Display device and signal transmission method thereof

Abstract

The present invention discloses a display device and a signal transmission method thereof, comprising: receiving a display signal and obtaining a refresh rate of the display signal, the display signal being used to drive a display panel to display an image; providing an impedance control signal based on the refresh rate; transmitting the impedance control signal to a display signal interface of a source driver circuit via a signal transmission line, the display signal interface being electrically connected to a built-in impedance of the source driver circuit; and adjusting the built-in impedance based on the impedance control signal so that the built-in impedance is used to achieve impedance matching with the signal transmission line. The present invention uses the signal transmission line impedance as a variable related to the display signal frequency, thereby achieving adaptation of the built-in impedance of the source driver circuit to the signal transmission line impedance, improving the quality of the display signal eye diagram and reducing radio frequency noise. Furthermore, the adjustment of the built-in impedance of the source driver circuit is achieved by a program within a register, facilitating improvements to existing products and saving design costs.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a display device and a signal transmission method thereof. Background Art

[0002] Currently, Low-Voltage Differential Signaling (LVDS) is widely used in information transmission in display devices due to its advantages of low power consumption, low bit error rate, low crosstalk and low radiation. The eye diagram is usually used as a criterion to judge the quality of the transmitted signal.

[0003] In order to obtain better display effects, existing display devices need to provide display images with higher frame rates. However, it is inevitable that the frequency of the display signal required for high frame rate display images will also increase. For display devices, higher frequency display signals often mean higher power consumption. In order to minimize the power consumption of display devices, existing display devices are usually able to switch between high and low frame rate displays. The problem caused by this is that the low-voltage differential signal with changing frequency often causes the output end of its signal transmission line to not always be in an impedance matching state, resulting in the quality of the low-voltage differential signal received by the receiving end deteriorating, which in turn causes the RF noise of the display device to be too high, making it difficult to meet the requirements. The quality of the differential signal is judged by the eye diagram.

[0004] Connect the differential probe to the + and - ends of the differential signal respectively. After processing, it will be displayed on the oscilloscope as follows Figure 1 The high and low level digital signals shown on the left are aligned with a certain reference point X in the time domain, and then the waveforms are superimposed to form the following Figure 1 The eye diagram shown on the right. The signal generally measured by the oscilloscope is a waveform of some bits or a certain period of time, which reflects more detailed signals. The eye diagram is a graph displayed by accumulating a series of digital signals on the oscilloscope, such as Figure 2 As shown, it reflects the overall characteristics of all digital signals transmitted on the link. It contains rich information. The influence of inter-symbol crosstalk and noise can be observed from the eye diagram, reflecting the overall characteristics of the digital signal, so as to estimate the quality of the system. Therefore, eye diagram analysis is the core of signal integrity analysis of high-speed interconnection systems.

[0005] In summary, a new signal transmission method and corresponding display device are needed, which can ensure that the output end of the signal transmission line is always in an impedance matching state during the change of the display signal frequency, thereby improving the eye diagram of the display signal and reducing the RF noise of the display device. Summary of the Invention

[0006] In view of the above problems, the object of the present invention is to provide a display device and a signal transmission method thereof, so as to achieve impedance matching between the display signal transmission line and the receiving end at different frequencies and improve the display signal eye diagram.

[0007] According to one aspect of the present invention, a signal transmission method is provided, comprising: receiving a display signal and obtaining a frame refresh rate of the display signal, the display signal being used to drive a display panel to display a frame; providing an impedance control signal according to the frame refresh rate; transmitting the impedance control signal to a display signal interface of a source driver circuit via a signal transmission line, the display signal interface being electrically connected to a built-in impedance of the source driver circuit; and adjusting the built-in impedance according to the impedance control signal so that the built-in impedance is used to achieve impedance matching with the signal transmission line.

[0008] Optionally, the built-in impedance of the source driver circuit is provided with a plurality of gears, and the step of adjusting the built-in impedance according to the impedance control signal includes adjusting the built-in impedance to a corresponding gear according to the impedance control signal.

[0009] Optionally, the step of providing an impedance control signal according to the picture refresh rate includes detecting a refresh rate range in which the picture refresh rate is located, and providing the corresponding impedance control signal according to the refresh rate range in which the picture refresh rate is located.

[0010] Optionally, the step of detecting the refresh rate range in which the picture refresh rate is located includes detecting whether the picture refresh rate is greater than or equal to a preset picture refresh rate. If so, providing the impedance control signal to adjust the built-in impedance to a first gear; otherwise, providing the impedance control signal to adjust the built-in impedance to a second gear, and the resistance value of the first gear is less than the resistance value of the second gear.

[0011] Optionally, the timing controller includes a register, a plurality of codes are preset in the register, the plurality of codes respectively correspond to the plurality of gears, and the impedance control signal includes at least one of the plurality of codes.

[0012] According to another aspect of the present invention, a display device is provided, which is used to execute the signal transmission method as described above, including: a timing controller for receiving a display signal to obtain a frame refresh rate of the display signal, and providing an impedance control signal according to the frame refresh rate; a source driver circuit including a display signal interface for receiving the display signal and an adjustable built-in impedance electrically connected to the display signal interface, the source driver circuit being used to drive a display panel to display a frame according to the display signal; a signal transmission line for transmitting the display signal from the timing controller to the display signal interface; wherein the source driver circuit receives the impedance control signal and adjusts the built-in impedance according to the impedance control signal, so that the built-in impedance is used to achieve impedance matching with the signal transmission line.

[0013] Optionally, the built-in resistor of the source driver circuit includes multiple gears, and the source driver circuit adjusts the built-in impedance to a corresponding gear according to the impedance control signal.

[0014] Optionally, the timing control circuit detects a refresh rate range in which the picture refresh rate is located, and provides the corresponding impedance control signal according to the refresh rate range in which the picture refresh rate is located.

[0015] Optionally, the timing control circuit detects whether the picture refresh rate is greater than or equal to a preset picture refresh rate. If so, the impedance control signal is provided to adjust the built-in impedance to a first gear; otherwise, the impedance control signal is provided to adjust the built-in impedance to a second gear, and the resistance value of the first gear is less than the resistance value of the second gear.

[0016] Optionally, the timing controller includes a register, a plurality of codes are preset in the register, the plurality of codes respectively correspond to the plurality of gears, and the impedance control signal includes at least one of the plurality of codes.

[0017] The display device and signal transmission method provided by the present invention detect the refresh rate of the display screen and adjust the built-in terminal resistance of the source drive circuit through a timing controller, thereby achieving impedance matching between the transmission line of the display signal and the receiving end. In the prior art, the impedance of the transmission line of the low-voltage differential signal carrying display information is regarded as a fixed value, so the impedance of the corresponding receiving end only needs to be adjusted to correspond to this fixed value. Such a signal transmission method will seriously affect the quality of the display signal eye diagram in the existing multi-frame rate display device. The signal transmission method of the present invention uses the impedance of the transmission line as a variable related to the frequency of the transmission signal. For a specific transmission line, the corresponding relationship between its impedance and signal frequency can be detected in advance. The timing controller can obtain the screen refresh rate and the corresponding signal frequency from the received display signal, and obtain the real-time impedance of the transmission line based on the above-mentioned corresponding relationship to adjust the receiving end, that is, the built-in impedance of the source drive circuit to achieve impedance matching. The signal transmission method and display device of the present invention can improve the eye diagram condition of the display signal, improve the display quality, and thus reduce the radio frequency noise of the display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0019] Figure 1 shows a schematic diagram of the conversion of differential signals to eye diagrams;

[0020] Figure 2 The eye diagram and the characteristics of the digital signal it reflects are shown;

[0021] Figure 3 shows a schematic diagram of signal transmission of a display device according to the prior art;

[0022] Figure 4 A schematic diagram of signal transmission of a display device according to an embodiment of the present invention is shown;

[0023] Figure 5 A schematic diagram showing a flow chart of a signal transmission method according to an embodiment of the present invention is shown;

[0024] Figure 6 A structural block diagram of a display device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0025] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical components or modules are represented by identical or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0026] Furthermore, certain terms are used in this patent specification and claims to refer to specific components. Those skilled in the art will appreciate that hardware manufacturers may use different terms to refer to the same component. This patent specification and claims do not distinguish components based on differences in name, but rather on differences in their functionality.

[0027] In addition, it should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0028] In the prior art, display devices use high-frequency signals. Due to the high frequency and short wavelength of high-frequency signals, the reflection problem of the transmission line needs to be considered. Specifically, when the wavelength is short enough to be comparable to the length of the transmission line, the superposition of the reflected signal and the original signal will change the shape of the original signal, thereby generating reflections at the receiving end, affecting the eye diagram quality of the transmitted signal and causing distortion of the transmitted signal. The usual method to reduce signal reflections is to achieve impedance matching (impedance matching) between the transmission line and the receiving end. Specifically, the characteristic impedance of the transmission line is equal to the impedance of the receiving end and has the same phase. This is called the impedance matching state of the output end of the transmission line, referred to as impedance matching. In the impedance matching state, all high-frequency microwave signals can be transmitted to the receiving end, and almost no signal is reflected back to the source point.

[0029] In the prior art, the transmission line impedance is considered to be a fixed value, and the built-in impedance of the receiving end is adjustable. Adjusting the built-in impedance of the receiving end to match the above-mentioned fixed value means that the transmission line and the receiving end can maintain an impedance matching state during the operation of the display device. Figure 3 FIG. 1 shows a schematic diagram of a timing controller 100 controlling a source driving circuit 210 in a display device of the prior art. Figure 3 As shown, in the prior art, the processor 300 transmits the display signal to the timing controller 100, and the timing controller 100 transmits the display information to the source driver circuit 210 in the form of a low-voltage differential signal. The built-in impedance of the source driver circuit 210 is marked as R S0, the timing controller 100 and the source driver circuit 210 are coupled to the two ends of the transmission line respectively, and the impedance of the transmission line is regarded as a fixed value, which is recorded as Z0. In the prior art, as long as the built-in impedance R S0 It only needs to match the transmission line impedance Z0, which results in poor quality of the signal eye diagram detected at the receiving end of the source driver circuit 210, that is, the output end of the transmission line, which cannot meet the requirements.

[0030] The present invention improves the existing signal transmission method and realizes the improvement of the display signal eye diagram without changing the hardware structure of the display device, thereby improving the display quality and reducing radio frequency noise.

[0031] Figure 4 FIG. 1 shows a schematic diagram of signal transmission in a display device according to an embodiment of the present invention. Figure 4 It should be understood that in order to clearly show the difference between the signal transmission method of the present invention and the prior art, Figure 4 Only the process of transmitting the display signal from the timing controller 100 to the source driver circuit 210 is described. The signal transmission method of the present invention can be used in the transmission process of the low voltage differential signal in any display device.

[0032] like Figure 4 As shown, in the signal transmission method of the present invention, the timing controller 100 receives the signal from the processor 300 and transmits the display signal to the source driver circuit 210 in the form of a low-voltage differential signal. Unlike the existing low-voltage differential signal transmission method, in the present invention, the impedance of the signal transmission line between the timing controller 100 and the source driver circuit 210 is variable. Specifically, the impedance of the transmission line is related to the signal frequency passing through the transmission line. For example, Figure 4 In the embodiment shown, for two display signals with different frequencies, the transmission line impedance and the corresponding built-in impedance of the source driver circuit 210 are also different. As a preferred embodiment, when the frequency of the display signal is less than 1 GHz, the impedance of the transmission line is regarded as Z1, and when the frequency of the display signal is greater than 1 GHz, the impedance of the transmission line is regarded as Z2. It should be understood that the corresponding built-in impedance of the source driver circuit 210 also changes accordingly, wherein the built-in impedance corresponding to Z1 is R S1 , the built-in impedance corresponding to Z2 is R S2 , the transmission line impedance Z1 corresponding to the low-frequency signal is greater than the transmission line impedance Z2 corresponding to the high-frequency signal. The present invention treats display signals of different frequencies separately, which is closer to production practice. For display signals of different frequencies and corresponding transmission lines of different impedances, the impedance of the receiving end is continuously adjusted to maintain the impedance matching state, thereby improving the eye diagram of the display signal and enhancing display quality.

[0033] It is worth noting that the signal transmission method of the present invention does not require the hardware structure of the display device. Figure 4 What is shown is only the difference in impedance between the transmission line and the source driver circuit 210 for different frequency display signals. In other words, Z1 and Z2 are the impedance expressions of the same transmission line for different frequency signals; the built-in impedance of the source driver circuit 210 is adjustable, for example, it can be controlled by the timing controller 100 according to the signal frequency. In other words, the above R S1 and R S2 It is also obtained by adjusting the same set of adjustable resistors according to the signal frequency. It should be understood that the above R S0 、R S1 and R S2 These are schematic representations. In actual products, they can be implemented using one or multiple resistors or adjustable resistors connected in series or parallel. The timing controller 100 can, for example, control the internal impedance of the source driver circuit 210 through built-in coding. Specifically, the timing controller 100 can include a register with multiple sets of codes preset to control the matching of the internal impedance of the source driver circuit 210 with the transmission line impedance. The signal transmission method of the present invention is implemented by writing a program into the timing controller of the display device, greatly facilitating the improvement of existing products and saving design costs.

[0034] It should be understood that the degree to which the transmission line impedance changes with signal frequency is related to the material, length, and thickness of the transmission line itself. In other words, the present invention does not use 1GHz as the only standard for dividing high and low frequencies. Different transmission lines can be divided into high and low frequencies according to their own characteristics. In addition, in some embodiments, the transmission line impedance changes more dramatically with frequency. In order to improve the accuracy, the change gears of the built-in impedance of the source driver circuit can also be greater than two, thereby improving the matching accuracy of the transmission line impedance and the built-in impedance of the source driver circuit. In other words, the present invention uses the transmission line impedance as a variable, and the receiving end impedance can be divided into several change gears according to the required accuracy and the range of change of the transmission line impedance. The present invention does not limit this.

[0035] See Figure 5 , Figure 5 FIG. 1 is a flow chart showing the signal transmission method of the present invention. Figure 5 As shown, the signal transmission method of the present invention includes the following steps:

[0036] Step S0: Detect the correspondence between the signal transmission line impedance and the signal frequency. In the present invention, the signal transmission line impedance is a variable that changes with the signal frequency. However, those skilled in the art should understand that the signal transmission line impedance and its matching relationship with the receiving end impedance seriously affect the signal transmission quality. If the impedance is not matched, the signal will be reflected at the receiving end and return to the transmitting end, resulting in a deterioration of the receiving end signal eye diagram. In other words, in order to achieve impedance matching, the receiving end impedance, that is, the built-in impedance of the source driver circuit 210, needs to change with the transmission line impedance, and the degree of change is determined by the above-mentioned correspondence.

[0037] It should be understood that step S0 is not essential. In some embodiments, the correspondence between the signal transmission line impedance and the signal frequency can be determined, for example, by parameters such as the material, length, and thickness of the transmission line itself. In other embodiments, this correspondence is pre-set. In short, this step is used to determine this correspondence; detection is not essential.

[0038] Step S1: The timing controller receives a display signal and obtains the frame refresh rate of the display signal. In an existing display device, the timing controller 100 receives a display signal from, for example, the processor 300. It should be understood that the display signal is a collection of information including picture information, frame rate (frame refresh rate) information, resolution information, etc. The timing controller 100 is configured to be able to at least partially decode the display signal to obtain the frame refresh rate. It should also be understood that the frame refresh rate and frequency of the display signal are, for example, positively correlated, that is, the frequency can be determined by detecting the frame refresh rate of the display signal.

[0039] Step S2: The timing controller obtains an impedance control signal based on the above-mentioned screen refresh rate. Specifically, the timing controller is capable of detecting and determining the size of the screen refresh rate. In some embodiments, the timing controller divides the screen refresh rate into several ranges. When it receives a display signal and determines the screen refresh rate of the display signal, the timing controller queries the corresponding screen refresh rate range and generates an impedance control circuit according to the corresponding range. Specifically, the timing controller includes, for example, a register, and the register is provided with a plurality of codes, which respectively correspond to the above-mentioned multiple screen refresh rate ranges, and the generated impedance control signal includes the corresponding codes.

[0040] In some embodiments, to reduce computational complexity, the timing controller is configured with a preset refresh rate (e.g., the refresh rate of the display signal having a frequency of 1 GHz). The timing controller determines the relationship between the refresh rate of the received display signal and the preset refresh rate. If the refresh rate is greater than or equal to the preset refresh rate, the timing controller determines the signal to be a high-frequency signal and outputs a corresponding impedance control signal with a first code. Otherwise, the timing controller determines the signal to be a low-frequency signal and outputs a corresponding impedance control signal with a second code.

[0041] Step S3: The source driver circuit receives the impedance control signal and the display signal via the signal transmission line. The source driver circuit includes a display signal interface, specifically, a differential signal interface. Accordingly, the signal transmission line is a differential signal transmission line, and the built-in impedance includes a set of adjustable differential impedances corresponding to the differential signal transmission line. The display signal interface of the source driver circuit is electrically connected to the built-in impedance, so that the built-in impedance can be changed in accordance with the impedance control signal.

[0042] Step S4: The source driver circuit adjusts the built-in impedance according to the impedance control signal so that the built-in impedance matches the impedance of the signal transmission line. In some embodiments, the built-in impedance of the source driver circuit is divided into a plurality of gears according to the impedance size, wherein each gear corresponds to a range of the screen refresh rate and also corresponds to a code in the timing register. Specifically, after receiving the impedance control signal including the corresponding code, the source driver circuit adjusts the built-in impedance to the corresponding gear according to the code, for example.

[0043] In some embodiments, the built-in impedance includes only a first gear corresponding to high-frequency signals and a second gear corresponding to low-frequency signals, and the impedance value of the first gear is smaller than that of the second gear. When the timing controller determines that the frame refresh rate of the received display signal is greater than or equal to a preset frame refresh rate, the source driver circuit receives an impedance control signal with a first code and adjusts the built-in impedance to the first gear according to the first code; when the timing controller determines that the frame refresh rate of the received display signal is less than the preset frame refresh rate, the source driver circuit receives an impedance control signal with a second code and adjusts the built-in impedance to the second gear according to the second code.

[0044] The signal transmission method of an embodiment of the present invention uses the impedance of the signal transmission line as a variable related to the display signal frequency, uses the timing controller 100 to obtain the frame refresh rate of the display signal, and then calculates the signal frequency to determine the impedance of the signal transmission line. Furthermore, the register in the timing controller 100 is used to control the built-in impedance of the source driver circuit 210, thereby achieving the adaptation of the built-in impedance of the source driver circuit 210 to the impedance of the signal transmission line, improving the quality of the display signal eye diagram, thereby improving the display quality and reducing radio frequency noise. In addition, the adjustment of the built-in impedance of the source driver circuit 210 is implemented by a program in the register, without involving hardware changes, facilitating the improvement of existing products and saving design costs.

[0045] The present invention also provides a display device for implementing the above signal transmission method, see Figure 6 , Figure 6 FIG. 1 shows a structural block diagram of a display device according to an embodiment of the present invention. Figure 6As shown, the display device of the present invention includes a processor 300, a timing control circuit 100, and a display panel 200. The display panel 200 also includes a source driver circuit 210. A signal transmission line STL is provided between the timing controller 100 and the source driver circuit 210. As described above, the timing controller 100 receives a display signal provided by the processor 300 and reads the frame refresh rate of the display signal. The impedance of the corresponding signal transmission line STL is calculated based on the frame refresh rate. A register (not shown in the figure) in the timing controller 100 receives the impedance of the signal transmission line STL and uses a preset program to control the built-in impedance of the source driver circuit 210 to match the impedance of the signal transmission line STL.

[0046] The embodiments of the present invention are as described above, but these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and modify and use it based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention and their equivalents.

Claims

1. A signal transmission method, comprising: The timing controller receives a display signal and obtains a refresh rate of the display signal, wherein the display signal is used to drive the display panel to display a picture; The timing controller provides an impedance control signal according to the picture refresh rate; The source driving circuit transmits the impedance control signal to the display signal interface of the source driving circuit through a signal transmission line, and the display signal interface is electrically connected to the built-in impedance of the source driving circuit; The source driving circuit adjusts the built-in impedance according to the impedance control signal so that the built-in impedance is used to achieve impedance matching with the signal transmission line; The timing controller is provided with a register, wherein a plurality of groups of codes are preset in the register to respectively control the matching between the built-in impedance of the source driving circuit and the impedance of the transmission line; The built-in impedance of the source driver circuit is provided with a plurality of gears, and the step of adjusting the built-in impedance according to the impedance control signal comprises adjusting the built-in impedance to a corresponding gear according to the impedance control signal; The step of providing an impedance control signal according to the picture refresh rate includes detecting a refresh rate range in which the picture refresh rate is located, and providing the corresponding impedance control signal according to the refresh rate range in which the picture refresh rate is located; The step of detecting the refresh rate range in which the picture refresh rate is located includes detecting whether the picture refresh rate is greater than or equal to the preset picture refresh rate. If so, providing the impedance control signal to adjust the built-in impedance to a first gear; otherwise, providing the impedance control signal to adjust the built-in impedance to a second gear, and the resistance value of the first gear is less than the resistance value of the second gear.

2. The signal transmission method according to claim 1, wherein: The plurality of codes respectively correspond to the plurality of gears, and the impedance control signal includes at least one of the plurality of codes.

3. A display device, configured to execute the signal transmission method according to any one of claims 1 to 2, comprising: A timing controller, configured to receive a display signal to obtain a frame refresh rate of the display signal, and provide an impedance control signal according to the frame refresh rate; a source driver circuit, comprising a display signal interface for receiving the display signal and an adjustable built-in impedance electrically connected to the display signal interface, wherein the source driver circuit is configured to drive the display panel to display an image according to the display signal; a signal transmission line, used for transmitting the display signal from the timing controller to the display signal interface; The source driver circuit receives the impedance control signal and adjusts the built-in impedance according to the impedance control signal, so that the built-in impedance is used to achieve impedance matching with the signal transmission line; The built-in resistor of the source driving circuit includes a plurality of gears, and the source driving circuit adjusts the built-in impedance to a corresponding gear according to the impedance control signal; The timing control circuit detects the refresh rate range of the picture refresh rate and provides the corresponding impedance control signal according to the refresh rate range of the picture refresh rate; The timing control circuit detects whether the picture refresh rate is greater than or equal to the preset picture refresh rate. If so, the impedance control signal is provided to adjust the built-in impedance to a first gear. Otherwise, the impedance control signal is provided to adjust the built-in impedance to a second gear, and the resistance value of the first gear is less than the resistance value of the second gear.

4. The display device according to claim 3, wherein The timing controller includes a register, a plurality of codes are preset in the register, the plurality of codes respectively correspond to the plurality of gears, and the impedance control signal includes at least one of the plurality of codes.

Images