LED driving device and LED driving method

Abstract

The present invention relates to an LED driving device and an LED driving method. The present invention relates to a technique for driving an LED, including sensing a forward voltage of the LED and determining whether the LED is defective by comparing the forward voltage with a comparison target voltage, wherein the comparison target voltage is continuously updated using the sensed forward voltage, so that the comparison target voltage can be set to a value that is not fixed, i.e., a value that reflects a current state of the LED. This allows more accurate detection of defects of the LED.

Description

Technical Field

[0001] This invention relates to a technique for driving light-emitting diodes (LEDs). Background Technology

[0002] As society becomes increasingly information-oriented, various display devices for visualizing information are being developed. Liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays, and plasma display panels (PDPs) are representative examples of display devices that have been developed or are under development to date. These display devices are being developed to properly display high-resolution images.

[0003] However, despite the advantages of high resolution, these display devices are difficult to scale up. For example, OLED displays developed to date have screen sizes of 80 inches (approximately 2 meters wide) or 100 inches (approximately 2.5 meters wide). Such displays are insufficient to be manufactured with a width greater than 10 meters.

[0004] To achieve larger display devices, there is growing interest in light-emitting diode (LED) display devices. According to LED display device technology, a larger panel can be manufactured by arranging a desired number of modular LED pixels on it. Furthermore, according to LED display device technology, a larger panel structure can be manufactured by including a desired number of unit panels (each unit panel has multiple LED pixels). Thus, LED display device technology allows the number of LED pixels to be increased as needed to achieve larger display devices.

[0005] LED display devices also offer advantages in terms of diversifying panel sizes and increasing panel size. According to this LED display device technology, by appropriately arranging the LED pixels, the horizontal and vertical dimensions of the panel can be diversified.

[0006] On the other hand, when a display device is enlarged or customized, the cost of manufacturing it increases, leading to greater concern for its maintenance. Therefore, if some pixels on a display device are defective, users are more likely, considering the cost, to try to repair them or prevent the defect from spreading to other pixels, rather than discarding the display device as they would have done previously. Summary of the Invention

[0007] In this context, one aspect of the present invention is to provide techniques for detecting defects in pixels in a light-emitting diode (LED) display device. Another aspect of the present invention is to provide techniques for determining short circuits in pixels in an LED display device. Yet another aspect of the present invention is to provide techniques for detecting pixels with incomplete short circuits in an LED display device.

[0008] Therefore, in one aspect, the present invention provides a light-emitting diode (LED) driving device, comprising: a driving circuit for driving a plurality of LEDs at different times according to a scan signal; and a protection circuit for sensing a first voltage corresponding to a forward voltage of a first LED among the plurality of LEDs at a first time, sensing a second voltage corresponding to a forward voltage of a second LED among the plurality of LEDs at a second time, and using the first voltage and the second voltage to determine the state of the second LED.

[0009] In another aspect, the present invention provides a light-emitting diode (LED) driving device, comprising: a driving circuit for sequentially driving a plurality of pixels using scan lines, each of the plurality of pixels including an LED; and a protection circuit for sensing a voltage formed at the position of each pixel as a first voltage, sensing the highest voltage of the first voltage for the pixel as a second voltage via a path provided with a voltage drop element, and determining the state of each pixel by comparing the first voltage and the second voltage.

[0010] The protection circuit can input the first voltage and the second voltage into a comparator that includes a hysteresis loop, and determine whether each pixel is defective based on the output from the comparator.

[0011] The driving circuit may include a switch for adjusting the brightness of each pixel according to a pulse width modulation (PWM) signal, and the switch may be controlled to be turned on or off according to a signal synthesized from the signal output from the comparator and the PWM signal.

[0012] In another aspect, the present invention provides an LED driving method, comprising: driving a plurality of LEDs respectively using a channel at different times; sensing a forward voltage of each LED using the channel at each driving time; storing a comparison target voltage, and updating the comparison target voltage using a voltage obtained by subtracting the predetermined voltage from the forward voltage in the one driving time if the forward voltage in one driving time is at least a predetermined voltage higher than the stored comparison target voltage; and comparing the forward voltage with the comparison target voltage to determine the state of the LED.

[0013] The LED driving method may further include generating a protection signal when the LED is determined to be defective, and identifying or storing the location of the LED determined to be defective by identifying the time point at which the protection signal is generated.

[0014] As described above, the present invention allows for the detection of defects in pixels of an LED display device. Furthermore, the present invention allows for the determination of short circuits in pixels of an LED display device, as well as the detection of pixels in a partially short-circuited state. Attached Figure Description

[0015] The above and other aspects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 This is a configuration diagram of a display device according to an embodiment;

[0017] Figure 2 This is a diagram showing the waveform of the scan signal in a display device according to an embodiment;

[0018] Figure 3 This is a diagram illustrating the configuration of the drive device according to an embodiment;

[0019] Figure 4 This is a diagram illustrating the configuration of the protection circuit according to an embodiment;

[0020] Figure 5 This is a typical protection circuit configuration diagram;

[0021] Figure 6 This is a diagram showing the main waveform of the drive device according to an embodiment;

[0022] Figure 7 This is a configuration diagram of the peak detection circuit according to an embodiment;

[0023] Figure 8 This is a diagram illustrating a first example of a voltage drop element according to an embodiment;

[0024] Figure 9 This is a diagram illustrating a second example of a voltage drop element according to an embodiment; and

[0025] Figure 10 This is a flowchart of a method for driving an LED according to an embodiment. Detailed Implementation

[0026] Figure 1 This is a configuration diagram of a display device according to an embodiment.

[0027] refer to Figure 1 The display device 100 may include a driving device 110 and a panel 120.

[0028] In the panel, it can be used in the first direction (e.g., in...). Figure 1 In the horizontal direction) and the second direction (e.g., in Figure 1 Multiple pixels P are arranged in the vertical direction to form a matrix.

[0029] Each pixel P may include at least one light-emitting diode (LED), and the brightness of pixel P may be determined by the brightness of the LED.

[0030] In panel 120, drive lines DL and scan lines SL can be arranged. The drive line DL can connect to one side of a pixel along a second direction, and the scan line can connect to the other side of the pixel along a first direction. For example, the anode side of an LED arranged in pixel P can be electrically connected to the drive line DL, and the cathode side of the LED can be electrically connected to the scan line SL. When the cathode sides of the LEDs are connected together... Figure 1 The structure shown may be referred to as a common cathode structure; however, the present invention is not limited thereto.

[0031] The scan line SL can include scan switches SWc1, SWc2, ..., SWcN respectively, and the scan line SL through which the supply drive current Ie passes can be determined according to the opening or closing of the scan switches SWc1, SWc2, ..., SWcN.

[0032] Figure 2 This is a diagram showing the waveform of the scan signal in the display device according to an embodiment.

[0033] refer to Figure 1 and Figure 2 In each frame, the scan signal Scan <1> Scan <2> Scan <n>This signal can be sequentially supplied to the corresponding scan switches SWc1, SWc2, ..., SWcN. Based on this scan signal, Scan... <1> Scan <2> Scan <n>The driving current Ie can be supplied sequentially to the first scan line, the second scan line, ..., the Nth scan line.

[0034] The scan line SL can be connected to a low-voltage portion of the display device 100, such as ground potential. The scan switches SWc1, SWc2, ..., SWcN can be arranged in the panel 120, in a separate substrate, or, according to an embodiment, inside the drive device 110.

[0035] Scan signal <1> Scan <2> Scan <n>It can be supplied by the drive unit 110 or by a separate control unit.

[0036] The brightness of the LEDs arranged in each pixel P can be determined based on the amount of driving power supplied within a predetermined time. The LEDs can be driven using pulse width modulation (PWM), and the brightness of the LEDs can be determined based on the ratio of the on-time to the PWM control time. When the LED is turned on by the driving current Ie, a positive voltage can be formed in the LED. By multiplying the positive voltage by the driving current Ie and accumulating these results over the on-time period within the PWM control time, the amount of driving power supplied to the LED can be obtained, and this amount of driving power can determine the brightness of the LED. Assuming that the levels of the LED's positive voltage and the driving current Ie are fixed variables, the amount of driving power can be considered proportional to the on-time within the PWM control time. Based on this principle, the driving device 110 can control the brightness of the LEDs and pixels P by controlling the on-time within the PWM control time.

[0037] The driving device 110 may include multiple (N) channels connected to the driving line DL, and each channel may supply driving current Ie to each pixel P.

[0038] On the other hand, if pixel P is defective, a voltage different from that when the pixel is in a normal state may be formed in pixel P. For example, if the pixel is defective, the forward voltage of the LED may be lower than the forward voltage when the pixel is in a normal state. The driving device 110 can sense such a voltage formed in pixel P and detect the defect of pixel P based on the sensed voltage.

[0039] Figure 3 This is a diagram illustrating the configuration of the drive device according to an embodiment.

[0040] refer to Figure 3 In terms of input and output, the driving device 110 may include an input terminal Ti and an output terminal To. Image data RGB is input through the input terminal Ti, and a driving current Ie controlled by the grayscale values ​​included in the image data RGB is output through the output terminal To. The driving device 110 may include a driving circuit 310 and a protection circuit 320.

[0041] The drive circuit 310 can use a channel CH to drive the scan signal Scan. <1> Scan <2> Scan <3> Multiple LEDs (LED1, LED2, LED3) are driven at different times. For example, a first scan signal Scan is supplied. <1> In this case, the driving circuit 310 can use one channel CH to drive the first LED (LED1) during the first scan time, and then supply the second scan signal Scan. <2> In this case, the driving circuit 310 can use one channel CH to drive the second LED (LED2) during the second scan time, and when the third scan signal Scan is supplied... <3> In this case, the driving circuit 310 can use one channel CH to drive the third LED (LED3) during the third scan time.

[0042] The channel CH may include a drive current source 330 and a drive switch SWp arranged in series, and the output of the channel may be connected to the output terminal To.

[0043] The driving circuit 310 can generate a PWM signal SP based on image data RGB or a control signal received from an external device to control the brightness of the LEDs (LED1, LED2, LED3), and can control the on-time of the drive switches SWp of each channel CH based on the PWM signal SP. When the drive switches SWp are on, the drive current Ie output from the drive current source 330 can be supplied to the LEDs (LED1, LED2, LED3) via the output terminal To and the drive line DL.

[0044] The driving circuit 310 may include a PWM generator 312 to convert image data RGB, including the grayscale values ​​of each pixel, into a PWM signal SP. Additionally, the driving circuit 310 may include an AND logic element 314. The AND logic element 314 can perform an AND operation on the PWM signal SP and a protection signal SF or the inverse of the protection signal SF, and output the result. Based on this AND operation, the supply of the PWM signal SP for driving the switch SWp can be stopped.

[0045] The protection circuit 320 can supply the protection signal SF to the drive circuit 310 to disconnect the drive switch SWp or keep the drive switch SWp in the off state.

[0046] The protection circuit 320 can sense the voltage of a pixel, use the sensed voltage to determine whether the pixel is defective, and generate a protection signal SF based on the determination result. For example, the protection circuit 320 can sense the positive voltage of an LED (LED1, LED2, LED3) or the voltage corresponding to its positive voltage, and use the sensed voltage to determine whether the LED (LED1, LED2, LED3) is defective. Subsequently, the protection circuit 320 can generate a protection signal SF based on the determination result.

[0047] The protection circuit 320 can sense the voltage generated in the output of each channel CH, for example, the voltage generated in the output terminal To. The output of each channel CH can be connected to the anode side of the LEDs (LED1, LED2, LED3). In this case, the voltage generated in the output of each channel CH can be the same as the voltage generated on the anode side of each LED (LED1, LED2, LED3). In this example, when the cathode side of the LEDs (LED1, LED2, LED3) is connected to ground potential, the voltage generated in the output of each channel CH can be approximately the same as the forward voltage of each LED (LED1, LED2, LED3).

[0048] The protection circuit 320 can compare the sensed voltage with a voltage, and if the sensed voltage differs from the voltage by at least a predetermined amount, determine that the corresponding pixel or the corresponding LED (LED1, LED2, LED3) is defective. Here, the protection circuit 320 can set the sensed voltage from a previous time period as a voltage to be compared with.

[0049] For example, the protection circuit 320 can sense a first voltage corresponding to the forward voltage of the first LED (LED1) at a first time, and can sense a second voltage corresponding to the forward voltage of the second LED (LED2) at a second time. Subsequently, the protection circuit 320 can set the first voltage as the voltage to be compared, and compare the second voltage with the first voltage to determine whether the second LED (LED2) is defective.

[0050] refer to Figure 3 It can sequentially supply the first scan signal Scan <1> Second scan signal Scan <2> and the third scan signal Scan <3> When the first scan signal Scan is supplied through a channel CH. <1> During the first scan time, the protection circuit 320 can sense a first voltage corresponding to the positive voltage of the first LED (LED1), and supply a second scan signal Scan through the channel CH. <2> During the second scan time, the protection circuit 320 can sense a second voltage corresponding to the positive voltage of the second LED (LED2), and when a third scan signal Scan is provided through a channel CH... <3> At that time, the protection circuit 320 can sense a third voltage corresponding to the positive voltage of the third LED (LED3) at the third time.

[0051] The protection circuit 320 can compare the voltage sensed in each scan time with a comparison target voltage, and determine whether a pixel or LED corresponding to each scan time is defective based on the comparison result. Here, the protection circuit 320 can use the voltage sensed in one of the previous scan times to generate the comparison target voltage. For example, the protection circuit 320 can use a first voltage in a first scan time to generate the comparison target voltage, and compare the generated comparison target voltage with a second voltage in a second scan time. Subsequently, the protection circuit 320 can use the second voltage in a second scan time to generate the comparison target voltage, and compare the generated comparison target voltage with a third voltage in a third scan time. Furthermore, the protection circuit 320 can subsequently use the third voltage in a third scan time to generate the comparison target voltage, and compare the generated comparison target voltage with the first voltage in the first scan time.

[0052] The comparison voltage can be stored and updated. The protection circuit 320 can store the sensed voltage as is or store the voltage obtained by subtracting a predetermined voltage from the sensed voltage to form the comparison voltage and update the comparison voltage at each scan time.

[0053] If the sensed voltage is lower than the comparison voltage, the protection circuit 320 can determine that the corresponding LED is defective. When the LEDs (LED1, LED2, LED3) are driven normally, their forward voltage is maintained at at least a predetermined level. Therefore, if the forward voltage is lower than the predetermined voltage (comparison voltage), this may mean that the LED is in a short-circuit state or in a partially short-circuit state. The protection circuit 320 can check the state of the LEDs (LED1, LED2, LED3) by comparing the sensed voltage with the comparison voltage at each scan time.

[0054] The forward voltage of an LED can typically be maintained at a predetermined level, such as 2-3V. Therefore, conventional drivers determine whether the LED is short-circuited by measuring its forward voltage and comparing it to a fixed reference voltage. However, the forward voltage of an LED may change due to aging. Conventional methods cannot reflect this change in forward voltage. In cases where the forward voltage of an LED decreases due to aging, the driver may even determine that the LED is defective when it is in normal operating condition. To minimize this problem, conventional drivers tend to set the reference voltage used for comparison to a low value. However, with a low reference voltage, another problem may arise: the incomplete short-circuit state of the LED cannot be detected. In other words, the following state cannot be detected: the forward voltage is lower than the voltage when the LED is in normal operating condition, but the forward voltage has a predetermined value.

[0055] To address this problem, the driving device according to an embodiment can generate a comparison voltage that reflects the current state of the LED. For example, the driving device according to an embodiment can use the voltage sensed during a previous scan time in a channel to generate the comparison voltage. In other words, the driving device according to an embodiment can generate a representative value of the voltage sensed during a previous scan time as the comparison voltage. Here, the representative value can be an average value, a median value, or a maximum value, etc.

[0056] Figure 4 This is a diagram illustrating the configuration of the protection circuit according to an embodiment.

[0057] refer to Figure 4 The protection circuit 320 may include a peak detection circuit 410, a comparison circuit 420, an AND logic element 430, a glitch removal circuit 440, and a protection logic circuit 450.

[0058] A voltage formed at the pixel location (e.g., the voltage formed by the anode of LEDs (LED1, LED2, LED3)) can be input as a first voltage through a terminal (e.g., the negative input terminal) of the comparator circuit 420. The first voltage can be input through a terminal of the comparator circuit 420 during each scan time.

[0059] The peak detection circuit 410 can sense the maximum first voltage among the first voltages of each pixel through a path with voltage drop elements, and use it as a second voltage. Subsequently, the peak detection circuit 410 can input the second voltage through another terminal (e.g., the positive input terminal of the comparator circuit 420).

[0060] The comparator circuit 420 compares a first voltage with a second voltage, and determines that the current pixel is defective if the first voltage is lower than the second voltage. The comparator circuit 420 then outputs the determination result as a comparison signal CM. The comparison signal CM can be high when the pixel is defective, and low when the pixel is in a normal state. Alternatively, the comparator circuit 420 can output a low-level comparison signal CM when the pixel is defective (i.e., when the first voltage is lower than the second voltage), and a high-level comparison signal CM when the pixel is in a normal state.

[0061] The comparator circuit 420 may include a comparator for generating a comparison signal CM. The comparator may receive a first voltage and a second voltage as inputs and output the comparison signal CM. Because the comparator includes a hysteresis loop, it can output a stable signal even when the first voltage and the second voltage have similar levels.

[0062] The logic element 430 can generate a composite signal CM' by combining the comparison signal CM and the PWM signal SP using an AND operation. The protection circuit 320 can also perform an AND operation on the comparison signal CM and the PWM signal SP to form the composite signal CM'. The AND operation ensures that the comparison signal CM only passes through the interval where the PWM signal SP has a high level. In this way, the protection circuit 320 can generate the composite signal CM'. The protection circuit 320 can determine whether a pixel is defective within the driving range of the LEDs (LED1, LED2, LED3), and the driving range of the LEDs (LED1, LED2, LED3) can be considered as the interval where the PWM signal SP has a high level.

[0063] The glitch removal circuit 440 generates a stable signal by removing glitch components included in the synthesized signal CM', and the protection logic circuit 450 generates a protection signal SF by performing final processing on signals transmitted via a series of components. The protection logic circuit 450 can generate the protection signal SF by inverting the input signal or by adding supplementary determinations.

[0064] Figure 5 It is a configuration diagram of a general protection circuit, and Figure 6 This is a diagram showing the main waveform of the drive device according to an embodiment.

[0065] refer to Figure 4 , Figure 5 and Figure 6 The second voltage Vp formed in the protection circuit can have a higher level than the reference voltage Vr used in a general protection circuit. Therefore, the driving device according to the embodiment can detect pixels even in a partially short-circuited state.

[0066] Figure 5 The general protection circuit 50 shown generates a protection signal SF' by comparing the voltage sensed using the output terminal To with a predetermined reference voltage Vr. However, since the decrease in the sensed voltage due to pixel aging needs to be considered, such a general protection circuit 50 may not set the reference voltage Vr high. Therefore, the general protection circuit 50 sets the reference voltage Vr low. However, such a low reference voltage Vr may prevent the detection of pixels in an incomplete short-circuit state as described above.

[0067] Since the driving device according to the embodiment uses a voltage reflecting the current state of the LED as a comparison voltage, the voltage level can be relatively high. If the second voltage used as the comparison voltage is high, and the sensed voltage subsequently decreases due to LED aging, the second voltage is also reduced, thus preventing erroneous defect determination due to LED aging.

[0068] refer to Figure 4 and Figure 6 To see a specific example of the driver, the first scan signal Scan was supplied. <1> During the first scan time, the drive current Ie can flow into the first LED (LED1). The voltage Vt formed in the output terminal during the first scan time (especially when the PWM signal SP is high) can correspond to the positive voltage of the first LED (LED1). The driving device can compare the voltage Vt (first voltage) with the peak voltage Vp (second voltage) generated in the peak detection circuit 410 to generate a protection signal SF. Since the voltage Vt (first voltage) formed in the output terminal during the first scan time is higher than the peak voltage Vp (second voltage), the protection signal SF can have a low level. On the other hand, during the second scan time, the voltage Vt (first voltage) formed in the output terminal is lower than the peak voltage Vp (second voltage). In this case, the protection signal SF can have a high level indicating that the corresponding pixel is defective.

[0069] Figure 7 This is a configuration diagram of the peak detection circuit according to an embodiment.

[0070] refer to Figure 7 The peak detection circuit 410 can be connected to the output terminal To on one side to receive the voltage Vt formed in the output terminal To, and can output the peak voltage Vp through the other side.

[0071] The peak detection circuit 410 may include a voltage drop element 710 disposed between one side and the other side. The peak voltage Vp can be formed by reducing a predetermined voltage Vds by the voltage Vt formed in the output terminal To.

[0072] The peak detection circuit 410 may also include a capacitor Cp to store the peak voltage Vp. The peak voltage Vp can be stored in the capacitor Cp during one scan time and used as the input voltage of the comparator circuit during another scan time.

[0073] Because capacitor Cp has internal resistance or leakage resistance, the level of the voltage stored therein may decrease over time. However, during each scan time, additional charge can be supplied from the output terminal To, and therefore, the voltage can be maintained at a predetermined level.

[0074] If the natural discharge rate of capacitor Cp is too slow, the voltage stored in capacitor Cp may not properly reflect the current state of the LED. To remedy this problem, a reset switch Sr can be connected in parallel with capacitor Cp. The driver can periodically or non-periodically turn on the reset switch Sr to release the charge stored in capacitor Cp and change the peak voltage Vp stored in capacitor Cp with a new peak voltage.

[0075] The sampling time limiting circuit 720 can be connected to the output terminal To. The sampling time limiting circuit 720 allows the voltage formed in the LED to be sensed as is when the PWM signal SP has a high voltage level. Conversely, the sampling time limiting circuit 720 can force the voltage in the output terminal To to be maintained at a predetermined voltage Vds to prevent the voltage in the output terminal To from affecting the peak voltage Vp when the PWM signal SP has a low voltage level.

[0076] In addition, the sampling time limiting circuit 720 can output a predetermined voltage Vds to the output terminal To in order to maintain a constant voltage on the drive line.

[0077] The sampling time limiting circuit 720 may include a limiting switch Sds for controlling the connection between the output terminal To and a predetermined voltage Vds, and a gate drive circuit 722 for using the inverse signal of the PWM signal Sp to control the gate of the limiting switch Sds.

[0078] Figure 8 This is a diagram illustrating a first example of a voltage drop element according to an embodiment, and Figure 9 This is a diagram illustrating a second example of a voltage drop element according to an embodiment.

[0079] refer to Figure 8 The voltage drop element may include at least one diode 810. Here, the anode of the diode 810 may be connected to the output terminal To, and its cathode may be connected to the capacitor Cp.

[0080] refer to Figure 9 The voltage drop element may include at least one diode-connected transistor 910. Here, the gate and drain of the diode-connected transistor 910 may be connected to each other, the drain may be connected to the output terminal To, and the cathode may be connected to the capacitor Cp. The transistor 910 may be a field-effect transistor (FET).

[0081] Figure 10 This is a flowchart of a method for driving an LED according to an embodiment.

[0082] refer to Figure 10 The LED driver can store the comparison voltage using channels (S1000). The comparison voltage can be stored in a capacitor or another component. Each channel can be connected to a drive line, and this drive line can be connected to multiple LEDs.

[0083] The LED driver can drive multiple LEDs at different times using a single channel (S1002). Multiple LEDs can be connected to a driving line at different times according to a scan signal, and receive driving current from that single channel.

[0084] The LED driver can use a channel to sense the forward voltage of each LED in each driving time (S1004).

[0085] Subsequently, the LED driver can compare the voltage obtained by subtracting a predetermined voltage from the sensed voltage with the comparison target voltage (S1006), and if the voltage obtained by subtracting the predetermined voltage from the sensed voltage is higher than the comparison target voltage ("yes" in S1006), the LED driver can update the comparison target voltage using the voltage obtained by subtracting the predetermined voltage from the sensed voltage in each driving time (S1008).

[0086] The comparison voltage can be stored in a capacitor. However, due to the parasitic elements of the capacitor, the comparison voltage can be naturally discharged, and due to this natural discharge, the comparison voltage can be frequently updated.

[0087] The comparison object voltage can be reset periodically or non-periodically. To prevent the comparison object voltage from being reset at the same time point in each frame, it can be reset at an interval different from the frame interval.

[0088] After determining the comparison target voltage, the LED driver can compare the sensed positive voltage with the comparison target voltage (S1010), and if the sensed positive voltage is lower than the comparison target voltage ("yes" in S1010), the LED driver can determine that the relevant LED is defective and generate a protection signal (S1012).

[0089] The foregoing describes techniques for driving LEDs according to embodiments. Such embodiments allow for the detection of defects in pixels in an LED display device, the determination of short circuits in pixels in an LED display device, and the detection of pixels in an LED display device that are in a state of incomplete short circuit.

[0090] Cross-reference to related applications

[0091] This application claims priority to Korean Patent Application No. 10-2020-0090201, filed on July 21, 2020, the entire contents of which are incorporated herein by reference.< / n> < / n> < / n>

Claims

1. An LED driving device, namely, a light-emitting diode driving device, comprising: The driving circuit is used to drive multiple LEDs at different times according to the scanning signal; as well as A protection circuit is configured to sense a first voltage corresponding to the forward voltage of a first LED among the plurality of LEDs at a first time, generate a comparison voltage using the first voltage, sense a second voltage corresponding to the forward voltage of a second LED among the plurality of LEDs at a second time, and determine the state of the second LED by comparing the comparison voltage and the second voltage. Wherein, the comparison object voltage is the first voltage or a voltage obtained by subtracting a preset voltage from the first voltage, and If the second voltage is lower than the voltage of the comparison object, the LED driver determines that the second LED is defective.

2. The LED driving device according to claim 1, wherein, The first LED and the second LED are different from each other and are connected to a drive line or a channel.

3. The LED driving device according to claim 1, wherein, The first voltage is the voltage formed on the anode side of the first LED, the second voltage is the voltage formed on the anode side of the second LED, and the protection circuit determines the state of the second LED by comparing the voltage obtained by subtracting the preset voltage from the first voltage with the second voltage.

4. The LED driver according to claim 1, wherein, The first voltage corresponds to the highest voltage among the voltages formed on the anode side of the plurality of LEDs.

5. An LED driver device, comprising: A driving circuit is used to sequentially drive multiple pixels using scan lines, each of the multiple pixels including an LED; as well as A protection circuit is used to sense the voltage formed at the location of each pixel as a first voltage, generate a comparison voltage using the first voltage, sense the highest voltage among the first voltages for a pixel via a path with voltage drop elements as a second voltage, and determine the state of each pixel by comparing the comparison voltage and the second voltage. Wherein, the comparison object voltage is the first voltage or a voltage obtained by subtracting a preset voltage from the first voltage, and If the second voltage is lower than the voltage of the comparison object, the LED driver determines that the corresponding LED is defective.

6. The LED driving device according to claim 5, wherein, The protection circuit senses the first voltage on the anode side of the LEDs arranged in each pixel.

7. The LED driver according to claim 5, wherein, The voltage drop element is a diode element or a field-effect transistor element with a diode connection, i.e., a FET element.

8. The LED driver according to claim 5, wherein, The protection circuit inputs the first voltage and the second voltage into a comparator that includes a hysteresis loop, and determines the state of each pixel based on the output from the comparator.

9. The LED driving device according to claim 8, wherein, The driving circuit includes a switch for adjusting the brightness of each pixel according to a pulse width modulation signal, i.e., a PWM signal, and the switch is controlled to be turned on or off according to a signal synthesized from the signal output from the comparator and the PWM signal.

10. The LED driving device according to claim 5, wherein, The second voltage is stored in a capacitor and is reset according to the periodic or non-periodic switching of a reset switch connected in parallel with the capacitor.

11. The LED driver according to claim 5, wherein, The plurality of pixels and the driving circuit are connected via driving lines, and the protection circuit uses the driving lines to sense the first voltage or the second voltage when driving current is supplied to the plurality of pixels, and supplies a predetermined voltage to the driving lines when driving current is not supplied to the plurality of pixels, wherein the predetermined voltage has a level that causes the plurality of pixels to be de-energized.

12. An LED driving method, comprising: Multiple LEDs are driven separately using channels at different times; The channel is used in each driving time to sense the forward voltage of each LED; The comparison target voltage is stored using a voltage sensed during one of the previous scan times, the comparison target voltage being either the voltage itself or a voltage obtained by subtracting a preset voltage from the voltage. If the positive voltage during a drive time is at least a predetermined voltage higher than the comparison object voltage, the comparison object voltage is updated using the voltage obtained by subtracting the predetermined voltage from the positive voltage during the drive time. as well as The positive voltage is compared with the voltage of the comparison object to determine the state of the LED. If the positive voltage is lower than the voltage of the comparison object, then the corresponding LED is determined to be defective.

13. The LED driving method according to claim 12, wherein, The voltage of the comparison object is stored in a capacitor and is naturally discharged by parasitic elements.

14. The LED driving method of claim 12 further includes generating a protection signal when the LED is determined to be defective, and identifying or storing the location of the LED determined to be defective by identifying the time point at which the protection signal is generated.

15. The LED driving method according to claim 12, further comprising resetting the voltage of the comparison object, wherein, The voltage of the comparison object is reset at an interval different from the frame interval.

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