Compared to the solution of increasing the voltage supply voltage to account for one or more of the above, heat losses are reduced. However, using such a solution, it is highly likely that some outlier uLEDs will be undriven or under-driven. Such undriven and / or under-driven uLEDs may appear as dark spots on the uLED array. A larger population of outliers may be prohibitive in some applications, especially if the undriven and / or under-driven uLEDs remain visible.

[0027] The embodiments may include a (e.g., simple) driving scheme that provides voltage compliance to the outlier uLED driver so that the corresponding uLED can be illuminated with little impact on heat loss or operational efficiency. Advantages provided by the embodiments may address one or more of the following challenges of pixelated matrix LEDs driven with linear driver schemes: (1) providing a cost-effective driving scheme for matrix uLEDs; (2) overcoming driver efficiency limitations; (3) overcoming voltage compliance limitations; or (4) addressing forward voltage distribution across a population of pixels when outliers compromise either voltage compliance or driver efficiency.

[0028] In an embodiment, an abnormally high V f may be the product of the dynamic series resistance of the uLED. The dynamic series resistance may be due to process tolerances that affect the quality of elements such as metal-semiconductor contacts. Based on these considerations, embodiments may include a current driver (uLED driver) that provides voltage compliance to outlier uLEDs that can operate normally or substantially light (light up to an intensity within a specified number or percentage of a specified lumen without considering the dynamic series resistance) with little impact on heat loss.

[0029] Embodiments can provide a uLED driver control technique that can identify outlier pixels by their sensed voltage (see, e.g., FIG. 9) and classify them as such. This can be done during the uLED die assembly process or periodically, e.g., during a diagnostic mode. Embodiments can provide a preset on-current value for the pulse-width modulated (PWM) current, V fA uLED driver control scheme can be provided that can adjust for those identified outlier uLEDs whose compliance voltage exceeds the average population compliance voltage (e.g., by a specified amount). This can be done during the uLED die assembly process or periodically, for example, during a diagnostic mode after uLED die processing.

[0030] In the embodiment, V of the outlier pixels f V LED The preset on current value of the PWM current is set to be sufficiently lower than the maximum PWM current (I PWM_MAX ) driver control technology that allows the local uLED driver unit to be in compliance voltage mode. In the embodiment, the preset on current value of the PWM current is I PWM_MAX The lower new value I PWM_O driver control techniques can be provided to reduce this value to the series dynamic resistance (R d ) is estimated approximately and / or in part from the difference between R d is set to different current levels (e.g. target I PWM_MAX Rd can be characterized periodically during the assembly process or during diagnostic mode by driving the pixel at a voltage (around V fmax and V th (See, for example, FIG. 10) PWM Therefore, the rand of Rd can be determined as [R dlow , R dhigh ] can be defined as R dlow =(V fmax -V th ) / I PWM_MAX Similarly, R dhigh =(V fmax -V th ) / I PWM_0 In addition, V th and I PWM_MAX is given by technology, design and operating conditions. By fixing these, V fmax(e.g., supply voltage) and R d A direct relationship is obtained between

[0031] FIG. 1 shows, by way of example, a diagram of an embodiment of a uLED control system 100. The illustrated system 100 includes a voltage source 102 that provides power distributed by multiple LED drivers to a matrix of uLEDs 104. The voltage source 102 supplies a constant direct current (DC) voltage V LED 106 and a constant reference voltage V GND 108. The voltage source 102 provides a voltage source V LED 106 DC level. This voltage does not change dynamically with the load line response (load of the uLED 104 array). Therefore, V LED 106 does not change dynamically during the pulse width modulation (PWM) of the current driver signal.

[0032] As mentioned earlier, V LED 106 is set to take into account outlier pixels in the array of uLEDs 104, the heat loss in the driver of the uLEDs will be high (even prohibitively high). LED If 106 is set without considering the Vf of the outlier uLED, the outlier uLED may remain undriven or underdriven. Such undriven or underdriven LEDs may appear as dark spots in the matrix of uLEDs 104.

[0033] Figure 2 shows the V f 2 shows a diagram of an embodiment of an array of uLEDs 200 driven without consideration of . As can be seen, some uLEDs remain undriven or underdriven, resulting in black or dark spots 220 in the array of uLEDs 200.

[0034] FIG. 3 shows, by way of example, a diagram of an embodiment of a graph 300 of efficiency of a driver circuit versus the relative dynamic series resistance of an outlier uLED (as a % of all uLEDs in the array of uLEDs 200). As can be seen, as the dynamic resistance of a uLED considered an outlier increases, the electrical efficiency of the driver circuit decreases. The goal can be to keep the electrical efficiency higher, for example, than 85%, 80%, a smaller percentage, or some percentage in between. Electrical efficiency is defined as the power output divided by the power provided. For example, an outlier R d If increases by 20% for the population of LEDs in the matrix of uLEDs 104, the driver efficiency drops from 86% (baseline efficiency not considering outliers) to 82%.

[0035] 4 illustrates, by way of example, a logical block diagram of an embodiment of a system 400 including an electrical backplane electrically coupled to a matrix of uLEDs 104. The electrical backplane includes a uLED driver 444 and a power delivery circuit. Further details of a linear driver version of the uLED driver 444 are provided with respect to FIG. 5. The power delivery circuit receives V LED 106 and the reference voltage V GND Includes 108. V LED 106 is provided to the power plane 442. GND 108 is provided to a ground plane 440. The uLED driver 444 receives the power from the power plane 442 LED 106. The uLED driver 444 controls individual or groups of uLEDs in the matrix of uLEDs 104 via electrical interconnects 446. The uLED driver 444 can control whether the uLEDs are on, off, duty cycled, or other power control of the uLEDs 104.

[0036] The matrix of uLEDs 104 is electrically coupled to a (respective) uLED driver 444 via an electrical interconnect 446. The matrix of uLEDs 104 is electrically coupled to a ground plane 440 via another electrical interconnect 448. A dielectric 450 electrically and physically isolates the uLED driver 444 from the ground plane 440. That is, the dielectric 450 is located between the uLED driver 444 and the ground plane 440 (e.g., directly) and between the ground plane 440 and the power plane 442 (e.g., directly).

[0037] 5 shows, by way of example, a logic diagram of one embodiment of a system 500 including a uLED driver 444 and a uLED 550 of a matrix of uLEDs 104. The uLED driver 444 controls an electrical signal 554 on an electrical interconnect 446. By controlling the electrical signal 554, the uLED driver 444 can inhibit or allow current flow to the uLEDs 550. Using this control, the uLED driver 444 can ultimately control whether and when individual or groups of uLEDs 550 are on, as well as the duty cycle of the uLEDs.

[0038] To overcome limitations of other uLED driving schemes and increase the electrical efficiency of the matrix of uLEDs 104, several improved driving schemes are provided. The embodiments consider a uLED die having individually addressable pixels. The uLED die includes a uLED driver 444 that includes a linear driver architecture operating in PWM mode. The control scheme can help minimize the total root mean square (RMS) and harmonic currents driven by the voltage source 102, at least in part, by the phase of the uLEDs' pulse width modulation (PWM) control signals being randomized.

[0039] An embodiment can include a voltage source 102 whose output voltage can be dynamically modulated and controlled by a load (e.g., a controller 990 for the load (see FIG. 9 )) with sufficient bandwidth response. An embodiment can include a control scheme that can identify outlier pixels (e.g., by sensed voltage and classify them as such (see FIG. 9 )) before or during run-time of the matrix of uLEDs 104. The controller 990 can adjust the voltage from the voltage source 102 to the dynamic resistance (R d ) up to a specified voltage value. Higher voltages can be specified as a function of the dynamic series resistance of the outlier uLED.

[0040] An embodiment may include a control scheme that repeatedly (e.g., periodically at predetermined intervals) increases the voltage supply to a specified voltage value during every cycle or every few cycles of the driver's PWM signal. Such a higher set voltage may be used to control the forward voltage (V f ) as a function of the LED forward voltage (V f ) is the voltage drop across the LED while it is lit.

[0041] Embodiments may include a control scheme for varying the voltage and current provided by the uLED driver 444 of the uLED 550. Embodiments may provide a control scheme that includes a modifiable set current for outlier pixels.

[0042] FIG. 6 shows an example of a uLED 104 matrix using an outlier pixel R d 6 shows a logic diagram of an embodiment of a system 600 that takes into account R. The system 600 is the same as or similar to the uLED control system 100. The system 600 includes a dThe uLED driver 444 includes a circuit that provides a control command 660 that causes the uLED driver 444 (see FIG. 4 ) to provide power based on the dynamic series resistance of the particular uLED 550 in the matrix of uLEDs 104. The control command 660 may indicate a voltage or a current based on the dynamic series resistance of the particular uLED 550 in the matrix of uLEDs 104. The control command 660 indicates a voltage to be supplied to the uLED driver 444. The control command 660 may be issued by a controller 990 coupled to the uLED driver 444.

[0043] The controller 990 may include a memory 988 (see FIG. 9) or at least may detect abnormally high R d For each uLED with R d The controller 990 may have access to a memory containing data indicating the forward voltage (V f ) is the supply voltage V LED can be set to be smaller than the maximum value of

[0044] FIG. 7 shows, as an example, the dynamic series resistance (R d ) distributions. One of the distributions 774 has an R d and R in the top quartile 772 d The majority of uLEDs have outlier R d Includes 776. Outlier R d is R d The highest percentile (e.g., 75%, 80%, 85%, 90%, 95%, or a higher percentage, or any percentage in between) of uLEDs in the matrix of uLEDs 104 ranked by R greater than a specified threshold. d (For example, R at a specified percentile d , R for a specified number of standard deviations above the mean d104 )。 The uLED 104 may be defined as a matrix of uLEDs having uLEDs.

[0045] V LED 106 is R d If the outlier R is set to a level that covers a specified percentile of uLEDs based on d The uLEDs 552 with 776 may be undriven or underdriven. As previously mentioned, this undriven or underdriven condition may result in dark spots or other aberrations in the image produced by the matrix of uLEDs 104.

[0046] FIG. 8 shows, as an example, a circuit diagram of one embodiment of a uLED pixel (uLED 550 and corresponding uLED driver 444 (e.g., a uLED driver 444 that drives only a single uLED 550 or a small group of uLEDs (less than 10 uLEDs)). In the circuit diagram 800 of FIG. 8, the uLED driver 444 is driven with a voltage VCS 880 that depends on the Rd of the uLED. The VCS 880 can be from a circuit (e.g., a resistor ladder and a multiplexer) that operates to provide various VCS 880 values. The controller 990 controls the V f The VCS 880 corresponding to the Rd of the uLED can be selected to reduce VLED 106 below VLED 106. This reduction in drive voltage (VCS 880) reduces the drive current provided by the uLED driver 444. The reduction in drive current in turn causes a reduction in the intensity of the uLED 550. The controller 990 can compensate for the reduction in intensity by increasing the duty cycle of the uLED 550.

[0047] 9 shows, by way of example, a diagram of an embodiment of a system 900 for analyzing the dynamic resistance (Rd) of a uLED die. To use the embodiment, a controller 990 can be used as part of the matrix of uLEDs 104, as described above. The controller 990 can have access to a memory 988 or can include the memory 212.

[0048] Memory 988 is a uLED with an unusually high R d (and the corresponding anomalously high V f ) can be stored. d An electrical stimulus 994 can be provided to the uLED driver 444 by test equipment 992 to determine whether the uLED driver 444 has a current or voltage that is in a range of 100 to 1500 V. The test equipment 992 can include a power source similar to the voltage source 102. The test equipment 992 can be operable to vary the amplitude, frequency, or other parameters of the current or voltage provided as the stimulus 994.

[0049] The stimulus 994 may include a voltage (VLED 106) that will be used to drive the uLED driver 444 most of the time. If a sufficient response 998 is detected, the uLED 996 may be considered healthy. If an insufficient response 998 is detected, the uLED 996 may be considered an outlier R d It can be thought of as having the following.

[0050] In response to an insufficient response 998 (current below the expected (threshold) current), the test equipment 992 can store the identity of the uLED 996 (e.g., by position in a matrix of uLEDs, such as row and column, or other identity) in the memory 988 of the controller 990 (or in a memory accessible by the controller 990). In this manner, the controller 990 can determine when to cause the uLED driver 444 to drive the uLED with a reduced current. One or more of the operations of FIG. 9 can be performed during manufacturing, after packaging, or during some other stage of manufacturing or distribution, or a combination thereof.

[0051] The controller 990 may include electrical or electronic components configured to perform its operations, including one or more transistors, resistors, capacitors, diodes, inductors, oscillators, switches, logic gates (e.g., AND, OR, XOR, negate, buffers, etc.), multiplexers, analog-to-digital converters, digital-to-analog converters, amplifiers, rectifiers, modulators, demodulators, processors (e.g., Central Processing Units (CPUs), Graphics Processing Units (GPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), etc.), memory devices (e.g., Random Access Memory (RAM), Read Only Memory (ROM), etc.), etc.

[0052] The driver 444 may include electrical or electronic components configured to implement power provision to the uLEDs of the matrix of uLEDs 104 (sometimes referred to as uLED dies). The electrical or electronic components may include one or more transistors, resistors, capacitors, diodes, inductors, oscillators, switches, logic gates, multiplexers, analog-to-digital converters, digital-to-analog converters, amplifiers, rectifiers, modulators, demodulators, processors, memory devices, etc.

[0053] Figure 10 shows an example of the outlier R d uLED with lower R d 10 shows a graph 1000 of current versus voltage for a uLED having a normal R d The dashed line 1012 corresponds to the uLED with the outlier R d As can be seen, the main difference between the lines 1010 and 1012 is R d(the inverse of the slope of lines 1010, 1012). In FIG. 10, assuming that both uLEDs are operated at the same temperature (note that this is not a requirement and the Vth of the uLEDs may be different), the threshold voltage 1022 (sometimes called the bandgap) is the same or similar for the uLEDs. These uLEDs are then driven with the same on-state current I PWM_MAX When driven with a MOSFET, the forward voltage is V fo 1018~V fmax The difference is R d It is determined by the difference.

[0054] The embodiment reduces the current driving the outlier pixel to a current level I PWM_0 Decrease to 1016. The outlier voltage is V f0 to voltage compliance V fmax The outlier pixels are then filtered to a lower current level I PWM_0 Powered by 1016. V fmax is the maximum V generated by the voltage source 102 LED Corresponds to.

[0055] In the driver diagram of FIG. 8, this is the control voltage V cs R d This is achieved by making it a function of V cs is the current provided to the uLED (I PWM ) is a voltage signal that controls

[0056] State-of-the-art linear current drivers for LED arrays use V cs is constant and substantially the same among all LEDs. In contrast, the embodiment d For uLEDs with V cs This allows the PWM on-state current (I PWM ), but I PWM_MAX (V LED The lower current shown in FIG. 10 is lower than the driver current generated in response to driving the uLED driver 444 with IPWM_0 1016. As the supply voltage changes, V cs The new value of is the outlier R d The forward voltage (V f ) is V LED The forward voltage (V f ) can be lowered.

[0057] 11 shows, as an example, a graph 1100 of peak driver current (%) versus dynamic series resistance of a uLED. To achieve this, detection of outlier uLEDs and, optionally, and according to this detection, V cs There are procedures to reduce R d The quasi-linear relationship between V and the required local reduction in PWM on-state current is shown in Figure 11. This is achieved by increasing V beyond that determined to drive the average population of pixels. LED Establish a maximum current capability imposed on the outlier pixel to avoid increasing Rd (and therefore driver losses). For example, according to Figure 11, a 30% increase in Rd of the average population reduces the PWM on-state current of that outlier uLED by about 23%. Without this proposed measure, the supply voltage V LED 106 is R d and may increase according to the corresponding driver current.

[0058] FIG. 12 shows an example of V LED 106 vs. outlier R d 12 shows a graph 1200 of the relative dynamic resistance of a uLED with 0.1 V, which, when followed by the controller 990, helps ensure driver voltage compliance for all uLEDs, including outliers. The corresponding efficiency penalty is shown in FIG. 3 (solid line). When using the embodiment solution, the efficiency is reduced as a function of forward voltage (V), as shown by the dashed line in FIG. 3. f ) remains independent.

[0059] Outlier uLEDs subject to the proposed peak current limit can continue to be properly driven if sufficient time margin is given for duty cycle correction (increasing the duty cycle in response to the reduction of the PWM on-state current). The number of under-driven outliers depends on the target light profile and the specific uLED die. A typical light profile in an application corresponds to a non-uniform light pattern (non-uniform color light pattern). Therefore, a large number of uLEDs are expected to operate with a correctable duty cycle in response to a reduction of the driver current (e.g., at low or medium duty cycle levels). Given such a profile, it can be seen that R d and the number of outliers can be estimated statistically.

[0060] 13 illustrates, by way of example, a diagram of an embodiment of a method 1300 for driving a uLED matrix die. The method 1300 can be performed, at least in part, by the voltage source 102, the matrix of uLEDs 104, the controller 990, the driver 444, other components, or combinations thereof. As shown, the method 1300 includes, in operation 1302, a controller of a micro light emitting diode (uLED) die, determining a dynamic series resistance (R d ) or forward voltage (V f ) and in operation 1304, by the controller, d Or V f Based on the maximum current level (I PWM_MAX ) lower current level (I PWM_0 ) and, in operation 1306, causing the controller to cause the uLED driver to supply current at the selected current level.

[0061] Method 1300 is PWM_0The method 1300 may further include increasing, by the controller, a pulse width modulation (PWM) on-time of the uLED in response to selecting R. The method 1300 may further include testing, by a test instrument, each uLED of the uLED die to determine whether the uLED has an R greater than a particular threshold. d Or V f The method 1300 may further include determining whether the uLED die includes a memory accessible by the controller that includes a R greater than a specified threshold. d The method 1300 may further include storing data indicating an identification (ID) of each uLED of the uLED die, including the identified R d Based on the V f is the maximum supply voltage (V LED ) so that I PWM_0 The method may further include determining:

[0062] The method 1300 includes determining whether the controller detects an R d Or V f For each uLED in the uLED die, including I PWM_0 The method 1300 may further include selecting an R across all uLEDs of the uLED die, where the identified threshold is R d Value or V f The method 1300 may further include determining whether the R d Or V f and the average R of non-outlier uLEDs of the uLED die d Or V f The maximum current level (I PWM_MAX ) lower current level (I PWM_0 ), and the outlier uLED is selected from the average R d Or V f R greater than a specified number of standard deviations d Includes.

[0063] Below are some details regarding the uLED 104 matrix and some application considerations followed by some examples.

[0064] FIG. 14 illustrates in more detail an embodiment of a chip-level implementation of a system 1400 supporting functionality such as that described in connection with FIGS. 6-13. The system 1400 includes a command and control module 1416 (sometimes referred to as a controller, which may be similar or identical to the controller 990 of FIG. 9) that can implement pixel or group pixel level control of amplitude and duty cycle for the circuits and procedures such as those described in connection with FIGS. 6-13 and elsewhere herein. In some embodiments, the system 1400 further includes a frame buffer 1410 for holding a generated or processed image that can be fed to a matrix of uLEDs 1420. Other modules include a serial bus (e.g., inter-integrated circuit (I-IC)) configured to transmit control data or commands or response data. 2 C) a serial bus) or a digital control interface such as a serial peripheral interface (SPI) (1414).

[0065] In operation, system 1400 can accept image or other data from a vehicle or other source arriving via SPI interface 1414. Sequential image or video data can be stored in image frame buffer 1410. When image data is not available, one or more standby images held in standby image buffer 1411 can be directed to image frame buffer 1410. Such standby images can include, for example, an intensity and spatial pattern consistent with a vehicle's legally permitted low beam headlamp radiation pattern, or a default light radiation pattern for architectural lighting or displays.

[0066] In operation, pixels in an image are used to define the response of corresponding LED pixels during activation, with the intensity and spatial modulation of the LED pixels being based on the image. To reduce data rate issues, in some embodiments, a group of pixels (e.g., a 5×5 block) can be controlled as a single block. In some embodiments, high speed and high data rate operation is supported, and pixel values ​​from successive images can be loaded as successive frames in an image sequence at a rate between 30 Hz and 100 Hz (60 Hz is typical). Using PWM, each pixel can be controlled to emit light in a pattern and intensity that depends at least in part on the image held in the image frame buffer 1410.

[0067] In some embodiments, the system 1400 includes dd Pin and V ss The active matrix can receive logic power through multiple VLEDs and V CathodeThe SPI 1414 receives power for LED array control through pins. The SPI 1414 can provide full duplex mode communication using a master-slave architecture with a single master. The master device originates frames for reading and writing. Multiple slave devices are supported through selection by individual slave select (SS) lines. Input pins can include master output slave input (MOSI), master input slave output (MISO), chip select (SC) and clock (CLK), all of which are connected to the SPI interface 1414. The SPI interface 1414 connects to an address generator, a frame buffer and a standby frame buffer. The pixels can have parameters set and signals or powers modified by the command and control module (e.g., by power gating before input to the frame buffer or after output from the frame buffer via pulse width modulation or power gating). The SPI interface 1414 can be connected to an address generation module 1418, which then provides row and address information to the active matrix 1420. The address generation module 1418 can then provide a frame buffer address to the frame buffer 1410.

[0068] In some embodiments, the command and control module 1416 can be externally controlled via the serial bus 1412. It can support clock (SCL) and data (SDA) pins, such as 7-bit addressing. The command and control module 1416 can include a digital-to-analog converter (DAC) and two analog-to-digital converters (ADC). The DAC and ADC each provide a V bias Set the maximum V f, which is used to determine the system temperature. An oscillator (OSC) is also connected to set a pulse width modulated oscillation (PWMOSC) for the active matrix 1420. In one embodiment, there are also bypass lines that allow addressing of individual pixels or blocks of pixels within the active matrix for diagnostic, calibration or test purposes. The active matrix 1420 may be further supported by row and column selects that are used to address individual pixels, which may include data lines, bypass lines, PWMOSC lines, V bias Line and V f Line is provided.

[0069] As will be appreciated by those skilled in the art, in some embodiments, the described circuits and active matrix 1420 can be packaged and optionally include a submount or printed circuit board connected to power and control light generation by the semiconductor LEDs. In certain embodiments, the printed circuit board can also include electrical vias, heat sinks, ground planes, electrical traces, and flip chip or other mounting systems. The submount or printed circuit board can be formed of any suitable material, such as ceramic, silicon, aluminum, etc. If the submount material is conductive, an insulating layer is formed on the substrate material and a metal electrode pattern is formed on the insulating layer. The submount can act as a mechanical support, provide an electrical interface between the electrodes on the LEDs and a power source, and can also provide a heat sink.

[0070] In some embodiments, the active matrix 1420 can be formed from light emitting elements of various types, sizes and layouts. In one embodiment, a one-dimensional or two-dimensional matrix array of individually addressable light emitting diodes (LEDs) can be used. In general, an N×M array can be used, where N and M are each between 2 and 1000. The individual LED structures can have square, rectangular, hexagonal, polygonal, circular, arcuate or other surface shapes. The array of LED assemblies or structures can be geometrically arranged in straight rows and columns, staggered rows or columns, curved, or semi-random or random layouts. The LED assemblies can include multiple LEDs formed such that an individually addressable pixel array is also supported. In some embodiments, radial or other non-rectangular grid arrangements of conductive lines to the LEDs can be used. In other embodiments, curved, wound, serpentine and / or other suitable non-linear arrangements of conductive lines to the LEDs can be used.

[0071] In some embodiments, an array of micro LEDs (μLEDs or uLEDs) can be used. uLEDs can support high density pixels with lateral dimensions less than 100 μm×100 μm. In some embodiments, uLEDs with dimensions of about 50 μm or less in diameter or width can be used. Such uLEDs can be used in the manufacture of color displays by closely aligning uLEDs containing red, blue and green wavelengths. In other embodiments, uLEDs can be defined on a monolithic gallium nitride (GaN) or other semiconductor substrate, segmented, partially or fully partitioned semiconductor substrate, or panels formed individually or assembled as groups of uLEDs. In some embodiments, the active matrix (matrix of uLEDs 104) can include a small number of uLEDs arranged on a centimeter-scale area or larger substrate. In some embodiments, the active matrix 1420 can support a uLED pixel array with hundreds, thousands or millions of LEDs arranged together on a centimeter-scale area substrate or smaller. In some embodiments, the uLEDs can include LEDs with sizes between 30 microns and 500 microns. In some embodiments, each of the light-emitting pixels in the light-emitting pixel array can be spaced at least 1 millimeter apart to form a sparse LED array. In other embodiments, the sparse LED array of light-emitting pixels can be spaced less than 1 millimeter apart and can be spaced apart by a distance ranging from 30 microns to 500 microns. The LEDs can be embedded in a solid or flexible substrate, which can be at least partially transparent. For example, the light-emitting pixel array can be at least partially embedded in a glass, ceramic, or polymer material.

[0072] Emitting matrix pixel arrays as discussed herein can support applications that benefit from fine intensity spatial and temporal control of light distribution. This may include, but is not limited to, precise spatial patterning of light emitted from pixel blocks or individual pixels. Depending on the application, the emitted light may be spectrally differentiated, adaptive over time, and / or environmentally responsive. Emitting pixel arrays may provide pre-programmed light distributions with various intensities, spatial or temporal patterns. The emitted light may be based at least in part on received sensor data and may be used for optical wireless communication. The associated optics may be separate at the pixel, pixel block or device level. An exemplary emissive pixel array may include a device with a commonly controlled central block of high brightness pixels with associated common optics, while edge pixels may have individual optics. Common applications supported by emissive pixel arrays include video lighting, automotive headlights, architectural and area lighting, street lighting, and information displays.

[0073] Emissive matrix pixel arrays can be used to selectively and adaptively illuminate buildings or areas for improved visual displays or to reduce lighting costs. In addition, emissive pixel arrays can be used to project media facades for decorative motion or video effects. With tracking sensors and / or cameras, selective illumination of pedestrian surrounding areas may be possible. Spectrally distinct pixels can be used to adjust the color temperature of the illumination as well as support wavelength specific horticultural illumination.

[0074] Street lighting is an application that can benefit from the use of emissive pixel arrays. A single emissive array can be used to mimic different street light types, for example allowing switching between a type I linear street light and a type IV semicircular street light by appropriate activation or deactivation of selected pixels. In addition, street lighting costs can be reduced by adjusting the intensity or distribution of the light beam depending on the environmental conditions and time of use. For example, the light intensity and distribution area may be reduced when there are no pedestrians. If the pixels of the emissive pixel array are spectrally distinct, the color temperature of the light can be adjusted according to the respective day, dusk or night conditions.

[0075] Light emitting arrays are also suitable to support applications requiring a direct or projected display. For example warning, emergency or information signs can all be displayed or projected using light emitting arrays. This allows for example to project color changing or flashing exit signs. If the light emitting array is composed of multiple pixels text or numerical information may be presented. Directional arrows or similar indicators may also be provided.

[0076] Vehicle headlamps are emissive array applications that require large pixel counts and high data refresh rates. Automotive headlights that actively illuminate only selected portions of the roadway can be used to reduce problems associated with glare or dazzle for oncoming drivers. Using an infrared camera as a sensor, the emissive pixel array activates only those pixels necessary to illuminate the roadway, while deactivating pixels that may dazzle pedestrians or oncoming drivers. In addition, off-road pedestrians, animals or signs can be selectively illuminated to improve the driver's awareness of the environment. If the pixels of the emissive pixel array are spectrally distinct, the color temperature of the light can be adjusted according to the respective daytime, twilight or nighttime conditions. Some pixels can be used for optical wireless vehicle-to-vehicle communication.

[0077] An LED light module may contain a matrix of LEDs, either alone or in conjunction with primary or secondary optics including lenses or reflectors. To reduce overall data management requirements, the light module may be limited to on / off functionality or switching between relatively few light intensity levels. Full pixel-level control of light intensity is not necessarily supported.

[0078] In operation, pixels in the image are used to define the response of corresponding LED pixels in the pixel module, with the intensity and spatial modulation of the LED pixels being based on the image. To reduce data rate issues, in some embodiments, a group of pixels (e.g., a 5x5 block) can be controlled as a single block. High speed and high data rate operation is supported, and pixel values ​​from successive images can be loaded as successive frames in an image sequence at a rate between 30Hz and 100Hz, with 60Hz being typical. In conjunction with the pulse width modulation module, each pixel in the pixel module can be operated to emit light in a pattern and intensity that depends at least in part on the image held in the image frame buffer.

[0079] In the above embodiment, the intensity of the uLEDs can be controlled and adjusted separately by setting the appropriate lamp time and pulse width for each LED pixel using appropriate lighting logic, control module and / or PWM module. Outlier pixel voltage management can provide LED pixel activation to provide reliable patterned illumination. A control system 1500 that can provide voltage source 102 voltage management is illustrated in FIG. 15. As seen in FIG. 15, a matrix micro LED array 1520 can include one or more arrays of thousands to millions of micro LED pixels that are actively emitting light and individually controlled. The current levels of micro LED pixels at different locations on the array are individually adjusted according to a particular image to emit light in a pattern or sequence that results in the display of an image. This can include PWM to turn the pixels on and off at a particular frequency. During operation of the PWM, the average DC current through the pixel is the product of the current amplitude and the PWM duty cycle, which is the ratio of the conduction time to the period or cycle time.

[0080] FIG. 15 illustrates a logical block diagram of a system 1500 including circuits that may be included in a uLED package, as an example. A processing module that facilitates efficient use of the system 1500 is illustrated in FIG. 15. The system 1500 includes a control module 1516 that may implement pixel or group pixel level control of amplitude and duty cycle for the circuits and procedures as described with respect to FIGS. 6-14. In some embodiments, the system 1500 further includes an image processing module 1504 for generating, processing or transmitting an image, and a digital control interface 1513, such as Inter-Integrated Circuit (I2C), Serial Peripheral Interface (SPI), Controller Area Network (CAN), Universal Asynchronous Receiver Transmitter (UART), etc., configured to transmit control data and / or instructions. The digital control interface 1513 and the control module 1516 may include a system microcontroller and any type of wired or wireless module configured to receive control inputs from an external device. As an example, the wireless module may include Bluetooth, Zigbee, Z-wave, mesh, WiFi, Near Field Communication (NFC), and / or a peer-to-peer module may be used. The microcontroller may be any type of dedicated computer or processor that may be incorporated into the LED lighting system and configured or configurable to receive inputs from wired or wireless modules or other modules in the LED system and provide control signals to other modules based thereon. The algorithms implemented by the microcontroller or other suitable control module 1516 may be implemented in a computer program, software, or firmware that is incorporated into a non-transitory computer-readable storage medium for execution by a special purpose processor. Examples of non-transitory computer-readable storage media include read-only memory (ROM), random access memory (RAM), registers, cache memory, and semiconductor memory devices. The memory may be included as part of the microcontroller or may be implemented elsewhere on or outside a printed circuit or electronic circuit board.

[0081] As used herein, the term module may refer to electrical and / or electronic components disposed on individual circuit boards that may be soldered to one or more electronic circuit boards. However, the term module may also refer to electrical and / or electronic components that provide similar functionality but that may be individually soldered to one or more circuit boards in the same or different areas.

[0082] A control module 1516 (similar or the same as the controller 990) controls the image processing module 1504 and the I 2 It may further include a digital control interface 1513 such as I / O. As will be appreciated, in some embodiments, image processing calculations may be performed by the control module 1516 through direct generation of a modulated image. Alternatively, a standard image file may be processed or otherwise converted to provide a modulation that matches the image. Image data, including primarily PWM duty cycle values, may be processed for all pixels within the image processing module 1504. Since the amplitude is a fixed value or a value that is rarely changed, amplitude related commands may be sent to the I / O. 2 These may be provided individually via a simpler digital interface such as 1512. C. The control module 1516 interprets the digital data, which can be used by the PWM generator 1510 to generate PWM signals for the pixels, and by the digital-to-analog converter (DAC) 1512 to generate control signals to obtain the required current source amplitudes.

[0083] In some embodiments, the matrix micro LED array 1520 of FIG. 15 may include m pixels including m common-anode LEDs. In one exemplary embodiment, the pixel unit includes a single LED, LED1, and three transconductance devices (MOSFET switches) M1-M3, and is connected to a voltage source V1 (V LEDThe current is supplied by a P-channel MOSFET (also called a PWM signal). M3 is an N-channel metal-oxide semiconductor field effect transistor (MOSFET) whose gate is coupled to the amplitude control signal to generate the required current source amplitude. P-channel MOSFET M1 is in parallel with LED1 and forms a totem pole pair with N-channel MOSFET M2. The gates of the M1 and M2 transistor pair are connected together and coupled to the PWM signal. Thus, when PWM is high, M1 is turned off and M2 is turned on. Current flows through LED1, M2, and M3 at a value determined by the amplitude control signal coupled to the M3 gate. When PWM is low, M1 is turned on and M2 is turned off. As a result, the current source of M3 is shut off and the LEDs are rapidly discharged through M1.

[0084] FIG. 16 illustrates, by way of example, a block diagram of an embodiment of a machine 1600 (e.g., a computer system) for implementing one or more embodiments. The machine 1600 can implement techniques for managing under-driven or undriven uLED dies. The controller 990, the test equipment 992, the voltage source 102, or components thereof can include one or more of the components of the machine 1600. The controller 990, the test equipment 992, the voltage source 102, or one or more of the components thereof can be implemented, at least in part, using the components of the machine 1600. One exemplary machine 1600 (in the form of a computer) can include a processing unit 1602, a memory 1603, a removable storage 1610, and a non-removable storage 1612. Although an exemplary computing device is illustrated and described as the machine 1600, the computing device may be in different forms in different embodiments. For example, the computing device may instead be a smartphone, a tablet, a smartwatch, or other computing device that includes the same or similar elements as those illustrated and described with respect to FIG. 16. Devices such as smartphones, tablets, and smartwatches are commonly collectively referred to as mobile devices. Additionally, although various data storage elements are illustrated as part of machine 1600, storage may also or alternatively include cloud-based storage accessible over a network such as the Internet.

[0085] The memory 1603 may include volatile memory 1614 and non-volatile memory 1608. The machine 1600 may include or have access to a computer environment that includes a variety of computer readable media, such as volatile memory 1614 and non-volatile memory 1608, removable storage 1610 and non-removable storage 1612. Computer storage includes Random Access Memory (RAM), Read Only Memory (ROM), Erasable Programmable Read Only Memory (EPROM) & Electrically Erasable Programmable Read Only Memory (EEPROM), Flash memory or other memory technology, Compact Disc Read Only Memory (CD ROM), Digital Versatile Disk (DVD) or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device capable of storing computer readable instructions to perform the functions described herein.

[0086] The machine 1600 may include an input 1606, an output 1604, and a communication connection 1616 or have access to its computing environment. The output 1604 may include a display device, such as a touch screen, which may also function as an input device. The input 1606 may include one or more of a touch screen, a touch pad, a mouse, a keyboard, a camera, one or more device-specific buttons, one or more sensors integrated within the machine 1600 or coupled to the machine 1600 via a wired or wireless data connection, and other input devices. The computer may operate in a network environment using the communication connection to connect to one or more remote computers, such as database servers, including cloud-based servers and storage. The remote computers may include personal computers (PCs), servers, routers, network PCs, peer devices or other common network nodes, etc. The communication connections may include a local area network (LAN), a wide area network (WAN), cellular, IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), Bluetooth, or other networks.

[0087] Computer readable instructions stored in the computer readable storage device are executable by the processing unit 1602 (sometimes called a processing circuit) of the machine 1600. Hard drives, CD-ROMs, and RAM are some examples of articles that include non-transitory computer readable media such as storage devices. For example, a computer program 1618 can be used to cause the processing unit 1602 to execute one or more of the methods or algorithms described herein. Non-transitory does not mean immovable (cannot move).

[0088] To further illustrate the apparatus and related methods disclosed herein, a non-limiting list of examples is provided below. Each of the following non-limiting examples can exist alone or can be combined with any one or more of the other examples in any permutation or combination.

[0089] In example 1, a method includes, by a controller of a micro light emitting diode (uLED) die, determining a dynamic series resistance (R d ) or forward voltage (V f ), and by the controller, d Or V f Based on this, the maximum current level (I PWM_MAX ) PWM_0 ) and causing the uLED driver to supply current at the selected current level by the controller.

[0090] In Example 2, Example 1 is I PWM_0 In response to selecting, increasing, by the controller, a pulse width modulated (PWM) on-time of the uLED.

[0091] In Example 3, at least one of Examples 1 or 2 further comprises testing each uLED of the uLED die with a test instrument to determine whether the uLED has an R greater than a specified threshold. d Or V f The method may further include determining whether the

[0092] In Example 4, Example 3 stores a R d The method may further include storing data indicating an identification (ID) of each uLED of the uLED die, the data including:

[0093] In Example 5, Example 4 isd Based on the V of the uLED f is the maximum supply voltage (V LED ) so that I PWM_0 The method may further include determining:

[0094] In Example 6, any one of Examples 3 to 5 further comprises: the controller detecting an R d Or V f For each uLED of the uLED die, including PWM_0 This may further include selecting:

[0095] In Example 7, any one of Examples 3 to 6 may further include a step of: d Value or V f It can further include being a specified percentile of the values.

[0096] In Example 8, in any one of Examples 1 to 7, the maximum current level (I PWM_MAX ) PWM_0 ) is the step of selecting the outlier uLED R d Or V f and the average R of the non-outlier uLEDs of the uLED die d Or V f The outlier uLED is based on the difference between the average R of the uLED d Or V f R greater than a specified number of standard deviations d Includes.

[0097] Example 9 may include a system including a micro light emitting diode (uLED) die including a uLED and a respective uLED driver, a power source coupled to the uLED die, and a controller coupled to the uLED die, the controller controlling a dynamic series resistance (R d ) or forward voltage (Vf ) and identifying the identified R d Or V f Based on the maximum current level (I PWM_MAX ) PWM_0 ) and causing the power supply to supply current at the selected current level to the uLED driver.

[0098] In Example 10, the controller of Example 9 is PWM_0 In response to selecting, the method may further include increasing a pulse width modulation (PWM) on-time of the uLED.

[0099] In Example 11, at least one of Examples 9 or 10 further comprises testing each uLED of the uLED die to determine whether the uLED has an R greater than a specified threshold. d Or V f The device may further include a test device configured to determine whether the

[0100] In Example 12, Example 11 is a graph showing the R d The uLED die may further include a memory accessible by the controller of the uLED die to store data indicating an identification (ID) of each uLED of the uLED die, including:

[0101] In example 13, example 12 further comprises: d Based on the V of the uLED f is the maximum supply voltage (V LED ) so that I PWM_0 The method may further include being further configured to determine:

[0102] In Example 14, at least one of Examples 11 to 13 further comprises: the controller detecting an R d Or V fFor each uLED of the uLED die, including PWM_0 This may further include selecting:

[0103] Example 15, when executed by a machine, causes the machine to measure the dynamic series resistance (R d ) or forward voltage (V f ) and identifying the identified R d Or V f Based on the maximum current level (I PWM_MAX ) PWM_0 ) and causing a power source to supply current at the selected current level to the uLED driver.

[0104] In Example 16, Example 15 is the same as Example 15, wherein the operation is I PWM_0 In response to selecting, the controller may further include increasing a pulse width modulated (PWM) on-time of the uLED.

[0105] In Example 17, at least one of Examples 15 or 16 further comprises: the operations further comprising testing each uLED of the uLED die to determine whether the uLED has an R greater than a specified threshold. d Or V f The method may further include determining whether the

[0106] In Example 18, Example 17 further comprises: d The method may further include storing in a memory data indicating an identification (ID) of each uLED of the uLED die, the data including:

[0107] In Example 19, at least one of Examples 17 or 18 is further characterized in that the specified threshold is R across all uLEDs of the uLED die. d Value or V fIt can further include being a specified percentile of the value.

[0108] In Example 20, at least one of Examples 15 to 19 further comprises: PWM_MAX ) PWM_0 ) is the step of selecting the outlier uLED R d Or V f and the average R of the non-outlier uLEDs of the uLED die d Or V f The outlier uLED is based on the difference between the average R of the uLED d Or V f R greater than a specified number of standard deviations d It can further include including.

[0109] While exemplary embodiments of the subject matter disclosed herein have been shown and described, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art upon reading and understanding the materials provided herein without departing from the subject matter disclosed. It will be understood that various alternatives to the embodiments of the subject matter disclosed herein may be used in implementing various embodiments of the subject matter. The following claims define the scope of the disclosed subject matter, and it is intended that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. A controller of a micro light emitting diode (uLED) die controls the dynamic series resistance (R ｄ ) or forward voltage (V ｆ ) identifying For each uLED of the uLED die, determining whether the uLED includes an R d or V f greater than a specified threshold; The controller ｄ Or V ｆ Based on this, the maximum current level (I ＰＷＭ＿ＭＡＸ ) ＰＷＭ＿０ ) selecting a causing the uLED driver to supply current at the selected current level by the controller; A method comprising:

2. I ＰＷＭ＿０ and increasing, by the controller, a pulse width modulation (PWM) on-time of the uLED in response to selecting The method of claim 1.

3. A memory accessible by the controller of the uLED die stores a R greater than the specified threshold. ｄ storing data indicating an identification (ID) of each uLED of the uLED die, The method of claim 1.

4. The identified R ｄ Based on this, the V ｆ is the maximum supply voltage (V ＬＥＤ ) so that I ＰＷＭ＿０ determining a The method according to claim 3.

5. The controller detects an R that is greater than the specified threshold. ｄ Or V ｆ For each uLED of the uLED die, ＰＷＭ＿０ Select The method of claim 1.

6. The specified threshold is R across all uLEDs of the uLED die. ｄ Value or V ｆ is a specified percentile of values, The method of claim 1.

7. The maximum current level (I ＰＷＭ＿ＭＡＸ ) ＰＷＭ＿０ The step of selecting the outlier uLED is ｄ Or V ｆ and the average R of the uLED of the uLED die ｄ Or V ｆ and the outlier uLED is based on the difference between the average R ｄ Or V ｆ Outliers R greater than a specified number of standard deviations ｄ A uLED comprising: The method of claim 1.

8. 1. A system comprising: a micro light emitting diode (uLED) die including a uLED and a respective uLED driver; a power source coupled to the uLED die; a controller coupled to the uLED die, the controller comprising: The uLED dynamic series resistance (R ｄ ) or forward voltage (V ｆ ) and For each uLED of the uLED die, determining whether the uLED includes an R d or V f greater than a specified threshold; The identified R ｄ Or V ｆ Based on this, the maximum current level (I ＰＷＭ＿ＭＡＸ ) ＰＷＭ＿０ ) and click causing the power source to supply current at the selected current level to the uLED driver; The system is configured as follows.

9. The controller is ＰＷＭ＿０ and further configured to increase a pulse width modulation (PWM) on-time of the uLED in response to selecting The system of claim 8.

10. R greater than the specified threshold ｄ a memory accessible by the controller of the uLED die for storing data indicative of an identification (ID) of each uLED of the uLED die, The system of claim 8.

11. The controller ｄ Based on this, the V ｆ is the maximum supply voltage (V ＬＥＤ ) so that I ＰＷＭ＿０ and further configured to determine The system of claim 10.

12. The controller detects an R that is greater than the specified threshold. ｄ Or V ｆ For each uLED of the uLED die, ＰＷＭ＿０ Select The system of claim 8.

13. When executed by a machine, the machine: The dynamic series resistance (R ｄ ) or forward voltage (V ｆ ) identifying For each uLED of the uLED die, determining whether the uLED includes an R d or V f greater than a specified threshold; The identified R ｄ Or V ｆ Based on this, the maximum current level (I ＰＷＭ＿ＭＡＸ ) ＰＷＭ＿０ ) selecting a causing a power source to supply current at the selected current level to the uLED driver; 16. A machine-readable medium comprising instructions for performing operations including:

14. The operation includes: I ＰＷＭ＿０ and increasing, by the controller, a pulse width modulation (PWM) on-time of the uLED in response to selecting 14. The machine-readable medium of claim 13.

15. The operation includes: R greater than the specified threshold ｄ storing in a memory data indicating an identification (ID) of each uLED of the uLED die, 14. The machine-readable medium of claim 13.

16. The specified threshold is R across all uLEDs of the uLED die. ｄ Value or V ｆ is a specified percentile of values, 14. The machine-readable medium of claim 13.

17. The maximum current level (I ＰＷＭ＿ＭＡＸ ) ＰＷＭ＿０ The step of selecting the outlier uLED is ｄ Or V ｆ and the average R of the uLED of the uLED die ｄ Or V ｆ and the outlier uLED is based on the difference between the average R ｄ Or V ｆ Outliers R greater than a specified number of standard deviations ｄ An LED comprising:

14. The machine-readable medium of claim 13.

Images