Display device, frequency correction circuit and frequency correction method thereof

Abstract

The present invention discloses a display device and its frequency correction circuit and frequency correction method, which include a receiving unit for receiving an external display signal and obtaining an external frequency clock signal according to the display signal; a frequency oscillator for generating an internal frequency clock signal; a temperature detection module for obtaining the current temperature of the display device; and a frequency tracking calculation unit for adjusting the internal parameters of the frequency oscillator based on the temperature obtained by the temperature detection module, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal, so as to ensure that accurate frequency correction can be obtained in high and low temperature and small resolution display situations.

Description

Technical Field

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

[0002] When an existing display device displays a picture, the display signal (display link) transmitted from the application processor AP (Application Processor) / CPU to the display chip IC is converted into a horizontal synchronization signal HS, a frame synchronization signal VS and an external clock signal CK_W after passing through a data receiver inside the display chip IC. An internal clock signal CK_D is generated inside the display chip IC. The frequency oscillator that generates the display signal inside the application processor AP usually uses an active quartz crystal oscillator, which generally does not produce frequency drift with temperature. The frequency oscillator that generates the internal clock signal CK_D usually uses a voltage-current crystal oscillator, which is easily affected by temperature and process variations and produces frequency drift. Therefore, it is necessary to correct the frequency of the internal clock signal CK_D through frequency tracking (Frequency Tracking: FT) to ensure that the frequency of the internal clock signal CK_D and the external clock signal CK_W are synchronized.

[0003] The frequency tracking of the prior art does not take into account that the frequency oscillator OSC that generates the internal frequency clock signal CK_D is more likely to produce frequency drift at high and low temperatures, and more statistics are needed to track the frequency. Therefore, the frequency tracking effect is poor at high and low temperatures. In addition, the existing frequency tracking will also have insufficient statistics when displaying at a small resolution, resulting in poor frequency tracking effect.

[0004] Therefore, a new frequency correction circuit is needed to solve the above problems. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a display device and a frequency correction circuit and a frequency correction method thereof to ensure that accurate frequency correction can be obtained under high and low temperature and low resolution display conditions.

[0006] According to one aspect of the present invention, there is provided a frequency correction circuit for a display device, comprising a receiving unit for receiving an external display signal and obtaining an external frequency clock signal according to the display signal; a frequency oscillator for generating the internal frequency clock signal; a temperature detection module for obtaining the current temperature of the display device; and a frequency tracking calculation unit for adjusting internal parameters of the frequency oscillator based on the temperature obtained by the temperature detection module, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal.

[0007] Optionally, the temperature detection module includes: a temperature sensor for obtaining the current temperature of the display device; a temperature processing unit for converting the current temperature into a digital signal; a temperature query table with a built-in mapping table of the current temperature and the counting time range, for obtaining the corresponding counting time range according to the current temperature.

[0008] Optionally, the frequency tracking calculation unit is configured to count the internal frequency clock signal within the counting time range, compare the internal frequency count value with an external frequency preset value corresponding to the counting time range, and adjust internal parameters of the frequency oscillator according to the comparison result.

[0009] Optionally, the frequency tracking calculation unit is further configured to output a correction signal to control the frequency of the internal frequency clock signal generated by the frequency oscillator to become faster or slower when the internal frequency count value is different from the external frequency preset value corresponding to the counting time range, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal;

[0010] The frequency tracking calculation unit is also configured to output no correction signal or output a correction signal that controls the frequency of the internal frequency clock signal generated by the frequency oscillator to remain unchanged when the internal frequency count value is the same as the external frequency preset value corresponding to the counting time range.

[0011] Optionally, the frequency tracking calculation unit pre-stores a mapping table between the counting time range and the external frequency preset value, and the external frequency preset value corresponding to the counting time range is obtained by searching the mapping table.

[0012] Optionally, the frequency tracking calculation unit is further configured to count the external frequency clock signal within the counting time range to obtain the external frequency preset value.

[0013] According to another aspect of the present invention, there is provided a frequency correction method for a display device, comprising receiving an external display signal and obtaining an external-frequency clock signal according to the display signal; obtaining a current temperature of the display device; and adjusting internal parameters of a frequency oscillator for generating an internal-frequency clock signal based on the current temperature so that the frequency of the internal-frequency clock signal is the same as the frequency of the external-frequency clock signal.

[0014] Optionally, the internal parameters of the frequency oscillator that generates the internal frequency clock signal based on the current temperature adjustment include: obtaining a counting time range according to the current temperature; counting the internal frequency clock signal within the counting time range, and comparing the internal frequency count value with an external frequency preset value corresponding to the counting time range, and adjusting the internal parameters of the frequency oscillator according to the comparison result.

[0015] Optionally, comparing the internal frequency count value and the external frequency preset value within the counting time range, and adjusting the internal parameters of the frequency oscillator according to the comparison result include: when the internal frequency count value and the external frequency preset value corresponding to the counting time range are different, outputting a correction signal to control the frequency of the internal frequency clock signal generated by the frequency oscillator to become faster or slower, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal; when the internal frequency count value and the external frequency preset value corresponding to the counting time range are the same, not outputting a correction signal or outputting a correction signal that controls the frequency of the internal frequency clock signal generated by the frequency oscillator to remain unchanged.

[0016] Optionally, the external frequency preset value is obtained by searching a pre-stored mapping table between the counting time range and the external frequency preset value.

[0017] Optionally, the external frequency preset value is obtained by counting the external frequency clock signal within the counting time range.

[0018] According to another aspect of the present invention, a display device is provided, comprising the frequency correction circuit as described above, and configured to execute the frequency correction method as described above.

[0019] The display device and its frequency correction circuit and frequency correction method provided by the present invention obtain the corresponding counting time range according to the current temperature of the display device detected by the temperature detection module, so that the frequency tracking calculation unit can timely adjust the internal parameters of the frequency oscillator according to the temperature change of the display device, so as to have sufficient statistics for frequency tracking when the frequency oscillator has frequency drift due to temperature change, and save the counting amount at normal temperature, thereby saving power consumption while accurately correcting the frequency.

[0020] In a preferred embodiment, the frequency correction circuit is further provided with a mapping table between resolution and counting time range, so that the counting time range can be adjusted according to the resolution to achieve the purpose of accurate frequency correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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:

[0022] Figure 1 A schematic diagram of the structure of a frequency correction circuit according to an embodiment of the present invention is shown;

[0023] Figure 2 shows a signal timing diagram of a frequency correction circuit according to an embodiment of the present invention;

[0024] Figure 3 A flow chart of a frequency correction method 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, the same elements or modules are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0026] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by programmable circuits. When an element or circuit is said to be "connected to" another element or an element or circuit is said to be "connected between" two nodes, it may be directly coupled or connected to another element or there may be an intermediate element, and the connection between the elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0027] At the same time, certain words are used in this patent specification and claims to refer to specific components. It should be understood by those skilled in the art that hardware manufacturers may use different terms to refer to the same component. This patent specification and claims do not use differences in names as a way to distinguish components, but rather use differences in components' functions as the criteria for distinction.

[0028] In addition, it should be noted that, in this article, relational terms such as and and the like 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 "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including 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, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0029] Figure 1 The structure diagram of the frequency correction circuit according to the embodiment of the present invention is shown. The frequency correction circuit is applied to a display device, and includes an application processor AP, a display driving unit 100, a temperature sensor 200 and a display chip 300.

[0030] The application processor AP is internally provided with an external frequency oscillator (not shown in the figure). The external frequency oscillator is, for example, an active quartz crystal oscillator, whose performance is not easily affected by temperature and whose frequency output is stable. The clock signal generated by the external frequency oscillator is used to provide the application processor AP to generate a display signal (display link). The application processor AP is connected to the display chip 300 to output a display signal and a control signal (Control link) to the display chip 300.

[0031] The display chip 300 includes a receiving unit RU, a frequency oscillator OSC, and a tracking frequency calculation unit FTU. The receiving unit RU includes, for example, a data receiver and a decoder. The data receiver is used to receive a display signal. The decoder is used to decode the display signal into a line synchronization signal HS, a frame synchronization signal VS, an external frequency clock signal CK_W, and display data Dp.

[0032] The frequency oscillator OSC is a voltage-current crystal oscillator, and its performance is easily affected by temperature, resulting in frequency drift and unstable frequency output. It is used to generate an internal frequency clock (Pixel clock) signal CK_D and output the internal frequency clock signal CK_D to the display driving unit 100. The display driving unit 100 controls the display panel to display the picture according to the display data Dp and the internal frequency clock signal CK_D.

[0033] The temperature sensor 200, the temperature lookup table LUT inside the display chip 300, and the temperature processing unit TSU together constitute a temperature detection module, wherein the temperature sensor 200 is used to sense the current temperature of the display device, the temperature processing unit TSU is used to convert the current temperature into a digital signal, and the temperature lookup table LUT is used to obtain a count time range (CTR) and a preset value of an external frequency clock signal corresponding to the count time range CTR according to the current temperature, hereinafter referred to as the external frequency preset value.

[0034] The tracking frequency calculation unit FTU includes a counter (not shown in the figure) for calculating the number of internal frequency clock signals CK_D within the counting time range CTR. The counter can be set to store the counting time range CTR and its corresponding internal frequency count value CUTR in the tracking frequency calculation unit FTU after a counting time range CTR ends, and clear the internal frequency count value CUTR. The tracking frequency calculation unit FTU is used to count the internal frequency clock signal CK_D according to the corresponding counting time range CTR, compare the internal frequency count value CUTR with the external frequency preset value corresponding to the counting time range CTR, and change the internal parameters of the frequency oscillator OSC according to the comparison result, so that the frequency of the internal frequency clock signal CK_D is the same as the frequency of the external frequency clock signal CK_W.

[0035] When the internal frequency count value CUTR within the counting time range CTR is equal to the external frequency preset value corresponding to the counting time range CTR, it means that the frequency oscillator OSC has no frequency drift, and the correction signal Adj is not output, or the output correction signal Adj controls the frequency of the internal frequency clock signal CK_D generated by the frequency oscillator OSC to remain unchanged; when the internal frequency count value CUTR within the counting time range CTR is different from the external frequency preset value corresponding to the counting time range CTR, it means that the frequency oscillator OSC has frequency drift, and at this time, the correction signal Adj is output to control the frequency of the internal frequency clock signal CK_D generated by the frequency oscillator OSC to become faster or slower, so that the frequency of the internal frequency clock signal CK_D is synchronized with the frequency of the external frequency clock signal CK_W.

[0036] The temperature lookup table LUT contains a mapping table of multiple temperature ranges of the display device, the counting time range CTR of the frequency tracking calculation unit FTU, and the external frequency preset value. For example, when the temperature is between 25°C and 40°C, the counting time range CTR of the frequency tracking calculation unit FTU is equal to X, and the external frequency preset value is equal to K, where X is a multiple unit of the external frequency clock signal CK_W; when the temperature is between 40°C and 70°C or between 10°C and 25°C, the counting time range CTR of the frequency tracking calculation unit FTU is increased to X+300, and the external frequency preset value is equal to K+A; when the temperature is above 70°C or between -20°C and 10°C, the counting time range CTR of the frequency tracking calculation unit FTU is increased to X+600, and the external frequency preset value is equal to K+B. Please refer to Table 1, which is an exemplary temperature lookup table LUT, where X is a positive real number, and K, A, and B are positive integers.

[0037] Table 1

[0038] Temperature range (Celsius) Counting time range FSB preset value Temperature between -20 and 10 X+600 K+B Temperature between 10 and 25 X+300 K+A Temperature between 25 and 40 X K Temperature between 40 and 70 X+300 K+A Temperature greater than 70 X+600 K+B

[0039] Table 1 is only an exemplary mapping table. In actual applications, the counting time range CTR of the frequency tracking calculation unit FTU can be determined according to the frequency drift of the frequency oscillator OSC at high and low temperatures. Generally speaking, the more severe the frequency drift, the longer the counting time range CTR required by the frequency tracking calculation unit FTU. Determining the counting time range CTR of the frequency tracking calculation unit FTU according to the temperature can ensure the accuracy of frequency correction at various temperatures, and the counting time range CTR can be set according to needs without causing waste of power consumption.

[0040] Furthermore, the display chip 300 further includes a control unit CU for receiving a control signal to control the operation of each unit inside the display chip 300 .

[0041] Furthermore, the external frequency preset value can also be obtained by counting the external frequency clock signal CK_W by the tracking frequency calculation unit FTU within the counting time range CTR.

[0042] Figure 2 FIG. 4 shows a signal timing diagram of a frequency correction circuit according to an embodiment of the present invention, taking the current temperature of the display device between 25° C. and 40° C. as an example. Figure 2 As shown, the value of the counting time range CTR of the tracking frequency calculation unit FTU is equal to X, and there are multiple line synchronization signals HS and a frame synchronization signal VS in the counting time range CTR. The external frequency preset value corresponding to the counting time range CTR is equal to K, and the internal frequency count value CUTR of the internal frequency clock signal CK_D is equal to K'. According to the comparison result of K' and K, the frequency error between the internal frequency clock signal CK_D and the external frequency clock signal CK_W is obtained, so as to output the correction signal Adj to make the frequency of the internal frequency clock signal CK_D faster or slower, so as to accurately correct the frequency of the internal frequency clock signal CK_D generated by the frequency oscillator OSC, so that the frequency of the internal frequency clock signal CK_D and the external frequency clock signal CK_W are synchronized. And when the temperature of the display device changes, considering the frequency drift degree of the frequency oscillator OSC, the counting time range CTR of the tracking frequency calculation unit FTU will be adjusted, so that the frequency can be accurately corrected.

[0043] Furthermore, the counting time range CTR of the present application at normal temperature is based on ensuring sufficient statistics even at a small resolution. Generally speaking, the counting time range CTR needs to be greater than the time of a line synchronization signal HS.

[0044] Furthermore, the display chip 300 of the present application is also provided with a judgment module, which contains a mapping table of resolution and counting time range CTR1. When the judgment module detects that the counting time range CTR is less than the counting time range CTR1, it outputs the counting time range CTR1 to the frequency tracking calculation unit FTU, otherwise it outputs the counting time range CTR to the frequency tracking calculation unit FTU. By comparing the numerical values ​​of the counting time range CTR and the counting time range CTR1, it can be ensured that the display chip 300 has sufficient statistics when displaying at different temperatures and different resolutions to accurately correct the frequency. The counting time range CTR1 is a multiple unit of the external frequency clock signal CK_W.

[0045] The frequency correction circuit provided by the embodiment of the present invention obtains the corresponding calculation time range CTR according to the current temperature of the display device detected by the temperature detection module, so that the frequency tracking calculation unit FTU can timely adjust the counting time range CTR according to the temperature change of the display device, so as to have sufficient statistics for frequency tracking when the frequency oscillator OSC has frequency drift due to temperature changes, and save the counting amount at normal temperature, thereby saving power consumption while accurately correcting the frequency.

[0046] An embodiment of the present invention further provides a frequency correction method for a display device, comprising the following steps:

[0047] Step S1: receiving an external display signal, and obtaining an external frequency clock signal CK_W according to the display signal;

[0048] In step S1, the application processor AP outputs a display signal to the receiving unit RU. The data receiver of the receiving unit RU receives the display signal, and the decoder of the receiving unit RU decodes the display signal into a frame synchronization signal VS, a line synchronization signal HS, display data Dp and an external clock signal CK_W.

[0049] Step S2: obtaining the current temperature of the display device;

[0050] In step S2 , the temperature sensor 200 senses the current temperature of the display device and outputs the current temperature to the temperature processing unit TSU, which converts the current temperature into a digital signal.

[0051] Step S3: adjusting internal parameters of the frequency oscillator OSC for generating the internal frequency clock signal CK_D based on the current temperature, so that the frequency of the internal frequency clock signal CK_D is the same as the frequency of the external frequency clock signal CK_W.

[0052] In step S3, the frequency tracking calculation unit FTU queries the corresponding counting time range CTR from the temperature query table LUT according to the current temperature, counts the internal frequency clock signal CK_D within the counting time range CTR, compares the internal frequency count value CUTR within the current counting time range CTR with the external frequency preset value corresponding to the counting time range CTR, and adjusts the internal parameters of the frequency oscillator OSC according to the comparison result.

[0053] When the internal frequency count value CUTR within the current counting time range CTR is equal to the external frequency preset value corresponding to the counting time range CTR, the frequency tracking calculation unit FTU does not output the correction signal Adj or outputs the correction signal Adj to control the frequency of the internal frequency clock signal CK_D generated by the frequency oscillator OSC to remain unchanged; when the internal frequency count value CUTR within the current counting time range CTR is different from the external frequency preset value corresponding to the counting time range CTR, the output correction signal Adj controls the frequency of the internal frequency clock signal CK_D generated by the frequency oscillator OSC to become faster or slower, so that the frequency of the internal frequency clock signal CK_D is the same as the frequency of the external frequency clock signal CK_W.

[0054] The external frequency preset value may be obtained by searching a pre-stored mapping table between the counting time range CTR and the external frequency preset value, or by counting the external frequency clock signal within the counting time range.

[0055] An embodiment of the present invention further provides a display device, comprising the frequency correction circuit as described above, and configured to execute the frequency correction method as described above.

[0056] According to the embodiments of the present invention, as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes 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 the modified use 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 frequency correction circuit for a display device, comprising: A receiving unit, used for receiving an external display signal and obtaining an external frequency clock signal according to the display signal; A frequency oscillator, used to generate an internal frequency clock signal; A temperature detection module, used to obtain the current temperature of the display device; The frequency tracking calculation unit is used to adjust the internal parameters of the frequency oscillator based on the temperature obtained by the temperature detection module, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal.

2. The frequency correction circuit according to claim 1, wherein: The temperature detection module comprises: A temperature sensor, used to obtain the current temperature of the display device; A temperature processing unit, used for converting the current temperature into a digital signal; The temperature query table has a built-in mapping table of the current temperature and the counting time range, and is used to obtain the corresponding counting time range according to the current temperature.

3. The frequency correction circuit according to claim 2, wherein: The frequency tracking calculation unit is configured to count the internal frequency clock signal within the counting time range, compare the internal frequency count value with the external frequency preset value corresponding to the counting time range, and adjust the internal parameters of the frequency oscillator according to the comparison result.

4. The frequency correction circuit according to claim 3, wherein: The frequency tracking calculation unit is further configured to output a correction signal to control the frequency of the internal frequency clock signal generated by the frequency oscillator to become faster or slower when the internal frequency count value is different from the external frequency preset value corresponding to the counting time range, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal; When the internal frequency count value is the same as the external frequency preset value corresponding to the counting time range, no correction signal is output or a correction signal is output to control the frequency of the internal frequency clock signal generated by the frequency oscillator to remain unchanged.

5. The frequency correction circuit according to claim 4, wherein: The temperature query table also includes a mapping table of the counting time range and the external frequency preset value, and the external frequency preset value corresponding to the counting time range is obtained by searching the mapping table.

6. The frequency correction circuit according to claim 4, wherein: The frequency tracking calculation unit is further configured to count the external frequency clock signal within the counting time range to obtain the external frequency preset value.

7. A frequency correction method for a display device, comprising: Receiving an external display signal, and obtaining an external frequency clock signal according to the display signal; Obtaining the current temperature of the display device; Based on the current temperature, internal parameters of a frequency oscillator that generates an internal frequency clock signal are adjusted so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal.

8. The frequency correction method according to claim 7, wherein: The internal parameters of the frequency oscillator for generating the internal frequency clock signal based on the current temperature adjustment include: Acquire a counting time range according to the current temperature; The internal frequency clock signal is counted within the counting time range, and the internal frequency count value is compared with the external frequency preset value corresponding to the counting time range, and the internal parameters of the frequency oscillator are adjusted according to the comparison result.

9. The frequency correction method according to claim 8, wherein: The comparing the internal frequency count value with the external frequency preset value corresponding to the counting time range, and adjusting the internal parameters of the frequency oscillator according to the comparison result comprises: When the internal frequency count value and the external frequency preset value corresponding to the counting time range are different, output a correction signal to control the frequency of the internal frequency clock signal generated by the frequency oscillator to become faster or slower, so that the frequency of the internal frequency clock signal is the same as the frequency of the external frequency clock signal; When the internal frequency count value is the same as the external frequency preset value corresponding to the counting time range, no correction signal is output or a correction signal is output to control the frequency of the internal frequency clock signal generated by the frequency oscillator to remain unchanged.

10. The frequency correction method according to claim 9, wherein: The external frequency preset value is obtained by searching a pre-stored mapping table between the counting time range and the external frequency preset value.

11. The frequency correction method according to claim 9, wherein: The external frequency preset value is obtained by counting the external frequency clock signal within the counting time range.

12. A display device, comprising the frequency correction circuit according to any one of claims 1 to 6, used to execute the frequency correction method according to any one of claims 7 to 11.

Images