LED backlight driving circuit and driving current precision control method

Abstract

The invention discloses an LED backlight driving circuit and a driving current precision control method, the LED backlight driving circuit comprises 2n LED driving channels, and each LED driving channel comprises an LED lamp string, an MOS switch tube, an operational amplifier and a driving resistor; the LED backlight driving circuit further comprises a DAC unit, the DAC unit comprises 2n groups of resistor network units, 2n first data selectors and a second data selector, each LED driving channel is in one-to-one correspondence with one resistor network, and in the semiconductor multilayer structure of the LED backlight driving circuit, the first data selectors are in one-to-one correspondence with the second data selectors, and the second data selectors are in one-to-one correspondence with the second data selectors. And the driving resistor in each LED driving channel and the resistor network corresponding to the LED driving channel are arranged in the same semiconductor layer. Therefore, the resistor network unit and the driving resistor of the LED driving channel are located at the same position to ensure the resistor matching precision, and the precision of the driving current is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of LED backlight, and in particular to an LED backlight driving circuit and a driving current precision control method. Background Art

[0002] Liquid crystal display (LCD) is the largest screen display application in modern display panels. The liquid crystal material used in LCD panels cannot emit light by itself, and needs to be provided by a backlight source. LED backlight sources have the advantages of energy saving, environmental protection, and high performance, and are widely used in LCD display panels. The performance of LED backlight drive circuits is crucial to LCD display panels.

[0003] like Figure 1 As shown, in the LED backlight driving system of the prior art, a global DAC unit is provided inside the chip, and the same reference voltage value is provided to the operational amplifiers of all LED driving channels based on the DAC unit to control all LED driving channels to dim at the same time with the same LED driving current. In the DAC unit, R is a DAC seed resistor, and the DAC resistor string is a total of N R resistors connected in series, and then the switch is selected by a digital control signal to realize an adjustable voltage output to the operational amplifiers of all LED driving channels. The output voltage of the DAC unit in each LED driving channel is divided by the R' resistor to obtain the final LED driving current, that is, I led =n*R*I dc / R', where n is the number of resistors between the selected tap and ground in the N resistor string. In order to maintain consistent resistance matching, R and R' are generally selected from the same type of resistor, that is, the ratio of R / R' is a fixed constant, such as R / R'=1, that is, R=R', then I led =n*R*I dc / R'≈I dc *n, but because the DAC unit in the existing design corresponds to multiple LED drive channels, and different LED drive channels are distributed on different chip semiconductor layers (different layout layers in the semiconductor layout), it is difficult to achieve high-precision N*R / R' resistance matching, so the LED current accuracy and consistency between LED drive channels will be relatively poor. Ultimately, the LED light strings with different LED drive channels will have different brightness when emitting light under the same brightness requirement.

[0004] It can be seen that a new LED backlight driving circuit is needed in the art, based on which the driving current difference between different LED driving channels caused by the resistance matching problem of the DAC unit can be reduced. Summary of the invention

[0005] The present invention provides an LED backlight driving circuit and a driving current precision control method. The LED backlight driving circuit can improve the matching precision between the resistor network unit in the DAC unit and the driving resistor of the LED driving channel, thereby improving the precision of the driving current.

[0006] Based on the above technical objectives, the present invention provides an LED backlight driving circuit, the LED backlight driving circuit comprising:

[0007] 2 n LED driving channels, each of which comprises an LED light string, a MOS switch tube, an operational amplifier and a driving resistor; and the driving current value of the LED light string is determined by the input voltage value of the operational amplifier and the resistance value R' of the driving resistor;

[0008] The LED backlight driving circuit further includes a DAC unit, wherein the DAC unit includes 2 n A group of resistor network units, each of which is composed of 2 m-n A first resistor string is formed by connecting identical seed resistors in series in sequence; wherein m is the maximum number of bits of the binary value input by the DAC unit;

[0009] At the same time, 2 n The resistor network units are connected in series in sequence to form a second resistor string, one end of the second resistor string is connected to the first potential end, and the other end is connected to the second potential end;

[0010] The resistor network unit also includes two m-n DAC voltage output terminals, each of the DAC voltage output terminals corresponding one-to-one to a binary value input by the DAC unit;

[0011] The DAC unit further includes two n first data selectors, each of which has two m-n data input terminal and a data output terminal, each of the first data selectors corresponds to a resistor network unit one by one, and the two first data selectors m-n The data input terminal is based on the 2 corresponding resistor network units. m-n The arrangement of the DAC voltage output terminals is similar to that of the 2 m-n Each DAC voltage output terminal corresponds one to one;

[0012] The DAC unit also includes a second data selector, the second data selector includes 2 n data input terminal and a data output terminal, the second data selector 2 nThe data input terminals are arranged in a manner consistent with the arrangement of the first data selector and the 2 n The output end of the second data selector corresponds to the output end of each of the first data selectors. The output end of the second data selector is connected to the input end of the operational amplifier in each LED driving channel to provide a reference voltage;

[0013] Each LED driving channel corresponds to a resistor network one by one, and in the semiconductor multilayer structure of the LED backlight driving circuit, the driving resistor in each LED driving channel and the resistor network corresponding to the LED driving channel are arranged in the same semiconductor layer.

[0014] In one embodiment, each of the resistor networks and its corresponding first data selector are disposed in the same semiconductor layer.

[0015] In one embodiment, the MOS switch tube is an NMOS switch tube, the first potential end is a ground end, and the second potential end is a current source power supply end.

[0016] In one embodiment, the MOS switch tube is a PMOS switch tube, the first potential end is a current source power supply end, and the second potential end is a ground end.

[0017] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0018] The LED backlight driving circuit improves the accuracy of the driving current by setting a DAC unit as a plurality of groups of resistor network units, and corresponding each resistor network to an LED driving channel, and keeping the resistor network unit and the driving resistor of the LED driving channel in the same position on the semiconductor structure to ensure the resistance matching accuracy.

[0019] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 It is a schematic diagram of the structure of an LED backlight driving circuit in the prior art; Figure 1 It is a schematic diagram of the structure of an LED backlight driving circuit in the prior art;

[0022] Figure 2It is a schematic diagram of the structure of an LED backlight driving circuit based on an NMOS switch tube according to the first embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of a resistor network unit in a first embodiment of the present invention;

[0024] Figure 4 is a schematic diagram of the arrangement of the resistor network unit and the driving resistor in the first embodiment of the present invention;

[0025] Figure 5 1 is a schematic diagram of the structure of an LED backlight driving circuit based on a PMOS switch tube according to a second embodiment of the present invention;

[0026] Figure 6 is a schematic diagram of a resistor network unit in a second embodiment of the present invention;

[0027] Figure 7 is a schematic diagram of the arrangement of the resistor network unit and the driving resistor in the second embodiment of the present invention; DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0029] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present invention necessarily has the first element, component, region, layer or part.

[0030] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0031] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0032] Example 1

[0033] like Figure 2-4 As shown, the LED backlight driving circuit in this embodiment includes: 2 n LED driving channels, each of which includes an LED light string, a MOS switch tube, an operational amplifier and a driving resistor; and the driving current value of the LED light string is determined by the input voltage value of the operational amplifier and the resistance value R' of the driving resistor.

[0034] The LED backlight driving circuit further includes a DAC unit, wherein the DAC unit includes 2 n A group of resistor network units, each of which is composed of 2 m-n A first resistor string is formed by connecting identical seed resistors in series in sequence; wherein m is the maximum number of bits of the binary value input by the DAC unit.

[0035] At the same time, 2 n The resistor network units are sequentially connected in series to form a second resistor string, one end of the second resistor string is connected to the first potential end, and the other end is connected to the second potential end.

[0036] The resistor network unit also includes two m-n DAC voltage output terminals, each of which corresponds one-to-one to a binary value input by the DAC unit.

[0037] The DAC unit further includes two n first data selectors, each of which has two m-n data input terminal and a data output terminal, each of the first data selectors corresponds to a resistor network unit one by one, and the two first data selectors m-n The data input terminal is based on the 2 corresponding resistor network units. m-n The arrangement of the DAC voltage output terminals is similar to that of the 2 m-n The DAC voltage output terminals correspond one to one.

[0038] The DAC unit also includes a second data selector, the second data selector includes 2 n data input terminal and a data output terminal, the second data selector 2 n The data input terminals are arranged in a manner consistent with the arrangement of the first data selector and the 2 n The output ends of the first data selectors correspond to each other one by one. The output end of the second data selector is connected to the input end of the operational amplifier in each LED driving channel to provide a reference voltage.

[0039] At the same time, each LED driving channel corresponds to a resistor network one by one, and in the semiconductor multilayer structure of the LED backlight driving circuit, the driving resistor in each LED driving channel and the resistor network corresponding to the LED driving channel are arranged in the same semiconductor layer.

[0040] Furthermore, each of the resistor networks and its corresponding first data selector are arranged in the same semiconductor layer.

[0041] In this embodiment, the MOS switch tube is an NMOS switch tube, the first potential end is a ground end, and the second potential end is a current source power supply end.

[0042] In this embodiment, n=3, m=10 is taken as an example, that is, the LED backlight driving circuit includes eight LED driving channels, each resistor network unit includes 2 7= 128 seed resistors, the maximum number of bits of the binary value input by the DAC unit is 10, and the maximum value of the binary value input by the DAC unit is 1111111111. If the maximum driving current value of the LED backlight driving circuit is set to 90mA, the binary value 1111111111 corresponds to 90mA.

[0043] When a 30mA driving current is to be provided to the LED driving channel, the binary value corresponding to the 30mA driving current is represented by 10 bits, that is, 0101010101. The upper three bits of the binary value are 010, and the corresponding decimal value is 2, so the input value of the third data input terminal in the second data selector is selected as the output value. The lower 7 bits of the binary value are 1010101, and the corresponding decimal value is 85, so the input value of the 86th data input terminal of each of the eight first data selectors is selected as the output value.

[0044] Example 2

[0045] like Figure 5-7 As shown, the LED backlight driving circuit in this embodiment includes: 2 n LED driving channels, each of which includes an LED light string, a MOS switch tube, an operational amplifier and a driving resistor; and the driving current value of the LED light string is determined by the input voltage value of the operational amplifier and the resistance value R' of the driving resistor.

[0046] The LED backlight driving circuit further includes a DAC unit, wherein the DAC unit includes 2 n A group of resistor network units, each of which is composed of 2 m-n A first resistor string is formed by connecting identical seed resistors in series in sequence; wherein m is the maximum number of bits of the binary value input by the DAC unit.

[0047] At the same time, 2 n The resistor network units are sequentially connected in series to form a second resistor string, one end of the second resistor string is connected to the first potential end, and the other end is connected to the second potential end.

[0048] The resistor network unit also includes two m-n DAC voltage output terminals, each of which corresponds one-to-one to a binary value input by the DAC unit.

[0049] The DAC unit further includes two n first data selectors, each of which has two m-ndata input terminal and a data output terminal, each of the first data selectors corresponds to a resistor network unit one by one, and the two first data selectors m-n The data input terminal is based on the 2 corresponding resistor network units. m-n The arrangement of the DAC voltage output terminals is similar to that of the 2 m-n The DAC voltage output terminals correspond one to one.

[0050] The DAC unit also includes a second data selector, the second data selector includes 2 n data input terminal and a data output terminal, the second data selector 2 n The data input terminals are arranged in a manner consistent with the arrangement of the first data selector and the 2 n The output ends of the first data selectors correspond to each other one by one. The output end of the second data selector is connected to the input end of the operational amplifier in each LED driving channel to provide a reference voltage.

[0051] At the same time, each LED driving channel corresponds to a resistor network one by one, and in the semiconductor multilayer structure of the LED backlight driving circuit, the driving resistor in each LED driving channel and the resistor network corresponding to the LED driving channel are arranged in the same semiconductor layer.

[0052] Furthermore, each of the resistor networks and its corresponding first data selector are arranged in the same semiconductor layer.

[0053] In this embodiment, the MOS switch tube is a PMOS switch tube, the first potential end is a current source power supply end, and the second potential end is a ground end.

[0054] In this embodiment, n=3, m=10 is taken as an example, that is, the LED backlight driving circuit includes eight LED driving channels, each resistor network unit includes 2 7 = 128 seed resistors, the maximum number of bits of the binary value input by the DAC unit is 10, and the maximum value of the binary value input by the DAC unit is 1111111111. If the maximum driving current value of the LED backlight driving circuit is set to 90mA, the binary value 1111111111 corresponds to 90mA.

[0055] When a 30mA driving current is to be provided to the LED driving channel, the binary value corresponding to the 30mA driving current is represented by 10 bits, that is, 0101010101. The upper three bits of the binary value are 010, and the corresponding decimal value is 2, so the input value of the third data input terminal in the second data selector is selected as the output value. The lower 7 bits of the binary value are 1010101, and the corresponding decimal value is 85, so the input value of the 86th data input terminal of each of the eight first data selectors is selected as the output value.

[0056] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An LED backlight driving circuit, characterized in that: The LED backlight driving circuit comprises: 2 n LED driving channels, each of which comprises an LED light string, a MOS switch tube, an operational amplifier and a driving resistor; and the driving current value of the LED light string is determined by the input voltage value of the operational amplifier and the resistance value R' of the driving resistor; The LED backlight driving circuit further includes a DAC unit, wherein the DAC unit includes 2 n A group of resistor network units, each of which is composed of 2 m-n A first resistor string is formed by connecting identical seed resistors in series in sequence; wherein m is the maximum number of bits of the binary value input by the DAC unit; At the same time, 2 n The resistor network units are connected in series in sequence to form a second resistor string, one end of the second resistor string is connected to the first potential end, and the other end is connected to the second potential end; The resistor network unit also includes two m-n DAC voltage output terminals, each of the DAC voltage output terminals corresponding one-to-one to a binary value input by the DAC unit; The DAC unit further includes two n first data selectors, each of which has two m-n data input terminal and a data output terminal, each of the first data selectors corresponds to a resistor network unit one by one, and the two first data selectors m-n The data input terminal is based on the 2 corresponding resistor network units. m-n The arrangement of the DAC voltage output terminals is similar to that of the 2 m-n Each DAC voltage output terminal corresponds one to one; The DAC unit also includes a second data selector, the second data selector includes 2 n data input terminal and a data output terminal, the second data selector 2 n The data input terminals are arranged in a manner consistent with the arrangement of the first data selector and the 2 n The output end of the second data selector corresponds to the output end of each of the first data selectors. The output end of the second data selector is connected to the input end of the operational amplifier in each LED driving channel to provide a reference voltage; Each LED driving channel corresponds to a resistor network one by one, and in the semiconductor multilayer structure of the LED backlight driving circuit, the driving resistor in each LED driving channel and the resistor network corresponding to the LED driving channel are arranged in the same semiconductor layer.

2. The LED backlight driving circuit according to claim 1, characterized in that: Each of the resistor networks and its corresponding first data selector are arranged in the same semiconductor layer.

3. The LED backlight driving circuit according to claim 1, characterized in that: The MOS switch tube is an NMOS switch tube, the first potential end is a ground end, and the second potential end is a current source power supply end.

4. The LED backlight driving circuit according to claim 1, characterized in that: The MOS switch tube is a PMOS switch tube, the first potential end is a current source power supply end, and the second potential end is a ground end.

5. An LED backlight panel, wherein the LED backlight panel uses the LED backlight driving circuit according to any one of claims 1 to 4 to achieve backlight illumination.

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