LED driving self-correction circuit, method, column driving chip and display device

Abstract

The application provides an LED driving self-correction circuit, a column driving chip and a display device. The LED driving self-correction circuit comprises: a reference voltage acquisition circuit, which is used for obtaining a correction reference voltage of a column driving chip according to an average forward conduction voltage of a plurality of LED lamp beads connected with the column driving chip; an error acquisition circuit, which is used for acquiring an error of the correction reference voltage relative to a reference voltage; and an error self-correction circuit, which is used for adding a pre-charging voltage and a corresponding error to obtain a target pre-charging voltage of the column driving chip, so as to correct the pre-charging voltage of the column driving chip. Through the self-correction of the pre-charging voltage, the pre-charging voltage output from each column driving chip to an LED display screen is consistent after correction, and the color block influence on the display screen is effectively eliminated.

Description

Technical Field

[0001] This application relates to the field of LED display driver technology, specifically to an LED driver self-calibration circuit, a column driver chip, and a display device. Background Technology

[0002] An LED display screen is composed of a light-emitting diode display array, row drivers, column drivers, etc. Figure 1 This is a display device 100 with an LED display unit board 130 (hereinafter referred to as an LED display or display) having a common cathode (i.e., the cathodes of LEDs D11~Dmn located in the same row are connected together, while the anodes are separated, and m and n are both integers greater than 1) connection. Of course, the LED display 130 can also be a common structure with a common anode (i.e., the anodes of LEDs D11~Dmn located in the same row are connected together, while the cathodes are separated). Figure 1 All LED beads D11~Dmn are reversed. The row driver chip 110 of the LED display 130 typically includes multiple switching power transistors Q11~Q1m, and the column driver chip 120 typically includes multiple constant current source driver chips. These constant current source driver chips usually contain multiple output channels, which are connected to… Figure 1 The system has multiple column drive lines (column 1, column 2... column n), and is controlled by multiple switching transistors Q21~Q2n.

[0003] In theory, LEDs used in the same LED display screen have identical characteristics, meaning the forward conduction voltage of each LED (D11~Dmn) is the same. Therefore, assuming the pre-charge voltage Vpre output by each column driver chip to the LED is also the same, the brightness of LEDs of the same model can be guaranteed to be the same. However, even if the driver chips undergo rigorous adjustment before leaving the factory, it cannot be guaranteed that the pre-charge voltage output by each column driver chip soldered to the display board will be the same. If there are differences in the pre-charge voltage output by each column driver chip to the LED, the display effect will be unsatisfactory, such as the appearance of color blocks. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides an LED driver self-calibration circuit, column driver chips, and a display device, which can self-calibrate the pre-charge voltage so that the pre-charge voltage output by each column driver chip to the LED display screen is consistent after calibration, thereby eliminating the influence of color blocks on the display screen.

[0005] According to a first aspect of this application, an LED driver self-calibration circuit is provided for self-calibrating the pre-charge voltage of a column driver chip to an LED bead, the LED driver self-calibration circuit comprising:

[0006] A reference voltage acquisition circuit is used to obtain a correction reference voltage for the column driver chip based on the average forward conduction voltage of a plurality of LED beads connected to the column driver chip.

[0007] An error acquisition circuit is used to acquire the error of the correction reference voltage relative to the reference voltage;

[0008] An error self-correction circuit is used to add the pre-charge voltage and the error to obtain the target pre-charge voltage of the column driver chip, thereby correcting the pre-charge voltage.

[0009] Optionally, the reference voltage is the calibration reference voltage of any column driver chip.

[0010] Optionally, both the correction reference voltage and the error are digital signals.

[0011] Optionally, the reference voltage acquisition circuit is configured as follows:

[0012] The forward conduction voltages of the multiple LED beads are collected sequentially, and the forward conduction voltages of the multiple LED beads are averaged to obtain the correction reference voltage.

[0013] Optionally, the LED driving self-calibration circuit includes multiple sampling capacitors connected in parallel with the plurality of LED beads;

[0014] The reference voltage acquisition circuit is configured as follows:

[0015] Using rows as units, after acquiring the forward conduction voltage of each row of LED beads based on multiple sampling capacitors in each row, the multiple sampling capacitors in each row are controlled to be connected in parallel to obtain the average conduction voltage of each row of LED beads. In addition, the average conduction voltage of multiple rows of LED beads is averaged to obtain the correction reference voltage.

[0016] Optionally, the reference voltage acquisition circuit includes:

[0017] An analog-to-digital converter is used to acquire the forward conduction voltage of an LED when it is lit and quantize it into a corresponding digital signal.

[0018] Memory, used to store the digital signal of the forward conduction voltage of LED beads;

[0019] The processing unit is used to average the digital signals of the forward conduction voltages of multiple stored LED beads to obtain the correction reference voltage.

[0020] Optionally, the reference voltage acquisition circuit includes:

[0021] Multiple first switches are respectively connected between the multiple LED beads and the multiple sampling capacitors. The multiple first switches are controlled by a first control signal and are in a closed state during a first time period when the row drive signal of the corresponding row is valid, so as to connect the sampling capacitors of the corresponding row to the acquisition channel of the forward conduction voltage of the multiple LED beads.

[0022] Multiple second switches are respectively connected between the first node and multiple sampling capacitors. The multiple second switches are controlled by a second control signal and are in a closed state during a second time period when the row drive signal of the corresponding row is valid, so as to control the multiple sampling capacitors of the corresponding row to be in a parallel state.

[0023] An analog-to-digital converter, with its input connected to the first node, is used to quantize the average on-state voltage of each row of LED beads into a corresponding digital signal.

[0024] The memory is used to store the digital signal of the average on-state voltage of each row of LED beads;

[0025] The processing unit is used to average the digital signal of the average on-state voltage of the stored multi-row LED beads to obtain the correction reference voltage.

[0026] Optionally, the error self-correction circuit includes:

[0027] A digital-to-analog converter (DAC) receives a digital error signal at a first input terminal and a reference signal at a second input terminal. The DAC is used to convert the digital error signal into an analog error signal, wherein the digital error signal is a digital signal representation of the error.

[0028] The adder receives the pre-charge voltage at its first input terminal, receives the analog error signal at its second input terminal, and outputs the target pre-charge voltage at its output terminal.

[0029] Optionally, the error self-correction circuit includes:

[0030] The scaling unit receives a digital error signal at a first input terminal and a scaling factor at a second input terminal. The scaling unit is used to scale the digital error signal according to the scaling factor to obtain a scaled signal of the digital error signal, wherein the digital error signal is a digital signal representation of the error.

[0031] A digital adder receives the scaling signal at its first input terminal, receives a digital adjustment signal at its second input terminal, and outputs a digital correction signal at its output terminal. The digital adjustment signal represents the error term of the column driver chip.

[0032] The digital-to-analog converter receives the digital correction signal at its input terminal, converts the digital correction signal into an analog correction signal, and outputs it to the pre-charge voltage output node of the column driver chip to obtain the target pre-charge voltage.

[0033] According to a second aspect of this application, an LED driving self-calibration method is provided, comprising:

[0034] The calibration reference voltage of the column driver chip is obtained based on the average forward conduction voltage of multiple LED beads connected to the column driver chip;

[0035] Obtain the error of the correction reference voltage of the column driver chip relative to the reference voltage;

[0036] The pre-charge voltage is added to the error to obtain the target pre-charge voltage of the column driver chip, thereby correcting the pre-charge voltage of the column driver chip.

[0037] Optionally, the reference voltage is the calibration reference voltage of any column driver chip.

[0038] Optionally, obtaining the correction reference voltage of the column driver chip based on the average forward conduction voltage of the plurality of LEDs connected to the column driver chip includes:

[0039] Collect the forward conduction voltage of each of the multiple LED beads;

[0040] The forward conduction voltages of the multiple LED beads are averaged to obtain the correction reference voltage.

[0041] Optionally, obtaining the correction reference voltage of the column driver chip based on the average forward conduction voltage of the plurality of LEDs connected to the column driver chip includes:

[0042] The forward conduction voltage of each row of LEDs is collected sequentially based on multiple sampling capacitors connected in parallel with the multiple LED beads.

[0043] Multiple sampling capacitors in each row are connected in parallel to obtain the average on-state voltage of the LED beads in each row;

[0044] The average on-state voltage of multiple rows of LED beads is averaged to obtain the correction reference voltage.

[0045] According to a third aspect of this application, a column driver chip is provided, comprising: an LED driver self-calibration circuit as described in any embodiment of this application.

[0046] According to a fourth aspect of this application, a display device is provided, comprising: at least one column driver chip as described in any embodiment of this application.

[0047] Optionally, when the number of column driver chips is two or more, the display device further includes:

[0048] The control card is connected to each column driver chip, receives the calibration reference voltage output by one of the column driver chips, and sends the received calibration reference voltage to each column driver chip as a reference voltage for each column driver chip.

[0049] Optionally, when there are two or more column driver chips, the two or more column driver chips transmit the calibration reference voltage output by one of the column driver chips to each column driver chip through cascading transmission, so as to serve as the reference voltage for each column driver chip.

[0050] The beneficial effects of this application include at least the following:

[0051] The LED driver self-calibration scheme disclosed in this application obtains the calibration reference voltage of the column driver chip based on the average forward conduction voltage of multiple LED beads connected to the column driver chip (for example, using the average forward conduction voltage of multiple LED beads connected to the column driver chip as the calibration reference voltage of the column driver chip). This allows the pre-charge voltage output by the column driver chip to be self-calibrated even after the column driver chip is soldered to the display board, using the obtained calibration reference voltage of the column driver chip. Specifically, by calculating the error between the calibration reference voltage of the column driver chip and the reference voltage (such as the calibration reference voltage of any selected column driver chip), and adding the original pre-charge voltage output by the column driver chip to the error, the final pre-charge voltage of the column driver chip to the LED beads can be obtained as the target pre-charge voltage of the column driver chip. This ensures that the final pre-charge voltage output by each column driver chip to the LED display screen is consistent, effectively eliminating color blocks on the display screen and avoiding the influence of high temperature during chip soldering on the chip output parameters.

[0052] It should be noted that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit this application. Attached Figure Description

[0053] Figure 1 A schematic diagram of the structure of a display device is shown;

[0054] Figure 2 Show Figure 1 A timing diagram of some drive signals in a display device;

[0055] Figure 3 Show Figure 1 A timing diagram of the actual pre-charge voltage in the display device;

[0056] Figure 4 This diagram illustrates the structure of a display device according to an embodiment of this application.

[0057] Figure 5 Show Figure 4 A schematic diagram of one embodiment of a reference voltage acquisition circuit in a display device;

[0058] Figure 6 Show Figure 5 A schematic diagram of the quantization process of the reference voltage acquisition circuit;

[0059] Figure 7 Show Figure 4 A schematic diagram of another implementation of the reference voltage acquisition circuit in a display device;

[0060] Figure 8 Show Figure 7 A schematic diagram of the quantization process of the reference voltage acquisition circuit;

[0061] Figure 9 Show Figure 4 A schematic diagram of one implementation of an error self-correction circuit in a display device;

[0062] Figure 10 Show Figure 4 A schematic diagram of another implementation of the error self-correction circuit in a display device;

[0063] Figure 11 This diagram illustrates an embodiment of an error transmission architecture in a display device according to an embodiment of this application.

[0064] Figure 12 A flowchart illustrating the LED driving self-calibration method provided according to an embodiment of this application is shown. Detailed Implementation

[0065] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application may be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0066] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0067] In the description of this application, words such as "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments. "A plurality of" in this document refers to two or more. Furthermore, for the purpose of clearly describing the technical solutions of the embodiments of this application, the terms "first," "second," etc., are used to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first," "second," etc., do not limit the quantity or execution order, and that "first," "second," etc., do not necessarily imply differences.

[0068] In addition, the same reference numerals in the figures indicate the same or similar structures, so repeated descriptions of them will be omitted. That is, the various parts in this specification are described in a combination of parallel and progressive manner. Each part focuses on the differences from other parts, and the same or similar parts between the various parts can be referred to each other.

[0069] Figure 1 A schematic diagram of a display device is shown. Figure 2 It shows Figure 1 A timing diagram of some drive signals in a display device. Figure 3 It shows Figure 1 A timing diagram of the actual pre-charge voltage in the display device.

[0070] refer to Figure 1 , Figure 2 and Figure 3The LED display screen 130 is equipped with an array of m rows and n columns of LED beads (hereinafter referred to as LEDs). During display, multiple row drive signals ROW[1]~ROW[m] control multiple power transistors Q11~Q1m to conduct sequentially, thereby controlling the m row drive lines on the LED display screen 130 to open sequentially. When a certain row drive line is in the open state, multiple column drive signals PWM[0]~PWM[n] control multiple switching transistors Q21~Q2n to conduct sequentially / simultaneously, thereby controlling the n column drive lines on the LED display screen 130 to open sequentially / simultaneously, connecting the current path of the LED beads in the corresponding row and column, and the current flowing through the LED beads makes the LED beads light up. In order to enable the LED display screen 130 to have a better display effect, before the corresponding column drive line is opened, the pre-charge signal Tpre will first control multiple switching transistors Q31~Q3n to conduct, thereby pre-charging the LED beads to a pre-set voltage, namely the pre-charge voltage Vpre.

[0071] In practical applications, the LED display screen 130 may have m rows and a*n columns of LED beads, where a is an integer greater than or equal to 1. Each m row and n column of LED beads is driven by a column driver chip 120. Correspondingly, the display device 100 contains multiple column driver chips 120, and each column driver chip 120 provides a pre-charge voltage Vpre, i.e. Figure 1 Only a portion of the display screen architecture and column driver chip architecture in the display device 100 are shown.

[0072] The display device 100 has high requirements for the accuracy of the pre-charge voltage Vpre, as different pre-charge voltages Vpre will result in different chip brightness. (Reference) Figure 3 Each LED has a parasitic capacitance C to ground. The LEDs used on the same LED display screen 130 have identical characteristics, therefore the forward voltage (denoted as VF) of each LED is the same. Taking LED D11 as an example, each time LED D11 is turned on, C*(VF-Vpre) of the current output from the constant current source I1 is charged onto the parasitic capacitance C of LED D11, rather than flowing through LED D11 itself. Therefore, if the pre-charge voltage Vpre provided by each column driver chip 120 to the LED display screen 130 is different, different charges will be applied to the parasitic capacitance of the LEDs. For example, during the active period of the pre-charge signal Trep, some column driver chips output pre-charge voltage Vpre1 ​​to the LEDs, while others output pre-charge voltage Vpre2. At this time, depending on the different pre-charge voltages Vpre provided by the column driver chips, the current flowing through the LEDs will be different, resulting in noticeable color blocks on the LED display screen 130.

[0073] To minimize the impact of color blocks on the display effect, the pre-charge voltage Vpre output by each column driver chip needs to be identical. A common method is calibration. After the column driver chips are manufactured, the pre-charge voltage Vpre of each column driver chip is calibrated using methods such as efuse (Electronic Fuse) or OTP (One-Time Programmable) memory. This reduces the impact of color blocks. However, the calibration process is performed at the chip manufacturing stage. After calibration, the chips are sent to the customer, who solders them onto the display board. During soldering, the column driver chips are exposed to high temperatures. This high temperature causes thermal expansion and contraction of the molding material and other structural materials of the column driver chips, resulting in stress on the chips. Consequently, the output pre-charge voltage Vpre deviates from the target value, ultimately causing the display screen to fail to achieve the desired display effect.

[0074] To address the aforementioned problems, embodiments of this application improve the structure of the column driver chip (also referred to herein as the driver chip or chip) in the display device, referring to... Figure 4 , Figure 4 This application shows a schematic diagram of the structure of a display device provided in an embodiment of the present application. The display device 200 is driven by a chip in each column. Figure 4 Only one column driver chip 220 is shown in the diagram. Other column driver chips in the display device 200 have the same internal structure as column driver chip 220 and can be understood by referring to each other. An LED driver self-calibration circuit is added to self-calibrate the pre-charge voltage of the chip to the LED beads, so that the final pre-charge voltage (i.e., the target pre-charge voltage) output by each column driver chip to the LED display screen (or LED display screen 230) is consistent, effectively eliminating color blocks on the display screen and avoiding the influence of high temperature during the chip soldering process on the chip output parameters.

[0075] like Figure 4 As shown, in this embodiment, the display device 200 includes: a row driver chip 210, a column driver chip 220, and an LED display screen 230.

[0076] The LED display screen 230 includes m row driving lines, a*n column driving lines, and an LED array consisting of m*(a*n) LEDs. The m*(a*n) LEDs are positioned at the intersections of the m row driving lines and the a*n column driving lines, where a, m, and n are all integers greater than or equal to 1. Since the a column driving chips 220 have identical internal structures, for simplicity, [the following is omitted]. Figure 4The diagram only shows one column driver chip 220, n column driver lines connected to the n constant current output channels of the column driver chip 220, and multiple LED beads D11~Dmn corresponding to the n column driver lines. Furthermore, this embodiment will only show... Figure 4 The technical solution is explained using the column driver chip 220 shown as an example. However, for other embodiments where the display device 200 includes multiple column driver chips (i.e., a is greater than 1), the following can be applied: Figure 4 The solution shown is derived by making simple extensions.

[0077] In addition, it should be noted that Figure 4 In the LED display screen 230 shown, each LED is connected with a common cathode, that is, the cathodes of LEDs in the same row are connected to the same row drive line, and the anodes are connected to different column drive lines respectively. However, other implementations are also possible. For example, each LED can also be connected with a common anode, that is, the anodes of LEDs in the same row are connected to the same row drive line, and the cathodes are connected to different column drive lines respectively. This application does not impose strict limitations on this.

[0078] The line driver chip 210 includes m line scanning switches Q11~Q1m, which are connected to m line driving lines respectively. The m line scanning switches Q11~Q1m are controlled by multiple line driving signals (also called line scanning signals) ROW[1]~ROW[m] to sequentially open the m line driving lines. For example, in each display frame, the ground path of each line driving line is sequentially connected.

[0079] In terms of internal structure, the internal structure of each of the a column driver chips 220 is basically the same. Each column driver chip 220 includes n constant current sources I1~In, n column driver switches Q21~Q2n, n precharge switches Q31~Q3n, a buffer 221, and an LED driver self-calibration circuit 222. Regarding output pins, the column driver chip 220 includes n constant current output terminals and n precharge output terminals. The n constant current output terminals are used to connect to n column driver lines respectively to provide constant current drive signals to the n column driver lines. The n precharge output terminals are each used to connect to n column driver lines respectively to provide precharge voltage to the n column driver lines. In some other embodiments, the n constant current output terminals and n precharge output terminals share n output terminals. In this case, the n output terminals are used to connect to the n column driver lines respectively, and each output terminal can output constant current drive signals and precharge voltages to the corresponding connected column driver lines in a time-sharing manner. Figure 4 The example shown is only an illustration of the column driver chip 220 having n constant current output terminals and n precharge output terminals.

[0080] exist Figure 4In the example shown, n column drive switches Q21~Q2n are connected between n constant current sources I1~In and n constant current output terminals, respectively. n precharge switches Q31~Q3n are connected between the output terminal of buffer 221 and n precharge output terminals, respectively. The n column drive switches Q21~Q2n are controlled by multiple column drive signals PWM[1]~PWM[n] to sequentially / simultaneously open n column drive lines. During the period when the column drive line is in the open state, a constant current signal is provided to the anode of the LED connected to the column drive line. The n precharge switches Q31~Q3n are controlled by the precharge signal Tpre to precharge the potential of the column drive line (i.e. the anode potential of the LED connected to the column drive line) to the target precharge voltage Vpre1 ​​before the column drive line is opened.

[0081] The LED driver self-calibration circuit 222 is used to self-calibrate the pre-charge voltage Vpre0 of the LED beads pre-charged by the column driver chip 220, so that the column driver chip 220 outputs the target pre-charge voltage Vpre1. The input terminal of the buffer 221 is connected to the output terminal of the LED driver self-calibration circuit 222, and is used to buffer the target pre-charge voltage Vpre1 ​​output by the LED driver self-calibration circuit 222 before outputting it.

[0082] The LED driver self-calibration circuit 222 further includes: a reference voltage acquisition circuit 223, an error acquisition circuit 224, and an error self-calibration circuit 225. The reference voltage acquisition circuit 223 obtains the calibration reference voltage Vref_pre1 of the column driver chip 220 based on the average forward conduction voltage of the multiple LED beads D11~Dmn connected to the column driver chip 220. The error acquisition circuit 224 obtains the error Diff_D between the calibration reference voltage Vref_pre1 and the reference voltage Vref_pre0. The error self-calibration circuit 225 adds the pre-charge voltage Vpre0 of the column driver chip 220 to the corresponding error Diff_D to obtain the target pre-charge voltage Vpre1 ​​of the column driver chip 220, thus calibrating the pre-charge voltage Vpre0 of the column driver chip 220. Both the calibration reference voltage Vref_pre1 and the error Diff_D are digital signals. It should be noted that the digital signals described herein can also be understood as digital codes.

[0083] It is understood that, in the embodiments of this application, when performing self-calibration on the pre-charge voltage of the a column driver chips 220 in the display device 200, for each column driver chip 220, the calibration reference voltage Vref_pre1 of the column driver chip 220 is obtained based on the average forward conduction voltage of the multiple LED beads connected to the column driver chip 220. For example, the average forward conduction voltage of the multiple LED beads connected to the column driver chip is used as its calibration reference voltage Vref_pre1. After the column driver chip 220 is soldered to the display lamp board, the error of the calibration reference voltage Vref_pre1 of the column driver chip 220 relative to the calibration reference voltage Vref_pre0 of any selected column driver chip can be calculated, and the initial pre-charge voltage Vpre0 output by the column driver chip 220 is added to the corresponding error to make the final pre-charge voltage (i.e., the target pre-charge voltage) Vpre1 ​​output by the column driver chip 220 to the LED display consistent with other column driver chips 220. This effectively eliminates color blocks on the display screen and avoids the influence of high temperature during chip soldering on the chip output parameters.

[0084] In some embodiments, the reference voltage acquisition circuit 223 is configured to: sequentially acquire the forward conduction voltage VF of multiple LED beads D11~Dmn connected to the corresponding column driver chip 220, and average the forward conduction voltages of the multiple LED beads D11~Dmn to obtain the correction reference voltage Vref_pre1 of the column driver chip 220.

[0085] In specific implementation, such as Figure 5 As shown, the reference voltage acquisition circuit 223 includes an analog-to-digital converter 2231, a memory 2232, and a processing unit 2233. The analog-to-digital converter 2231 acquires the forward conduction voltage VF of the LED when it is lit and quantizes it into a corresponding digital signal. The memory 2232 stores the digital signal of the forward conduction voltage VF of the LED. The processing unit 2233 averages the stored digital signals of the forward conduction voltages of multiple LEDs D11~Dmn to obtain the correction reference voltage Vref_pre1 of the column driver chip 220.

[0086] Optionally, the reference voltage used by the analog-to-digital converter 2231 when performing analog-to-digital signal conversion is the pre-charge voltage (i.e., the initial pre-charge voltage) Vpre0 before self-calibration. The initial pre-charge voltage Vpre0 can be provided, for example, by a pre-charge voltage generation circuit provided inside or outside the column driver chip 220. If the error of the initial pre-charge voltage Vpre0 is taken into account, the initial pre-charge voltage Vpre0 can be expressed as Vpre*(1+δ), where δ represents the error term of the initial pre-charge voltage Vpre0.

[0087] Combination Figure 5 and Figure 6 In this embodiment, the operation of the reference voltage acquisition circuit 223 is roughly as follows:

[0088] First, after the display device 200 is powered on, the row drive signal ROW[1] is set to an active state (e.g., logic 1), and the row drive switch Q11 is controlled to open the first row drive line, connecting the cathodes of the first row LED beads D11~D1n to the reference ground;

[0089] Next, during the period when the first row drive line is turned on, n column drive signals PWM[1]~PWM[n] are set to active states in sequence (e.g., logic 1), and the n column drive lines are turned on in sequence. The constant current signal is output to the first row of LED beads D11~D1n in sequence. When each LED bead is lit, the forward conduction voltage VF of the LED bead is collected in sequence using the analog-to-digital converter 2231. 1i (Table 1 below represents the first row, i represents the i-th column, i is an integer greater than or equal to 1 and less than or equal to n), and after analog-to-digital conversion (i.e. quantization), the forward conduction voltage in digital signal form (i.e. the quantized value or digital code of the forward conduction voltage) is output to the memory 2232, thereby storing the digital code of the forward conduction voltage of the LED beads D11~D1n in the first row.

[0090] Then, repeat the above process to sequentially collect and store the digital code of the forward conduction voltage of each LED bead in rows 2 to m.

[0091] Finally, the processing unit 2233 performs average processing on the digital signals of the forward conduction voltages of the LED beads in each row stored in the storage to obtain the correction reference voltage Vref_pre1 of the column driver chip 220.

[0092] It is understood that the reference voltage acquisition circuit 223 disclosed in this embodiment has a relatively flexible method for acquiring and quantizing the forward conduction voltage of multiple LED beads D11~Dmn.

[0093] In some other embodiments, the LED driver self-calibration circuit 222 includes multiple sampling capacitors connected in parallel with multiple LED beads D11~Dmn respectively. In this case, the reference voltage acquisition circuit 223 is configured to: take rows as units, after acquiring the forward conduction voltage of each row of LED beads based on the multiple sampling capacitors of each row, control the multiple sampling capacitors of each row to be connected in parallel to obtain the average conduction voltage of each row of LED beads, and perform averaging processing on the average conduction voltage of multiple rows of LED beads to obtain the calibration reference voltage Vref_pre1 of the column driver chip 220.

[0094] In specific implementation, such as Figure 7 As shown, the reference voltage acquisition circuit 223 includes: multiple sampling capacitors, multiple first switches, multiple second switches, an analog-to-digital converter 2234, a memory 2235, and a processing unit 2236. The multiple first switches are respectively connected between multiple LED beads D11~Dmn and the first terminals of the multiple sampling capacitors. The second terminals of the multiple sampling capacitors are connected to the corresponding row drive lines. The multiple first switches are controlled by a first control signal PS and are in a closed state during a first time period when the row drive signal of the corresponding row is valid, thereby connecting the acquisition channels of the multiple sampling capacitors of the corresponding row for the forward conduction voltage of the multiple LED beads. The multiple second switches are respectively connected between a first node A and the first terminals of the multiple sampling capacitors. The multiple second switches are controlled by a second control signal PH and are in a closed state during a second time period when the row drive signal of the corresponding row is valid, thereby controlling the multiple sampling capacitors of the corresponding row to be in a parallel state. The input terminal of the analog-to-digital converter 2234 is connected to the first node A and is used to quantize the average conduction voltage of each row of LED beads into a corresponding digital signal. The memory 2235 is used to store the digital signal of the average conduction voltage of each row of LED beads. The processing unit 2236 is used to perform averaging processing on the digital signal of the average conduction voltage of the stored multi-row LED beads to obtain the correction reference voltage Vref_pre1 of the column driver chip 220.

[0095] Combination Figure 7 and Figure 8 In this embodiment, the operation of the reference voltage acquisition circuit 223 is roughly as follows:

[0096] First, after the display device 200 is powered on, the row drive signal ROW[1] is set to an active state (e.g., logic 1), and the row drive switch Q11 is controlled to open the first row drive line, connecting the cathodes of the first row LED beads D11~D1n to the reference ground;

[0097] Next, during the first stage of the first row of drive lines being turned on, the first control signal PS is set to an active state (e.g., logic 1), and the second control signal PH is set to an inactive state (e.g., logic 0). This connects the sampling capacitors C11~C1n of the first row to the acquisition channel for the forward conduction voltage of the multiple LED beads D11~D1n in the first row. A constant current signal is simultaneously output to the sampling capacitors C11~C1n of the first row, and the forward conduction voltage VF of the multiple LED beads D11~D1n in the first row is obtained on the sampling capacitors C11~C1n. 11 ~VF 1n ;

[0098] Secondly, during the second stage of the first row of drive lines being turned on (this second stage is later than the first stage), the first control signal PS is set to an invalid state (e.g., logic 0), and the second control signal PH is set to an active state (e.g., logic 1). The acquisition channel for the forward conduction voltage of the multiple sampling capacitors C11~C1n in the first row to the multiple LED beads D11~D1n in the first row is disconnected. The multiple sampling capacitors C11~C1n in the first row are then connected in parallel. Based on the principle of charge conservation, the average conduction voltage of the multiple LED beads D11~D1n in the first row is obtained at the first node A. After analog-to-digital conversion (i.e., quantization), the average on-state voltage of the multiple LED beads D11~D1n in the first row is output as a digital signal (i.e., the average on-state voltage of the LED beads in the first row). (quantized value or digital code) D The digital signal D of the average on-state voltage of the first row of LEDs is sent to memory 2235. Store;

[0099] Then, repeat the above process to sequentially acquire and store the digital signal D of the average on-state voltage of each LED bead in rows 2 to m. ;

[0100] Finally, the processing unit 2236 uses the digital signal D of the average on-state voltage of each row of LED beads stored in the database. The average value is calculated to obtain the correction reference voltage Vref_pre1 of the column driver chip 220.

[0101] It is understood that the reference voltage acquisition circuit 223 disclosed in this embodiment requires less processing time for the acquisition and quantization of the forward conduction voltages of multiple LED beads D11~Dmn, which can improve conversion efficiency and reduce self-calibration time.

[0102] Optionally, the reference voltage used by the analog-to-digital converter 2234 when performing analog-to-digital signal conversion is the pre-charge voltage (i.e., the initial pre-charge voltage) Vpre0 before self-calibration. The initial pre-charge voltage Vpre0 can be provided, for example, by a pre-charge voltage generation circuit provided inside or outside the column driver chip 220. If the error of the initial pre-charge voltage Vpre0 is taken into account, the initial pre-charge voltage Vpre0 can be expressed as Vpre*(1+δ), where δ represents the error term of the initial pre-charge voltage Vpre0.

[0103] by Figure 7 Taking the reference voltage acquisition circuit 223 shown as an example, the digital signal D of the average on-state voltage of each row of LED beads it obtains is... (j represents the row number, where j is a positive integer greater than or equal to 1 and less than or equal to m) can be represented as:

[0104] D (1),

[0105] The correction reference voltage Vref_pre1 obtained by the column driver chip 220 can be expressed as:

[0106] (2),

[0107] in, This represents the average forward conduction voltage of each LED bead in the display area controlled by the column driver chip 220 (i.e., each LED bead in the LED display screen 130 connected to the column driver chip 220), and across the entire LED board. It is usually a constant.

[0108] In this embodiment, the reference voltage Vref_pre1 used by the column driver chip 220 can be selected as the correction reference voltage of any one of the a column driver chips in the display device 200, and the a column driver chips select the same reference voltage Vref_pre0. For example, when a is greater than 1, that is, when the display device 200 contains two or more column driver chips 220, the display device 200 is also provided with an error transmission architecture. After obtaining the correction reference voltage Vref_pre1 of each of the a column driver chips in the display device 200 using the above embodiments, the correction reference voltage Vref_pre1 of a certain column driver chip (e.g., the first column driver chip) is selected as the reference voltage Vref_pre0. The column driver chip sends the reference voltage Vref_pre0 (i.e., the correction reference voltage Vref_pre1 it obtained) to each column driver chip in the form of a register. In this way, all chips will receive the correction reference voltage Vref_pre1 (i.e., the reference voltage Vref_pre0) of the first column driver chip. Optionally, this transmission process can be as follows: first, the calibration reference voltage Vref_pre1 (i.e., the reference voltage Vref_pre0) of the first column driver chip is sent to the control card, and then the control card sends it to each column driver chip. Alternatively, the user can read back the calibration reference voltage Vref_pre1 (i.e., the reference voltage Vref_pre0) of the first column driver chip and then send it to all column driver chips through the register.

[0109] For example, in Figure 11In the example shown, the column driver chips 220 in the display device 200 include, for example, column driver chips 220_0, 220_1, 220_2, ..., 220_a. The display device 200 also includes a control card 30, which is connected to each column driver chip. The control card 30 receives the calibration reference voltage output by one of the column driver chips (such as column driver chip 220_0) and sends the received calibration reference voltage to each column driver chip as the reference voltage Vref_pre0 required by each column driver chip during pre-charge voltage self-calibration. Optionally, the control card 30 can be integrated with a column driver chips, integrated within one of the a column driver chips, or configured separately.

[0110] In addition, in some other embodiments, instead of setting up a control card 30 in the display device 200, the calibration reference voltage output by one of the column driver chips can be transmitted to each of the other column driver chips in a cascaded transmission manner, so as to serve as the reference voltage Vref_pre0 required by each column driver chip when performing pre-charge voltage self-calibration.

[0111] It should be noted that in the foregoing embodiments, the signal transmission protocol that can be used between the column driver chips or between the control card 30 and the column driver chips is not limited. For example, a single-bus transmission protocol, I2C protocol, SPI protocol, or other multi-line transmission protocols, high-speed transmission protocols, etc. can be used.

[0112] For example, the reference voltage Vref_pre0 can be sent to the error acquisition circuit 224 in the LED driver self-calibration circuit of each column driver chip, so that the error acquisition circuit 224 can determine the error Diff_D of the correction reference voltage Vref_pre1 of the corresponding column driver chip relative to the reference voltage Vref_pre0. (See reference...) Figure 11 Taking column driver chip 220_1 as an example, the error acquisition circuit 224 inside column driver chip 220_1 can obtain the error Diff_D of the correction reference voltage Vref_pre1 relative to the reference voltage Vref_pre0 by subtracting the correction reference voltage Vref_pre1 and the reference voltage Vref_pre0 in column driver chip 220_1. This error Diff_D can be expressed as:

[0113] (3),

[0114] Among them, δ1 and δ2 are the error terms of column driver chip 220_0 and column driver chip 220_1 when generating the pre-charge voltage, respectively.

[0115] In some implementations, reference Figure 9 The error self-correction circuit 225 further includes a digital-to-analog converter 2251 and an adder 2252. The first input terminal of the digital-to-analog converter 2251 receives a digital error signal Diff_D, and the second input terminal receives a reference signal VREF. The digital-to-analog converter 2251 converts the digital error signal Diff_D into an analog error signal Diff_A based on the reference signal VREF, where the digital error signal Diff_D is a digital representation of the error. The first input terminal of the adder 2252 receives a pre-charge voltage Vpre0, the second input terminal receives the analog error signal Diff_A, and the output terminal of the adder 2252 outputs a target pre-charge voltage Vpre1.

[0116] Taking column driver chip 220_1 as an example, after the error acquisition circuit 224 within it obtains the corresponding error Diff_D, the error Diff_D is sent as a digital signal to the digital-to-analog converter 2251 in the error self-correction circuit 225. The digital-to-analog converter 2251 converts the error Diff_D into a corresponding analog signal Diff_A based on the reference voltage VREF. Then, the adder 2252 adds the analog signal error (i.e., the analog error signal) Diff_A to the initial pre-charge voltage Vpre0 of column driver chip 220_1 to obtain the target pre-charge voltage Vpre1 ​​of column driver chip 220_1, which can be expressed as:

[0117]

[0118] (4),

[0119] Where δ1 and δ2 represent the error terms of column driver chip 220_0 and column driver chip 220_1 when generating the pre-charge voltage, respectively, and γ represents the error term of the reference voltage VREF.

[0120] In the above formula (4), δ1, δ2, and γ can all be regarded as infinitesimals. Therefore, the product of any two of δ1, δ2, and γ can be ignored in the above formula (4). At this time, the above formula (4) can be simplified to:

[0121] (5).

[0122] In formula (5), if we let =0, that is, the reference voltage VREF of the digital-to-analog converter 2251 is configured as VREF= Then the target precharge voltage Vpre1 ​​of column driver chip 220_1 will eventually become Vpre0(1+δ1), that is, the target precharge voltage of column driver chip 220_0 and column driver chip 220_1 will become the same. Similarly, the target precharge voltage of all column driver chips in display setting 200 will become Vpre0(1+δ1), thereby effectively eliminating the color blocks on the light board.

[0123] In other embodiments, reference is made to Figure 10 The error self-correction circuit 225 further includes: a scaling unit 2253, a digital adder 2254, and a digital-to-analog converter 2255. The scaling unit 2253 receives a digital error signal Diff_D at its first input and a scaling factor k0 at its second input. The scaling unit 2253 scales the digital error signal Diff_D according to the scaling factor k0 to obtain a scaled signal (denoted as bit1). The digital error signal Diff_D is a digital representation of the error. The digital adder 2254 receives the scaled signal bit1 at its first input and a digital adjustment signal bit0 at its second input. The digital adder 2254 outputs a digital correction signal bit2 at its output. The digital adjustment signal bit0 represents the initial correction of the error term of the column driver chip. The digital-to-analog converter 2255 receives the digital correction signal bit2 at its input. The digital-to-analog converter 2255 converts the digital correction signal bit2 into an analog correction signal and outputs it to the pre-charge voltage output node B of the column driver chip 220 to obtain the target pre-charge voltage Vpre1. The digital-to-analog converter 2255 includes N current sources (I, 2I, ..., NI) and N switches. The N switches are turned on by the digital correction signal bit2, thereby realizing the digital-to-analog conversion function.

[0124] Compared to Figure 9In the example shown, this embodiment sets up a scaling unit 2253 and a digital adder 2254 in the error self-calibration circuit 225. During self-calibration, the digital error signal Diff_D can be scaled by multiplying it with a pre-set register scaling factor, so as to modify the error more flexibly. Then, the scaled signal bit1 obtained after scaling is added to the digital adjustment signal bit0, and the final error digital code, i.e., the digital correction signal bit2, is sent to the digital-to-analog converter 2255. The digital-to-analog converter 2255 uses N current sources (I, 2I, ..., NI) and N switches to perform digital-to-analog conversion on the error digital code and then superimposes it onto the pre-charge voltage output node B of the column driver chip. The pre-charge voltage output node B is the connection node between the pre-charge current source Ipre and the resistor R in the column driver chip. The column driver chip 220 generates an initial pre-charge voltage Vpre0 across the resistor R based on the pre-charge current source Ipre. After self-calibration, the column driver chip 220 outputs the target pre-charge voltage Vpre1 ​​at this node B. In this embodiment, the digital trimming signal bit0 can trim the chip's pre-charge voltage Vpre0 during the FT stage to correct the initial pre-charge voltage.

[0125] It is understood that this embodiment is capable of achieving the same level of... Figure 9 Based on the same self-calibration function as the example shown, it can also adjust the pre-charge voltage. While ensuring that the target pre-charge voltage of all column driver chips in the display setting 200 is consistent, thereby eliminating the color blocks on the lamp board, it further improves the accuracy of the pre-charge voltage output by the column driver chip, making the solution simpler and more practical.

[0126] Furthermore, this application also discloses an LED driving self-calibration method, applied to the display device 200 shown in the foregoing embodiments, with reference to... Figure 12 The method includes performing the following steps on each column driver chip in the display device 200:

[0127] In step S10, the correction reference voltage of the column driver chip is obtained based on the average forward conduction voltage of the multiple LED beads connected to the column driver chip.

[0128] In step S20, the error of the column driver chip's correction reference voltage relative to the reference voltage is obtained.

[0129] In this step, the reference voltage is the calibration reference voltage for any column driver chip.

[0130] In step S30, the pre-charge voltage is added to the error to obtain the target pre-charge voltage of the column driver chip, thereby correcting the pre-charge voltage of the column driver chip.

[0131] In some embodiments, step S10 further includes: acquiring the forward conduction voltage of each of the plurality of LED beads; averaging the forward conduction voltages of the plurality of LED beads to obtain the correction reference voltage of the driver chip.

[0132] In some embodiments, step S10 further includes: acquiring the forward conduction voltage of each row of LED beads based on multiple sampling capacitors connected in parallel with multiple LED beads; controlling the multiple sampling capacitors in each row to be connected in parallel to obtain the average conduction voltage of each row of LED beads; and averaging the average conduction voltage of multiple rows of LED beads to obtain the correction reference voltage of the driver chip.

[0133] In practice, the specific implementation of each step in the LED driving self-calibration method described above and the technical effects that can be achieved can be found in the various embodiments of the aforementioned display device 200, and will not be repeated here.

[0134] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating this application and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. An LED driving self-correction circuit, provided in a plurality of column driving chips of a display device respectively, for self-correcting a pre-charge voltage of the column driving chips pre-charging to LED lamp beads, so as to make the pre-charge voltages of the column driving chips pre-charging to LED lamp beads consistent, the LED driving self-correction circuit comprising: a reference voltage obtaining circuit, configured to obtain a correction reference voltage of the column driving chip according to average forward conduction voltages of a plurality of LED lamp beads connected to the column driving chip; an error obtaining circuit, configured to obtain an error of the correction reference voltage relative to a reference voltage, the reference voltage being a correction reference voltage of any column driving chip in the plurality of column driving chips; and an error self-correction circuit, configured to add the pre-charge voltage and the error to obtain a target pre-charge voltage of the column driving chip, so as to correct the pre-charge voltage. The correction reference voltage and the error are both digital signals. The reference voltage obtaining circuit is configured to: sequentially collect forward conduction voltages of the plurality of LED lamp beads, and average the forward conduction voltages of the plurality of LED lamp beads to obtain the correction reference voltage. The LED driving self-correction circuit comprises a plurality of sampling capacitors connected in parallel with the plurality of LED lamp beads respectively.

2. The LED drive self-correction circuit of claim 1, wherein, The reference voltage obtaining circuit is configured to: take a row as a unit, after collecting forward conduction voltages of LED lamp beads of each row based on a plurality of sampling capacitors of each row, control the plurality of sampling capacitors of each row to be connected in parallel to obtain average conduction voltages of LED lamp beads of each row, and average the average conduction voltages of LED lamp beads of a plurality of rows to obtain the correction reference voltage.

3. The LED drive self-correcting circuit of claim 2, wherein, The reference voltage obtaining circuit comprises: an analog-to-digital converter, configured to collect forward conduction voltages of LED lamp beads when the LED lamp beads are lighted, and quantize the forward conduction voltages of the LED lamp beads into corresponding digital signals; a memory, configured to store the digital signals of the forward conduction voltages of the LED lamp beads; and a processing unit, configured to average the digital signals of the forward conduction voltages of a plurality of LED lamp beads stored to obtain the correction reference voltage. The reference voltage obtaining circuit comprises: a plurality of first switches, respectively connected between the plurality of LED lamp beads and a plurality of the sampling capacitors, the plurality of first switches being controlled by a first control signal to be in a closed state in a first time period during which a row driving signal of a corresponding row is valid, so as to connect the plurality of sampling capacitors of the corresponding row to a collecting channel of the forward conduction voltages of the plurality of LED lamp beads; a plurality of second switches, respectively connected between a first node and the plurality of sampling capacitors, the plurality of second switches being controlled by a second control signal to be in a closed state in a second time period during which the row driving signal of the corresponding row is valid, so as to control the plurality of sampling capacitors of the corresponding row to be connected in parallel; an analog-to-digital converter, having an input end connected to the first node, and configured to quantize the average conduction voltages of LED lamp beads of each row into corresponding digital signals; and a memory, configured to store the digital signals of the average conduction voltages of LED lamp beads of each row.

4. The LED drive self-correcting circuit of claim 1, wherein, ​ ​ ​ 5. The LED drive self-correcting circuit of claim 3, wherein, ​ ​ ​ ​ 6. The LED drive self-correcting circuit of claim 4, wherein, ​ ​ ​ ​ ​ The processing unit is configured to average the digital signals of the average forward voltages of the plurality of LED lamp beads to obtain the correction reference voltage.

7. The LED drive self-correcting circuit of claim 2, wherein, The error self-correction circuit comprises: The digital-to-analog converter has a first input end receiving the digital error signal and a second input end receiving the reference signal, and is configured to convert the digital error signal into an analog error signal. The adder has a first input end receiving the pre-charge voltage and a second input end receiving the analog error signal, and outputs the target pre-charge voltage.

8. The LED drive self-correcting circuit of claim 2, wherein, The error self-correction circuit comprises: The scaling unit has a first input end receiving the digital error signal and a second input end receiving a scaling coefficient, and is configured to scale the digital error signal according to the scaling coefficient to obtain a scaled signal of the digital error signal. The digital adder has a first input end receiving the scaled signal and a second input end receiving a digital trimming signal, and outputs a digital correction signal, wherein the digital trimming signal represents an error term of the column driving chip. The digital-to-analog converter has an input end receiving the digital correction signal, and is configured to convert the digital correction signal into an analog correction signal and output the analog correction signal to a pre-charge voltage output node of the column driving chip to obtain the target pre-charge voltage.

9. An LED driving self-correction method for self-correcting pre-charge voltages of a plurality of column driving chips pre-charged to LED lamp beads in a display device to make the pre-charge voltages of the plurality of column driving chips pre-charged to the LED lamp beads consistent, the LED driving self-correction method comprising: obtaining a correction reference voltage of a column driving chip according to average forward voltages of a plurality of LED lamp beads connected to the column driving chip; obtaining an error of the correction reference voltage of the column driving chip relative to a reference voltage, wherein the reference voltage is the correction reference voltage of any column driving chip; adding the pre-charge voltage and the error to obtain a target pre-charge voltage of the column driving chip, thereby correcting the pre-charge voltage of the column driving chip.

10. The LED drive self-correction method of claim 9, wherein, The method comprises: collecting the forward voltage of each LED lamp bead in the plurality of LED lamp beads one by one; averaging the forward voltages of the plurality of LED lamp beads to obtain the correction reference voltage.

11. The LED drive self-correction method of claim 9, wherein, The method comprises: collecting the forward voltage of each row of LED lamp beads based on a plurality of sampling capacitors connected in parallel with the plurality of LED lamp beads; controlling the plurality of sampling capacitors in parallel in each row to obtain the average forward voltage of each row of LED lamp beads; averaging the average forward voltages of the plurality of rows of LED lamp beads to obtain the correction reference voltage.

12. A column driver chip comprising: The LED driving self-correction circuit according to any one of claims 1-8.

13. A display device comprising: A plurality of column driving chips as claimed in claim 12.

14. The display device of claim 13, wherein, The display device further comprises: A control card connected with each column driving chip respectively, receiving the calibration reference voltage outputted by one of the column driving chips, and sending the received calibration reference voltage to each column driving chip as a reference voltage of each column driving chip.

15. The display device of claim 13, wherein, The plurality of column driving chips respectively transmit the calibration reference voltage outputted by one of the column driving chips to each column driving chip through cascaded transmission as a reference voltage of each column driving chip. The plurality of column driving chips respectively transmit the calibration reference voltage outputted by one of the column driving chips to each column driving chip through cascaded transmission as a reference voltage of each column driving chip.

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