Downclocking control method in PWM dimming mode in LED backlight

Abstract

The invention discloses a frequency reduction control method in a PWM dimming mode in LED backlight, and the method comprises the steps: dividing the brightness adjustment range of an LED backlight panel into a plurality of brightness intervals, and setting a corresponding PWM dimming signal control mode for each brightness interval; at least one of the plurality of control modes comprises the following steps: forming a PWM dimming signal group by n PWM dimming signal periods, wherein n is greater than 1; resetting the duty ratio of the n PWM dimming signals in the PWM dimming signal group; the duty ratios of the n PWM dimming signals are respectively set as D1, D2,..., Dn; and when the dimming brightness is m, m = (D1 + D2 +... + Dn) / n.

Description

Technical Field

[0001] The present invention relates to the technical field of LED backlight driving, and in particular to a frequency reduction control method in a PWM dimming mode in an LED backlight. Background Art

[0002] In current LCD screens, LEDs are widely used as backlight sources. The brightness control of LED backlights usually has two dimming modes: DC regulation and PWM regulation. Among them, PWM regulation has the advantages of consistent current size and low heat generation. However, when using the PWM mode to control the brightness of LED backlights, the current rising and falling edges of different LED channels are not consistent due to the inconsistency of parasitic resistance and capacitance between different LED light-emitting channels. Figure 1 shown.

[0003] When the brightness is high, the duty cycle of the corresponding PWM dimming signal is relatively large. At this time, the rise or fall time of the rising or falling edge of the LED conduction current is relatively small compared to the high level duration of the PWM dimming signal. The resulting brightness difference between channels will not be recognized by the human eye.

[0004] When the brightness is low, the duty cycle of the corresponding PWM dimming signal is relatively small, that is, the high level duration of the PWM dimming signal itself is relatively short, so the climbing or falling time of the current rising or falling edge accounts for a large proportion relative to the high level duration of the PWM dimming signal. Therefore, the difference in rising and falling edges between different channels will lead to a large brightness difference. And when the PWM dimming signal frequency is higher, the high level time of the PWM dimming signal is shorter, and this effect is more obvious.

[0005] It can be seen that there is a need in the art for a new control method for LED backlight in PWM dimming mode that can effectively suppress the brightness difference of different LED light emitting channels under low brightness conditions. Summary of the invention

[0006] Based on the above technical objectives, the present invention provides a frequency reduction control method in a PWM dimming mode in an LED backlight, the method comprising:

[0007] The brightness adjustment range of the LED backlight panel is divided into multiple brightness intervals, and each brightness interval is provided with a corresponding PWM dimming signal control mode;

[0008] At least one of the plurality of control modes comprises:

[0009] n PWM dimming signal cycles constitute a PWM dimming signal group, where n is greater than 1;

[0010] The duty ratios of the n PWM dimming signals in the PWM dimming signal group are reset; the duty ratios of the n PWM dimming signals are set to D1, D2, ..., D n ; and when the dimming brightness is m, we have:

[0011] m=(D1+D2+……+D n ) / n.

[0012] In one embodiment, there is a minimum value among the n duty cycle values ​​of the n PWM dimming signals.

[0013] In one embodiment, the minimum value is zero.

[0014] In one embodiment, different brightness ranges are set between different LED channels.

[0015] In one embodiment, the method includes reducing the frequency of the PWM signal in all control modes.

[0016] 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

[0017] 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:

[0018] Figure 1 It is a schematic diagram of the PWM dimming signal waveform in the prior art;

[0019] Figure 2 is a schematic diagram of a PWM dimming signal waveform according to an embodiment of the present invention;

[0020] Figure 3 It is a flowchart of a frequency reduction control method in a PWM dimming mode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Example 1

[0026] like Figure 2-3As shown, the frequency reduction control method in the PWM dimming mode of the present invention includes:

[0027] S100, the brightness adjustment range of the LED backlight panel is divided into a plurality of brightness intervals, and each brightness interval is provided with a corresponding PWM dimming signal control mode. For example, in the embodiment, the overall brightness adjustment range of the LED backlight panel from 0% to 100% is divided into a first brightness interval (0%, 5%) and a second brightness interval (5%, 100%). The first control mode is used for the first brightness interval, and the second control mode is used for the second brightness interval.

[0028] S101, at least one of the multiple control modes includes forming a PWM dimming signal group with multiple PWM dimming signal cycles. For example, in this embodiment, when the dimming brightness m (i.e., the brightness that the current LED backlight channel needs to display is m) is in the first brightness interval, the PWM dimming signal at this time is divided into a PWM dimming signal group consisting of four PWM dimming cycles, and each PWM dimming signal group includes four PWM dimming cycles, i.e., four PWM dimming signals. At the same time, in this embodiment, the second control mode for sampling other LED channels whose dimming brightness is in the second brightness interval is to maintain the original PWM dimming control mode, i.e., no processing is performed on the PWM dimming signal.

[0029] S102, resetting the duty ratios of the multiple PWM dimming signals in the PWM dimming signal group. When the PWM dimming signal group is composed of n PWM dimming signal cycles, the duty ratios of the n PWM dimming signals are respectively set to D1, D2, ..., D n . And when the dimming brightness is m, then:

[0030] m=(D1+D2+……+D n ) / n.

[0031] For example, in this embodiment, when the dimming brightness m is 3%, the duty cycles of the four PWM dimming signals are respectively set to D1=5%; D2=5%; D3=2%; D4=0%; so as to ensure that the average duty cycle in each PWM dimming signal group is still 3%. However, for the PWM dimming signals with duty cycles D1=5% and D2=5%, the LED current change edge and high level ratio are reduced, thereby improving the brightness difference between different LED channels. In addition, since the duty cycle D4=0%, the frequency of the LED current envelope can be reduced.

[0032] In this embodiment, the number n of PWM dimming cycles included in each PWM dimming signal group is 4, but those skilled in the art should understand that the value of n can be changed as needed. Any value greater than 1 can be used to implement the technical solution of the present invention.

[0033] In this embodiment, the overall brightness adjustment range of the LED backlight panel from 0% to 100% is divided into a first brightness interval and a second brightness interval. However, those skilled in the art should understand that the present invention is not limited to dividing the brightness interval into two brightness intervals, and the present invention can divide the brightness interval into more brightness intervals as needed.

[0034] In this embodiment, the first control mode is adopted for the first brightness interval of low brightness, that is, multiple PWM dimming signal cycles constitute a PWM dimming signal group. However, those skilled in the art can understand that according to actual engineering needs, when it is necessary to divide the brightness interval more finely, the first control mode can be implemented in multiple brightness intervals, specifically, the first control mode can be implemented in multiple low brightness intervals.

[0035] In this embodiment, a zero duty cycle may be set or not set in the multiple reset duty cycles in the PWM dimming signal group. It should be understood by those skilled in the art that when a zero duty cycle is set, the current envelope frequency can be effectively reduced. In addition, the arrangement order of the PWM signals of each duty cycle in the group is not limited in this embodiment, and the arrangement order does not affect the average duty cycle value of the PWM dimming signal group.

[0036] In this embodiment, at least one of the multiple reset duty cycle values ​​is the minimum value relative to the other duty cycle values. Only in this way can the effect of increasing the other duty cycle values ​​be achieved, thereby improving the influence of the rising and falling edges on the duty cycle.

[0037] The method of the present invention further comprises reducing the frequency of the PWM signal in all control modes.

[0038] The present invention may be a system, method and / or computer program product at any possible level of integrated technical detail. The computer program product may include a computer-readable storage medium (or multiple media) having computer-readable program instructions thereon for causing a processor to perform various aspects of the present invention.

[0039] A computer readable storage medium may be a tangible device that can retain and store instructions used by an instruction execution device. The computer readable storage medium may 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. A non-exhaustive list of more specific examples of computer readable storage media 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 disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device such as a punch card or a raised structure in a groove on which instructions are recorded, and any suitable combination of the above. A computer readable storage medium, as used herein, should not be interpreted as a transient 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., a light pulse through a fiber optic cable), or an electrical signal transmitted by a wire.

[0040] The computer-readable program instructions described herein may 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 may include copper transmission cables, optical transmission fibers, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The 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 to be stored in a computer-readable storage medium within the corresponding computing / processing device.

[0041] The computer-readable program instructions for performing the operation of the present invention may be assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent 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 process programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer by 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., by using the Internet of an Internet service provider). In certain embodiments, the 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 the state information of the computer-readable program instructions to personalize the electronic circuit, thereby performing aspects of the present invention.

[0042] Various aspects of the present invention are described herein with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It is understood that each block of the flowchart illustration and / or block diagram, and the combination of blocks in the flowchart illustration and / or block diagram, can be implemented by computer-readable program instructions.

[0043] These computer-readable program instructions may be provided to a processor of a computer or other programmable data processing device to produce a machine so that the instructions executed by the processor of the computer or other programmable data processing device create instructions for implementing the flowcharts and / or block diagrams. Figure 1 These computer-readable program instructions may also be stored in a computer-readable storage medium capable of booting a computer, a programmable data processing device and / or other device that operates in a specific manner, so that the computer-readable storage medium having the instructions stored therein includes a manufactured product that includes instructions that implement aspects of the functions / actions specified in the flowchart and / or block diagram blocks.

[0044] Computer readable program instructions may also be loaded into a computer, other programmable data processing device, or other device to cause a series of operating steps to be performed on the computer, other programmable devices or other devices for producing a computer-implemented process, so that the instructions executed on the computer, other programmable device or other device implement the functions / actions specified in the flowchart and / or block diagram blocks.

[0045] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the system, method and computer program product 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 an instruction, which includes one or more executable instructions for implementing a specified logical function. In some optional implementations, the functions indicated in the block may occur outside the order indicated in the figure. For example, in fact, two blocks shown in succession can be completed as a step, and depending on the functions involved, they can be executed concurrently, substantially concurrently, in a partially or fully time-overlapping manner, or sometimes these blocks can be executed in reverse order. It will also be noted that each block of the block diagram and / or flowchart illustration, as well as the combination of blocks in the block diagram and / or flowchart illustration, can be implemented by a dedicated hardware-based system that performs a specified function or action or performs a combination of dedicated hardware and computer instructions.

[0046] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, apparatuses (devices) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0047] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0048] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

Claims

1. A frequency reduction control method in PWM dimming mode in LED backlight, characterized in that: The method comprises: The brightness adjustment range of the LED backlight panel is divided into multiple brightness intervals, and each brightness interval is provided with a corresponding PWM dimming signal control mode; At least one of the plurality of control modes comprises: n PWM dimming signal cycles constitute a PWM dimming signal group, where n is greater than 1; The duty ratios of the n PWM dimming signals in the PWM dimming signal group are reset; the duty ratios of the n PWM dimming signals are set to D1, D2, ..., D n ; and when the dimming brightness is m, we have: m=(D1+D2+……+D n ) / n。 2. The method according to claim 1, characterized in that There is a minimum value among the n duty cycle values ​​of the n PWM dimming signals.

3. The method according to claim 2, characterized in that The minimum value is zero.

4. The method according to claim 1, characterized in that Different brightness ranges are set between different LED channels.

5. The method according to claim 1, characterized in that The method includes reducing the frequency of the PWM signal in all control modes.

6. An LED backlight panel, characterized in that: The LED backlight panel uses the method described in any one of claims 1-5 to adjust the backlight brightness.

7. An LED display panel, characterized in that: The LED backlight panel as claimed in claim 6 is used in the LED display panel.

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