TWI884808B - Drive current calibration circuit, display drive chip and information processing device - Google Patents

Abstract

The present invention mainly discloses a driving current calibration circuit, which is applied to a display driving chip including a pre-charge voltage and a storage module. Since the high welding temperature experienced by the display driving chip during the process of being fixed to the circuit board will cause the driving current outputted therefrom to drift, the present invention designs the driving current calibration circuit to include a trimming code adjustment module and a current trimming unit, wherein the trimming code adjustment module is used to read a first trimming code from the storage module, and adjust the first trimming code to a second trimming code according to a calibration signal. On the other hand, the current trimming unit is used to generate an adjusted reference current according to the second trimming code and transmit it to each current source to trim the driving current generated by each current source to a target driving current. It is worth noting that, taking the calibration signal as a 3-bit code as an example, the 3-bit code can be changed successively to adjust the driving current successively so that it approaches the target driving current.

Description

Drive current calibration circuit, display drive chip and information processing device

The present invention relates to the technical field of LED display, and more particularly to a driving current calibration circuit integrated into an LED display driver chip for calibrating the driving current output by each current source in the chip.

FIG1 is a basic structure diagram of a known LED display. As shown in FIG1 , the known LED display 1a mainly includes: an LED display panel 11a and a display driver chip 12a, wherein the LED display panel 11a includes M lines and N columns of LED elements, M and N are positive integers, and the display driver chip 12a is an LED constant current driver chip, and therefore includes N current sources (i.e., N source driver modules). It is worth noting that the display driver chip 12a is also provided with a pre-charge circuit 121a. Before the N current sources provide driving current to the N source lines of the LED display panel 11a, the pre-charge circuit is enabled to charge the N LED elements in the same row to a predetermined voltage (Vpre). It should be noted that the LED elements themselves have a parasitic capacitance, so they can be pre-charged. In addition, practical experience shows that the use of pre-charge operation can achieve optimized visual effects on the LED display 1a.

Furthermore, FIG. 2 is a block diagram of a known LED display. As shown in FIG. 2 , a plurality of display driver chips 12a are used in a medium or large-sized LED display 1a, wherein each display driver chip 12a is responsible for driving a display block of the LED display panel 11a. During normal operation, a host computer (such as a laptop) transmits display data and related control signals to a control card 10a, and the control card 10a controls each of the display driver chips 12a to drive the display block for which it is responsible.

According to practical experience, process errors will cause component parameter drift, so that the reference current generating circuits built into the multiple display driver chips 12a cannot generate the same reference current, resulting in inconsistency in the multiple drive currents output by the multiple display driver chips 12a to the LED display panel 11a, thereby causing the LED display panel 11a to have obvious dark or bright blocks when displaying grayscale images. Therefore, before the chips are shipped out, the chip manufacturer will trim the reference current of each display driver chip 12a to ensure that all shipped display driver chips 12a have the same reference current built in. However, long-term usage data shows that in the process of assembling multiple display driver chips 12a and the LED display panel 11a to form the LED display 1a, the high temperature of welding will cause the baseline current of the display driver chip 12a to drift, resulting in differences in the baseline currents of the multiple display driver chips 12a.

In summary, it should be considered to add a drive current calibration circuit in the display driver chip 12a, so that after the client completes the board assembly, it can first run this calibration circuit to uniformly calibrate the built-in current source of each display driver chip 12a.

From the above description, it can be seen that a driving current calibration circuit is urgently needed in the art.

The main purpose of the present invention is to provide a driving current calibration circuit for integration into a display driver chip, to read a first trimming code from a storage module contained in the display driver chip, and then adjust the first trimming code to a second trimming code according to a calibration signal, and generate an adjusted reference current according to the second trimming code. The adjusted reference current is transmitted to each current source built into the display driver chip to trim the driving current generated by each current source to a target driving current.

Taking the calibration signal as a 3-bit code as an example, the 3-bit code can be changed successively to gradually adjust the driving current so that it approaches the target driving current.

In order to achieve the above-mentioned purpose, the present invention proposes an embodiment of the driving current calibration circuit, which is applied to be integrated in a display driver chip, wherein the display driver chip contains a plurality of current sources and a storage module, and each of the current sources is used to generate a driving current; and the driving current calibration circuit includes: A trim code adjustment module, coupled with a calibration signal and the storage module, and configured to read a first trim code from the storage module, and adjust the first trim code to a second trim code according to the calibration signal; and A current trimming unit is coupled to the trimming code adjustment module and is configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current.

In a feasible embodiment, the trimming code adjustment module includes: a control unit coupled to the calibration signal and configured to generate a control signal according to the calibration signal; and an adjustment unit coupled to the control unit and the storage module and configured to adjust the first trimming code read from the storage module to the second trimming code according to the control signal.

In another feasible embodiment, the trimming code adjustment module includes: A control unit coupled to the calibration signal and configured to adjust the first trimming code read from the storage module to the second trimming code according to the calibration signal.

In one embodiment, the calibration signal includes M bits, and the first trimming code and the second trimming code both include N bits; M and N are both positive integers.

Furthermore, the present invention also discloses an embodiment of a display driver chip, which is used to drive a LED display panel, and includes a plurality of current sources and a storage module; wherein each current source is used to generate a driving current; and, characterized in that the display driver chip includes a driving current calibration circuit, and the driving current calibration circuit includes: A trim code adjustment module, coupled to a calibration signal and the storage module, and configured to read a first trim code from the storage module, and adjust the first trim code to a second trim code according to the calibration signal; and A current trimming unit is coupled to the trimming code adjustment module and is configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current.

In a feasible embodiment, the plurality of LED elements are electrically connected to a plurality of gate lines and a plurality of source lines of the LED display panel in a common cathode connection manner, and the display driver chip is a multi-channel constant current driver chip of a current source type.

In one embodiment, the trimming code adjustment module includes: a control unit coupled to the calibration signal and configured to generate a control signal according to the calibration signal; and an adjustment unit coupled to the control unit and the storage module and configured to adjust the first trimming code read from the storage module to the second trimming code according to the control signal.

In another feasible embodiment, the plurality of LED elements are electrically connected to a plurality of gate lines and a plurality of source lines of the LED display panel in a common anode connection manner, and the display driver chip is a current sink type multi-channel constant current driver chip.

In one embodiment, the trim code adjustment module includes: A control unit coupled to the calibration signal and configured to adjust the first trim code read from the storage module to the second trim code according to the calibration signal.

In one embodiment, the calibration signal includes M bits, and the first trimming code and the second trimming code both include N bits; M and N are both positive integers.

Furthermore, the present invention also provides an embodiment of an information processing device, which has at least one LED display, and is characterized in that the LED display has an LED display panel and at least one display driver chip of the present invention as described above.

In one embodiment, the information processing device is an electronic device selected from the group consisting of a TV wall, an electronic billboard, a smart TV, a tablet computer, a laptop computer, an all-in-one computer, an in-vehicle entertainment device, a kiosk, a video door machine, a smart watch, a digital camera, and a head-mounted display device.

In order to enable the Review Committee to further understand the structure, features, purpose, and advantages of the present invention, the following are attached with drawings and detailed descriptions of preferred specific embodiments.

FIG3 is a basic structural diagram of an LED display including a driving current calibration circuit of the present invention. As shown in FIG3, the LED display 1 mainly includes: an LED display panel 11 and a display driver chip 12, wherein the LED display panel 11 includes X rows and Y columns (i.e., X lines, Y columns) of LED elements, and X and Y are positive integers. On the other hand, FIG4 is a first structural diagram of the LED display panel 11 shown in FIG3. As shown in FIG3 and FIG4, in a feasible embodiment, the X×Y LED elements 111 are electrically connected to the Y gate lines and the X source lines of the LED display panel 11 in a common anode connection manner. Furthermore, the display driver chip 12 is a current sink type multi-channel constant current driver chip, and includes Y current sources 121 and Y first switch elements 122 for adjusting the luminous brightness.

Further, as shown in FIG. 3 and FIG. 4 , the display driver chip 12 includes a pre-charge circuit 12P, and the pre-charge circuit 12P includes a (pre-charge) voltage generating unit 12P0, a pre-charge voltage providing unit 12P1 and Y second switch elements 12P2, wherein the voltage generating unit 12P0 is used to generate a pre-charge voltage (Vpre), and the pre-charge voltage providing unit 12P1 is a voltage follower for transmitting the pre-charge voltage to each second switch element 12P2. In normal operation, before the Y current sources 121 provide driving currents to the Y source lines of the LED display panel 11, the pre-charge circuit 12P is enabled to charge the Y LED elements 111 in the same row to the pre-charge voltage. It should be noted that the LED element 111 itself has a parasitic capacitor, so it can be pre-charged.

Of course, the LED display panel 11 can also be a common cathode panel. FIG. 5 is a second structural diagram of the LED display panel 11 shown in FIG. 3. As shown in FIG. 3 and FIG. 5, in another feasible embodiment, the X×Y LED elements 111 are electrically connected to the Y gate lines and the X source lines of the LED display panel 11 in a common cathode connection manner. In addition, the display driver chip 12 is a current source type multi-channel constant current driver chip, and includes Y current sources 121 and Y first switch elements 122 for adjusting the luminous brightness.

As shown in FIG3 , the driving current calibration circuit 2 of the present invention is integrated into the display driver chip 12. It is worth noting that when the driving current calibration circuit 2 of the present invention is included, the customer can operate an electronic device (such as a laptop) to transmit a calibration signal to the display driver chip 12. In this way, the driving current calibration circuit 2 of the present invention reads a first trim code (Trim code 1) from a storage module 120 contained in the display driving chip 12, and then adjusts the first trim code to a second trim code (Trim code 2) according to the calibration signal, and generates an adjusted reference current according to the second trim code and transmits it to each of the current sources 121 to control the current source 121 to adjust its output driving current to a target driving current, wherein the storage module 120 can be a programmable memory, an OTP (one-time programmable memory) or a static random access memory.

FIG6 is a block diagram of a driving current calibration circuit of the present invention. As shown in FIG6, the driving current calibration circuit 2 of the present invention mainly includes a trimming code adjustment module 21 and a current trimming unit 22. As shown in FIG3 and FIG6, the trimming code adjustment module 21 is coupled to the storage module 120 and a calibration signal sent by the customer operating his electronic device, and is configured to read a first trimming code from the storage module 120, and adjust the first trimming code to a second trimming code according to the calibration signal. On the other hand, the current trimming unit 22 is coupled to the trimming code adjustment module 21 and is configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources 121, thereby controlling the current source 121 to adjust its output driving current to a target driving current.

FIG7 is a first block diagram of the trimming code adjustment module 21 shown in FIG6. As shown in FIG7, in one embodiment, the trimming code adjustment module 21 includes a first control unit 211 and an adjustment unit 212, wherein the first control unit 211 is coupled to the calibration signal and is configured to generate a control signal according to the calibration signal. Furthermore, the adjustment unit 212 is coupled to the first control unit 211 and the storage module 120 and is configured to adjust the first trimming code read from the storage module 120 to a second trimming code according to the control signal. Specifically, the calibration signal includes M bits (e.g., code[M:0]), and the first trim code and the second trim code both include N bits (e.g., Trim code 1[N:0], Trim code 2[N:0]); and, as shown in the following table (1), M and N are both positive integers, for example, M=3. Table (1) Calibration signal code[M:0] First adjustment code Second adjustment code 000 Trim code 1[N:0] = Trim code 1[N:0] 001 Trim code 1[N:0] = Trim code 1[N:0]＋1 010 Trim code 1[N:0] = Trim code 1[N:0]＋2 011 Trim code 1[N:0] = Trim code 1[N:0]＋3 100 Trim code 1[N:0] = Trim code 1[N:0] 101 Trim code 1[N:0] = Trim code 1[N:0]－1 110 Trim code 1[N:0] = Trim code 1[N:0]－2 111 Trim code 1[N:0] = Trim code 1[N:0]－3

As shown in the above table (1), taking the calibration signal as a 3-bit code as an example, the customer can operate his electronic device to gradually change the 3-bit code (for example: 000à001à010à011), thereby gradually adjusting the driving current, and finally making the driving current approach the target driving current.

Specifically, when the driving current output by the display driver chip 12 deviates from the target value due to the high temperature of the soldering during the upper board assembly, the LED display panel 11 driven by the display driver chip 12 may have dark blocks when displaying a grayscale image; at this time, it can be understood that the driving current generated by each current source 121 of the display driver chip 12 is low. In this case, a calibration signal code[2:0]=3'b001 can be sent to the display driver chip 12 to control the trim code adjustment module 21 to add 1 to the first trim code (trim code1[N:0]) read from the storage module 120 to generate a second trim code (trim code2[N:0]). Thus, the current trimming unit 22 generates a corresponding adjusted reference current according to the second trimming code and transmits it to each of the current sources 121 to increase the driving current output by the current source 121, thereby achieving the effect of increasing the brightness of the dark block.

If the dark block is still too dark (not bright enough), a calibration signal code[2:0]=3'b010 can be continuously sent to the display driver chip 12 to control the trim code adjustment module 21 to add 2 to the first trim code (trim code1[N:0]) read from the storage module 120 to generate a second trim code (trim code2[N:0]). In this way, the current trimming unit 22 generates a corresponding adjusted reference current according to the second trim code and transmits it to each of the current sources 121 to further increase the drive current output by the current source 121, thereby further improving the brightness of the dark block. Similarly, the drive current can be adjusted successively to make it approach the target drive current successively.

On the other hand, when the driving current output by the display driver chip 12 deviates from the target value due to the high temperature transfer of the soldering during the upper board assembly, the LED display panel 11 driven by the display driver chip 12 may have bright blocks when displaying a medium grayscale image; at this time, it can be understood that the driving current generated by each of the current sources 121 of the display driver chip 12 is too high. In this case, a calibration signal code[2:0]=3'b101 can be sent to the display driver chip 12 to control the trim code adjustment module 21 to add 1 to the first trim code (trim code1[N:0]) read from the storage module 120 to generate a second trim code (trim code2[N:0]). Thus, the current trimming unit 22 generates a corresponding adjusted reference current according to the second trimming code and transmits it to each of the current sources 121 to reduce the driving current output by the current source 121, thereby achieving the effect of reducing the brightness of the bright block.

If the bright block is still too bright (not dark enough), a calibration signal code[2:0]=3'b110 can be continuously sent to the display driver chip 12 to control the trim code adjustment module 21 to perform a subtraction operation on the first trim code (trim code1[N:0]) read from the storage module 120 to generate a second trim code (trim code2[N:0]). In this way, the current trimming unit 22 generates a corresponding adjusted reference current according to the second trim code and transmits it to each of the current sources 121 to further reduce the driving current output by the current source 121, thereby achieving the effect of further reducing the brightness of the bright block.

Further, FIG8 is a first block diagram of the trim code adjustment module 21 shown in FIG6. As shown in FIG8, in another embodiment, the trim code adjustment module 21 includes a second control unit 213, which is coupled to the calibration signal and is configured to adjust the first trim code read from the storage module 120 to the second trim code (trim code 1 à trim code 2) according to the calibration signal. In other words, the second control unit 213 has the functions of the aforementioned first control unit 211 and the aforementioned adjustment unit 212 at the same time.

Thus, the above description has completely and clearly explained the driving current calibration circuit of the present invention; and, from the above description, it can be known that the present invention has the following advantages:

(1) The present invention provides a driving current calibration circuit, which is applied to be integrated in a display driver chip, and is used to read a first trimming code from a storage module contained in the display driver chip, and then adjust the first trimming code to a second trimming code according to a calibration signal, and generate an adjusted reference current according to the second trimming code. The adjusted reference current is transmitted to each current source built into the display driver chip to adjust the driving current generated by each current source to a target driving current. For example, the calibration signal is a 3-bit code, and the 3-bit code can be changed successively to adjust the driving current successively so that it approaches the target driving current.

(2) Furthermore, the present invention also provides a display driver chip for driving an LED display panel comprising X×Y LED elements, wherein the display driver chip contains a drive current calibration circuit as described above.

(3) Furthermore, the present invention also provides an information processing device having at least one display device, and characterized in that the LED display has an LED display panel and at least one display driver chip of the present invention as described above. In one embodiment, the information processing device is an electronic device selected from the group consisting of a TV wall, an electronic advertising billboard, a smart TV, a tablet computer, a laptop computer, an all-in-one computer, a car entertainment device, a kiosk, a video door machine, a smart watch, a digital camera, and a head-mounted display device.

It must be emphasized that what is disclosed in the aforementioned case is a preferred embodiment. Any partial changes or modifications that are derived from the technical ideas of this case and are easily inferred by people familiar with the art do not deviate from the scope of the patent rights of this case.

In summary, this case shows that its purpose, means and effects are very different from the known technology, and it is the first invention that is practical and indeed meets the patent requirements for invention. We sincerely request the review committee to examine this carefully and grant a patent as soon as possible to benefit the society. This is our utmost prayer.

1a: LED display 11a: LED display panel 12a: Display driver chip 121a: Pre-charge circuit 10a: Control card 1: LED display 11: LED display panel 111: LED component 12: Display driver chip 120: Storage module 121: Current source 122: First switch component 12P: Pre-charge circuit 12P0: Voltage generation unit 12P1: Pre-charge voltage supply unit 12P2: Second switch component 2: Drive current calibration circuit 21: Trim code adjustment module 211: First control unit 212: Adjustment unit 213: Second control unit 22: Current trim unit

FIG. 1 is a basic structural diagram of a known LED display; FIG. 2 is a block diagram of a known LED display; FIG. 3 is a basic structural diagram of an LED display including a driving current calibration circuit of the present invention; FIG. 4 is a first structural diagram of the LED display panel shown in FIG. 3; FIG. 5 is a second structural diagram of the LED display panel shown in FIG. 3; FIG. 6 is a block diagram of a driving current calibration circuit of the present invention; FIG. 7 is a first block diagram of the trim code adjustment module shown in FIG. 6; and FIG. 8 is a second block diagram of the trim code adjustment module shown in FIG. 6.

120: Storage module

121: Current source

2: Driving current calibration circuit

21: Modify the code adjustment module

22: Current adjustment unit

Claims (10)

A driving current calibration circuit is used for integration in a display driver chip, wherein the display driver chip contains a plurality of current sources and a storage module, and each current source is used to generate a driving current; and the driving current calibration circuit includes: A trimming code adjustment module, coupled with a calibration signal and the storage module, and configured to read a first trimming code from the storage module, and adjust the first trimming code to a second trimming code according to the calibration signal; and A current trimming unit is coupled to the trimming code adjustment module and is configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current; Wherein, the trimming code adjustment module includes: a control unit, coupled to the calibration signal, and configured to generate a control signal according to the calibration signal; and an adjustment unit, coupled to the control unit and the storage module, and configured to adjust the first trimming code read from the storage module to the second trimming code according to the control signal. A driving current calibration circuit is used for integration in a display driver chip, wherein the display driver chip contains a plurality of current sources and a storage module, and each current source is used to generate a driving current; and the driving current calibration circuit includes: A trimming code adjustment module, coupled with a calibration signal and the storage module, and configured to read a first trimming code from the storage module, and adjust the first trimming code to a second trimming code according to the calibration signal; and A current trimming unit, coupled to the trimming code adjustment module, and configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current; Wherein, the trimming code adjustment module includes: A control unit, coupled to the calibration signal, and configured to adjust the first trimming code read from the storage module to the second trimming code according to the calibration signal. A driving current calibration circuit as described in claim 1 or 2, wherein the calibration signal comprises M bits, and the first trimming code and the second trimming code both comprise N bits; M and N are both positive integers. A display driver chip is used to drive an LED display panel, and includes a plurality of current sources and a storage module, wherein each current source is used to generate a driving current; the characteristic is that the display driver chip includes a driving current calibration circuit, and the driving current calibration circuit includes: A trim code adjustment module, coupled with a calibration signal and the storage module, and configured to read a first trim code from the storage module, and adjust the first trim code to a second trim code according to the calibration signal; and A current trimming unit is coupled to the trimming code adjustment module and is configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current; Wherein, the trimming code adjustment module includes: a control unit, coupled to the calibration signal, and configured to generate a control signal according to the calibration signal; and an adjustment unit, coupled to the control unit and the storage module, and configured to adjust the first trimming code read from the storage module to the second trimming code according to the control signal. A display driver chip as described in claim 4, wherein the plurality of LED elements of the LED display panel are electrically connected to the plurality of gate lines and the plurality of source lines of the LED display panel in a common cathode connection manner, and the display driver chip is a multi-channel constant current driver chip of a current source type. A display driver chip as described in claim 4, wherein the calibration signal comprises M bits, and the first trimming code and the second trimming code both comprise N bits; M and N are both positive integers. A display driver chip as described in claim 4, wherein the plurality of LED elements of the LED display panel are electrically connected to the plurality of gate lines and the plurality of source lines of the LED display panel in a common anode connection manner, and the display driver chip is a multi-channel constant current driver chip of a current sink type. A display driver chip is used to drive an LED display panel, and includes a plurality of current sources and a storage module, wherein each current source is used to generate a driving current; the characteristic is that the display driver chip includes a driving current calibration circuit, and the driving current calibration circuit includes: A trim code adjustment module, coupled with a calibration signal and the storage module, and configured to read a first trim code from the storage module, and adjust the first trim code to a second trim code according to the calibration signal; and A current trimming unit, coupled to the trimming code adjustment module, and configured to generate an adjusted reference current according to the second trimming code and transmit it to each of the current sources to trim the driving current generated by each of the current sources to a target driving current; Wherein, the trimming code adjustment module includes: A control unit, coupled to the calibration signal, and configured to adjust the first trimming code read from the storage module to the second trimming code according to the calibration signal. A display driver chip as described in claim 8, wherein the calibration signal comprises M bits, and the first trimming code and the second trimming code both comprise N bits; M and N are both positive integers. An information processing device has at least one LED display, wherein the LED display has an LED display panel and at least one display driver chip as described in any one of claims 4 to 9.

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