LED Backlight Driving Control Method Based on Multiple Current Alignment Modes

Abstract

The present invention discloses an LED backlight driving control method based on multiple current alignment modes, characterized in that N preset alignment points P are set in each PWM dimming period T, and the N preset alignment points P are distributed at different time points of the entire PWM dimming period T. Each preset alignment point P corresponds to a front-back segmentation ratio of the entire PWM dimming period T, and each segmentation ratio corresponds to an alignment mode. When the channel brightness exceeds a preset brightness threshold, a first driving mode is adopted. In the first driving mode, at least one LED channel uses an alignment mode different from that used by other LED channels. When the channel brightness does not exceed the preset brightness threshold, a second driving mode is adopted, and all LED channels use the same alignment mode.

Description

Technical Field

[0001] The present invention relates to the technical field of image display, and in particular to an LED backlight driving control method based on multiple current alignment modes. Background Art

[0002] Liquid crystal displays (LCDs) are the most widely used type of display panel in modern display applications. The liquid crystal material used in LCD panels cannot emit light by itself and requires a backlight source to provide display light. LED backlight sources have advantages such as energy conservation, environmental protection, and high performance, and are widely used in LCD display panels. The performance of the LED backlight driving circuit is crucial for the LCD display panel.

[0003] As Figure 1 shown, in the prior art, when using the PWM dimming method, generally three pulse alignment methods are adopted, namely head alignment, middle alignment, and tail alignment. The so-called head alignment means that the high-level pulse for controlling the LED to turn on in each PWM dimming cycle is aligned with the starting end of the PWM dimming cycle; middle alignment means that the high-level pulse for controlling the LED to turn on in each PWM dimming cycle is aligned with the middle of the PWM dimming cycle; tail alignment means that the high-level pulse for controlling the LED to turn on in each PWM dimming cycle is aligned with the end of the PWM dimming cycle. When using the above pulse alignment modes, in the case of high brightness, the current peak value on the high-side drive side will be relatively large (for example, if all channels adopt the same alignment mode, the overall peak current of the backlight panel will be too large in the case of high brightness), which will affect the dynamic characteristics of the DC / DC power supply and cause system-level problems.

[0004] With the system-level requirements, each manufacturer has also proposed more flexible control methods. Different LED channels can be set with different alignment methods, generally supporting three alignment methods: head alignment, tail alignment, and center alignment. This can reduce the peak current of the DC / DC power supply load. However, at the same time, another problem will be caused. At low brightness, affected by board-level parasitic parameters (parasitic capacitance), especially the actual display brightness of the channels in the head alignment or tail alignment mode will be affected, and its brightness will be lower than that under center alignment, resulting in uneven brightness of the overall panel at low brightness.

[0005] Therefore, there is a need in the prior art for a method that can simultaneously avoid the high peak current of the high-end drive of the backlight panel for a long time and avoid the uneven brightness problem of the LED backlight panel at low brightness. Summary of the Invention

[0006] The technical purpose to be achieved by the present invention is to provide an LED backlight drive control method based on multiple current alignment modes. This method can effectively reduce the peak current of the high-side drive in the LED backlight drive system and eliminate the uneven backlight brightness under low brightness conditions.

[0007] Based on the above technical objectives, the present invention provides an LED backlight drive control method based on multiple current alignment modes, the method comprising:

[0008] N preset alignment points P are set in each PWM dimming cycle T. The N preset alignment points P are distributed at different time points throughout the PWM dimming cycle T. Each preset alignment point P corresponds to a front-to-back division ratio of the entire PWM dimming cycle T, and each division ratio corresponds to an alignment mode.

[0009] When the brightness of the channel exceeds a preset brightness threshold, a first driving mode is adopted, in which the alignment mode used by at least one LED channel is different from the alignment modes used by other LED channels;

[0010] When the channel brightness does not exceed the preset brightness threshold, the second driving mode is adopted, and all LED channels adopt the same alignment mode.

[0011] In one embodiment, the number N of the preset alignment points P matches the number of LED control channels.

[0012] In one embodiment, the number N of the preset alignment points P is 4, 8, 16 or 32.

[0013] In one embodiment, in the first driving mode, different LED channels use different alignment modes.

[0014] In one embodiment, in the second driving mode, the alignment mode used by all LED channels is one of the alignment modes used in the first driving mode.

[0015] In one embodiment, the N preset alignment points P are evenly distributed within the entire PWM dimming cycle T.

[0016] The present invention also provides another LED backlight driving control method based on multiple current alignment modes, the method comprising:

[0017] N preset alignment points P are set in each PWM dimming cycle T. The N preset alignment points P are distributed at different time points throughout the PWM dimming cycle T. Each preset alignment point P corresponds to a front-to-back division ratio of the entire PWM dimming cycle T, and each division ratio corresponds to an alignment mode.

[0018] When the channel brightness exceeds a preset brightness threshold, a first driving mode is adopted. In the first driving mode, the alignment mode used by at least one LED channel is different from the alignment modes used by other LED channels;

[0019] When the channel brightness does not exceed the preset brightness threshold, a second driving mode is adopted. In the second driving mode, the alignment mode used by any LED channel is one of the multiple alignment modes used in the first driving mode, and at the same time satisfies:

[0020] T n × duty ≤ t; and (T - T n ) × duty ≤ t'.

[0021] Wherein, T n is the duration from the starting point of the PWM dimming period T to the nth preset alignment point P n , t is the duration required for the rising edge of the high-side drive to stabilize, t' is the duration required for the falling edge of the high-side drive to stabilize, and duty is the duty cycle corresponding to the channel brightness.

[0022] In one embodiment, in the first driving mode, the alignment modes used by different LED channels are different.

[0023] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0024] In the present invention, by setting multiple preset alignment points, multiple selectable alignment modes are realized, so that different LED channels can select and configure different alignment modes, thereby reducing the peak current of the high-side drive. At the same time, in the low-brightness state, all LED channels are configured with the same alignment mode, or configured with an alignment mode that can avoid the rising edge or falling edge of the high-side drive, thereby eliminating the problem of uneven brightness.

[0025] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures specifically pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic diagram of the PWM dimming alignment mode in the prior art;

[0028] Figure 2 It is a schematic diagram of brightness non-uniformity caused by different alignment modes at low brightness in the prior art;

[0029] Figure 3 It is a schematic diagram of the PWM dimming alignment mode in the first driving mode of the first embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the PWM dimming alignment mode in the second driving mode of the first embodiment of the present invention; Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may 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 may be denoted as the second element, component, region, layer or part. And when discussing the second element, component, region, layer or part, it does not imply that the present invention necessarily has a first element, component, region, layer or part.

[0033] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures with other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "below" other elements or features will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "below" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0034] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the related listed items.

[0035] Example 1

[0036] As Figures 3 - 4 shown in the schematic diagrams of various PWM dimming pulse alignment modes of the present embodiment, in this embodiment, N preset alignment points P are set in each PWM dimming period T. For example, 5 preset alignment points P0, P1, P2, P3 and P4 are set; or 9 preset alignment points P0, P1, P2, ……, P8; or 17 preset alignment points P0, P1, P2, ……, P 16 . The N preset alignment points P are distributed at different time points throughout the PWM dimming period T, and the front and back division ratios of each preset alignment point with respect to the entire PWM dimming period T can all be expressed as: T n / T - T n , where T n is the duration from the starting point of the PWM dimming period T to the preset alignment point P n . It can be seen from this that each preset alignment point P corresponds to a front and back division ratio of the entire PWM dimming period T, and each division ratio corresponds to an alignment mode, that is, N preset alignment points correspond to N preset alignment modes.

[0037] In this embodiment, taking 9 preset alignment points P0, P1, P2, ……, P8 as an example, when the channel brightness is set to 30% brightness (30% duty cycle), the alignment diagrams of the 9 alignment modes corresponding to the 9 preset alignment points are as Figure 3 shown. For each alignment mode, the actual alignment point P' within the PWM pulse width duration T' corresponding to the channel brightness is time-aligned with the preset alignment point P in this alignment mode, and the division ratio of the actual alignment point P' within the PWM pulse width duration T' corresponding to the channel brightness to the PWM pulse width duration T' is the same as the front and back division ratio of the PWM dimming period T corresponding to the alignment point Pn in this mode.

[0038] In this embodiment, for example, 9 preset alignment points P0, P1, P2, ……, P8 are evenly distributed throughout the PWM dimming period T, that is:

[0039] For the first alignment mode, the preset alignment point P0 is located at the starting point of the entire PWM dimming period T. Then, in the first alignment mode, the starting point of the PWM pulse with a channel brightness of 30% also starts from the starting point of the PWM dimming period T.

[0040] For the second alignment mode, the preset alignment point P1 is at the first 1 / 8 position of the entire PWM dimming period T. Then, in the second alignment mode, the actual alignment point P' of the PWM pulse width duration T' with a channel brightness of 30% is also at the first 1 / 8 position of the PWM pulse width duration T', and the preset alignment point P1 is aligned with the actual alignment point P' in time.

[0041] For the third alignment mode, the preset alignment point P2 is at the first 2 / 8 position of the entire PWM dimming period T. Then, in the third alignment mode, the actual alignment point P' of the PWM pulse width duration T' with a channel brightness of 30% is also at the first 2 / 8 position of the PWM pulse width duration T', and the preset alignment point P2 is aligned with the actual alignment point P' in time.

[0042] For the fourth alignment mode, the preset alignment point P3 is at the first 3 / 8 position of the entire PWM dimming period T. Then, in the fourth alignment mode, the actual alignment point P' of the PWM pulse width duration T' with a channel brightness of 30% is also at the first 3 / 8 position of the PWM pulse width duration T', and the preset alignment point P3 is aligned with the actual alignment point P' in time.

[0043] And so on.

[0044] In this embodiment, nine alignment points are taken as an example to illustrate the technical solution of the present invention. However, those skilled in the art should understand that the setting of the alignment points is not limited to the number mentioned in this embodiment, but can be selected according to actual engineering needs. Specifically, it can be adaptively adjusted according to the number of channels for controlling the LED string set on the LED driving chip. For example, if there are 4 channels for controlling the LED string on the LED driving chip, that is, one LED driving chip can control 4 LED strings simultaneously, then the number of alignment points of the present invention can be set to 5.

[0045] In this embodiment, different LED channels select the above different alignment modes, thus avoiding the problem that the high-side drive peak current is too large for a long time due to the same alignment mode in the high-brightness state. However, in order to further solve the problem of uneven brightness in the low-brightness state, a brightness threshold is also set for the channel brightness in this embodiment. When the channel brightness exceeds the brightness threshold, the first driving mode is adopted, and the first driving mode is that different LED channels select the above different alignment modes. When the channel brightness is less than the brightness threshold, the second driving mode is adopted, and the second driving mode is as Figure 4As shown. In the second driving mode, all LED channels adopt the same alignment mode, and the alignment mode adopted in the second driving mode can be any one of the foregoing N alignment modes. Since the alignment modes adopted by all channels are the same, even if affected by the rising and falling edges of the high-side driving voltage within the PWM pulse width duration T', the effects on all LED channels are consistent, and thus there will be no brightness difference between different LED channels, so the defect of uneven brightness is eliminated.

[0046] In this embodiment, the brightness threshold can be configured according to engineering requirements, such as 3%, 5%, 10%.

[0047] The present invention can be any possible system, method, and / or computer program product at the level of integrated technical details. The computer program product can include a computer-readable storage medium (or multiple media) having computer-readable program instructions thereon for causing a processor to execute aspects of the present invention.

[0048] The computer-readable storage medium can be a tangible device that can retain and store instructions used by an instruction execution device. The computer-readable storage medium can be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing devices. A non-exhaustive list of more specific examples of the computer-readable storage medium includes the following: a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device, such as a punched card or raised structure in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer-readable storage medium, as used herein, should not be construed as being an instantaneous signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., an optical pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0049] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to a corresponding computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical transmission fibers, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the corresponding computing / processing device.

[0050] The computer-readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuits, or source code or object code written in any combination of one or more programming languages and procedural programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter case, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, an electronic circuit, including, for example, a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA), may execute the computer-readable program instructions by utilizing state information of the computer-readable program instructions to personalize the electronic circuit, thereby performing aspects of the present invention.

[0051] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0052] These computer-readable program instructions may be provided to a processor of a computer, or to other programmable data processing apparatus, to produce a machine, such that the instructions executed via the processor of the computer or other programmable data processing apparatus create means for implementing the functions / acts specified in the flowchart and / or block Figure 1 diagrams. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, a programmable data processing apparatus, and / or other devices to operate in a particular manner, such that the computer-readable storage medium in which the instructions are stored comprises a manufacture including instructions for implementing aspects of the functions / acts specified in the flowchart and / or block diagrams.

[0053] The computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer-implemented process, such that the instructions executed on the computer, other programmable apparatus, or other devices implement the functions / acts specified in the flowchart and / or block diagrams.

[0054] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of instructions that includes one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, in fact, two consecutive blocks shown may be completed as one step, concurrently, substantially concurrently, in a partially or fully time-overlapped manner, depending on the functions involved, or sometimes the blocks may be executed in the reverse order. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by a system based on dedicated hardware that performs the specified functions or actions or a combination of dedicated hardware and computer instructions.

[0055] Embodiments of the present application are described with reference to the flowcharts and / or block diagrams of methods, apparatuses (devices), and computer program products according to embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and combinations of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a means for implementing the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0056] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

Claims

1. An LED backlight driving control method based on multiple current alignment modes, characterized in that The method includes: In each PWM dimming cycle T, there are N preset alignment points P. The N preset alignment points P are distributed at different time points throughout the PWM dimming cycle T. Each preset alignment point P corresponds to a front - to - back division ratio of the entire PWM dimming cycle T, and each division ratio corresponds to an alignment mode; for each alignment mode, the actual alignment point P' within the PWM pulse width duration T' corresponding to the channel brightness is aligned in time with the preset alignment point P in this alignment mode, and the division ratio of the PWM pulse width duration T' by the actual alignment point P' within the PWM pulse width duration T' corresponding to the channel brightness is the same as the front - to - back division ratio of the PWM dimming cycle T corresponding to the alignment point Pn in this mode; When the channel brightness exceeds a preset brightness threshold, a first driving mode is adopted. In the first driving mode, the alignment mode used by at least one LED channel is different from the alignment modes used by other LED channels; When the channel brightness does not exceed the preset brightness threshold, a second driving mode is adopted, and all LED channels adopt the same alignment mode.

2. The LED backlight driving control method according to claim 1, wherein The number N of the preset alignment points P matches the number of LED control channels.

3. The LED backlight driving control method according to claim 1, wherein, The number N of the preset alignment points P is 4, 8, 16, or 32.

4. The LED backlight driving control method according to claim 1, wherein, In the first driving mode, the alignment modes used by different LED channels are different.

5. The LED backlight driving control method according to claim 1, wherein In the second driving mode, the alignment mode used by all LED channels is one of the multiple alignment modes used in the first driving mode.

6. The LED backlight driving control method according to claim 1, wherein The N preset alignment points P are evenly distributed throughout the PWM dimming cycle T.

7. A computer-readable storage medium having computer instructions stored thereon, wherein, When the computer instruction is executed by a processor, it implements the steps of the method according to any one of claims 1 - 6.

8. An LED backlight driving control chip, where the LED backlight driving control chip is used to execute the method according to any one of claims 1 - 6 for LED backlight driving control.

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