A method of detecting LED reverse connection

Abstract

The application discloses a method for detecting LED reverse connection, and relates to the technical field of LED display screen detection. The method configures an open circuit detection voltage to a driving chip and starts a detection process. The driving chip scans each port in turn, and determines that a port with an output voltage exceeding a threshold value is an LED open circuit or reverse connection. An MCU reads the result and compares it with an expected template, thereby locating the reverse connection LED and lighting an indicator. The method can automatically and efficiently complete reverse connection detection without complex equipment.

Description

Technical Field

[0001] This invention belongs to the field of LED reverse connection detection technology, and particularly relates to a method for detecting LED reverse connection. Background Technology

[0002] Dot matrix LED displays typically consist of multiple LEDs arranged in an irregular pattern, and their driver chips are divided into two types: separate row and column signals and multiplexed row and column signals. This technology mainly focuses on the driving scheme of multiplexed row and column signals.

[0003] In row-column multiplexing drive mode, the MCU sends the grayscale value of each LED to the driver chip. The driver chip controls each port to be in a floating, low-voltage, or high-voltage state to achieve row-by-row scanning and brightness control. Specifically, when a port is at a low level as a row signal (GRID), other ports, as column signals (SEG), control the corresponding LED to light up or turn off by outputting a high voltage or floating, thereby achieving time-division driving of multiple LEDs.

[0004] Currently, the common testing method in factories is to set the grayscale value of all LEDs to the maximum value on the MCU, and then manually observe whether all LEDs are lit. If all are lit, the screen is considered to be without problems. However, this method has a significant drawback: if the positive and negative terminals of a certain LED are reversed, it can still be lit under certain port state combinations, making it impossible for humans to identify the reverse connection fault. For example, if an LED that should be lit when Port1 is a row signal and Port3 is a column signal is reversed, it will not light up in that state, but will light up when Port3 is a row signal and Port1 is a column signal. In subsequent normal use, if this LED needs to be controlled individually, a display error will occur.

[0005] Therefore, existing testing methods cannot effectively identify LED reverse connection problems, posing a risk of missed detection and affecting product quality and reliability. Summary of the Invention

[0006] This invention proposes a method for detecting reverse connection of LEDs to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides a method for detecting reverse connection of an LED, comprising: Send grayscale values ​​to the driver chip to light up all LEDs; Configure the open-circuit detection voltage of the driver chip; Send an open-circuit detection command to the driver chip to start the open-circuit detection process; wherein, the open-circuit detection process includes: sequentially setting each port to low voltage, and while the port is at low voltage, setting all other ports to high voltage; determining the LED corresponding to the port whose voltage value exceeds the open-circuit detection voltage during the high voltage output period as open circuit or reverse connection; Read the open circuit detection result from the driver chip; When the open circuit detection results indicate that an LED is reverse-connected, the corresponding LED is lit to provide an indication.

[0008] Optionally, sending grayscale values ​​to the driver chip to light up all LEDs includes: The MCU configures the grayscale values ​​of all LEDs in the driver chip's frame buffer to the maximum value.

[0009] Optionally, configuring the open-circuit detection voltage of the driver chip includes: The MCU sends a write register instruction to the driver chip to set the open circuit detection voltage level.

[0010] Optionally, the method further includes: The open-circuit detection circuit of the driver chip writes the detection result of whether it is an open circuit or reverse connection into the corresponding address of the grayscale buffer of the driver chip.

[0011] Optionally, reading the open-circuit detection result from the driver chip includes: The MCU reads the detection value corresponding to each LED from the grayscale buffer of the driver chip.

[0012] Optionally, determining the presence of LED reverse connection based on the open-circuit detection result includes: The read detection value is compared with the expected open circuit determination template pre-stored in the MCU. If they are inconsistent, it is determined that there is an LED reverse connection.

[0013] Optionally, illuminating the corresponding LED for indication includes: If the LED for PortA (row signal) and PortB (column signal) is detected to be reversed, the LED for PortB (row signal) and PortA (column signal) will be lit to prompt the operator to confirm the reversed connection position.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention utilizes the voltage comparison function and open-circuit detection mechanism integrated within the driver chip, combined with the MCU's automatic comparison and analysis of the detection results, to accurately identify reverse connection faults that are invisible to the naked eye. This method significantly simplifies the detection process and reduces equipment dependence, eliminating the need for external cameras, image analysis systems, or complex testing fixtures. The entire detection process can be completed using only the driver chip, MCU, and simple buttons, greatly reducing testing costs and operational complexity. Simultaneously, this method effectively improves detection efficiency and applicability, particularly suitable for irregularly arranged LED dot matrix screens. The detection process is automatically and quickly completed by the chip hardware, facilitating rapid deployment on production lines. Furthermore, it provides intuitive fault location indicators, clearly marking the fault location for maintenance personnel by illuminating specific LED beads, greatly facilitating subsequent maintenance work. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the dot matrix LED display screen structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the principle of LED reverse connection leading to erroneous lighting in an embodiment of the present invention; Figure 3 This is a schematic diagram of LED group detection in the prior art according to an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the implementation of the method according to an embodiment of the present invention; Figure 5 This is a schematic diagram of an example of LED reverse connection detection according to an embodiment of the present invention; Figure 6 This is a flowchart of a method according to an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] The basic principle of row-column multiplexing dot matrix LED displays is as follows: The MCU sends the grayscale value of each LED to the driver chip. The driver chip controls the state of each port based on the brightness value: floating, low voltage, high voltage; by Figure 1 For example, each port takes turns being in a low-voltage state: When Port1 is at low voltage, Port2 / 3 / 4 are either floating or at high voltage, which can control the three lights in the first row.

[0019] When Port2 is at low voltage, Ports 1 / 3 / 4 are either floating or at high voltage, which can control the three lights in the second row.

[0020] When Port3 is at low voltage, Ports 1 / 2 / 4 are either floating or at high voltage, which can control the three lights in the third row.

[0021] When Port4 is at low voltage, Ports 1 / 2 / 3 are either floating or at high voltage, which can control the three lights in the fourth row.

[0022] By analogy, when PortN is at a low voltage, Port1~N-1 are floating or at a high voltage, which can control the N-1 lights in the Nth row.

[0023] A port in a low voltage state is usually called a row signal (or GRID signal), while a port in a floating or high voltage state is usually called a column signal (or SEG signal).

[0024] When the port is in a signal state, the LED lights up when the output voltage is high and turns off when it is floating. The ratio of high voltage to floating time determines the brightness of the LED.

[0025] like Figure 1 As shown, there are two lights between any two ports, for example, between Port1 and Port2: The LED circled in red lights up when Port1 is at low voltage and Port2 is outputting current.

[0026] The LED circled in blue lights up when Port2 is at low voltage and Port1 is outputting current.

[0027] The factory's testing method: The MCU sets the grayscale value of all LEDs to the maximum value, and the workers observe whether all the lights are lit. If all the lights are lit, the screen is considered to be fine.

[0028] However, this detection method has a problem: if the positive and negative terminals of one light are reversed, all the lights will still appear to be lit. For example... Figure 2The LEDs with Port1 (row signal) and Port3 (column signal) are connected in reverse. This reverse connection results in the following: when Port1 is the column signal and Port3 is the row signal, both LEDs are lit; when Port1 is the row signal and Port3 is the column signal, no LEDs are lit.

[0029] During factory testing, this reversed LED will still light up when Port1 is the column signal and Port3 is the row signal, meaning the problem cannot be detected.

[0030] During normal use, if you try to turn on the light that is a row signal (Port1) and a column signal (Port3) while turning off the light that is a column signal (Port1) and a row signal (Port3), an error will occur.

[0031] Currently, LED reverse connection is typically detected by adding equipment. The detection process is as follows: like Figure 3 The LED light is divided into two parts: Part A: Row signal Port number > Column signal Port number; Part B: Row signal Port number < Column signal Port number. For example, the red LED in the diagram below represents Part B; the blue LED represents Part A.

[0032] Light up part A, take a picture of the light panel, and analyze the picture with a computer to check if part A is lit up, and also check if part B is not lit up.

[0033] Light up part B, take a picture of the light panel, and analyze the picture with a computer to check if part B is lit up, and at the same time check if part A is not lit up.

[0034] If an LED is reverse-connected, during testing, it will be found that the light does not light up when it should, and lights up when it should not.

[0035] The image above is a schematic diagram of the circuit, so it looks regular. However, the positions of these LEDs on the PCB are irregular. It is difficult for the human eye to distinguish between some LEDs A and some LEDs B. Only computer software can identify them.

[0036] Before analyzing the photos on the computer, reference images should be set in advance: which points on a normal light panel will light up when part A is lit; which points on a normal light panel will light up when part B is lit.

[0037] This approach can solve the problem, but the testing equipment is quite complex.

[0038] The LED board must have test points connected to the GPIO of the MCU. The MCU detects the voltage change of the GPIO: a single voltage change at the test point will light up LEDs in section A; a second voltage change at the test point will light up LEDs in section B.

[0039] During testing, the pins of the testing fixture are connected to the test points on the light board; then the computer controls the testing fixture to change the voltage at the test points; then the computer controls the camera to take pictures and analyzes the pictures to obtain the test results.

[0040] A factory may produce many types of LED panels, each with different LED positions and quantities. Manual testing can only determine whether all LEDs are on or off; only a computer can accurately determine whether half are on and half are off, which makes the testing equipment quite complex.

[0041] Regarding the above content, such as Figure 4 and Figure 6 As shown, this embodiment provides a method for detecting LED reverse connection, including: Send grayscale values ​​to the driver chip to light up all LEDs; Configure the open-circuit detection voltage of the driver chip; Send an open-circuit detection command to the driver chip to start the open-circuit detection process; wherein, the open-circuit detection process includes: sequentially setting each port to low voltage, and while the port is at low voltage, setting all other ports to high voltage; determining the LED corresponding to the port whose voltage value exceeds the open-circuit detection voltage during the high voltage output period as open circuit or reverse connection; Read the open circuit detection result from the driver chip; When the open circuit detection results indicate that an LED is reverse-connected, the corresponding LED is lit to provide an indication.

[0042] The MCU configures the grayscale values ​​of all LEDs in the driver chip's frame buffer to the maximum value.

[0043] Since the brightness of an LED light is related to its current, in order to ensure that all lights have the same brightness, the column signal output of the LED driver chip is not a fixed voltage, but a fixed current.

[0044] When the column signal outputs a high voltage, the output voltage will automatically adjust until the output current reaches the predetermined value. If an LED is off, meaning the current can never reach the predetermined value, the output voltage of the column signal will be a very high value, far exceeding the normal situation when there is an LED.

[0045] The normal column signal voltage is determined by the VF (forward conduction voltage) of the LED. For example, the VF of a red LED is around 1.8V, so the predetermined current can be output when the column signal voltage is slightly higher than 1.8V. If the LED is not present, the column signal voltage will be much higher, for example, exceeding 3V. By adding a comparator to the driver chip to detect the voltage when the column signal output is high, it can be determined whether the LED is connected correctly.

[0046] The MCU sends a write register instruction to the driver chip to set the open circuit detection voltage level.

[0047] Specifically, the driver chip adds a circuit to generate an open-circuit detection voltage, and the MCU can configure this voltage by writing to the driver chip's registers, for example, with 2.5V, 3V, 3.5V, 4V, etc.

[0048] A comparator is added to the driver chip. One end of the comparator is connected to the open-circuit detection voltage, and the other end is connected to each PORT (each PORT is turned on in turn during use).

[0049] The driver chip adds an open-circuit detection circuit, and the MCU can start the open-circuit detection function with a single instruction.

[0050] The driver chip has an internal cache used to store the grayscale of each LED, for example: The first byte stores the grayscale value of the lamp with Port1 as the row signal and Port2 as the column signal; The second byte stores the grayscale value of the lamps where Port1 is the row signal and Port3 is the column signal; ......; The (N-1)th byte stores the grayscale values ​​of the lights where Port1 is the row signal and PortN is the column signal; The Nth byte stores the grayscale value of the lamp with Port2 as the row signal and Port1 as the column signal; The (N+1)th byte stores the grayscale value of the lamp with Port2 as the row signal and Port3 as the column signal; ......; The second (N-1) byte stores the grayscale values ​​of the lights where Port2 is the row signal and PortN is the column signal; ......; The (N-1)+1th byte stores the grayscale value of the lamp with PortN as the row signal and Port1 as the column signal; The (N-1)+2nd byte stores the grayscale value of the lamp with PortN as the row signal and Port2 as the column signal; ......; The (N-1)Nth byte stores the grayscale value of the lamp with PortN as the row signal and PortN-1 as the column signal; The open circuit detection results are stored in this grayscale cache. During normal screen refresh, a certain address stores the grayscale value of the light with Portx as the row signal and Porty as the column signal; during open circuit detection, this address stores the open circuit detection results of the light with Portx as the row signal and Porty as the column signal (0 indicates normal, 1 indicates open circuit).

[0051] When the MCU sends an open-circuit detection command to the driver chip, the MCU reads the detection value corresponding to each LED from the grayscale buffer of the driver chip, and the driver chip will start the open-circuit detection process: (1) PORT1 outputs low voltage, PORT2~PORTN output high voltage, and the voltage of PORT2~PORTN is detected; If the voltage of a certain PORT is less than the open-circuit detection voltage, write 0 to the corresponding address in the grayscale buffer; If the voltage of a certain PORT is greater than or equal to the open-circuit detection voltage, write 1 to the corresponding address in the grayscale buffer.

[0052] (2) PORT2 outputs low voltage, PORT1 and PORT3~PORTN output high voltage, and the voltage of PORT1 and PORT3~PORTN is detected; If the voltage of a certain PORT is less than the open-circuit detection voltage, write 0 to the corresponding address in the grayscale buffer; If the voltage of a certain PORT is greater than or equal to the open-circuit detection voltage, write 1 to the corresponding address in the grayscale buffer; ......; (N) PORTN outputs low voltage, PORT1~PORTN-1 output high voltage, and the voltage of PORT1~PORTN-1 is detected; If the voltage of a certain PORT is less than the open-circuit detection voltage, write 0 to the corresponding address in the grayscale buffer; If the voltage of a certain PORT is greater than or equal to the open-circuit detection voltage, write 1 to the corresponding address in the grayscale buffer.

[0053] The entire testing process is as follows: (1) There is a button on the lamp board. The button is connected to the GPIO of the MCU. When the tester presses the button, the MCU starts the test. (2) The MCU sends grayscale values ​​to the driver chip to light up all the lights. The testing personnel then observe whether all the lights are lit. If any lights are not working, proceed with the repair process and fix the non-working lights first. This step ensures that every position on the light panel that should have a light has one and can be lit. If all the lights are on, the inspector presses the button again, and the MCU starts detecting reverse LED connection. (3) The MCU sends a write register instruction to the driver chip to configure the open circuit detection voltage; (4) The MCU sends an open circuit detection command to the driver chip, and the driver chip completes the open circuit detection; (5) The MCU reads the open circuit detection result from the driver chip; (6) The MCU checks the open circuit test results, finds the reverse-connected lamp, and lights up the reverse-connected lamp. When the tester observes that a lamp is lit, he knows that a lamp is reverse-connected.

[0054] Note 1: If the LED with "PortA as row signal and PortB as column signal" is detected to be connected in reverse, the MCU must turn on the LED with "PortB as row signal and PortA as column signal" in order to turn on the LED connected in reverse.

[0055] Note 2: It is possible that two lights will light up, both the "PortA is the row signal and PortB is the column signal" and the "PortB is the row signal and PortA is the column signal" lights up when connected in reverse; it is also possible that only one light will light up, as the "PortB is the row signal and PortA is the column signal" light does not exist on this board.

[0056] For example Figure 5 : A hollow LED light indicates that an LED light can be connected at this location, but no LED light was connected to this light panel.

[0057] Black LEDs indicate LEDs that have been properly soldered.

[0058] A red LED indicates that one of the LEDs is connected backwards.

[0059] The MCU has an internal array that stores the correct open-circuit detection results: 1 for hollow LEDs and 0 for the rest. The value corresponding to the LEDs for "Port1 is the row signal and Port3 is the column signal" is 0.

[0060] After the MCU reads the detection result, it compares it with the correct open circuit detection result. It finds that the value of "the lamp with row signal for Port1 and column signal for Port3" is 1 in the detection result, so it knows that the lamp with row signal for Port1 and column signal for Port3 is reversed.

[0061] The MCU sends grayscale values ​​to the driver, lighting up the LEDs with "Port3 as row signal and Port1 as column signal". At this time, two LEDs will light up on the LED board, which are the two LEDs circled in green.

[0062] The inspectors only need to check the two lights that are lit, one of which is reversed.

[0063] The advantages of this method are: it is simple, efficient, and does not require a computer; workers can tell if there is a problem by pressing a couple of buttons.

[0064] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for detecting reverse connection of an LED, characterized in that, include: Send grayscale values ​​to the driver chip to light up all LEDs; Configure the open-circuit detection voltage of the driver chip; Send an open-circuit detection command to the driver chip to start the open-circuit detection process; wherein, the open-circuit detection process includes: sequentially setting each port to low voltage, and while the port is at low voltage, setting all other ports to high voltage; determining the LED corresponding to the port whose voltage value exceeds the open-circuit detection voltage during the high voltage output period as open circuit or reverse connection; Reading open circuit detection results from the driver chip; reading open circuit detection results from the driver chip includes: the MCU reading the detection value corresponding to each LED from the driver chip; When it is determined that an LED is reverse-connected based on the open-circuit detection result, the read detection value is compared with the expected open-circuit judgment template pre-stored in the MCU. If they are inconsistent, it is determined that an LED is reverse-connected, and the corresponding LED is lit up for indication.

2. The method according to claim 1, characterized in that, Sending grayscale values ​​to the driver chip to light up all LEDs includes: The MCU configures the grayscale values ​​of all LEDs in the driver chip's frame buffer to the maximum value.

3. The method according to claim 1, characterized in that, The configuration of the open-circuit detection voltage of the driver chip includes: The MCU sends a write register instruction to the driver chip to set the open circuit detection voltage level.

4. The method according to claim 1, characterized in that, The method further includes: The open-circuit detection circuit of the driver chip writes the detection result of whether it is an open circuit or reverse connection into the corresponding address of the grayscale buffer of the driver chip.

5. The method according to claim 1, characterized in that, The step of illuminating the corresponding LED light for indication includes: If the LED for PortA (row signal) and PortB (column signal) is detected to be reversed, the LED for PortB (row signal) and PortA (column signal) will be lit to prompt the operator to confirm the reversed connection position.

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