TWI742674B - Operation method for display device - Google Patents

Abstract

An operation method for a display device includes: receiving a V-sync signal of a next frame; completely receiving a dimming data of the next frame; judging whether an LED current cycle of a current frame is completely output; and when it is judged that the LED current cycle of the current frame is completely output, outputting an LED current of the next frame to an LED backlight unit of the display device based on the dimming data of the next frame.

Description

Operation method of display device

The present invention relates to an operating method of a display device.

Liquid crystal displays have the advantages of low radiation and low power, and have long become the mainstream of displays.

If the processing unit of the host (for example, graphics processor GPU) outputs new screen data immediately after processing the data, it will cause the screen displayed on the display panel to have a sense of tearing. The reason is that the output of the display panel is halfway and the panel timing The controller (TCON) receives the updated data from the GPU, and the data that is not output in time will be overwritten by the newly received data.

In order to solve this problem, it has been proposed to fix the panel output frequency. After the vertical synchronization (V-Sync) is turned on, the GPU is forced to delay the update of the picture until the display starts to output a new cycle.

However, when the "vertical sync" technology is combined with global dimming, because the backlight is always bright, the backlight will not have flicker problems, but it will cause problems such as light leakage and poor contrast when the panel displays a black screen. .

Therefore, the local dimming technology has been developed at present. The respective dimming areas of the display partitions of the display panel will adjust the corresponding brightness according to the corresponding picture to solve the light leakage problem and improve the picture contrast. Have a back Light flicker problem. But the price is that the higher the number of display partitions, the more current controllers (Current sinks) needed, and the more LED drive circuits.

According to an embodiment of this embodiment, an operating method of a display device is proposed, which includes: receiving a vertical synchronization signal of a next frame; completely receiving a dimming data of the next frame; determining a light-emitting diode of a current frame Whether the LED current cycle has been output; if it is judged that the LED current cycle of the current frame has been output, the next frame is output according to the dimming data of the next frame An LED current to an LED backlight unit of the display device.

In order to have a better understanding of the above and other aspects of the present invention, the following specific examples are given in conjunction with the accompanying drawings to describe in detail as follows:

100: display device

110: processing unit

120: timing controller

130: source driver and gate driver

140: LCD panel

150: LED drive circuit

160: LED backlight unit

170: LED power management unit

180: power switching unit

610~680: steps

FIG. 1 is a functional block diagram of a display device according to an embodiment of the present application.

FIG. 2 shows a signal timing diagram of the display device according to an embodiment of the present application.

FIG. 3 shows a signal timing diagram of the display device according to another embodiment of the present application.

FIG. 4 is a functional block diagram of the display device according to an embodiment of the present application.

FIG. 5 shows a signal timing diagram of the display device according to an embodiment of the present application.

Fig. 6 shows a flowchart of the operation method of the display device according to an embodiment of the present case.

The technical terms in this specification refer to the idioms in the technical field, If some terms are explained or defined in this specification, the explanation of that part of terms shall be based on the explanation or definition in this specification. Each embodiment of the present disclosure has one or more technical features. Under the premise of possible implementation, those skilled in the art can selectively implement some or all of the technical features in any embodiment, or selectively combine some or all of the technical features in these embodiments.

Please refer to FIG. 1, which shows a functional block diagram of a display device according to an embodiment of the present invention. As shown in Figure 1, the display device 100 according to an embodiment of the present case includes: a processing unit 110, a timing controller 120, a source driver and gate driver 130, an LCD panel 140, an LED driving circuit 150, an LED backlight unit 160, The LED power management unit 170 and the power switching unit 180. The LCD panel 140 includes a plurality of display partitions; and the LED backlight unit 160 can also be divided into a plurality of LED backlight channels correspondingly to illuminate the display partitions of the LCD panel 140 respectively. The display device 100 of an embodiment of the present case uses bilateral driving to drive the backlight LEDs.

The processing unit 110 is coupled to the timing controller 120, and the processing unit 110 outputs screen data to the timing controller 120.

The timing controller 120 is coupled to the processing unit 110, the source driver and gate driver 130, and the LED driving circuit 150. The timing controller 120 outputs timing control signals to the source driver and the gate driver 130. The timing controller 120 converts the brightness data corresponding to each display area of the LCD panel 140 into dimming data to be transmitted to the LED driving circuit 150.

The LCD panel 140 is coupled to the source driver and the gate driver 130, It is driven by the source driver and the gate driver 130 to perform screen display.

The LED driving circuit 150 is coupled to the timing controller 120 and the LED backlight unit 160. The LED driving circuit 150 includes two registers. The first register (which can be referred to as a receiving-level register) receives the dimming data of the next frame. When triggered by the update flag, the dimming data of the next frame temporarily stored in the first register will be transferred to the second register (which can be called the output stage register). The LED driving circuit 150 can use the dimming data of the next frame temporarily stored in the second register to control the LED current corresponding to each display zone of the LCD.

The LED backlight unit 160 is coupled to the LED driving circuit 150. The LED backlight unit 160 is driven by the LED driving circuit 150 to provide backlight to the LCD panel 140. In addition, the LED backlight unit 160 can feedback the LED current to the LED driving circuit 150 for current feedback control.

The LED power management unit 170 provides LED power to the power switching unit 180, and the power switching unit 180 switches and outputs a plurality of LED voltage signals VLEDm (m=1~n, n is a positive integer) accordingly. For example, divide 240 backlight channels Z1~Z240 into 4 groups, the first group includes backlight channels Z1~Z60, the second group includes backlight channels Z61~Z120, and the third group includes backlight channels Z121~Z180. And, the fourth group includes backlight channels Z181~Z240, n=4. Each backlight channel is responsible for illuminating a display area. The LED voltage signal VLED1 is provided to the first group (including the backlight channel Z1~Z60), the LED voltage signal VLED2 is provided to the second group (including the backlight channel Z61~Z120), and the LED voltage signal VLED3 is provided to the third group (including the backlight channel Z61~Z120). Backlight channel Z121~Z180), LED voltage signal VLED4 is provided to the fourth group (Including backlight channels Z181~Z240). The above example is only for illustration, and this case is not limited to this.

FIG. 2 shows a signal timing diagram of the display device according to an embodiment of the present application. As shown in Figure 2, F1 to F6 represent the six frames output by the processing unit 110. In Figure 2, the frame rates of the frames F1 to F6 can be the same or different from each other. For example, the frame rates of frames F1 to F6 may be 60Hz, 120Hz, 144Hz, 106Hz, 144Hz, 144Hz, but this case is not limited to this.

The processing unit 110 outputs the screen data after computing it. The timing controller 120 receives the image data of the processing unit 110 and controls the LCD panel 140 to display; moreover, the timing controller 120 outputs a vertical synchronization (V-sync) signal and dimming data to the LED driving circuit 150.

In the embodiment of this case, the update flag is set in the LED drive circuit 150, and the trigger condition for the update flag is, for example, but not limited to, (1) receiving the vertical synchronization signal of the next frame; (2) LED The driving circuit has completely received the dimming data of the next frame; and (3) The ILED scanning current cycle of the current frame has been output completely. Please note that these three conditions must all be met to allow the triggering of the update flag.

In order to ensure that the LED current ILED of the double-sided drive (or XY Scan) can be output completely (that is, there will be no screen cut off, no flicker problem), in this embodiment, when the LED drive circuit 150 receives After the vertical synchronization signal of the next frame (as shown in the timing T1, which represents the vertical synchronization signal of the frame F2 is received), the LED driving circuit 150 starts to wait for the input of the dimming data of the next frame. F1_D~F6_D respectively represent the individual dimming data of frame F1~F6.

When the LED driving circuit 150 completely receives the dimming data of the next frame (as shown in timing T2, which represents the complete reception of the dimming data F2_D of the frame F2), the LED driving circuit 150 confirms the current ILED current of the frame. Whether the output period T_ILED is over (that is, whether the ILED current is completely output). If the output period T_ILED has not ended, the LED drive circuit 150 waits until the output period T_ILED ends (as shown in timing T3, which means that the current output period T_ILED of frame F1 has ended), the LED drive circuit 150 triggers the internal update flag (such as timing T4), and start to output the LED current ILED of the next frame, as shown by F2_DOUT (that is, transfer the received dimming data of the next frame from the first register to the second register , And output the dimming data of the next frame stored in the second register to the LED backlight unit 160). In the second figure, the symbols F1_DOUT~F5_DOUT respectively represent the output of the LED current ILED in the frame F1~F5. In addition, ILED_Z1~ILED_Z60 represent the LED current of the first group (including the backlight channel Z1~Z60); ILED_Z61~ILED_Z120 represent the LED current of the second group (including the backlight channel Z61~Z120); ILED_Z121~ILED_Z180 represent the third group (Including backlight channel Z121~Z180) LED current; ILED_Z181~ILED_Z240 represents the fourth group (including backlight channel Z181~Z240).

In addition, through the embodiment of the present application, the output period T_ILED of the LED current ILED can be accelerated, and the delay time D_ILED between the display of the panel image and the backlight can be reduced.

That is, from the first and second figures, by adding the update flag In the LED driving circuit 150, when the update flag is triggered, the dimming data of the next frame is output. Therefore, the current output of the LED current ILED of the frame will not be cut off, so there is no flicker problem.

Please refer to Figure 1 and Figure 3. FIG. 3 shows a signal timing diagram of the display device according to another embodiment of the present application. FIG. 3 shows a schematic diagram of the PWM (Pulse Width Modulation) duty cycle D of the LED current ILED input to the LED backlight unit and the cross voltage of the power transistor of the power switching unit 180.

When the PWM duty cycle D of the LED current ILED input to the LED backlight unit is less than 100% (as in frame F1, the PWM duty cycle D of ILED_Z1 is 50%; as in frame F2, the PWM duty cycle D of ILED_Z1 0%), when ILED_Z1 is output to the LED backlight unit 160, the current sink transistor in the power switching unit 180 is turned on, and the drain-source cross voltage Vds of the current control transistor will be equal to the potential Vcs_1; When the LED current ILED stops outputting, the current control transistor is turned off, and the drain-source voltage Vds of the current control transistor will return from the Vcs_1 potential to the VLED potential (that is, one of VLED1~VLED4 is related to VLED, and ILED_Z1 is related to VLED1, the rest can be deduced by analogy), as shown in timing T5 in Figure 3.

When the PWM duty cycle D of the LED current ILED input to the LED backlight unit is equal to 100% (as in frame F1, the PWM duty cycle D of ILED_Z2~ILED_Z60 are all 100%), the current control transistor will continue to conduct, but Because the switching between LED voltage VLED1~VLED4 will cause the drain-source voltage Vds of the current control transistor to return from the Vcs_1 potential to the relevant VLED potential After that, it returns to the Vcs_1 potential, as shown in timing T6 in Figure 3.

As for how to trigger the update flag in Figure 3, it can be as shown in Figure 2, which will not be repeated here.

Please refer to FIG. 4, which shows a functional block diagram of a display device according to an embodiment of the present invention. As shown in Figure 4, the display device 400 according to an embodiment of the present case includes: a processing unit 110, a timing controller 120, a source driver and gate driver 130, an LCD panel 140, an LED driving circuit 150, an LED backlight unit 160, LED power management unit 170. The LCD panel 140 includes a plurality of display partitions. The display device 400 of an embodiment of this case utilizes unilateral driving to drive the backlight LEDs. Compared with FIG. 1, the display device 400 in FIG. 4 does not include the power switching unit 180, and the operations and functions of other components are similar or the same as the corresponding components in FIG. 1.

FIG. 5 shows a signal timing diagram of the display device according to an embodiment of the present application.

In Figure 5, similar to Figure 2, the update flag is set in the LED drive circuit 150, and the trigger condition for the update flag is, for example, but not limited to, (1) receiving the vertical synchronization of the next frame Signal; (2) the LED drive circuit has completely received the dimming data of the next frame; and (3) the ILED current cycle of the current frame has been output completely. Please note that these three conditions must all be met to allow the triggering of the update flag.

In order to ensure that the unilaterally driven LED current ILED can be fully output (that is, there will be no screen cut off, no flicker problem), in the present embodiment In Figure 5, after the LED driving circuit 150 receives the vertical synchronization signal of the next frame, the LED driving circuit 150 starts to wait for the input of the dimming data of the next frame.

After the LED driving circuit 150 completely receives the dimming data of the next frame, the LED driving circuit 150 confirms whether the output period T_ILED of the LED current ILED of the current frame is over (that is, whether the ILED current is completely output). If the output period T_ILED has not ended, the LED drive circuit 150 waits until the output period T_ILED ends, and the LED drive circuit 150 triggers the internal update flag and starts to output the LED current ILED in the next frame, as shown by F2_DOUT (that is, The received dimming data of the next frame is transferred from the first register to the second register, and the dimming data of the next frame stored in the second register is output to the LED backlight unit 160).

In addition, through the embodiment of the present case in Fig. 5, the output period T_ILED of the LED current ILED can be accelerated, and the delay time D_ILED between the display of the panel image and the backlight can be reduced.

That is, as seen from Figures 4 and 5, by adding an update flag to the LED drive circuit 150, when the update flag is triggered, the dimming data of the next frame will be output. Therefore, the current frame The output of the LED current ILED will not be cut off, so there is no flicker problem.

Fig. 6 shows a flowchart of the operation method of the display device according to an embodiment of the present case. In step 610, the timing controller receives the screen data. In step 620, the timing controller performs data calculation processing. In step 630, the timing controller outputs the LCD screen data to the source driver and the gate driver, and outputs the modulation The light data is given to the LED drive circuit. In step 640, the LED driving circuit receives the vertical synchronization signal of the next frame output by the timing controller. In step 650, the LED driving circuit completely receives the dimming data of the next frame. In step 660, the LED driving circuit checks whether the LED current cycle of the current frame has been output. If step 660 is no, the process returns to step 660. If step 660 is YES, then in step 670, the LED driving circuit triggers the internal update flag, so that the dimming data of the next frame is transferred from the first register of the LED driving circuit to the second register. In step 680, the LED driving circuit outputs the LED current of the next frame to the LED backlight unit according to the dimming data.

In the above-mentioned embodiment of this case, the timing controller 120 outputs the vertical synchronization signal signal and the dimming data to the LED driving circuit 150, and other operations (for example, when to trigger the update flag, when to output the dimming data of the next frame to the LED The backlight unit 160) can be determined and processed by the LED driving circuit 150 by itself. Therefore, there is no need to make special changes to the design of the timing controller.

In the above-mentioned embodiment of this case, the vertical synchronization function is combined with the PWM area dimming technology to solve the problem of LED flicker. And since the output cycle T_ILED of the LED current ILED can be accelerated, the delay time D_ILED between the display of the panel image and the backlight can be reduced.

In addition, in the above-mentioned embodiment of this case, regardless of whether the frame update rate of the continuity frame changes instantaneously (for example, but not limited to, 144Hz→30Hz→144Hz) or slowly changes (for example, but not limited to, 144Hz→ 120Hz→100Hz→...→30Hz→60Hz→...→144Hz), the above embodiment of this case can ensure the backlight Will not flicker.

In summary, although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to those defined by the attached patent application scope.

610~680: steps

Claims (7)

An operating method of a display device includes: receiving a vertical synchronization signal of the next frame; completely receiving a dimming data of the next frame; judging whether the current period of a light emitting diode (LED) of a current frame is The output has been completed; if it is determined that the LED current cycle of the current frame has been output, an LED current of the next frame is output to the display according to the dimming data of the next frame An LED backlight unit of the device. The operating method of the display device according to claim 1, wherein, if it is determined that the light emitting diode (LED) current cycle of the current frame has been output, the LED current of the next frame is output to the display Before the LED backlight unit of the device, an internal update flag of an LED driving circuit of the display device is triggered, so that the dimming data of the next frame is transferred from a first register of the LED driving circuit to A second register. The operation method of the display device according to claim 2, wherein after the dimming data of the next frame is transferred to the second register of the LED driving circuit, the LED driving circuit is temporarily stored in The dimming data of the next frame in the second register outputs the LED current of the next frame to the LED backlight unit. The operating method of the display device according to claim 1, wherein the LED backlight unit is driven by unilateral driving. The operating method of the display device according to claim 1, wherein the LED backlight unit is driven by bilateral driving. The operation method of the display device according to claim 5, wherein when a PWM duty cycle of the LED current input to the LED backlight unit is less than 100%, it responds to a current in a power switching unit of the display device The control transistor is turned on, a drain-source voltage of the current control transistor is equal to a first potential; and when the LED current stops outputting, in response to the current control transistor being turned off, the current control transistor is turned off. The drain-source cross voltage returns from the first potential to the relevant LED voltage of one of the plurality of LED voltages. The operation method of the display device according to claim 6, wherein when the PWM duty cycle of the LED current input to the LED backlight unit is equal to 100%, the current control transistor is continuously turned on in response to the LED voltage After switching between the current control transistors, the drain-source cross voltage of the current control transistor returns to the relevant LED voltage from the first potential, and then returns to the first potential.

Images