Apparatus and method for detecting faults including built-in self-test

Abstract

Embodiments of the present disclosure relate to built-in self testing for light emitting diodes. In some examples, a device includes a built-in self test to detect a fault on a light emitting diode (LED) or a driver of the LED. The device includes a pair of pads configured to be connected to the LED. The built-in self test is configured to control the driver to turn on respective pass switches connected with pads in the pair of pads. The built-in self test is configured to determine a voltage level at each pad in the pair of pads. The built-in self test can determine whether a fault exists on the LED, across a first anode pad and a first cathode pad, or on the driver based on the voltage level at each pad.

Description

Technical Field

[0001] This disclosure relates to circuit arrangements for driving light sources such as light-emitting devices. Background Technology

[0002] A driver circuit can operate or drive one or more light sources, such as a light-emitting diode (LED). The driver circuit can control the light intensity output by the LED by changing the average current flowing through the LED and / or by changing the average forward voltage across the LED. For example, the driver circuit can increase the duty cycle of the current supplied to the LED to increase the light intensity generated by the LED. Similarly, the driver circuit can decrease the duty cycle of the current supplied to the LED to decrease the light intensity generated by the LED. At high switching frequencies, the human eye can perceive changes in the current duty cycle as changes in the brightness or intensity of the light generated by the LED.

[0003] Modern automotive LED headlights are characterized by multiple pixelated light sources, allowing for individual control of the brightness of activated pixel circuits or groups of pixel circuits. This control enables new lighting features such as glare-free high beam systems, adaptive drive beams, and symbol projection. To provide these specific features, as well as others, the headlights can deliver high-resolution light to the driver's entire field of vision.

[0004] Headlights can comprise a matrix array of numerous LEDs (e.g., over 16,000 LEDs) with fine pixel-to-pixel circuit pitch or fine display resolution. Headlights can be constructed using the concept of chip-on-chip stacking, where a second chip of LEDs is mounted on a first chip, which includes a light source matrix and drivers, using a mixing process. A first company can manufacture the first chip, while a second company can perform the mixing process. The manufacturing and mixing processes (especially when performed by different companies) can introduce multiple potential points of failure into the finished product. Summary of the Invention

[0005] This disclosure describes techniques for testing drivers and / or light-emitting diodes (LEDs) using built-in self-tests. The built-in self-test may include processing circuitry configured to test drivers and / or LEDs one after another (or in batches). The built-in self-test may be configured to test for faults on the driver, across pad pairs, or on the respective LEDs by activating the corresponding pass device and measuring the forward voltage across the pass device or at the corresponding anode pad and at the corresponding cathode pad.

[0006] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will become apparent from the specification, the drawings, and the claims. Attached Figure Description

[0007] Figure 1 This is a conceptual block diagram of a device including a driver for controlling the operation of a light source, based on the technology disclosed herein.

[0008] Figure 2 The circuit diagram of the amplifier for controlling the device according to the technology of this disclosure, wherein the device is connected in series with a light-emitting diode (LED).

[0009] Figure 3 This is a circuit diagram for three possible failure modes of a driver or LED, based on the technology disclosed herein.

[0010] Figure 4 This is a circuit diagram for calibrating a sensing resistor according to the technology disclosed herein.

[0011] Figure 5 and Figure 6 It is a circuit diagram for fault detection based on the technology of this disclosure.

[0012] Figure 7 This is a flowchart illustrating an example technique for detecting faults according to the present disclosure.

[0013] Figure 8 This is a circuit diagram for measuring the cathode voltage of two LEDs according to the technology disclosed herein.

[0014] Figure 9A and Figure 9B These are diagrams of two example test patterns that can be implemented using the built-in self-test according to the technology disclosed herein.

[0015] Figure 10 This is a circuit diagram of a device including a differential analog-to-digital converter according to the technology of this disclosure, the device being used to measure the forward voltage across an LED.

[0016] Figure 11 This is a flowchart illustrating an example technique for detecting faults between two LEDs according to the present invention. Detailed Implementation

[0017] This disclosure describes apparatus, methods, and techniques for testing light sources using a built-in self-test (BIST). The BIST can be configured to detect faults on the light source, across pad pairs, and / or in drivers configured to turn on the light source. The BIST can be configured to test the drivers before and / or after the light source is connected to the drivers (e.g., before mixing). For example, the BIST can be configured to perform front-end testing of the functionality of each current source (e.g., each driver) prior to the mixing process.

[0018] After the mixing process is complete, each light-emitting diode (LED) can be connected (e.g., soldered) to a dedicated current source. Therefore, each cathode (for low-side configuration) or each anode (for high-side configuration) may no longer be accessible, which could hinder testability, field return analysis, and self-diagnostic functions. For example, the BIST of this disclosure can be configured to inspect the quality of the component and distinguish whether a fault has occurred inside the LED chip, inside the current source driver chip, or across the pads used to mount the LED chip.

[0019] Figure 1 This is a conceptual block diagram of a device 100 according to the technology of this disclosure, which includes a driver 130 for controlling the operation of a light source 150. Figure 1 In the example, device 100 includes processing circuitry 110, BIST 120, driver 130, pass device 140, and pads 160 and 170. LED 150 and power supply 180 are optional components and may be part of device 100 in some examples. Additionally or alternatively, LED 150 and / or power supply 180 may be external components that can be connected, attached, and / or mounted to device 100. In some examples, device 100 may be a lighting device for vehicles, buildings, and any other systems that include lighting equipment.

[0020] Processing circuitry 110 can be configured to control driver 130 to operate LED 150. For example, processing circuitry 110 can be configured to cause one or more drivers 130 to turn on one or more corresponding devices 140, thereby turning on one or more corresponding LEDs 150. For example, processing circuitry 110 can pass a low-power control signal to driver 130, which can then generate a higher-power driver signal based on the control signal. Processing circuitry 110 can also be configured to receive a sensed signal indicating a positive voltage across one of the LEDs or corresponding pad pairs 160 and 170.

[0021] Processing circuitry 110 may include any suitable arrangement of hardware, software, firmware, or any combination thereof to perform the techniques attributed to processing circuitry 110 herein. Examples of processing circuitry 110 include any one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, and any combination of such components. When processing circuitry 110 includes software or firmware, it also includes any hardware for storing and executing the software or firmware, such as one or more processors or processing units. In an example where device 100 is mounted on a vehicle, processing circuitry 110 may be implemented by a headlight controller.

[0022] Typically, a processing unit may include one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuit devices, and any combination of these components. Although in Figure 1 Although not shown, the processing circuitry 110 may include a memory configured to store data. The memory may include any volatile or non-volatile medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, etc. In some examples, the memory may be external to the processing circuitry 110 (e.g., external to the package housing the processing circuitry 110).

[0023] Driver 130 can be configured to drive pass device 140 based on a signal received from processing circuitry device 110. Driver 130 may include amplifiers and / or level shifters to generate a relatively high-power signal based on a low-power signal received from processing circuitry device 110. For example, driver 130 may include a first driver configured to drive a first pass device and a second driver configured to drive a second pass device, wherein each pass device is configured to be connected to an LED. Additional example details of drivers for light-emitting diodes can be found in jointly assigned U.S. Patent No. 9,930,748, entitled “Synchronization for Light-Source Driver Circuitry,” issued March 27, 2018, and jointly assigned U.S. Patent No. 10,297,190, entitled “Pixel Selection Method for a Light-Source Matrix Driver,” issued May 21, 2019, the entire contents of which are incorporated herein by reference.

[0024] Device 140 can be used as a switch to turn on and off. Additionally or alternatively, device 140 can be operated as an analog device capable of operating in a linear mode. In some examples, driver 130 can be configured to drive device 140 to increase or decrease the current level conducted through device 140.

[0025] LED 150 may include two or more light sources, such as light-emitting diodes (LEDs) or any other suitable light source. Although described in the context of LEDs, the techniques disclosed herein can also be applied to other light sources. LED 150 may be arranged in a matrix or grid of rows and columns, and each light source may be a pixel circuit. In some examples, LED 150 may include 16,384 light sources arranged in a grid of 128 light sources by 128 light sources. Alternatively, LED 150 may include 1,024 light sources arranged in a grid of 32 light sources by 32 light sources.

[0026] Each LED 150 can be driven by a corresponding pass device 140. In some examples, each LED can be connected in series with a corresponding pass device between two power rails (e.g., power supply 180). LED 150 can be part of an external device, which can be mounted on and electrically connected to pads 160 and 170. Pad 160 can be connected to the cathode of LED 150, while pad 170 can be connected to the anode of LED 150. Alternatively, pad 160 can be connected to the anode of LED 150, while pad 170 can be connected to the cathode of LED 150, and power supply 180 can be connected to pass device 140. LED 150 can be as follows: Figure 1 The arrangement of the connection shown between the power supply 180 and the pass device 140, or between the pass device 140 and the LED 150, can be reversed so that the pass device 140 can be connected between the power supply 180 and the LED 150 (see, for example, see...). Figure 2 ).

[0027] Power supply 180 can be configured to supply power to LED 150 via pads 170 and 182. Power supply 180 may include a battery or other power storage unit, a connection to a mains power supply, and / or one or more power conversion circuits. In some examples, power supply 180 may be external to device 100, but in other examples, power supply 180 may be part of device 100. Device 100 may include one or more pads 182 to allow power supply 180 to be mounted on and electrically connected to device 100.

[0028] External device 192 can be connected to diagnostic interface 190 to communicate with processing circuitry 110 and BIST 120. For example, processing circuitry 110 can be configured to transmit data related to the operation of device 100 to external device 192. In some examples, BIST 120 can receive command signals (e.g., one or more bits) from external device 192 and can be configured to perform a built-in self-test in response to receiving a command signal. Additionally or alternatively, BIST 120 can be configured to perform built-in self-tests during manufacturing and / or at predetermined time intervals. BIST 120 can be configured to perform self-tests before or after the mixing process is completed (e.g., front-end or back-end), after the assembled device is soldered to a printed circuit board (PCB), and / or when the device is ready to operate in an end-use system (e.g., an automobile).

[0029] When LED 150 is mounted on driver 130, testing for faults in LED 150 or driver 130 can be difficult. When LED 150 is mounted on driver 130, the nodes between the LED and the corresponding driver may be hidden or covered by the LED chip. Because some nodes are inaccessible, test probes may not be able to reach these nodes to measure current or voltage.

[0030] Simulation test equipment can be used to measure the forward voltage across each LED or pad pair, but for matrices with thousands of LEDs, the measurement time is very long. As the number of LEDs in the matrix steadily increases, simulation testing becomes extremely time-consuming and expensive.

[0031] It is important to check the functionality of the LEDs and drivers to ensure that the final LED device will operate correctly. Testing at multiple points during manufacturing and assembly allows for the rapid detection of faults. Testing at intermediate points also allows for the identification of the type and location of each fault, which can be used to troubleshoot and optimize the manufacturing and assembly process.

[0032] According to the technology disclosed herein, BIST 120 can be configured to detect faults in driver 130, pass device 140, and / or LED 150 by individually testing each driver of driver 130 or individually testing each LED of LED 150. To individually test the first driver or the first LED, BIST 120 can be configured such that the first driver turns on the first pass device, which is configured to connect to the first LED. BIST 120 can then be configured to determine the voltage level at the corresponding pad pair 160 and 170 when the first pass device is activated. BIST 120 can be configured to individually test each LED of LED 150 after LED 150 has been connected to pads 160 and 170. Based on the voltage level, BIST 120 can determine whether a fault exists in the first LED or the first driver.

[0033] In some examples, BIST 120 can also be configured to determine the voltage across each driver of driver 130 individually. Based on the voltage across the drivers, BIST 120 can be configured to determine whether a fault exists on the driver and / or on the corresponding LED. BIST 120 can be configured to test each driver of driver 130 individually before and / or after LED 150 is connected to pads 160 and 170.

[0034] When performing the built-in self-test, BIST 120 can store a fault count in memory 112. For example, BIST 120 can be configured to increment a counter in response to identifying each fault. Multiple counters can exist to record multiple fault types. BIST 120 can store data indicating different categories of faults, such as short-circuit faults, open-circuit faults, LED faults, driver faults, etc., in memory 112. BIST 120 can be configured to store the location and / or index of each faulty LED or driver. BIST 120 can also store data related to the positive voltage measured by processing circuitry 110. BIST 120 can be configured to output data related to the built-in self-test to external device 192.

[0035] Processing circuitry 110 can be configured to perform remedial actions in response to a detected fault. For example, processing circuitry 110 can be configured to set a fault indicator bit to prevent the driver from activating the corresponding LED by turning on the corresponding device. The user can define actions to be taken in response to one or more possible faults. Processing circuitry 110 can store one or more user-selected options in memory 112, allowing processing circuitry 110 to employ associated options.

[0036] The BIST 120 can be configured to execute test routines in the digital domain, which can be much faster than testing in the analog domain. For example, the BIST 120 can be configured to test each LED in ten to twenty microseconds. In comparison, analog test routines can take approximately five to ten milliseconds to test each LED. Therefore, test routines implemented with the BIST 120 can be significantly faster than other testing methods such as analog testing.

[0037] Furthermore, the test routines implemented by the BIST 120 include voltage measurements at two points. One of these measurement points can be either the positive or negative power supply, which is more easily accessible than the node between the LED and the driver. The BIST 120 can be configured to use a connection network to access the node between the LED and the driver, eliminating the need for manual connection to internal nodes.

[0038] Figure 2 This is a circuit diagram of amplifiers 230A-230C connected in series with LEDs 250A-250C via devices 240A-240C, according to the technology of this disclosure. The apparatus of this disclosure may include processing circuitry 210, amplifiers 230A-230C, via devices 240A-240C, cathode pads 260A-260C, anode pads 270A-270C, and power pads 282. In some examples, the apparatus may also include LEDs 250A-250C and / or one or more power supplies connected to cathode pads 260A-260C and / or power pads 282.

[0039] Processing circuitry 210 may include digital logic configured to generate low-power control signals and pass them to amplifiers 230A-230C. In some examples, each driver may include separate digital logic, rather than a single centralized block of processing circuitry 210. Additionally or alternatively, the device may include multiple digital logic blocks, each generating control signals for more than one driver. Figure 2 The term "driver" as used in the description includes one of amplifiers 230A-230C and a corresponding pass device among pass devices 240A-240C. For example, a first driver may include amplifier 230A and pass device 240A, a second driver may include amplifier 230B and pass device 240B, and a third driver may include amplifier 230C and pass device 240C. Alternatively, the term driver may also include digital logic for generating control signals.

[0040] Amplifiers 230A-230C can be configured to generate a higher-power driver signal (e.g., by amplifying a lower-power control signal) to drive devices 240A-240C. Amplifiers 230A-230C can pass the driver signal to control terminals (e.g., gate or base terminals) of devices 240A-240C. For example, amplifier 230A can activate device 240A by passing a driver signal to its gate. Amplifiers 230A-230C can also be configured to regulate the current flowing through devices 240A-240C by operating devices 240A-240C as analog devices, rather than as digital devices with only two states (on and off).

[0041] Devices 240A-240C may include, but are not limited to, any type of field-effect transistor (FET), bipolar junction transistor (BJT), insulated-gate bipolar transistor (IGBT), high electron mobility transistor (HEMT), and / or another element controlled by voltage. Devices 240A-240C may include n-type transistors and / or p-type transistors. Devices 240A-240C may include elements such as silicon, silicon carbide, and / or gallium nitride. In some examples, devices 240A-240C include a freewheeling diode connected in parallel with the transistor to prevent reverse breakdown of the transistor.

[0042] LEDs 250A-250C can be individually formed on separate chips along with processing circuitry 210, amplifiers 230A-230C, and pass-through devices 240A-240C. The chips for LEDs 250A-250C can be attached after manufacturing the device including processing circuitry 210, amplifiers 230A-230C, and pass-through devices 240A-240C. LEDs 250A-250C can be attached to pads 260A-260C and 270A-270C during a bonding process that includes mounting and electrically connecting LEDs 250A-250C to pads 260A-260C and 270A-270C. Another attachment process can be used to connect power to pad 282, allowing the power supply to deliver power to pass-through devices 240A-240C.

[0043] In some examples, the ratio of LEDs to pass-through devices and amplifiers can be one to one. For instance, an LED matrix may include approximately 16,000 LEDs, with the LED matrix block mounted on a device having approximately 16,000 pass-through devices and approximately 16,000 amplifiers. As another example, an LED matrix may include approximately 1,000 LEDs, with the LED matrix block mounted on a device having approximately one pass-through device and approximately one amplifier. Alternatively, the number of pass-through devices and amplifiers may be less than the number of LEDs, and each pass-through device may be configured to control more than one LED.

[0044] Figure 2 The configuration shown is merely an example. The orientation of LEDs 250A-250C can be reversed, such that through-devices 240A-240C are connected to the cathode of LEDs 250A-250C. Additionally, there may be only one cathode pad instead of multiple cathode pads 260A-260C, where the cathodes of LEDs 250A-250C can be connected together within the LED chip. In the example of a single cathode pad, "pad pair" refers to one of the anode pads 270A-270C and a single cathode pad. In some examples, LEDs 250A-250C may be part of the same device as amplifiers 230A-230C and through-devices 240A-240C, such that pads 260A-260C and 270A-270C are internal nodes rather than external pads.

[0045] A fault may exist on one of the LEDs 250A-250C. The fault can be a short circuit across the LED (low resistance or no resistance) or an open circuit (high resistance or infinite resistance). The processing circuit device 210 can be configured to detect a short circuit across the LED by determining that the voltage across the LED is less than a minimum threshold voltage when the LED is activated. The processing circuit device 210 can be configured to detect an open circuit across the LED by determining that the voltage across the LED is greater than a maximum threshold voltage when the LED is activated. The minimum and maximum threshold voltages can be limitations on the acceptable voltage range of the activated LED. In response to determining a fault on the LED, the processing circuit device 210 can store the LED's position or index and / or increment a counter.

[0046] A fault may exist in one of the amplifiers 230A-230C or in one of the pass devices 240A-240C. The fault may be a short circuit (low resistance or no resistance) or an open circuit (high resistance or infinite resistance) across the pass device, or some other fault on the amplifier. The processing circuitry 210 may be configured to detect a short circuit across the pass device by determining that the voltage across the pass device is greater than a first threshold voltage. The processing circuitry 210 may be configured to detect an open circuit across the pass device by determining that the voltage of the activated pass device is less than a second threshold voltage.

[0047] Processing circuitry 210 can be configured to detect the presence of a fault in the amplifier or pass device before the LEDs 250A-250C are attached to pads 260A-260C and 270A-270C. For example, a sensing resistor can be connected to the anode and cathode pads, and processing circuitry 210 can detect the voltage across the sensing resistor. Processing circuitry 210 can be configured to detect a short circuit across the pass device by determining that the voltage across the sensing resistor is greater than a first threshold voltage when the pass device is activated. Processing circuitry 210 can be configured to detect an open circuit across the pass device by determining that the voltage across the LED is less than a second threshold voltage when the pass device is activated. The first and second threshold voltages can include an acceptable window of voltage across the sensing resistor prior to the mixing process, wherein voltages outside the acceptable window indicate a fault in the pass device.

[0048] Figure 3 This is a circuit diagram illustrating three possible failure modes for driver 330A or LED 350A according to the technology of this disclosure. Section 302 includes drivers 330A and 330B, each driver including devices 340A and 340B, LEDs 350A and 350B, and pads 360A, 360B, 370A, and 370B. In some examples, LEDs 350A and 350B may be part of a device separate from drivers 330A and 330B.

[0049] Drivers 330A and 330B are described as current sources because turning on the device allows current to flow through the corresponding LED. For example... Figure 2 As shown, each of drivers 330A and 330B may include an amplifier configured to drive a pass device. When the pass device is turned on, current can flow from power supply 380 through the pass device and the LED to power supply 384. When the pass device is turned off, a current source IALi may draw or supply current. Current source IALi may be part of driver 330A, and current source IALj may be part of driver 330B.

[0050] Semiconductor dies, including LEDs 350A and 350B, can be mounted on pads 360A, 360B, 370A, and 370B during the mixing process. In addition to LEDs 350A and 350B and power supplies 380 and 384, individual semiconductor dies or semiconductor substrates may include... Figure 3All components are shown. In the example where a single anode pad exists instead of multiple pads 370A and 370B, the anode terminals of LEDs 350A and 350B can be connected to the single anode pad during the mixing process. In the example where a single anode pad exists, each anode pad in cathode pads 360A and 360B can be paired with the single anode pad.

[0051] Resistors 322, 324, and 326 represent potential faults within section 302. Resistor 322 represents a potential short-circuit or open-circuit fault across pads 360A and 370A (before mixing) or across LED 350A (after mixing). Before mixing, an open circuit is expected across pads 360A and 370A. BIST can be configured to detect short-circuit faults across pads 360A and 370A or across LED 350A by determining that the forward voltage across pads 360A and 370A is less than a minimum threshold voltage. BIST can be configured to detect open-circuit faults across pads 360A and 370A or across LED 350A by determining that the forward voltage across pads 360A and 370A is greater than a maximum threshold voltage.

[0052] Resistor 324 indicates a possible short-circuit or open-circuit fault between pads 360A and 360B (before or after mixing) or between the anodes of LEDs 350A and 350B (after mixing). BIST can be configured to detect faults between pads 360A and 360B based on the forward voltage across LED 350A and the forward voltage across LED 350B. Figure 3 As shown, LEDs 350A and 350B are adjacent LEDs, but in some examples, faults between two non-adjacent LEDs can be detected.

[0053] Resistor 326 indicates a possible short-circuit or open-circuit fault across driver 330A before or after the mixing process to attach LEDs 350A and 350B. BIST can be configured to detect a short-circuit fault across driver 330A by determining that the voltage across driver 330A is less than a lower threshold voltage. BIST can be configured to detect an open-circuit fault across driver 330A by determining that the voltage across driver 330A is greater than an upper threshold voltage.

[0054] A short circuit can be defined as a resistance less than the minimum threshold resistance, not necessarily zero resistance. Therefore, the voltage across a short circuit can be zero or a small non-zero voltage. An open circuit can be defined as a resistance greater than the maximum threshold resistance, not necessarily infinite resistance. The voltage across an open circuit can be infinite or a large finite voltage.

[0055] Power supplies 380 and 384 can be part of another external device. For example, pads 382 and 386 can be mounted on a PCB that includes connections to power supplies 380 and 384. In some examples, each pad 382 and 386 may include multiple individual pads for parallel connection to, for example, bonding wires. Power supplies 380 and 384 may include power rails for positive and negative power supplies, such as VDDP and reference ground. Power supplies 380 and 384 may include power supplies such as batteries or connections to a main power supply.

[0056] Figure 4 This is a circuit diagram for calibrating a sense resistor 424 according to the technology of this disclosure. Logic 410 can be configured to calibrate the sense resistor 424 for front-end testing (e.g., before mixing) to reduce or eliminate resistance spread. Calibration of the sense resistor 424 can provide a more accurate measurement of the absolute value of the current flowing through each LED in segment 402. Logic 410 can be configured to calibrate the sense resistor 424 by changing the resistance of the adjustable resistor 426.

[0057] Logic 410 can be configured to determine an adjustment factor representing the resistance of adjustable resistor 426. Logic 410 can store the adjustment factor in a factor storage device 412, which may include one-time programmable memory, flash memory, or electrically erasable programmable read-only memory. Logic 410 can be configured to use the adjustment factor stored in the application field in addition to front-end testing. Adjustment is optional; alternatives include external resistors or unadjusted internal resistors. In some examples, the device may include an internal sensing resistor and pads for connecting an optional external sensing resistor. Alternatively, in the absence of any internal sensing resistor, the device may include pads for an external resistor. External resistors can increase the number of components on the application board (e.g., a PCB). Using an unadjusted internal resistor can cause diffusion of the actual resistance value, potentially introducing inaccuracies in voltage sensing. Therefore, the resulting Gaussian distribution of resistance may have an average value that deviates from the expected value.

[0058] The network connection 432 includes switches S1 and S2. N and S R This is used to select and sense individual nodes in segment 402. To calibrate the sensing resistor 424, calibration routine 414 can be configured to switch S1 to S... N Disconnect and turn switch S RA closed loop connects the sensing resistor 424 and the adjustable resistor 426 to the test pad 438. A current source 436 can force an external current from the power supply 480 to flow through the sensing resistor 424 and the adjustable resistor 426. A differential analog-to-digital converter (ADC) 422 can convert the voltage across the sensing resistor 424 into a digital number. A calibration routine 414 can be configured to perform a calibration routine by changing the equivalent resistance of the adjustable resistor 426. The calibration routine 414 can be configured to store adjustment coefficients into a coefficient storage device 412. Further example details of the adjustment can be found in commonly assigned U.S. Patent No. 10,069,399, entitled “Selecting an Aspect Ratio for Current Monitoring,” published September 4, 2018, the entire contents of which are incorporated herein by reference.

[0059] although Figures 4 to 6 as well as Figure 10 A single ADC is depicted, but in some examples, the device may include multiple ADCs to allow for parallel testing of LEDs. For example, the device may include four ADCs, where each ADC is configured to test a subset (e.g., a quarter) of the LEDs in the device. A device with multiple ADCs can be configured to execute multiple test routines in parallel, where each test routine uses one of the ADCs.

[0060] Figure 5 and Figure 6 This is a circuit diagram for fault detection based on the technology disclosed herein. Figure 5 The test routine setup shown allows logic 510 to read the positive voltage of each LED. Figure 5 The test routines shown can be used for front-end testing (e.g., before mixing), as well as back-end testing, end-of-line testing, and application field testing. Logic 510 can be configured to evaluate whether LEDs have been connected across pad pairs, or conversely, whether there are open or short circuits across pad pairs.

[0061] To enable the routine, the finite state machine (FSM) 514 can be configured to control the connection network 532 by disconnecting switch S. R The ADC 522 is then disconnected from the sensing resistor 524. The FSM 514 can then be configured to... (The sentence is incomplete and requires more context to translate accurately.) FSM The ADC 522 is connected to test pad 538. Test pad 538 is shared by all LEDs in segment 502, and logic 510 can be configured to connect LEDs one by one to test pad 538. FSM 514 can turn on the LEDs by activating their drivers one by one, while the ADC 522 can be activated by controlling switches S1 to S2 connected to the ADC 522. NThe FSM 514 sequentially senses the forward voltage of the LEDs. Alternatively, it can turn on all LEDs connected in parallel, but this method results in higher power consumption. The FSM 514 can also turn on all LEDs at once and then continue determining the forward voltage across each LED.

[0062] The ADC 522 converts a forward voltage across a current source 530A into a digital number. An internal logic calculator within logic 510 can be configured to evaluate whether the digital number is greater than a maximum threshold voltage or less than a minimum threshold voltage. The current source 530A is an example used to control LED drivers (e.g., amplifiers and pass-through devices).

[0063] In response to determining that the voltage across current source 530A is greater than an upper threshold voltage, logic 510 can be configured to store the corresponding pixel circuit index and report an open-circuit condition. In response to determining that the voltage across current source 530A is less than a lower threshold voltage, logic 510 can be configured to store the corresponding pixel circuit index and report a short-circuit condition. The upper and lower threshold voltages may include an acceptable window for the voltage across current source 530A. Logic 510 can be configured to store the count of each fault in register 512. Logic 510 can then report the fault count and the location of each fault to an external device via diagnostic interface 590.

[0064] Logic 510 can be configured to run test routines in an application environment (e.g., during normal operation) by enabling test routines upon device startup. Logic 510 can be configured to execute test routines at regular and / or predetermined intervals, and / or logic 510 can be configured to execute test routines in response to, for example, receiving a command signal from an external device via diagnostic interface 590. Logic 510 can be configured to transmit the results of the test routines to an external device via diagnostic interface 590 to notify the user of faulty pixel circuits and fault counts. Test results can allow the user to screen out defective components and evaluate the results of the mixing process.

[0065] Figure 6 Test routines for measuring output current during front-end or back-end testing are described. For front-end testing (e.g., before the mixing process), logic 610 can be configured to check the functionality of each current source within a reasonable timeframe to obtain statistics for testing and data storage at a low cost. Logic 610 can be configured to test each current source in front-end post-assembly or back-end (e.g., after the mixing process), assess the impact of the assembly process on the output current, and distinguish whether a fault exists on the LED attachment side or the current source side. Post-assembly testing can be important for locating faults and for field return analysis.

[0066] The sensing resistor 624 may include an internal resistor (e.g., unadjusted or previously adjusted) or an external resistor. Logic 610 may be configured to control the connection network 632 such that current from the driver flows across the sensing resistor 624. Logic 610 may be configured to test drivers one by one by connecting the sensing resistor 624 to a first driver, then connecting the sensing resistor 624 to a second driver, and so on. ADC 622 may be configured to sense the voltage across the sensing resistor 624, indicating the voltage across a selected LED. ADC 622 may convert the voltage across the sensing resistor 622 into a digital number. The positive input of ADC 622 is configured to receive a first signal indicating a voltage level at a first end of the sensing resistor 624 (e.g., the end connected to power supply 680). The negative input of ADC 622 is configured to receive a second signal indicating a voltage level at a second end of the sensing resistor 624 (e.g., the end connected to test pad 638).

[0067] To enable automatic routines, the FSM 614 can be configured to switch S... FSM Close the circuit to connect the ADC 622 to the sensing resistor 624, and switch S... R The ADC 622 is connected to the test pad 638. The FSM 614 can be configured to turn on each driver one by one (or alternatively, all drivers in parallel at once), and each current source is sequentially connected to the sense resistor 624. The current from the attached driver will flow through the sense resistor 624, and the ADC 622 can convert the voltage across the sense resistor 624. Based on Ohm's law and the known resistance of the sense resistor 624, logic 610 can determine the current conducted by the respective driver. Logic 610 can be configured to determine whether a fault exists on the driver based on whether the determined current falls within an acceptable range.

[0068] To determine if a fault exists in the driver, logic 610 can be configured to evaluate whether the number of digits output by ADC 622 is outside an acceptable range, defined by a maximum threshold voltage and a minimum threshold voltage. For example, in response to determining that the forward voltage across LED 650A is greater than the maximum threshold voltage, logic 610 can be configured to determine that an open circuit exists across pads 660A and 670A. In response to determining that the forward voltage across LED 650A is less than the minimum threshold voltage, logic 610 can be configured to determine that a short circuit exists across pads 660A and 670A. Logic 610 can also be configured to determine whether the cathode terminal of LED 650A is correctly connected to cathode pad 670A, or whether that connection is missing or obstructed.

[0069] In response to determining that the number of digits is outside an acceptable range, logic 610 can be configured to store an indication of the pixel circuit index and / or fault type. Logic 610 can also be configured to store data such as the number of fault counts, minimum and maximum voltages (e.g., the number of digits output by ADC 622), and / or average voltage into coefficient storage device 612. The minimum, maximum, and average voltages can be based on all voltages sensed by ADC 622.

[0070] Logic 610 can be configured to store test parameters into a set of registers. Test parameters may include bits for enabling an output current measurement routine, bits for enabling a VLED forward voltage measurement routine, and bits for enabling sense resistor calibration. Test parameters may also include set times between two consecutive current source selections, the number of repetitions on the same current source, high-side and low-side limits (e.g., maximum and minimum threshold voltages), and maximum, minimum, and average threshold current and voltage values. Test parameters may also include maximum and minimum pixel circuit coordinate values ​​for testing, and one or more counters for the number of faults detected.

[0071] Logic 610 can be configured to report all stored data to external devices via diagnostic interface 690. Using all the data stored in the diagnostic registers, logic 610 can read the maximum, minimum, and average values ​​of the digital counts and evaluate the Gaussian distribution and process capability index (CPK) without needing to know the statistics for all current sources. Logic 610 can execute test routines before or after the LED is mounted on the current source. For example, a sense resistor 624 can be connected in parallel to the LED. With an appropriately selected resistance value, current can be partially or completely bypassed from the LED, allowing current from the driver to flow across the sense resistor 624. By setting the resistance of the sense resistor 624 low enough, logic 610 can measure the current conducted by the driver by measuring the voltage across the sense resistor 624.

[0072] In the example where logic 610 identifies a fault on an LED, logic 610 can be configured to check for a fault in the LED and / or the corresponding driver by connecting a sensing resistor 624 in series with the driver. Logic 610 can use Figure 6 The configuration shown is used to distinguish between LED faults and driver faults using output current measurements.

[0073] Figure 7 This is a flowchart illustrating an example technique for fault detection according to the present disclosure. (Reference) Figure 2 The circuit shown describes Figure 7 This is one technology, but other components can exemplify similar technologies.

[0074] exist Figure 7 In the example, processing circuitry 210 causes amplifier 230A of the first driver to be turned on via device 240A (700). Processing circuitry 210 can pass a control signal to amplifier 230A, and amplifier 230A can generate a higher power driver signal based on the control signal. In the example where LED 250A is mounted on pads 260A and 270A, processing circuitry 210 can turn on LED 250A by controlling amplifier 230A to be activated via device 240A.

[0075] exist Figure 7 In the example, processing circuitry 210 determines (702) the voltage levels at anode pad 270A and cathode pad 260A. To sense the voltage levels, processing circuitry 210 can be configured to control a network of switches to connect a sensing resistor across pads 260A and 270A. A differential ADC can be configured to convert the voltage across the sensing resistor into a digital number indicating the voltage across pads 260A and 270A (e.g., the voltage difference between pads 260A and 270A).

[0076] exist Figure 7 In one example, processing circuitry 210 determines (704) a fault in the driver or LED 250A based on the voltage levels at pads 260A and 270A. In an example where LED 250A is not yet mounted on pads 260A and 270A, processing circuitry 210 may be configured to determine a fault in the driver (e.g., amplifier 230A or through device 240A) or across the gap between pads 260A and 270A, which should be open before LED 250A is attached.

[0077] In an example where LED 250A is mounted on pads 260A and 270A, processing circuitry 210 can be configured to first determine the voltage drop across device 240A when LED 250A is turned on. In response to detecting that the voltage drop across device 240A is outside an acceptable range, processing circuitry 210 can then determine the voltage across pads 260A and 270A to determine if a fault exists on device 240A and / or LED 250A. In an example where processing circuitry 210 determines that both voltage levels are outside an acceptable range, processing circuitry 210 can be configured to store indications of two different faults.

[0078] Figure 8This is a circuit diagram for measuring the cathode voltage of two LEDs 850A and 850B according to the technology of this disclosure. To detect a fault between LEDs 850A and 850B, logic 810 can be configured to control connection network 832 to connect cathode pads 860A and 860B sequentially to test pad 838. For example, when cathode pad 860A is connected to test pad 838, current source 836 can draw current from LED 850A.

[0079] Current sensor 834 is configured to measure the current conducted by current source 836. With cathode pad 860A connected to test pad 838 and cathode pad 860B connected to test pad 838, logic 810 can determine the presence of an LED-to-LED fault based on the current sensed by current sensor 834. For example, logic 810 can be configured to force current through LED 850A (e.g., by activating driver 830A) and check for current on cathode pad 860B. Current from LED 850A should not be present on cathode pad 860B unless there is a relatively low resistance path between cathode pads 860A and 860B.

[0080] Figure 9A and Figure 9B This diagram illustrates two example test patterns 900A and 900B, implemented by BIST according to the technology of the present invention. BIST can be configured to automatically execute low-power test routines using test patterns 900A and 900B. Test patterns 900A and 900B use complementary checkerboard patterns. BIST can be configured to use test patterns 900A and 900B to detect a specific fault mode: LED-to-LED short circuits.

[0081] Test patterns 900A and 900B, along with the automatic measurement of internal parameters via a differential ADC, allow for fully automated detection of LED-to-LED faults (e.g., for verifying inter-channel crosstalk). For each test pattern in test patterns 900A and 900B, BIST can create a complementary checkerboard pattern by setting the state of the i-th cell to 100% (activated) and setting the state of the (i+1)-th cell to 0% (deactivated). The cells can be numbered sequentially such that the first cell is adjacent to the second cell, the second cell is adjacent to the third cell, and so on. If the sixteenth cell is at the end of a row, then the seventeenth cell is at the beginning of the next row. Test pattern 900B is the inversion of test pattern 900A.

[0082] For test pattern 900A, BIST can be configured to turn on a first subset of LEDs. The first subset may include a first LED, a third LED, a fifth LED, etc. For test pattern 900A, BIST can also be configured to turn off a second subset of LEDs. The second subset may include a second LED, a fourth LED, a sixth LED, etc. The first and second subsets of LEDs can form a pattern as follows: Figure 9A and Figure 9B The test pattern shown is a checkerboard or checkerboard design. Other test patterns are also possible, such as circular or striped patterns. For example, a test pattern could be used to sense a fault between two diagonally positioned LEDs (e.g., different rows and different columns).

[0083] Figure 10 This is a circuit diagram of a device including a differential ADC 1022, according to the technology of this disclosure, for measuring the forward voltage across an LED. When a specific light pattern is applied, logic 1010 can be configured to execute an automatic routine involving using ADC 1022 to measure the forward voltage across each LED in the entire matrix. To enable the automatic routine, logic 1010 can be configured to control connection network 1032 to connect ADC 1022 to power supply 1080 and the cathode pads 1060A or 1060B of the selected pixel circuitry using a switch labeled DIAG_SEL.

[0084] Logic 1010 may include an internal FSM configured to automatically enable ADC 1022 to convert the forward voltage of each LED into a digital number. An internal logic calculator may be configured to evaluate whether the forward voltage of the activated LED pixel circuit is within the acceptable range for the activated LED. The internal logic calculator may also be configured to evaluate whether the forward voltage of the deactivated LED pixel circuit is within the acceptable range for the deactivated LED. Figure 10 In the example shown, LED 1050A is the activated LED, while LED 1050B is the deactivated LED.

[0085] Each acceptable range may include a corresponding upper threshold and a corresponding lower threshold. The acceptable range for an activated LED may include the typical forward voltage for the LED, which, depending on the type of LED, may be between 1.7 volts and 3.3 volts. The upper threshold voltage for an activated LED may be in the range of four to five volts, such as 4.5 volts. In an example where LED 1050A includes multiple LEDs connected in series, the typical voltage may be higher than 3.3 volts. The acceptable range for a deactivated LED may include zero volts. Each acceptable range may be wider than the typical voltage; for example, the acceptable range for a deactivated LED may be -0.3 volts to +0.6 volts. Therefore, to determine whether a fault exists between cathode pads 1060A and 1060B, logic 1010 may be configured to determine whether the forward voltage of LED 1050A is less than the lower threshold voltage of the activated LED and whether the forward voltage of LED 1050B is greater than the upper threshold voltage of the deactivated LED.

[0086] In some examples, for the activated LED, the expected forward voltage at the GND node is approximately 3 volts higher than the reference ground, and the voltage level of VDDP is 4 volts higher than the reference ground. Therefore, the expected voltage level at cathode pad 1060A is approximately one volt higher than the reference ground. Logic 1010 can be configured to detect a short circuit or some other fault from cathode pad 1060A to VDDP in response to determining that the voltage level at cathode pad 1060A is greater than an upper threshold voltage, such as two volts higher than the reference ground. Logic 1010 can also be configured to detect a short circuit from cathode pad 1060A to the reference ground in response to determining that the voltage level at cathode pad 1060A is less than a lower threshold voltage, such as 0.5 volts higher than the reference ground.

[0087] If the conversion value of the forward voltage across LEDs 1050A and 1050B exceeds the corresponding acceptable range, it means that a dirty resistor has been placed between adjacent pixel circuits. For example, an open circuit (e.g., high resistance) is desirable between cathode pads 1060A and 1060B. If the resistance drops below an acceptable level, the voltage measured by the ADC1022 at cathode pads 1060A and 1060B will be outside the acceptable voltage range.

[0088] The logic 1010 can be configured to store the number of detected faults and the location of each fault in memory. The logic 1010 can be further configured to report this data to an external device via a diagnostic interface. Fault testing between LEDs can be performed at the back end, line end, or field. Back end testing can be performed after the mixing process is complete, line end testing can be performed after the LED equipment is fully assembled, and field testing can be performed after the equipment is installed and operated.

[0089] Test parameters for LED-to-LED testing may include stored values ​​for checkerboard pattern types, values ​​for set times between two consecutive current source selections, the number of repeated transitions on the same current source, high-side and low-side limits (e.g., maximum and minimum threshold voltages), and maximum, minimum, and average threshold current and voltage values. Test parameters may also include maximum and minimum pixel circuit coordinate values ​​for testing, and one or more counters for the number of faults detected.

[0090] Figure 11 This is a flowchart illustrating an example technique for detecting faults between two LEDs according to the present invention. (Reference) Figure 10 The circuit shown is used to describe Figure 11 This is one technique, but other components can also exemplify similar techniques.

[0091] exist Figure 11 In the example, logic 1010 activates LED 1050A (1000) and deactivates LED 1050B (1002). Logic 1010 can activate LED 1050A by causing driver 1030A to activate the pass device connected to LED 1050A. Activating the pass device allows current to flow through LED 1050A. Logic 1010 can deactivate LED 1050B by causing driver 1030B to deactivate the pass device connected to LED 1050AB. Activating the pass device prevents or reduces the current flowing through LED 1050B.

[0092] exist Figure 11 In the example, logic 1010 determines the forward voltage across LED 1050A (1004) and the forward voltage across LED 1050B (1006). Logic 1010 can measure the forward voltage across LED 1050A by connecting ADC 1022 across pads 1060A and 1070A. Logic 1010 can be configured to subsequently control connection network 1032 to disconnect ADC 1022 from pads 1060A and 1070A and connect ADC 1022 to pads 1060B and 1070B; however, in other examples, the anode pads of adjacent LEDs may not be directly connected. Figure 10 In the example, anode pad 1070A is connected to anode pad 1070B. ADC 1022 can convert each positive voltage into a number of digits stored in memory by logic 1010.

[0093] exist Figure 11 In the example, logic 1010 determines (1008) whether a fault exists between LEDs 1050A and 1050B based on the forward voltage across LEDs 1050A and 1050B. For example, logic 1010 can be configured to determine whether each of the forward voltages is within an acceptable voltage range. Logic 1010 can also be configured to measure the voltage across drivers 1030A and / or 1030B to determine whether a fault exists across a single LED or across a single driver. In response to determining that a fault exists between cathode pads 1070A and 1070B, logic 1010 can be configured to increment a fault counter and store the location of LEDs 1050A and 1050B.

[0094] This disclosure attributes functionality to processing circuitry devices 110 and 210, BIST 120, and logic devices 410, 510, 610, 810, and 1010. Processing circuitry devices 110 and 210, BIST 120, and logic devices 410, 510, 610, 810, and 1010 may include one or more processors. Processing circuitry devices 110 and 210, BIST 120, and logic devices 410, 510, 610, 810, and 1010 may include any combination of integrated circuits, discrete logic circuits, analog circuits (such as one or more microprocessors), digital signal processors (DSPs), application-specific integrated circuits (ASICs), and / or field-programmable gate arrays (FPGAs). In some examples, processing circuitry devices 110 and 210, BIST 120, and logic devices 410, 510, 610, 810, and 1010 may include multiple components, such as one or more microprocessors, one or more DSPs, one or more ASICs, or one or more FPGAs, and any combination of other discrete or integrated logic circuits and / or analog circuits.

[0095] The techniques described in this disclosure can also be implemented or encoded in articles of manufacture including non-transitory computer-readable storage media, such as processing circuit devices 110 and 210, BIST 120 and logic 410, 510, 610, 810 and 1010. Examples of non-transitory computer-readable storage media may include RAM, ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, hard disk, magnetic media, optical media or any other computer-readable storage device or tangible computer-readable medium. The term "non-transitory" can indicate that the storage medium is not embodied in a carrier wave or a propagating signal. In some examples, a non-transitory storage medium may store data that can change over time (e.g., in RAM or cache).

[0096] The following numbered examples illustrate one or more aspects of this disclosure.

[0097] Example 1. A method for detecting faults using a built-in self-test, the method comprising: causing a first driver in a driver set to turn on a corresponding first pass device, wherein each driver in the driver set includes a pass device configured to be electrically connected to a corresponding pad in at least one anode pad or at least one cathode pad, and wherein each driver in the driver set is configured to control whether a corresponding LED in an LED set is turned on or off. The method further comprises: determining a first voltage level at a first anode pad of at least one anode pad, and determining a first voltage level at a first cathode pad of at least one cathode pad. The method further comprises determining, based on the first voltage levels at the first anode pad and the first cathode pad, whether a fault exists on the first driver, across the first anode pad and the first cathode pad, or on the first LED.

[0098] Example 2. The method according to Example 1 further includes: when connecting a sensing resistor across the first anode pad and the first cathode pad, determining a first voltage level at the first anode pad and the first cathode pad by determining the voltage drop across the connected sensing resistor.

[0099] Example 3. The method according to Example 1 or Example 2 further includes: testing each driver in the driver set individually or testing each LED in the LED set individually by connecting a sensing resistor across at least one anode pad to a second cathode pad in at least one cathode pad, and determining a second voltage level at the second anode pad and the second cathode pad when the sensing resistor is connected across the second anode pad and the second cathode pad.

[0100] Example 4. The method according to Examples 1 to 3 or any combination thereof, wherein testing each driver individually or testing each LED individually comprises: causing a second driver in the driver set to turn on a second corresponding device.

[0101] Example 5. The method according to Examples 1 to 4 or any combination thereof, wherein testing each driver or each LED individually includes determining the presence of a fault in the second driver or the second LED based on the voltage level at the second anode pad and the second cathode pad.

[0102] Example 6. The method according to Examples 1 to 5 or any combination thereof, wherein testing each driver individually or testing each LED individually includes: controlling the connection network to connect a sensing resistor across a first anode pad and a first cathode pad before determining a first voltage level.

[0103] Example 7. The method according to Examples 1 to 6 or any combination thereof, wherein testing each driver individually or testing each LED individually includes: controlling the connection network to disconnect the sensing resistor from the first anode pad and the first cathode pad before determining the second voltage level.

[0104] Example 8. The method according to Examples 1 to 7 or any combination thereof, wherein testing each driver individually or testing each LED individually includes: controlling the connection network to connect a sensing resistor across the second anode pad and the second cathode pad before determining the second voltage level.

[0105] Example 9. The method according to Examples 1 to 8 or any combination thereof further includes: outputting a digital number to a processing circuit device by a differential ADC, the digital number indicating the voltage drop across a sensing resistor.

[0106] Example 10. The method according to Examples 1 to 9 or any combination thereof, wherein the presence of a fault is determined based on the number of numbers.

[0107] Example 11. The method according to Examples 1 to 10 or any combination thereof further includes causing a current source to deliver a test current to the sensing resistor when the sensing resistor is disconnected from at least one anode pad and at least one cathode pad.

[0108] Example 12. The method according to Examples 1 to 11 or any combination thereof further includes determining the voltage drop across the sensing resistor when the test current is applied to the sensing resistor.

[0109] Example 13. The method according to Examples 1 to 12 or any combination thereof further includes changing the resistance of the sensing resistor based on the determined voltage drop across the sensing resistor.

[0110] Example 14. The method according to Examples 1 to 13 or any combination thereof further includes using an adjustment factor to change the resistance of the sensing resistor.

[0111] Example 15. The method according to Examples 1 to 14 or any combination thereof further includes storing the adjustment coefficient in memory.

[0112] Example 16. The method according to Examples 1 to 15 or any combination thereof, wherein determining the presence of a fault includes determining that the difference between a first voltage level at the first anode pad and a voltage level at the first cathode pad is greater than an upper limit threshold.

[0113] Example 17. The method according to Examples 1 to 16 or any combination thereof, wherein determining the presence of a fault includes determining that an open circuit exists across the first anode pad and the first cathode pad in response to determining that the difference between the first voltage levels is greater than an upper threshold.

[0114] Example 18. The method according to Examples 1 to 17 or any combination thereof, wherein determining the presence of a fault includes determining that the difference between a first voltage level at the first anode pad and a voltage level at the first cathode pad is less than a lower threshold.

[0115] Example 19. The method according to Examples 1 to 18 or any combination thereof, wherein determining the presence of a fault includes: in response to determining that the difference between first voltage levels is less than a lower threshold, determining that a short circuit exists between the first anode pad and the first cathode pad.

[0116] Example 20. The method according to Examples 1 to 19 or any combination thereof further includes storing the fault count in a memory.

[0117] Example 21. The method according to Examples 1 to 20 or any combination thereof further includes storing a first count of detected open-circuit faults in memory and storing a second count of detected short-circuit faults in memory.

[0118] Example 22. The method according to Examples 1 to 21 or any combination thereof further includes outputting a fault count to an external device via a diagnostic interface.

[0119] Example 23. The method according to Examples 1 to 22 or any combination thereof further includes determining whether the fault count is greater than a threshold number, and outputting the fault count to an external device in response to determining that the fault count is greater than the threshold number.

[0120] Example 24. The method according to Examples 1 to 23 or any combination thereof further includes determining a minimum voltage difference across each corresponding anode pad in at least one anode pad and each corresponding cathode pad in at least one cathode pad.

[0121] Example 25. The method according to Examples 1 to 24 or any combination thereof further includes determining the maximum value of the voltage difference across each corresponding anode pad in at least one anode pad and each corresponding cathode pad in at least one cathode pad.

[0122] Example 26. The method according to Examples 1 to 25 or any combination thereof further includes determining an average value of the voltage difference across each corresponding anode pad in at least one anode pad and each corresponding cathode pad in at least one cathode pad.

[0123] Example 27. The method according to Examples 1 to 26 or any combination thereof further includes storing the minimum, maximum and average values ​​in memory.

[0124] Example 28. The method according to Examples 1 to 27 or any combination thereof further includes outputting the minimum, maximum and average values ​​to an external device via a diagnostic interface.

[0125] Example 29. The method according to Examples 1 to 28 or any combination thereof, further comprising: batch simultaneously testing multiple drivers in a driver set or multiple LEDs in an LED set by causing at least a plurality of drivers to sequentially turn on corresponding plurality of pass devices; sequentially determining multiple voltage differences when a pass device in the corresponding plurality of pass devices is turned on; and determining the presence of a fault based on the multiple voltage differences. The plurality of drivers includes fewer than all drivers in the driver set, and the plurality of LEDs includes fewer than all LEDs in the LED set.

[0126] Example 30. The method according to Examples 1 to 29 or any combination thereof, further comprising: receiving a signal from an external device via a diagnostic interface; and determining, in response to receiving the signal from the external device, whether a fault exists.

[0127] Example 31. The method according to Examples 1 to 30 or any combination thereof, wherein it is determined whether a fault occurs before and after the mixing process.

[0128] Example 32. The method according to Examples 1 to 31 or any combination thereof further includes determining, prior to the mixing process, whether a fault exists across the first anode pad and the first cathode pad.

[0129] Example 33. The method according to Examples 1 to 32 or any combination thereof, wherein it is determined whether a fault occurs on the first LED after the mixing process.

[0130] Example 34. The method according to Examples 1 to 33 or any combination thereof, wherein the mixing process includes mounting the device on a structure including an LED assembly and electrically connecting a switch assembly to the LED assembly.

[0131] Example 35. An apparatus including a built-in self-test for detecting faults, the apparatus further comprising: at least one anode pad configured to be connected to the anode of an LED set and at least one cathode pad configured to be connected to the cathode of the LED set. The apparatus also includes a driver set, wherein each driver in the driver set includes a pass device configured to be electrically connected to a corresponding pad in the at least one anode pad or at least one cathode pad, and wherein each driver in the driver set is configured to control whether a corresponding LED in the LED set is turned on or off. The apparatus further includes processing circuitry configured to individually test each driver in the driver set or individually test each LED in the LED set by at least causing a first driver in the driver set to turn on a first corresponding pass device; determine a first voltage level at the first anode pad in the at least one anode pad; determine a first voltage level at the first cathode pad in the at least one cathode pad; and determine, based on the first voltage levels at the first anode pad and the first cathode pad, that a fault exists on the first driver, across the first anode pad and the first cathode pad, or on the first LED.

[0132] Example 36. The device according to Example 35 further includes a sensing resistor configured to be connected to a first anode pad and a first cathode pad.

[0133] Example 37. The device according to Example 35 or Example 36 further includes a differential ADC configured to measure the voltage across a sensing resistor.

[0134] Example 38. The device according to Examples 35 to 37 or any combination thereof further includes a connection network configured to connect to the first anode pad and the first cathode pad.

[0135] Example 39. The device according to Examples 35 to 38 or any combination thereof further includes a memory configured to store adjustment coefficients for the sensing resistor.

[0136] Example 40. The device according to Examples 35 to 39 or any combination thereof further includes a memory configured to store the minimum, maximum, and average values ​​of the voltage difference across each LED, across each pad pair, and / or across each driver.

[0137] Example 41. The device according to Examples 35 to 40 or any combination thereof, wherein the processing circuitry includes a state machine configured such that, as part of a self-test, the set of drivers will be turned on or off one by one through the devices.

[0138] Example 42. The apparatus according to Examples 35 to 41 or any combination thereof, wherein the processing circuitry is configured to perform the method according to Examples 1 to 34 or any combination thereof.

[0139] Example 43. An apparatus comprising a computer-readable medium having executable instructions stored thereon, the computer-readable medium being configured to be executed by a processing circuit means to cause the processing circuit means to perform the method according to Examples 1 to 34 or any combination thereof.

[0140] Example 44. A system comprising components for performing the method according to Examples 1 to 34 or any combination thereof.

[0141] Example 45. A method for detecting a fault between a first LED and a second LED in an LED set via a built-in self-test, the method comprising: causing a first driver in a driver set to turn on a first corresponding via. Each driver in the driver set includes a via configured to be electrically connected to a corresponding pad in at least one anode pad or at least one cathode pad, and wherein each driver in the driver set is configured to control whether the corresponding LED in the LED set is turned on or off. The method further comprises causing a second driver in the driver set to control a second corresponding via to turn off a second LED; determining a first forward voltage across the first LED and determining a second forward voltage across the second LED. The method further comprises determining, based on the first forward voltage and the second forward voltage, that a fault exists between the first LED and the second LED in the LED set.

[0142] Example 46. The method according to Example 45 further includes determining whether the first positive voltage is outside a first acceptable range of the activated LED.

[0143] Example 47. The method according to Example 45 or Example 46 further includes determining whether the second positive voltage is outside a second acceptable range for the deactivated LED.

[0144] Example 48. The method according to Examples 45 to 47 or any combination thereof, wherein determining the presence of a fault includes determining that the first positive voltage is outside a first acceptable range.

[0145] Example 49. The method according to Examples 45 to 48 or any combination thereof, wherein determining the presence of a fault includes determining that the second positive voltage is outside the second acceptable range.

[0146] Example 50. The method according to Examples 45 to 49 or any combination thereof, wherein determining whether the first positive voltage is outside a first acceptable range includes determining that the first positive voltage is less than a first threshold level of the activated LED.

[0147] Example 51. The method according to Examples 45 to 50 or any combination thereof, wherein determining whether the second positive voltage is outside the second acceptable range includes determining that the second positive voltage is greater than a second threshold level of the deactivated LED.

[0148] Example 52. The method according to Examples 45 to 51 or any combination thereof, further comprising: outputting a digital number to a processing circuit device via a differential ADC, the digital number indicating a first positive voltage across a first LED or indicating a second positive voltage across a second LED.

[0149] Example 53. The method according to Examples 45 to 52 or any combination thereof further includes: causing a first input of the differential ADC to receive a first signal, the first signal indicating a voltage level at the anode pad of the first pad pair.

[0150] Example 54. The method according to Examples 45 to 53 or any combination thereof further includes causing a second input of the differential ADC to receive a second signal indicating a voltage level at the cathode pad of the first pad pair.

[0151] Example 55. The method according to Examples 45 to 54 or any combination thereof further includes: causing the first input of the differential ADC to receive a third signal instead of receiving a first signal, the third signal indicating a voltage level at the anode pad of the second pad pair.

[0152] Example 56. The method according to Examples 45 to 55 or any combination thereof, further comprising: causing the second input of the differential ADC to receive a fourth signal instead of a first signal, the fourth signal indicating a voltage level at the cathode pad of the second pad pair.

[0153] Example 57. The method according to Examples 45 to 56 or any combination thereof further includes incrementing a counter in response to determining that a fault exists between the first LED and the second LED.

[0154] Example 58. The method according to Examples 45 to 57 or any combination thereof further includes: outputting the value of the counter to an external device via a diagnostic interface.

[0155] Example 59. The method according to Examples 45 to 58 or any combination thereof further includes storing the positions of the first LED and the second LED in a memory in response to determining that a fault exists between the first LED and the second LED.

[0156] Example 60. The method according to Examples 45 to 59 or any combination thereof further includes outputting the positions of the first LED and the second LED to an external device via a diagnostic interface.

[0157] Example 61. The method according to Examples 45 to 60 or any combination thereof, further comprising: turning on a first subset of the LED set and turning off a second subset of the LED set.

[0158] Example 62. The method according to Examples 45 to 61 or any combination thereof, wherein the first subset and the second subset form a chessboard pattern.

[0159] Example 63. The method according to Examples 45 to 62 or any combination thereof, wherein the first subset and the second subset form a ring pattern or a striped pattern.

[0160] Example 64. The method according to Examples 45 to 63 or any combination thereof further includes receiving signals from an external device via a diagnostic interface.

[0161] Example 65. The method according to Examples 45 to 64 or any combination thereof further includes determining whether a fault exists between the first LED and the second LED in response to receiving a signal from an external device.

[0162] Example 66. The method according to Examples 45 to 65 or any combination thereof further includes performing a built-in self-test in response to receiving a signal from an external device.

[0163] Example 67. The method according to Examples 45 to 66 or any combination thereof further includes determining, during the startup phase of the device, whether a fault exists between the first LED and the second LED.

[0164] Example 68. The method according to Examples 45 to 67 or any combination thereof, wherein the first LED is adjacent to the second LED.

[0165] Example 69. The method according to Examples 45 to 68 or any combination thereof, wherein the first LED and the second LED are arranged diagonally in a matrix.

[0166] Example 70. The method according to Examples 45 to 69 or any combination thereof, wherein determining the presence of a fault includes determining that there is a short circuit between the cathode pads of the first pad pair and the cathode pads of the second pad pair.

[0167] Example 71. The method according to Examples 45 to 70 or any combination thereof further includes controlling the connection network to connect the ADC to a terminal of the first LED or a terminal of the second LED each time.

[0168] Example 72. An apparatus including a built-in self-test for detecting a fault between a first LED and a second LED in a set of LEDs, the apparatus including a set of pads including a first pad pair configured to be connected to the first LED and a second pad pair configured to be connected to the second LED. The apparatus also includes a set of drivers, wherein each driver in the set of drivers includes a pass device configured to be electrically connected to a corresponding pad in the set of pads, and wherein each driver in the set of drivers is configured to control whether a corresponding LED in the set of LEDs is turned on or off. The apparatus also includes processing circuitry configured to cause the first driver in the set of drivers to turn on a first corresponding pass device, and to cause the second driver in the set of drivers to control a second corresponding pass device to turn off the second LED. The processing circuitry is further configured to determine a first forward voltage across the first LED; determine a second forward voltage across the second LED; and determine, based on the first and second forward voltages, that a fault exists between the first LED and the second LED in the set of LEDs.

[0169] Example 73. The device according to Example 72 further includes a sensing resistor configured to be connected to the first anode pad and the first cathode pad.

[0170] Example 74. The device according to Example 72 or Example 73 further includes a differential ADC configured to measure the voltage across a sensing resistor.

[0171] Example 75. The device according to Examples 72 to 74 or any combination thereof further includes a connection network configured to connect to the first anode pad and the first cathode pad.

[0172] Example 76. The device according to Examples 72 to 75 or any combination thereof further includes a memory configured to store adjustment coefficients for the sensing resistor.

[0173] Example 77. The device according to Examples 72 to 76 or any combination thereof further includes: a memory configured to store the minimum, maximum, and average values ​​of the voltage difference across each LED, across each pad pair, and / or across each driver.

[0174] Example 78. The device according to Examples 72 to 77 or any combination thereof, wherein the processing circuitry includes a state machine configured such that, as part of a self-test, the set of drivers will be turned on and off one by one through the devices.

[0175] Example 79. The apparatus according to Examples 72 to 78 or any combination thereof, wherein the processing circuitry is configured to perform the method according to Examples 45 to 71 or any combination thereof.

[0176] Example 80. An apparatus comprising a computer-readable medium having executable instructions stored thereon, the executable instructions being configured to be executed by a processing circuit means to cause the processing circuit means to perform the method according to Examples 45 to 71 or any combination thereof.

[0177] Example 81. A system including components for performing the method according to Examples 45 to 71 or any combination thereof.

[0178] Various examples of this disclosure have been described. Any combination of the systems, operations, or functions described is contemplated. These and other examples are within the scope of the appended claims.

Claims

1. A device including a built-in self-test for detecting faults, the device comprising: At least one anode pad is configured to be connected to the anode of the LED assembly; At least one cathode pad is configured to be connected to the cathode of the LED assembly; A driver set, wherein each driver in the driver set includes a pass device configured to be electrically connected to a corresponding pad in the at least one anode pad or the at least one cathode pad, and wherein each driver in the driver set is configured to control whether a corresponding LED in the LED set is turned on or off; as well as The processing circuitry is configured to test each driver in the driver set individually, or each LED in the LED set individually: This causes the first driver in the driver set to activate the first response via the device; Determine a first voltage level at the first anode pad in the at least one anode pad; Determine a first voltage level at the first cathode pad in the at least one cathode pad; as well as Based on the first voltage level at the first anode pad and the first cathode pad, a fault is determined to exist on the first driver, across the first anode pad and the first cathode pad, or on the first LED.

2. The device of claim 1, further comprising a sensing resistor configured to be connected to the first anode pad and the first cathode pad. The processing circuitry is configured to determine the first voltage level at the first anode pad and the first cathode pad by determining the voltage drop across the sensing resistor when the sensing resistor is connected across the first anode pad and the first cathode pad.

3. The apparatus of claim 2, wherein the processing circuitry is configured to test each driver in the driver set individually or each LED in the LED set individually: The sensing resistor is connected across the second anode pad in the at least one anode pad and the second cathode pad in the at least one cathode pad; This causes the second driver in the driver set to turn on the second response through the device; When the sensing resistor is connected across the second anode pad and the second cathode pad, a second voltage level is determined at the second anode pad and the second cathode pad; and Based on the second voltage level at the second anode pad and the second cathode pad, a fault is determined to exist in the second driver or the second LED.

4. The device of claim 3, further comprising a connection network, wherein the processing circuitry is configured to individually test each driver in the driver set or individually test each LED in the LED set at least by: Before determining the first voltage level, the connection network is controlled to connect the sensing resistor across the first anode pad and the first cathode pad; Before determining the second voltage level, the connection network is controlled to disconnect the sensing resistor from the first anode pad and the first cathode pad; as well as Before determining the second voltage level, the connection network is controlled to connect the sensing resistor across the second anode pad and the second cathode pad.

5. The device according to claim 2, further comprising a differential analog-to-digital converter (ADC), wherein the differential ADC is configured to: A first signal is received at the first input of the differential ADC, the first signal indicating the voltage level at the first end of the sensing resistor; A second signal is received at the second input of the differential ADC, the second signal indicating the voltage level at the second end of the sensing resistor; as well as The digital number indicating the voltage drop across the sensing resistor is output to the processing circuitry. The processing circuitry is configured to determine, based on the number of digits, whether the fault exists in the first driver or the first LED.

6. The apparatus of claim 2, wherein the processing circuitry is further configured to: When the sensing resistor is disconnected from the at least one anode pad and the at least one cathode pad, a current source delivers a test current to the sensing resistor. Determine the voltage drop across the sensing resistor when the test current is applied to it; as well as The resistance of the sensing resistor is changed based on the determined voltage drop across the sensing resistor.

7. The device according to claim 6, The processing circuitry is configured to use an adjustment factor to change the resistance of the sensing resistor, and The processing circuitry is further configured to store the adjustment coefficients in a memory.

8. The device of claim 1, wherein the processing circuitry is configured to determine the presence of the fault by: Determining that the difference between the first voltage level at the first anode pad and the voltage level at the first cathode pad is greater than an upper threshold; and In response to determining that the difference between the first voltage levels is greater than the upper threshold, an open circuit is determined to exist across the first anode pad and the first cathode pad.

9. The device of claim 1, wherein the processing circuitry is configured to determine the presence of the fault by: Determining that the difference between the first voltage level at the first anode pad and the voltage level at the first cathode pad is less than a lower threshold; and In response to determining that the difference between the first voltage levels is less than the lower threshold, a short circuit is determined to exist across the first anode pad and the first cathode pad.

10. The device of claim 1, further comprising a memory, wherein the processing circuitry is further configured to store a fault count in the memory.

11. The device of claim 10, wherein the processing circuitry is further configured to store the fault count in the memory in such a manner as: The first count of the detected open-circuit faults is stored in the memory; and The second count of the detected short-circuit faults is stored in the memory.

12. The device of claim 10, wherein the processing circuitry is further configured to output the fault count to an external device via a diagnostic interface.

13. The device according to claim 12, The processing circuitry is further configured to determine whether the fault count is greater than a threshold number, and The processing circuitry is configured to output the fault count to the external device in response to determining that the fault count is greater than the threshold number.

14. The apparatus of claim 1, wherein the processing circuitry is further configured to: Determine the voltage difference across each corresponding anode pad in the at least one anode pad and each corresponding cathode pad in the at least one cathode pad; Determine the minimum voltage difference; Determine the maximum value of the voltage difference; Determine the average value of the voltage difference; as well as The minimum value, the maximum value, and the average value are stored in the memory.

15. The device of claim 14, wherein the processing circuitry is further configured to output the minimum value, the maximum value, and the average value to an external device via a diagnostic interface.

16. The apparatus of claim 1, wherein the processing circuitry is further configured to simultaneously test, in batches, a plurality of drivers in the driver set or a plurality of LEDs in the LED set, at least by means of: This causes the plurality of drivers to turn on the corresponding plurality of devices one by one; When one of the corresponding plurality of through devices is turned on, the plurality of voltage differences across the corresponding pads are determined one by one; and The presence of any fault is determined based on the multiple voltage differences. The plurality of drives includes fewer than all the drives in the set of drives, and The plurality of LEDs includes fewer than all the LEDs in the LED set.

17. The device of claim 1, wherein the processing circuitry includes a state machine configured to, as part of a self-test, cause the driver assembly to be switched on and off one by one via the devices.

18. The device of claim 1, wherein the processing circuitry is configured to receive a signal from an external device via a diagnostic interface, and wherein the processing circuitry is configured to determine whether the fault exists in response to receiving the signal from the external device.

19. The device according to claim 1, The processing circuitry is configured to determine whether the fault exists on the first driver before and after the mixing process. The processing circuitry is configured to determine whether the fault exists across the first anode pad and the first cathode pad. The processing circuitry is configured to, after the mixing process, determine whether the fault exists on the first LED, and The mixing process includes: The device is installed on a structure that includes the LED assembly; as well as Connect the switch assembly to the LED assembly.

20. A method for detecting a built-in self-test, the method comprising: The first driver in the driver set turns on a first corresponding pass device, wherein each driver in the driver set includes a pass device configured to be electrically connected to a corresponding pad in at least one anode pad or at least one cathode pad, and wherein each driver in the driver set is configured to control whether a corresponding LED in the LED set is turned on or off. Determine a first voltage level at the first anode pad in the at least one anode pad; Determine a first voltage level at the first cathode pad in the at least one cathode pad; as well as Based on the first voltage level at the first anode pad and the first cathode pad, a fault is determined to exist on the first driver, across the first anode pad and the first cathode pad, or on the first LED.

21. The method of claim 20, further comprising: Each driver in the driver set, or each LED in the LED set, shall be tested individually at least in the following manner: Before determining the first voltage level, the connection network is controlled to connect the sensing resistor across the first anode pad and the first cathode pad; Before determining a second voltage level at the second anode pad of the at least one anode pad and the second cathode pad of the at least one cathode pad, the connection network is controlled to disconnect the sensing resistor from the first anode pad and the first cathode pad. as well as Before determining the second voltage level, the connection network is controlled to connect the sensing resistor across the second anode pad and the second cathode pad.

22. A built-in self-test device includes a computer-readable medium having executable instructions stored thereon, the executable instructions being configured to be executed by a processing circuitry means to cause the processing circuitry means to perform the following operations: The first driver in the driver set turns on a first corresponding pass device, wherein each driver in the driver set includes a pass device configured to be electrically connected to a corresponding pad in at least one anode pad or at least one cathode pad, and wherein each driver in the driver set is configured to control whether a corresponding LED in the LED set is turned on or off. Determine a first voltage level at the first anode pad in the at least one anode pad; Determine a first voltage level at the first cathode pad in the at least one cathode pad; as well as Based on the first voltage level at the first anode pad and the first cathode pad, a fault is determined to exist on the first driver, across the first anode pad and the first cathode pad, or on the first LED.

23. The built-in self-test device of claim 22, wherein the instructions are configured to be executed by the processing circuitry to further cause the processing circuitry to test each driver in the driver set individually or each LED in the LED set individually, at least in the following manner: Before determining the first voltage level, the connection network is controlled to connect the sensing resistor across the first anode pad and the first cathode pad; Before determining a second voltage level at the second anode pad of the at least one anode pad and the second cathode pad of the at least one cathode pad, the connection network is controlled to disconnect the sensing resistor from the first anode pad and the first cathode pad. as well as Before determining the second voltage level, the connection network is controlled to connect the sensing resistor across the second anode pad and the second cathode pad.

Images