VF detection compensation circuit, driving chip and display device

Abstract

This invention provides a VF detection and compensation circuit, a driver chip, and a display device, relating to the field of LED display driving technology. The VF detection and compensation circuit includes a VF detection circuit, a processing circuit, and a pre-charge compensation circuit and / or current compensation circuit. The VF detection circuit collects the VF value of each LED and outputs it to the processing circuit. Based on the VF value of each LED, the processing circuit determines the compensation coefficient for the pre-charge and / or drive current of each LED. During display, when a row of LEDs is scanned, the pre-charge compensation circuit and / or current compensation circuit perform display correction on each LED in that row based on its respective compensation coefficient. This invention can perform on-chip point-by-point correction of display effect differences caused by differences in the forward conduction voltage (VF) of each LED, achieving high correction accuracy and good low-grayscale display effect.

Description

Technical Field

[0001] This invention relates to the field of LED display driving technology, and more specifically, to a VF detection and compensation circuit, a driving chip, and a display device. Background Technology

[0002] The brightness of LED display chips is related to the driving current. Theoretically, to ensure that LED chips of the same model have the same brightness, each LED chip needs to be provided with a constant driving current. However, even among rigorously selected LED chips, the forward voltage VF of different chips still varies, resulting in differences in luminous efficiency. Therefore, even if the LED display driver chip provides a constant driving current to each LED chip, the final brightness produced by each chip will still differ.

[0003] To address the aforementioned issues, existing technologies involve point-by-point grayscale calibration of the LED display's LED beads. First, specialized instruments are used to measure the actual display brightness of each LED bead at full grayscale. Then, a corresponding coefficient is multiplied by the grayscale level of each LED bead to ensure that all LED beads display the same brightness after grayscale modulation. However, due to the inherent configuration of current control cards and driver chips, this method easily leads to the sacrifice of low grayscale levels, resulting in poor low-grayscale display performance. Summary of the Invention

[0004] The purpose of this invention is to provide a VF detection and compensation circuit, a driver chip, and a display device, which can perform on-chip point-by-point correction on the display effect difference caused by the difference in the forward conduction voltage VF of each LED bead, with high correction accuracy and good low gray display effect.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a VF detection and compensation circuit, including a VF detection circuit, a processing circuit, and a pre-charge compensation circuit and / or a current compensation circuit.

[0007] The VF detection circuit is used to collect the VF value of each LED and output it to the processing circuit;

[0008] The processing circuit determines the compensation coefficient for the pre-charge and / or drive current of each LED based on the VF value of each LED.

[0009] During the display process, when a row of LED beads is scanned, the pre-charge compensation circuit and / or current compensation circuit perform display correction for each LED bead in that row based on its respective compensation coefficient.

[0010] In practice, the VF value represents the forward voltage of the LED chip, and different LED chips may have different VF values. Based on this difference, the inventors discovered a monotonicity between the VF value and the brightness of the LED chip. Therefore, they proposed a method to determine the pre-charge and / or drive current compensation coefficients for each LED chip based on its VF value. Then, during the display process, when a row of LED chips is scanned, the pre-charge compensation circuit and / or current compensation circuit perform display correction for each LED chip in that row based on its respective compensation coefficient. That is, the pre-charge compensation circuit performs display correction for each LED chip in the row based on its pre-charge compensation coefficient, and the current compensation circuit performs display correction for each LED chip in the row based on its drive current compensation coefficient.

[0011] Since this embodiment of the invention corrects for display effect differences caused by VF value differences among different LEDs with the same constant current drive current and the same grayscale, the display effect differences among different LEDs are not significant. The compensation coefficient of this embodiment is directly related to the display effect of each LED, i.e., it is related to the VF value of the LED. Therefore, the display correction of each LED based on the compensation coefficient of its pre-charge and / or drive current can be understood as a fine-tuning of the LED's display effect, with very high correction accuracy. Because this embodiment uses the compensation coefficient of pre-charge and / or drive current to correct the LED display, compared to existing methods that correct the grayscale value of LEDs point by point, the correction method of this invention is independent of the grayscale of each LED, avoiding the sacrifice of low grayscale values. Low grayscale display correction has a better effect, improving the overall display effect of the screen. Furthermore, this embodiment performs display correction on a row of LEDs during the display process when a row of LEDs is scanned. Therefore, the pre-charge compensation circuit and the current compensation circuit are located within the driver chip, meaning this invention is an on-chip point-by-point correction method with higher real-time performance.

[0012] Furthermore, the pre-charge compensation coefficient includes at least one of the pre-charge voltage compensation coefficient, the pre-charge speed compensation coefficient, and the pre-charge time compensation coefficient.

[0013] The pre-charge compensation circuit includes at least one of a pre-charge voltage compensation module, a pre-charge speed compensation module, and a pre-charge time compensation module; wherein:

[0014] The pre-charge voltage compensation module corrects the pre-charge voltage of the LED based on the LED's voltage compensation coefficient and outputs the target pre-charge voltage.

[0015] The pre-charge speed compensation module corrects the charging speed of the LED's pre-charge voltage based on the LED's pre-charge speed compensation coefficient.

[0016] The pre-charge time compensation module corrects the duration of the pre-charge voltage of the LED based on the pre-charge time compensation coefficient of the LED.

[0017] Furthermore, the compensation coefficient for the drive current includes at least one of the following: the current compensation coefficient for the drive current, the constant current turn-on speed compensation coefficient, and the constant current turn-off speed compensation coefficient.

[0018] The current compensation circuit includes a current compensation module and / or a constant current velocity compensation module;

[0019] The current compensation module corrects the drive current of the LED chip based on the current compensation coefficient of the LED chip.

[0020] The constant current speed compensation module corrects the turn-on speed of the constant current switching transistor controlling the drive current output based on the constant current turn-on speed compensation coefficient, and / or

[0021] The constant current speed compensation module corrects the turn-off speed of the constant current switch based on the constant current turn-off speed compensation coefficient.

[0022] Optionally, the pre-charge voltage compensation module includes: a first selector, a second selector, multiple fixed resistors, and a current source;

[0023] Multiple fixed resistors are connected in series and connected to a current source. The first selector selects one of the resistor nodes as the input terminal of the pre-charge voltage based on the input first selection signal. The second selector selects the voltage at one of the resistor nodes as the target pre-charge voltage output of the LED based on the voltage compensation coefficient of the LED.

[0024] Optionally, the current compensation module includes: a third selector, a fourth selector, an intermediate resistor, and a variable current source;

[0025] The third selector is connected to the first terminal of the intermediate resistor, and the fourth selector is connected to the second terminal of the intermediate resistor. The variable current source provides a variable current to the intermediate resistor according to the current compensation coefficient of the LED.

[0026] The third selector selects the first end of the intermediate resistor as the input or output terminal based on the input second selection signal, and the fourth selector selects the second end of the intermediate resistor as the output or input terminal based on the input second selection signal.

[0027] The input terminal is connected to voltage VDI, and the output terminal outputs voltage VDO, which is the bias voltage of the constant current drive channel of the driver chip.

[0028] Optionally, the VF detection compensation circuit also includes a memory and M sets of N-bit latch circuits. The M sets of N-bit latch circuits correspond one-to-one with the M constant current drive channels of the driver chip. Each set of latch circuits is connected to the pre-charge compensation circuit and / or current compensation circuit in the corresponding constant current drive channel.

[0029] Each latch circuit includes: latch one and latch two;

[0030] In the i-th display row, latch 1 in the M-group N-bit latch circuit latches the compensation coefficients of the LED beads in the (i+1)-th row read from the memory.

[0031] In the (i+1)th display row, latch 2 in the M-group N-bit latch circuit latches the compensation coefficients of each LED in the (i+1)th row output by latch 1 and sends them to the pre-charge compensation circuit or current compensation circuit to perform display correction on the LEDs in the (i+1)th row.

[0032] Optionally, the VF detection compensation circuit also includes a memory, which is connected to multiple constant current drive channels, each of which includes a pre-charge compensation circuit and / or a current compensation circuit.

[0033] Within the i-th display row, the compensation coefficients of each LED in the i-th row are read from the memory and sent to the pre-charge compensation circuit or current compensation circuit in multiple constant current drive channels to perform display correction on the LEDs in the i-th row.

[0034] Furthermore, the processing circuit is used for:

[0035] The first mean value is calculated based on the VF value of each LED.

[0036] VF values ​​that deviate from the first mean according to preset conditions are selected, and the second mean is calculated based on the selected VF values.

[0037] Calculate the difference between the VF value of each LED and the second mean value, and based on the difference and the preset coefficients of pre-charge and drive current, determine and store the compensation coefficient of pre-charge and drive current for each LED.

[0038] In a second aspect, the present invention provides a driver chip, including a VF detection and compensation circuit as described in any of the foregoing embodiments.

[0039] Thirdly, the present invention provides a display device including a driver chip as described in the foregoing embodiments.

[0040] This invention provides a VF detection and compensation circuit, a driver chip, and a display device. The VF detection circuit collects the VF value of each LED and outputs it to a processing circuit. Based on the VF value of each LED, the processing circuit determines the compensation coefficient of the pre-charge and / or drive current of each LED. During the display process, when a row of LEDs is scanned, the pre-charge compensation circuit and / or current compensation circuit perform display correction on each LED in that row based on its respective compensation coefficient. Thus, this invention can perform on-chip point-by-point correction of the display effect difference caused by the difference in the forward conduction voltage VF of each LED, with high correction accuracy and good low-gray display effect. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of a VF detection and compensation circuit provided in an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of a display row according to an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of a common anode driver chip channel circuit;

[0045] Figure 4 A schematic diagram of a pre-charge compensation circuit provided in an embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of a pre-charging method provided in an embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of a pre-charge voltage compensation module provided in an embodiment of the present invention;

[0048] Figure 7 A schematic diagram of a current compensation circuit provided in an embodiment of the present invention;

[0049] Figure 8 A schematic diagram of a current compensation module provided in an embodiment of the present invention;

[0050] Figure 9 A schematic diagram of an M-group N-bit latch circuit provided in an embodiment of the present invention;

[0051] Figure 10 A schematic diagram of a set of latching circuits provided in an embodiment of the present invention;

[0052] Figure 11 A schematic diagram of the pre-charge voltage correction timing provided in an embodiment of the present invention;

[0053] Figure 12 This is a partial structural diagram of a driver chip provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0055] It should be noted that the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0056] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0057] Please refer to Figure 1 , Figure 1 A schematic diagram of a VF detection and compensation circuit according to an embodiment of the present invention is shown. The VF detection and compensation circuit includes a VF detection circuit, a processing circuit, a pre-charge compensation circuit, and a current compensation circuit.

[0058] The VF detection circuit is electrically connected to the processing circuit. The VF detection circuit is used to collect the VF value of each LED and output it to the processing circuit. Both the VF detection circuit and the processing circuit can be located within the driver chip.

[0059] The processing circuit calculates the pre-charge compensation coefficient and drive current compensation coefficient for each LED based on the VF value of each LED, or calculates the pre-charge compensation coefficient or drive current compensation coefficient for each LED.

[0060] During the display process, when a row of LED beads is scanned, the pre-charge compensation circuit and / or current compensation circuit perform display correction for each LED bead in that row based on its respective compensation coefficient.

[0061] In this embodiment of the invention, when a row of LEDs is scanned, it should not be understood as the instantaneous moment of scanning that row of LEDs, but rather as the time for displaying one row. The time for displaying one row = 1 / frame rate / display group / row scan count, which includes the display time of that row of LEDs, pre-charging time, and other waiting times.

[0062] refer to Figure 2 This illustrates a schematic diagram of a display row. That is, 1 / frame rate = a complete display frame, within which there are multiple display groups, such as... Figure 2 The P display groups shown represent the time it takes for the LEDs in the first row to the last row to be scanned at least once. Figure 2The time shown represents the scanning time from row 1 to row m. The scanning time for a particular row is considered as one complete display row within a display group. A complete display row comprises multiple display areas, with a blank time interval between each display area. A display area can be understood as the time during which the LEDs display based on a PWM signal; this PWM signal can be greater than 0 or equal to 0. During this blank time, the LEDs can be pre-charged or scanned. In this embodiment, multiple pre-charging operations can be performed within the time of one complete display row. Even when the PWM signal for a certain display area is 0, pre-charging can still be performed in that display area.

[0063] For example, for a driver chip that uses a 64-line scan, one constant current drive channel of the driver chip can drive a maximum of 64 lines of LEDs for display. The time for each display line is 1 / 60 / 64 / 64 ≈ 4µs. That is, in this embodiment, each LED in the line can be corrected for display based on its own compensation coefficient within the time of 4µs.

[0064] Since the driver chip is a multi-constant current drive channel chip, each constant current drive channel is connected to the LEDs in that column via column lines. When a row of LEDs is scanned, the LEDs driven by each constant current drive channel within that row are fixed. That is, within the 4µs time period, display correction is performed on each LED in that row based on its respective compensation coefficient. This should be understood as multiple constant current drive channels simultaneously driving their respective corresponding LEDs within that 4µs time period. In other words, the time for display correction of each LED based on its compensation coefficient is 4µs. Within these 4µs, display correction can be performed on the LED based on at least one of the LED's drive current and pre-charge compensation coefficient.

[0065] It should be noted that in actual displays, each group of LEDs generally includes three types of LEDs: red (R), green (G), and blue (B), with the anode or cathode connected together. The display calibration of each LED referred to in this invention refers to the display calibration of the monochrome LEDs within each group, such as the display calibration of the red LEDs.

[0066] When a row of LEDs is scanned, the pre-charge compensation circuit and / or the current compensation circuit perform display correction for each LED in that row based on its respective compensation coefficient. This can be further understood as follows: within the display row of LEDs, the pre-charge compensation circuit performs display correction for each LED in that row based on its respective pre-charge compensation coefficient, and / or, the current compensation circuit performs display correction for each LED in that row based on its respective drive current compensation coefficient. It is worth noting that in various embodiments of the present invention, A and / or B indicate that A and B can be present simultaneously, or only A or only B can exist. For example, the VF detection compensation circuit can include both the pre-charge compensation circuit and the current compensation circuit, or it can include only the pre-charge compensation circuit or the current compensation circuit.

[0067] In practice, the output terminal of the constant current drive circuit of the driver chip is connected to the same terminal as the output terminal of the pre-charge circuit, as shown in the reference. Figure 3 As shown, the pre-charge circuit outputs a pre-charge voltage based on a reference potential and a pre-charge control signal, such as the corrected target pre-charge voltage mentioned in this invention; the constant current drive circuit outputs a drive current based on display data, i.e., grayscale data. In the driver chip, the constant current drive circuit and the pre-charge circuit are not activated simultaneously; that is, the constant current output of the constant current drive circuit and the pre-charge operation of the pre-charge circuit are not performed concurrently. Therefore, in this embodiment of the invention, display correction based on the compensation coefficient of the LED's drive current is achieved when the constant current drive circuit is activated, and display correction based on the compensation coefficient of the LED's pre-charge is achieved when the pre-charge circuit is activated.

[0068] Furthermore, the pre-charge compensation coefficient includes at least one of the following: pre-charge voltage compensation coefficient, pre-charge speed compensation coefficient, and pre-charge time compensation coefficient. For example... Figure 4 As shown, the pre-charge compensation circuit includes a pre-charge voltage compensation module, a pre-charge speed compensation module, and a pre-charge time compensation module.

[0069] Current LED displays are generally composed of m rows * n columns of LEDs, driven by row driver chips and constant current source driver chips. Due to parasitic capacitance on the row and column lines, coupling occurs during LED display. Furthermore, parasitic capacitance can cause ghosting (upper and lower shadows) on the display. To reduce the impact of parasitic capacitance, the traditional method is to pre-charge the LEDs with an anti-ghosting voltage before display, clamping them to the same voltage. The voltage jump generated during this process releases the charge from the parasitic capacitance. This method solves the upper and lower shadow ghosting phenomena to some extent, but its effect on the coupling phenomenon of the display is not ideal. This invention further considers that the parasitic capacitance to be eliminated for each LED may be different. Based on the VF value differences of each LED on the display, a pre-charging voltage compensation coefficient, a pre-charging speed compensation coefficient, and a pre-charging time compensation coefficient are determined for each LED. This allows for real-time on-chip correction of the pre-charging process using the individual pre-charging compensation coefficients of each LED, resulting in better decoupling.

[0070] The pre-charge voltage compensation module corrects the pre-charge voltage of the LED based on its voltage compensation coefficient and outputs a target pre-charge voltage. In this embodiment, the pre-charge voltage reduces the impact of parasitic capacitance on display coupling. Therefore, the pre-charge voltage does not actually light up the LED; instead, it provides a voltage jump to release the charge generated by the parasitic capacitance. Based on the formula Q = CV, where Q represents charge, C represents capacitance, and V represents voltage, the parasitic capacitance C of a given LED is fixed. Therefore, the amount of charge released to eliminate the parasitic capacitance depends on the voltage value. A voltage jump is needed to release the charge from the parasitic capacitance, and the pre-charge voltage creates this voltage jump to release the charge generated by the parasitic capacitance. When an adjacent LED is lit, the LED will not become slightly conductive due to the parasitic capacitance, thus reducing coupling.

[0071] Since constant current output and pre-charge will not occur simultaneously, refer to... Figure 5 For example, one pre-charging method is as follows: Within a display unit, when the PWM is greater than 0, the operating states of the pre-charging circuit are sequentially pre-charging voltage V1, pre-charging off, and pre-charging voltage V2. The constant current drive circuit illuminates the LEDs based on the PWM in the region corresponding to pre-charging off, at which time the channel output voltage is V3. Within a display unit, when the PWM is equal to 0, the constant current drive circuit is off, and the output states of the pre-charging circuit are sequentially pre-charging voltage V4, pre-charging voltage V5, and pre-charging voltage V6. Figure 5 The display unit shown can be understood as Figure 2 The diagram shows a display area plus the blank time on its left and right sides. In this example, within a display unit, if the PWM of the display area is greater than 0, this embodiment of the invention can correct the pre-charge voltage V1 and pre-charge voltage V2 based on the voltage compensation coefficient of the LED beads; if the PWM of the display area is equal to 0, this embodiment of the invention can perform time-division correction on the pre-charge voltage V4, pre-charge voltage V5, and pre-charge voltage V6 based on the voltage compensation coefficient of the LED beads.

[0072] In one embodiment, the pre-charge voltage compensation module includes a first selector, a second selector, a plurality of fixed resistors, and a current source.

[0073] Multiple fixed resistors are connected in series with the current source. There can be one or two current sources. When there are two current sources, they are identical, and the multiple fixed resistors are connected in series between them. The current source mentioned in this embodiment can be a fixed current source or a variable current source. When there are two variable current sources, their output currents are adjusted synchronously. When the resistance of the fixed resistors is sufficiently large, the current source can consist of a single current source. That is, when the resistance of the fixed resistors is greater than or equal to the built-in resistance of the first selector, the current source can consist of a single current source. The first end of the series connection of multiple fixed resistors is connected to this current source, and the other end can be grounded or connected to VCC.

[0074] In one possible example, refer to Figure 6 The current source can include a third power supply i3 and a fourth power supply i4, which are respectively connected across the two ends of a series circuit formed by multiple fixed resistors. That is, the third power supply i3 and the fourth power supply i4 can be connected to the first and last resistor nodes of the multiple resistor nodes, respectively.

[0075] The first selector, based on the input first selection signal, selects one resistor node from the plurality of fixed resistors as the input terminal of the pre-charge voltage. The second selector, based on the voltage compensation coefficient of the LED, selects the voltage at one resistor node from the plurality of fixed resistors as the target pre-charge voltage output for that LED. The first selector can be a 2-to-1 data selector, and the second selector can be a multiplexer. The number of fixed resistors depends on the actual adjustment requirements and is not limited here.

[0076] In one possible example, such as Figure 6 As shown, there are 4 fixed resistors R. The 4 fixed resistors R are connected in series to form 5 resistor nodes n0 to n4. All 5 resistor nodes n0 to n4 are connected to the second selector MUX2. The positive and negative input terminals of the first selector MUX1 are connected to resistor nodes n0 and n4 respectively.

[0077] The first selector MUX1 is used to determine the input terminal of the pre-charge voltage VPRE from resistor nodes n0 and n4 according to the first selection signal. The second selector MUX2 is used to select a resistor node from resistor nodes n0-n4 according to the voltage compensation coefficient, and connects the voltage of the selected resistor node as the target pre-charge voltage to one input terminal of the first amplifier AMP1. The other input terminal of the operational amplifier AMP1 is connected to its output terminal. Its output terminal can be connected to the pin terminal of the constant current drive channel with or without a switch. When the constant current drive circuit is turned off, this output terminal outputs the target pre-charge voltage.

[0078] When VF_CAL[P] = 1, VPRE = VT, and at this time, VPRE_CAL = VPRE - I*R*VF_CAL[P-1:0].

[0079] When VF_CAL[P] = 0, VPRE = VB, and at this time, VPRE_CAL = VPRE + I*R*VF_CAL[P-1:0].

[0080] Wherein, VF_CAL[P] is the first selection signal, VF_CAL[P-1:0] is the voltage compensation coefficient, VPRE is the pre-charge voltage, VT is the voltage at resistor node n0, VB is the voltage at resistor node n4, I is the first synchronization current output by the third power supply and the fourth power supply, and VPRE_CAL is the target pre-charge voltage output.

[0081] In other words, in the pre-charge voltage compensation module, the fixed resistors act as voltage divider resistors. The first synchronous current flows through each fixed resistor, and a voltage of I*R is generated on each fixed resistor.

[0082] When the first selection signal VF_CAL[P] is 1, resistor node n0 serves as the input terminal of the pre-charge voltage. The voltage of resistor node n0 is VT = VPRE. The second selector MUX2 selects a resistor node ns (s is an integer from 0 to 4) from resistor nodes n0-n4 according to the voltage compensation coefficient. The voltage of the resistor node ns is the target pre-charge voltage VPRE_CAL output by the second selector MUX2. Its magnitude is the voltage of resistor node n0 minus all the voltage divisions generated by the fixed resistor between resistor node n0 and resistor node ns.

[0083] When the first selection signal VF_CAL[P] is 0, resistor node n4 serves as the input terminal of the pre-charge voltage. The voltage of resistor node n4 is VB = VPRE. The second selector MUX2 selects a resistor node ns (s is an integer from 0 to 4) from resistor nodes n0-n4 according to the voltage compensation coefficient. The voltage of the resistor node ns is the target pre-charge voltage VPRE_CAL output by the second selector MUX2. Its magnitude is the voltage of resistor node n4 plus all the voltage division generated by the fixed resistor between resistor nodes ns and resistor node n4.

[0084] For example, assuming VPRE is 0.4V, I is 0.1A, R is 1Ω, VF_CAL[P] = 1, and VF_CAL[P-1:0] is 3, then the target pre-charge voltage VPRE_CAL output at this time is 0.1V at resistor node n3. It should be noted that this example is only one illustration; the specific data for actual applications should be based on the actual application, and no limitations are imposed here.

[0085] The pre-charge speed compensation module corrects the charging speed of the LED's pre-charge voltage based on the pre-charge speed compensation coefficient. By correcting the charging speed, it enables the LED to quickly reach the corresponding pre-charge voltage (potential), thereby improving the display effect. For example, the pre-charge speed compensation coefficient can be used to correct the charging speed of the pre-charge voltages V1, V2, and V4 respectively, allowing them to quickly reach the corresponding potential from 0. Although pre-charge voltages V4, V5, and V6 exhibit potential jumps, these jumps are relatively small and do not require correction based on the pre-charge speed compensation coefficient.

[0086] Based on the formula Q = CV = it, we know that t = CV / i, where V is the voltage of the constant current drive channel of the driver chip, which can be considered a fixed value. Therefore, theoretically, t can be adjusted by adjusting i and C. Based on this, the pre-charge speed compensation module (not shown in the figure) may include at least one of a first current control unit and a first capacitor control unit. The first current control unit controls the charging current of the pre-charge circuit based on the pre-charge speed compensation coefficient, and the first capacitor control unit controls the size of the charging capacitor in the pre-charge circuit based on the pre-charge speed compensation coefficient. The larger the current, the faster the pre-charge speed and the shorter the time to pre-charge to a certain potential; conversely, the smaller the current, the slower the pre-charge speed and the longer the time to pre-charge to a certain potential. The larger the charging capacitor value, the faster the pre-charge speed, and vice versa.

[0087] In implementation, the first current control unit can control the magnitude of the charging current in the pre-charging circuit by changing the magnitude of the bias current IB or the mirror ratio of the current mirror based on the pre-charging speed compensation coefficient. The first capacitor control unit can control the size of the charging capacitor in the pre-charging circuit by controlling the number or capacitance of the charging capacitors based on the pre-charging speed compensation coefficient. The specific implementation circuits of the first current control unit and the first capacitor control unit can be based on specific circuit variations of the pre-charging circuit, and this invention does not impose limitations on them.

[0088] The pre-charge time compensation module corrects the duration of at least one pre-charge voltage of the LED based on a pre-charge time compensation coefficient, thereby improving the display effect of the LED. For example, the pre-charge time compensation coefficient can be used to correct the pre-charge duration of one or more of the aforementioned pre-charge voltages V1, V2, V4, V5, and V6. The pre-charge time compensation module can be implemented based on relevant timing circuits, that is, by controlling the timing of a certain pre-charge voltage through the pre-charge time compensation coefficient, such as extending or shortening its duration. The relevant circuits for controlling the duration of the pre-charge voltage can be found in existing technologies and will not be elaborated here.

[0089] Furthermore, the compensation coefficient for the drive current includes at least one of the following: the drive current compensation coefficient, the constant current turn-on speed compensation coefficient, and the constant current turn-off speed compensation coefficient; such as Figure 7 As shown, the current compensation circuit includes a current compensation module and a constant current velocity compensation module.

[0090] The current compensation module corrects the driving current of the LED based on the current compensation coefficient of the LED.

[0091] In this embodiment of the invention, the driving current is also referred to as the constant current driving current. When the constant current switch of the control driver chip is turned on, the constant current driving module outputs driving current to the LED beads based on the PWM signal, and the LED beads display. When the constant current switch is turned off, the constant current output stops, and the LED beads do not display. The current compensation coefficient of the LED beads can be used to correct the same driving current generated by the driver chip. For example, a larger driving current may result in a brighter LED bead. Since the current compensation coefficients of each LED bead are different, the final driving current flowing through each LED bead will also be slightly different. Therefore, the difference in luminous efficiency caused by different VF values ​​of the LED beads can be optimized, so that the LED beads can have the same display brightness when displaying the same grayscale.

[0092] In one embodiment, the current compensation module includes a third selector, a fourth selector, an intermediate resistor, and a variable current source.

[0093] The third selector is connected to the first terminal of the intermediate resistor, and the fourth selector is connected to the second terminal of the intermediate resistor. The variable current source provides a variable current to the intermediate resistor according to the current compensation coefficient of the LED. The third selector selects the first terminal of the intermediate resistor as the input or output terminal based on the input second selection signal, and the fourth selector selects the second terminal of the intermediate resistor as the output or input terminal based on the input second selection signal. The input terminal is connected to the voltage VDI, and the output terminal outputs the voltage VDO, which is the bias voltage of the constant current drive channel of the driver chip.

[0094] In this implementation, the variable current source provides a variable current to the intermediate resistor according to a current compensation coefficient. There can be one or two variable current sources. When there are two, the first and second variable current sources are connected across the intermediate resistor, respectively. When the resistance of the intermediate resistor is sufficiently large, the variable current source consists of a single variable current source. That is, when the resistance of the intermediate resistor is greater than or equal to the built-in resistance of the third and fourth selectors, the variable current source can consist of a single variable current source, with the intermediate resistor connected across its two ends.

[0095] Optionally, the third and fourth selectors can be the same type of two-to-one data selector.

[0096] by Figure 8Taking the current compensation module shown as an example, this invention introduces the working principle of the current compensation module.

[0097] The positive input terminal of the third selector MUX3 is connected to the negative input terminal of the fourth selector MUX4, with a corresponding voltage of VDI. The negative input terminal of the third selector MUX3 is connected to the positive input terminal of the fourth selector MUX4, with a corresponding voltage of VDO.

[0098] The output terminals of the third selector MUX3 and the fourth selector MUX4 are connected to the first terminal N1 and the second terminal N2 of the intermediate resistor Rc, respectively. The first variable current source i1 and the second variable current source i2 are connected to the first terminal N1 and the second terminal N2 of the intermediate resistor Rc, respectively.

[0099] Based on the second selection signal I_CAL[T], the third selector MUX3 is used to select the first terminal N1 of the intermediate resistor Rc as either the input or output terminal, and the fourth selector MUX4 correspondingly selects the second terminal of the intermediate resistor Rc as either the output or input terminal. Two variable current sources i1 and i2 are used to provide the second synchronous current according to the current compensation coefficient.

[0100] When I_CAL[T]=1, VDO=VDI-Ic*I_CAL[T-1:0]*Rc, ΔI≈-Ic*I_CAL[T-1:0]*Rc*gdsNM_CM.

[0101] When I_CAL[T]=0, VDO=VDI+Ic*I_CAL[T-1:0]*Rc, ΔI≈Ic*I_CAL[T-1:0]*Rc*gdsNM_CM.

[0102] Where I_CAL[T] is the second selection signal, I_CAL[T-1:0] is the current compensation coefficient, Ic*I_CAL[T-1:0] is the second synchronization current provided by the first variable current source i1 and the second variable current source i2 according to the current compensation coefficient, Rc is the resistance value of the intermediate resistor, gdsNM_CM is the drain-source conductance of the N-channel MOS transistor in the third and fourth selectors, and ΔI is the compensation current between the input and output terminals.

[0103] In other words, in the current compensation module, the sign of the compensation current is determined by the second selection signal, and the magnitude of the compensation current is determined by the current compensation coefficient, thereby changing the bias voltage VDO of the constant current drive channel, and thus changing the magnitude of the drive current output from the constant current drive channel. The second synchronous current flows through the intermediate resistor, and the voltage division generated on the intermediate resistor is Ic*I_CAL[T-1:0]*Rc.

[0104] When the second selection signal is 1, the first terminal N1 of the intermediate resistor serves as the input terminal with a voltage of VDI; the second terminal N2 of the intermediate resistor serves as the output terminal with a voltage of VDO. That is, the output voltage VDO is obtained by subtracting the voltage division from the intermediate resistor from the input voltage VDI. Correspondingly, the resulting compensation current ΔI is negative.

[0105] When the second selection signal is 0, the first terminal N1 of the intermediate resistor acts as the output terminal with a voltage of VDO; the second terminal N2 of the intermediate resistor acts as the input terminal with a voltage of VDI. That is, the output voltage VDO is obtained by adding the input voltage VDI to the voltage divided by the intermediate resistor. Correspondingly, the resulting compensation current ΔI is positive.

[0106] Specifically, the constant current speed compensation module corrects the turn-on speed of the constant current switch controlling the drive current output based on the constant current turn-on speed compensation coefficient. The constant current speed compensation module also corrects the turn-off speed of the constant current switch based on the constant current turn-off speed compensation coefficient.

[0107] The correction principle of the constant current speed compensation module in this embodiment is similar to that of the pre-charge speed compensation module, and its principle will not be elaborated here. The constant current speed compensation module may include at least one of a second current control unit and a second capacitor control unit. The second current control unit controls the gate current of the constant current switch based on a constant current turn-on speed compensation coefficient or a constant current turn-off speed compensation coefficient. The second capacitor control unit controls the size of the charging capacitor that controls the turn-on or turn-off of the constant current switch based on the constant current turn-on speed compensation coefficient or a constant current turn-off speed compensation coefficient. In implementation, the capacitor controlled by the second capacitor control unit can be the capacitor in the operational amplifier AMP2 connected to the gate of the constant current switch, such as a Miller correction capacitor used for loop stabilization. Of course, in practice, the capacitor can also be other types of capacitors, and this invention does not limit this.

[0108] The circuit principles of the pre-charge compensation circuit and the current compensation circuit have been described in detail above with reference to specific embodiments. Next, it will be explained how the pre-charge compensation circuit and / or the current compensation circuit perform display correction on each LED in the row based on its respective compensation coefficient.

[0109] In one embodiment, the VF detection compensation circuit further includes a memory and M sets of N-bit latch circuits, as referenced. Figure 9 M groups of N-bit latch circuits correspond one-to-one with the M constant current drive channels of the driver chip. Each group of latch circuits is connected to the pre-charge compensation circuit and the current compensation circuit in the corresponding constant current drive channel. In various embodiments of the present invention, the constant current drive channel should not be simply understood as a physical pin (physical pins are referred to as constant current drive channel pin terminals in this document), but can be understood as a constant current drive channel circuit, for example... Figure 12The circuit shown can have its pre-charge compensation circuit and current compensation circuit located in the constant current drive channel circuit.

[0110] Each latch circuit includes: latch one and latch two;

[0111] Specifically, in the i-th display row, latch one in the M-group N-bit latch circuit latches the compensation coefficients of each LED in the (i+1)-th row read from the memory; in the (i+1)-th display row, latch two in the M-group N-bit latch circuit latches the compensation coefficients of each LED in the (i+1)-th row output by latch one and sends them to the pre-charge compensation circuit or current compensation circuit to perform display correction on the LEDs in the (i+1)-th row.

[0112] The core idea of ​​this implementation is to cache the compensation coefficients of the next row of LEDs in advance within the current display row, and when the next row of LEDs begins display correction, cache the compensation coefficients of the next row of LEDs within its display row.

[0113] Each latch circuit can include latch one and latch two based on a ping-pong structure. Latch one in the M groups of N-bit latch circuits latches the corresponding compensation coefficients based on the latch signal LATCH-EN[(M-1):0]. The latch signal LATCH-EN[(M-1):0] corresponds to M constant current drive channels, such as the latch signal for constant current drive channel 0 being LATCH-EN[0] and the latch signal for constant current drive channel 1 being LATCH-EN[1]. Latch two in the M groups of N-bit latch circuits is connected to the same line feed signal ROW and outputs the latched compensation coefficients of the current row LED corresponding to the line feed signal ROW to the pre-charge compensation circuit or the current compensation circuit, such as in Figure 3 When the pre-charging circuit shown is activated, it outputs the compensation coefficient of the current LED bead to the pre-charging compensation circuit. Further, based on the current type of the compensation coefficient, it outputs it to one or more of the pre-charging voltage compensation module, pre-charging speed compensation module, and pre-charging time compensation module within the pre-charging compensation circuit. Figure 3 When the constant current drive circuit shown is turned on, it outputs the compensation coefficient of the current LED bead to the current compensation circuit. Furthermore, based on the type corresponding to the current compensation coefficient, it outputs it to at least one of the current compensation module and the constant current speed compensation module in the constant current drive circuit.

[0114] Both latch one and latch two are N bits, corresponding to the magnitude of the compensation coefficient CAL[(N-1):0]. For example... Figure 10The latching circuit corresponding to the constant current drive channel 0 shown includes N latches 1 and N latches 2 connected in a one-to-one correspondence. The N latches 1 are connected to the same latching signal LATCH-EN[0]. Based on the latching signal LATCH-EN[0], the N latches 1 sequentially latch the compensation coefficients VF_CAL[(N-1)] to VF_CAL[0]. The N latches 2 are connected to the line feed signal ROW, and after latching the compensation coefficients transmitted by the latches 1, they are output as OUT[(N-1):0], i.e. Figure 10 As shown, N latches output OUT[(N-1)] to OUT[0] respectively.

[0115] Taking the voltage compensation coefficient of the pre-charge voltage as an example, the driver configuration enables the correction function of the pre-charge voltage compensation module. The correction timing is as follows: Figure 11 As shown, the driver chip has 16 constant current drive channels, namely D[0]-D

[15] , and the voltage compensation coefficient of each lamp bead is VF_CAL[5:0], totaling 6 bits.

[0116] In the i-th display row, latch one in the 16 groups of 6-bit latch circuits latches the compensation coefficients VF_CAL[5:0] of each LED in the (i+1)-th row based on the latch signal LATCH-EN[15:0]. For example, latch one in the latch circuit corresponding to constant current drive channel 0 latches the compensation coefficients VF_CAL[5], VF_CAL[4], VF_CAL[3], VF_CAL[2], VF_CAL[1], and VF_CAL[0] sequentially based on the latch signal LATCH-EN[0]. When the rising edge of the row feed signal ROW of the (i+1)-th row of LEDs arrives, that is, after latch two receives the row feed signal ROW, it indicates that it is currently in the (i+1)-th display row. Each latch two latches the compensation coefficient output by its corresponding latch one and sends it to the pre-charge voltage compensation module. The compensation coefficients of the LED beads in the (i+1)th row that are finally latched by latch 2 in the 16 latching circuits are represented as VF_CAL_CH[15:0], which correspond to the 16 constant current drive channels D[15:0].

[0117] In another embodiment, the VF detection compensation circuit further includes a memory connected to a plurality of constant current drive channels, each constant current drive channel including a pre-charge compensation circuit or a current compensation circuit.

[0118] Within the i-th display row, the compensation coefficients of each LED in the i-th row are read from memory and sent to the pre-charge compensation circuit or current compensation circuit in the multiple constant current drive channels to perform display correction on the i-th row of LEDs. This implementation is generally applicable to special circuits, such as when the compensation coefficient of each LED is 6 bits of data, and the driver chip has 16 constant current drive channels, resulting in a total of 96 bits of data. The compensation coefficients of the i-th row of LEDs are read from memory according to the address of the LEDs and then sent to the pre-charge compensation circuits in these 16 constant current drive channels to achieve display correction on the i-th row of LEDs.

[0119] The above content provides a detailed description of the key features of this invention. The implementation of the VF detection circuit and processing circuit will be described below.

[0120] Since the embodiments of the present invention are applicable to LED displays, the VF detection circuit can collect the VF value of each LED bead on the LED display through the following steps:

[0121] 1) The system configures the constant current drive channel current to the actual operating current IOUT through register configuration (VF is related to the current magnitude, so the actual channel current magnitude needs to be set during detection).

[0122] 2) Configure VF_DET_EN = 1 to enable VF detection;

[0123] 3) Detect the VF value (also known as VF quantization code value) of the m row LED beads corresponding to the constant current drive channel channel0;

[0124] a) Enable the channel output of the row driver connected to the row line of the first row of LEDs;

[0125] b) Send a PWM signal to channel 0 to ensure that the current flowing through the LED bead under test is IOUT;

[0126] c) After the output voltage of channel 0 stabilizes, the VF detection circuit's built-in ADC samples and quantizes it, so that the detected VF voltage value is converted into binary data of a specified precision, that is, the VF quantization code value is binary data.

[0127] d) Store the VF quantization code value corresponding to the first row and first column of LEDs into the memory for later processing;

[0128] e) Sequentially turn on the output of the row driver connected to the row lines of row LEDs 2 to m, and repeat steps b to d until the VF values ​​of all row LEDs corresponding to channel 0 have been detected, and store the corresponding quantization code values ​​into the memory.

[0129] 4) Sequentially detect the m rows of LEDs corresponding to constant current drive channels channel1 to (n-1), with the specific steps being similar to step 3), until the VF of all m rows and n columns of LEDs is detected, and store the corresponding quantization code values ​​into the memory.

[0130] In this embodiment of the invention, the principle circuit for acquiring the VF voltage value of the LED bead after the output voltage of the constant current drive channel has stabilized is not limited here, and can be implemented with reference to relevant prior art. The VF detection circuit in this embodiment of the invention acquires the VF voltage value only after the output voltage of the constant current drive channel has stabilized, thus obtaining a more accurate VF voltage value.

[0131] After obtaining the VF value of each LED, the processing circuit processes the VF value.

[0132] In one implementation, the compensation coefficients are related to preset coefficients of various types, and the processing circuit can obtain the compensation coefficients of the LEDs based on the following steps:

[0133] Step 1: Calculate the first mean value based on the VF value of each LED.

[0134] The processing circuit adds up the VF values ​​of all the LEDs collected by the VF detection circuit and calculates the average value as the first mean.

[0135] Step 2: Filter out VF values ​​whose deviation from the first mean meets the preset conditions, and calculate the second mean based on the filtered VF values;

[0136] For example, if the VF value of a certain LED deviates from the first average by more than 50%, it may indicate that the LED is short-circuited or open-circuited. The processing circuit will select VF values ​​from all LEDs that deviate from the first average by less than 50%, and calculate an average value based on the selected VF values ​​as the second average.

[0137] Step 3: Calculate the difference between the VF value of each LED and the second average value, and based on the difference and the preset coefficients of pre-charging and driving current, determine and store the compensation coefficient of pre-charging and / or driving current for each LED.

[0138] As mentioned above, the pre-charge compensation coefficient includes at least one of the pre-charge voltage compensation coefficient, the pre-charge speed compensation coefficient, and the pre-charge time compensation coefficient. The drive current compensation coefficient includes at least one of the drive current current compensation coefficient, the constant current turn-on speed compensation coefficient, and the constant current turn-off speed compensation coefficient. Therefore, the preset coefficients of the present invention can be set only for pre-charge and drive current, or they can be refined for the pre-charge voltage, pre-charge speed, and pre-charge time under pre-charge. Similarly, they can also be refined for the drive current itself, the constant current turn-on speed, and the constant current turn-off speed.

[0139] In one embodiment, the voltage compensation coefficient for the pre-charge voltage of the LED bead can be VF_CAL[P:0] = ΔVF*K1; the current compensation coefficient for the drive current of the LED bead can be I_CAL[T:0] = ΔVF*K2. Wherein, ΔVF is the difference between the VF value of the LED bead and the second average value, K1 is the first preset coefficient, and K2 is the second preset coefficient. K1 and K2 can be preset according to the actual display effect required.

[0140] In this embodiment of the invention, after obtaining the compensation coefficient of at least one of the driving current and pre-charging for each LED, the corresponding compensation coefficient for each LED can be stored, i.e., written into a memory. This memory can be the SRAM (Static Random Access Memory) within the driver chip. In one implementation, the memory can also be configured for each type of compensation coefficient. For example, a memory can be configured for the voltage compensation coefficient, the pre-charging speed compensation coefficient, and the pre-charging time compensation coefficient for pre-charging, and a memory can be configured for the current compensation coefficient, the constant current turn-on speed compensation coefficient, and the constant current turn-off speed compensation coefficient for the driving current.

[0141] In each memory, each LED has a corresponding address. By reading this address, the corresponding compensation coefficient for that LED can be obtained. For example, addresses 0 to 15 are the addresses of the LEDs in the first row. By reading addresses 0 to 15, the compensation coefficients of the LEDs in the first row can be obtained.

[0142] In another possible implementation based on obtaining the compensation coefficients by reading the address, a memory can be used to store all the compensation coefficients of each LED, but this reading method is more complicated.

[0143] The present invention also provides a driver chip, which includes the VF detection and compensation circuit described in the above embodiments. Please refer to [link to relevant documentation]. Figure 12 , Figure 12 A partial structural schematic diagram of a driver chip provided in an embodiment of the present invention is shown. The driver chip includes the aforementioned VF detection and compensation circuit, as well as a reference voltage generation circuit, a bias circuit, a current output circuit, and a pre-charge generation circuit.

[0144] The reference voltage generation circuit is used to generate the reference current Iref and the reference voltage. Among them, C[0:L] is an L+1 bit wide control signal, which can control the magnitude of the reference current Iref, and thus control the range of the output current.

[0145] The bias module is used to generate a first bias voltage VD, a second bias voltage VGI, and a bias current based on a reference voltage.

[0146] The pre-charge generation circuit is electrically connected to the reference voltage generation circuit and is used to output the pre-charge voltage to the pre-charge compensation module of the VF detection and compensation circuit. The output terminal of the pre-charge compensation module is connected to the constant current drive channel terminal. In this example, the reference voltage generation circuit and the pre-charge compensation module can be understood as part of the aforementioned pre-charge module.

[0147] The current output circuit is electrically connected to the bias circuit and is used to output the corresponding output current based on the second bias voltage VGI and the bias current. One input terminal of the operational amplifier AMP2 is connected to the first bias voltage VD, and the other input terminal is connected to the voltage VDI. The output terminal is connected to the gate of the constant current switch NM_C1, and the drain terminal of the constant current switch NM_C1 is connected to the pin terminal of the constant current drive channel. The current compensation module is connected between the voltage VDI and the source terminal of NM_C1. OE[0:N] represents the column drive line control signal of the LED array. The operational amplifier AMP2 effectively controls the constant current switch NM_C1 to turn on based on OE, so that the drive current corrected based on the current compensation coefficient I_CAL[T-1:0] is output through the pin terminal of the constant current drive channel.

[0148] For details regarding the reference voltage generation circuit, bias circuit, current output circuit, precharge generation circuit, and the specific circuit structure and description of the operational amplifier AMP2, please refer to the relevant existing technologies; they will not be elaborated upon here.

[0149] Based on the above embodiments, the present invention also provides a display device, which may include the above-described driver chip.

[0150] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An LED display driver chip, characterized in that, It includes multiple constant current drive channels, as well as VF detection circuitry and processing circuitry. Each constant current drive channel includes a pre-charge compensation circuit and / or a current compensation circuit. Each constant current drive channel is used to connect the LEDs in that column via column lines. The VF detection circuit is used to collect the VF value of each LED and output it to the processing circuit; The processing circuit determines the compensation coefficient for the pre-charge and / or drive current of each LED based on the VF value of each LED. During the display process, when a row of LED beads is scanned, the pre-charge compensation circuit and / or the current compensation circuit in the plurality of constant current drive channels perform display correction for each LED bead in that row based on its respective compensation coefficient.

2. The LED display driver chip according to claim 1, characterized in that, The pre-charge compensation coefficient includes at least one of the pre-charge voltage compensation coefficient, the pre-charge speed compensation coefficient, and the pre-charge time compensation coefficient. The pre-charge compensation circuit includes at least one of a pre-charge voltage compensation module, a pre-charge speed compensation module, and a pre-charge time compensation module; wherein: The pre-charge voltage compensation module corrects the pre-charge voltage of the LED based on the voltage compensation coefficient of the LED and outputs the target pre-charge voltage. The pre-charge speed compensation module corrects the charging speed of the pre-charge voltage of the LED based on the pre-charge speed compensation coefficient of the LED. The pre-charge time compensation module corrects the duration of the pre-charge voltage of the LED based on the pre-charge time compensation coefficient of the LED.

3. The LED display driver chip according to claim 1, characterized in that, The compensation coefficient of the drive current includes at least one of the following: the current compensation coefficient of the drive current, the constant current turn-on speed compensation coefficient, and the constant current turn-off speed compensation coefficient. The current compensation circuit includes a current compensation module and / or a constant current velocity compensation module. The current compensation module corrects the driving current of the LED chip based on the current compensation coefficient of the LED chip. The constant current speed compensation module corrects the turn-on speed of the constant current switching transistor controlling the drive current output based on the constant current turn-on speed compensation coefficient, and / or The constant current speed compensation module corrects the turn-off speed of the constant current switch based on the constant current turn-off speed compensation coefficient.

4. The LED display driver chip according to claim 2, characterized in that, The pre-charge voltage compensation module includes: a first selector, a second selector, multiple fixed resistors, and a current source; The plurality of fixed resistors are connected in series and connected to the current source. The first selector selects one of the resistor nodes of the plurality of fixed resistors as the input terminal of the pre-charge voltage based on the input first selection signal. The second selector selects the voltage at one of the resistor nodes of the plurality of fixed resistors as the target pre-charge voltage output of the lamp based on the voltage compensation coefficient of the lamp.

5. The LED display driver chip according to claim 3, characterized in that, The current compensation module includes: a third selector, a fourth selector, an intermediate resistor, and a variable current source; The third selector is connected to the first terminal of the intermediate resistor, the fourth selector is connected to the second terminal of the intermediate resistor, and the variable current source provides a variable current to the intermediate resistor according to the current compensation coefficient of the lamp bead. The third selector selects the first end of the intermediate resistor as the input or output end based on the input second selection signal, and the fourth selector selects the second end of the intermediate resistor as the output or input end based on the input second selection signal. The input terminal is connected to voltage VDI, and the output terminal outputs voltage VDO, which is the bias voltage of the constant current drive channel of the driver chip.

6. The LED display driver chip according to any one of claims 1-5, characterized in that, It also includes a memory and M sets of N-bit latch circuits, wherein the M sets of N-bit latch circuits correspond one-to-one with the M constant current drive channels of the driver chip, and each set of latch circuits is connected to the pre-charge compensation circuit and / or the current compensation circuit in the corresponding constant current drive channel. Each latch circuit includes: latch one and latch two; In the i-th display row, the latch in the M-group N-bit latch circuit latches the compensation coefficients of the LED beads in the (i+1)-th row read from the memory. In the (i+1)th display row, latch two in the M-group N-bit latch circuit latches the compensation coefficients of each LED in the (i+1)th row output by latch one and sends them to the pre-charge compensation circuit or the current compensation circuit to perform display correction on the LEDs in the (i+1)th row.

7. The LED display driver chip according to any one of claims 1-5, characterized in that, It also includes a memory connected to a plurality of constant current drive channels, each constant current drive channel including the precharge compensation circuit and / or the current compensation circuit; Within the i-th display row, the compensation coefficients of each LED bead in the i-th row are read from the memory and sent to the pre-charge compensation circuit or the current compensation circuit in the plurality of constant current drive channels to perform display correction on the LED beads in the i-th row.

8. The LED display driver chip according to claim 1, characterized in that, The processing circuit is used for: The first mean value is calculated based on the VF value of each LED. VF values ​​that deviate from the first mean according to preset conditions are selected, and the second mean is calculated based on the selected VF values. Calculate the difference between the VF value of each LED and the second mean value, and based on the difference and the preset coefficients of pre-charge and drive current, determine and store the compensation coefficient of pre-charge and the compensation coefficient of drive current for each LED.

9. A display device, characterized in that, Includes the LED display driver chip as described in any one of claims 1-8.

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