CN114708830A - LED display panel and control method thereof - Google Patents

Abstract

A light emitting diode display panel and a control method thereof. The LED display panel has a light-emitting diode (LED) 2^MGradation value. The control method comprises the following steps. The luminance corresponding to the 1 st-a-th gray scale value is generated by a first driving current and a first driving frequency. Generating a second driving current and a second driving frequency corresponding to the (a +1) -2^M-a brightness of 1-step grey scale value. The first drive current is less than the second drive current or the first drive frequency is higher than the second drive frequency.

Description

LED display panel and control method thereof

technical field

The present disclosure relates to a display panel and a control method thereof, and in particular, to a light emitting diode display panel and a control method thereof.

Background technique

With the development of display technology, a light-emitting diode display panel has been developed. The resolution of the LED display panel is determined by the frame rate, the driving frequency (GCLK frequency) and the number of scans. As shown in Table 1 below, when the number of scans increases, the resolution (number of bits) displayed is less, and the discrimination at low gray levels is poor. If the number of scans is reduced and the display resolution is increased, the number of driving chips used will increase, and the cost will also increase.

Table I

In order to keep the number of used driver chips from increasing, how to improve the discrimination of low gray levels without increasing the resolution has become an important research and development direction in the industry.

SUMMARY OF THE INVENTION

The present disclosure relates to a light-emitting diode display panel and a control method thereof, which reduce the brightness of low grayscale values to improve the discrimination of low grayscale values.

According to an aspect of the present disclosure, a control method of a light emitting diode display panel is provided. The light emitting diode display panel has 2 ^M gray scale values. The control method includes the following steps. A first driving current and a first driving frequency are used to generate brightness corresponding to the gray scale values of the first to a levels. Using a second driving current and a second driving frequency, the luminance corresponding to the gray scale values of a+1˜2 ^M −1 is generated. The first driving current is smaller than the second driving current, or the first driving frequency is higher than the second driving frequency.

According to another aspect of the present disclosure, a light emitting diode display panel is provided. The light-emitting diode display panel has a second ^M -level grayscale value. The light emitting diode display panel includes a source driving circuit. The source driving circuit includes a current switching circuit, a frequency switching circuit and a control circuit. The current switching circuit is used for switching between a first driving current or a second driving current. The frequency switching circuit is used for switching between a first driving frequency or a second driving frequency. The control circuit is connected to the current switching circuit and the frequency switching circuit, so as to control the current switching circuit and the frequency switching circuit to generate brightness corresponding to the gray-scale values of the first to a levels with the first driving current and the first driving frequency, and use the second driving current and the first driving frequency The current and the second driving frequency generate brightness corresponding to the grayscale values of the a+1˜2 ^M −1 th levels. The first driving current is smaller than the second driving current, or the first driving frequency is higher than the second driving frequency.

In order to have a better understanding of the above-mentioned and other aspects of the present disclosure, the following specific embodiments are given and described in detail in conjunction with the accompanying drawings in the description as follows:

Description of drawings

FIG. 1 illustrates a relationship between grayscale values and luminance according to an embodiment.

FIG. 2 illustrates a light emitting diode display panel according to an embodiment.

3 shows a block diagram of a source driver circuit according to an embodiment.

FIG. 4 shows a relationship diagram of a driving signal and a scanning signal according to an embodiment.

FIG. 5 shows a flowchart of a control method of a light emitting diode display panel according to an embodiment.

Figure 6 shows a comparison of three Gamma 2.2 curves.

FIG. 7 shows a gamma value distribution diagram according to the curve CV12 and the curve CV13 of FIG. 6 .

Description of reference numbers:

100: LED display panel

110: Source drive circuit

111: Current switching circuit

1111: First current generator

1112: Second current generator

1113: Multiplexer

112: Frequency switching circuit

1121: First frequency generator

1122: Second frequency generator

1123: Multiplexer

113: Control circuit

114: Displacement temporary storage circuit

115: Scratch memory

116: Scrambling circuit

117: Output buffer circuit

118: Regulator circuit

119: Bit count control circuit

120: Scanning drive circuit

130: LEDs

a,b,n,x: numeric values

CS1: The first control signal

CS2: Second control signal

CV1, CV2, CV3, CV11, CV12, CV13, CV22, CV23: Curves

GCLK1: first drive frequency

GCLK2: Second drive frequency

GP: level difference

Igain1: first drive current

Igain2: The second drive current

L1, L2, L3: Columns

OUT1-OUTm: output terminal

S1: drive signal

S2: scan signal

S110, S120, S130, S140, S150, S160, S170, S180, S190: Steps

Ts: non-display time

Detailed ways

Please refer to FIG. 1 , which illustrates a relationship between grayscale values and luminance according to an embodiment. As shown in the curve CV1 of FIG. 1 , before adjustment, the grayscale value and the brightness have a linear relationship, for example. When the number of bits is M, there are 2 ^M -level grayscale values in total. The brightness corresponding to the first-level gray-level value to the a-th gray-level value is relatively high, so that the discrimination degree of the first-level gray-level value to the a-th gray-level value is poor.

In one embodiment, as shown by the curve CV2, the present technology reduces the brightness of the first grayscale value to the a-th grayscale value so as to correspond to the first grayscale value to the a-th grayscale value The brightness of the 1st-level grayscale value becomes lower, so as to improve the discrimination degree of the first-level gray-level value to the a-th level gray-level value.

For example, with the a-th grayscale value as the boundary, for the 1st-a-level gray-scale values, the first driving current Igain1 and the first driving current GCLK1 are used to generate luminance corresponding to the 1st-a-level gray-scale values. For a+1-2M-1th grayscale value, the second driving current ^Igain2 and the second driving current GCLK2 are used to generate luminance corresponding to a ⁺ 1-2M-1th grayscale value. The following three ways can reduce the brightness corresponding to the 1st to a-level grayscale values:

(1) The first drive current Igain1 is smaller than the second drive current Igain2;

(2) the first driving frequency GCLK1 is higher than the second driving frequency GCLK2; or

(3) The first driving current Igain1 is smaller than the second driving current Igain2 and the first driving frequency GCLK1 is higher than the second driving frequency GCLK2.

In another embodiment, in order to avoid the curve CV2 from forming a stage difference GP between the a-th gray-scale value and the a+1-th gray-scale value, as shown in the curve CV3, the present technology is more closely corresponding to the a+1-th gray-scale value. The brightness of the gray-scale value is the same as the brightness corresponding to the a-th gray-scale value. That is to say, the present technology can control the PWM width of the brightness corresponding to the a+1th grayscale value to be nT, so that the brightness corresponding to the a+1th grayscale value is substantially equal to and slightly higher than the brightness corresponding to the a+1th grayscale value. The brightness of the grayscale value.

In addition, in order to allow high grayscale values to be supplemented with due brightness, the present technology increases the magnitude of the brightness change from the bth grayscale value.

For example, with the b-th grayscale value as the boundary, for the 1st to bth grayscale values, the PWM width increase rate is controlled to be 1T, so as to generate brightness corresponding to the 1st to bth grayscale values. For b+1˜2 ^M −1 th grayscale values, the PWM width increase rate is controlled to be 2T, so as to generate brightness corresponding to b+1˜2 ^M −1 th grayscale values.

As shown in the curve CV3 of FIG. 1 , for the gray-scale values of the first to a levels, the first driving current Igain1 and the first driving current GCLK1 are used, and the PWM width increase rate is controlled to be 1T. For the a+1-bth grayscale values, the second driving current Igain2 and the second driving current GCLK2 are used, and the PWM width increase rate is controlled to be 1T. For the b+1 to 2 ^M −1 gray-scale values, the second driving current Igain2 and the second driving current GCLK2 are used, and the PWM width increase rate is controlled to be 2T.

Please refer to Table 2 below, which illustrates a grayscale value with a bit number of 13 and its corresponding brightness control as an example. In the example in Table 2 below, M is 13, a is 255, b is 7947, and n is 12.

Table II

The 255th grayscale value is used as the boundary, the first driving current Igain1 and the first driving current GCLK1 are used to generate the brightness corresponding to the 1st to 255th grayscale values, and the second driving current Igain2 and the second driving frequency GCLK2 are generated. The brightness corresponding to the 256th to 8191st grayscale values.

In addition, the PWM width for controlling the brightness corresponding to the 256th grayscale value is 12T, so that the brightness corresponding to the 256th grayscale value is substantially equal to and slightly higher than the brightness corresponding to the 255th grayscale value.

In addition, taking the 7947th grayscale value as the boundary, for the 1st to 7947th grayscale values, the PWM width increase rate is controlled to be 1T to generate brightness corresponding to the 1st to 7947th grayscale values. For the 7948th to 8191st grayscale values, the PWM width increase rate is controlled to be 2T to generate brightness corresponding to the 7948th to 8191st grayscale values.

Please refer to FIG. 2 , which illustrates a light emitting diode display panel 100 according to an embodiment. The LED display panel 100 includes a source driver circuit 110 , a scan driver circuit 120 and a plurality of LEDs 130 . The source driving circuit 110 is connected to the light emitting diode 130 to provide the driving signal S1 to the output terminals OUT1 ˜OUTm. The scan driving circuit 120 is connected to the light emitting diode 130 to provide the scan signal S2. Through the control of the scan signal S2, the light emitting diodes 130 can be driven column by column L1, L2, L3, . . .

Please refer to FIG. 3 , which shows a block diagram of the source driver circuit 110 according to an embodiment. The source driving circuit 110 includes a current switching circuit 111 , a frequency switching circuit 112 , a control circuit 113 , a Shift Register 114 , a temporary memory 115 , a Scrambler 116 , and an output A buffer circuit (OutputBuffer) 117 , a regulator circuit (Regulator) 118 and a bit-count controller (Bit-count Controller) 119 .

The current switching circuit 111 is connected to the control circuit 113 . The current switching circuit 111 includes a first current generator 1111 , a second current generator 1112 and a multiplexer 1113 . The input terminal of the multiplexer 1113 is connected to the first current generator 1111 and the second current generator 1112 , and the output terminal of the multiplexer 1113 is connected to the adjustment circuit 118 . The first current generator 1111 is used for generating the first driving current Igain1, and the second current generator 1112 is used for generating the second driving current Igain2.

The frequency switching circuit 112 is connected to the control circuit 113 . The frequency switching circuit 112 includes a first frequency generator 1121 , a second frequency generator 1122 and a multiplexer 1123 . The input end of the multiplexer 1123 is connected to the first frequency generator 1121 and the second frequency generator 1122 , and the output end of the multiplexer 1123 is connected to the bit count control circuit 119 . The first frequency generator 1121 is used for generating the first driving frequency GCLK1, and the second frequency generator 1122 is used for generating the second driving frequency GCLK2.

After receiving the numerical value a and the numerical value n, the control circuit 113 calculates the numerical value b according to the numerical value a and the numerical value n (shown in FIG. 1 ). For example, the control circuit 113 can perform the calculation according to the following formula (1):

b= ^2M -1-(a+1)+n……………………………………………………(1)

After the control circuit 113 obtains the values a, b, and n, it can output the first control signal CS1 and the second control signal CS2 according to the order of the gray scale values.

The multiplexer 1113 selects and outputs the first driving current Igain1 or the second driving current Igain2 according to the first control signal CS1 output by the control circuit 113 .

The multiplexer 1123 selects and outputs the first driving frequency GCLK1 or the second driving frequency GCLK2 according to the second control signal CS2 output by the control circuit 113 .

Please refer to FIG. 4 , which shows a relationship diagram between the driving signal S1 and the scanning signal S2 according to an embodiment. The scan signal S2 turns on the LEDs in each column in sequence. During the switching process, there will be a period of non-display time Ts. The current switching circuit 111 switches the first driving current Igain1 and the second driving current Igain2 during the non-display time Ts. The frequency switching circuit 112 switches the first driving frequency GCLK1 and the second driving frequency GCLK2 during the non-display time Ts.

Please refer to FIG. 5 , which shows a flowchart of a control method of the light emitting diode display panel 100 according to an embodiment. The following process steps are illustrated with the block diagram of FIG. 3 as an example. In step S110, the control circuit 113 obtains the numerical value a and the numerical value n, and calculates the numerical value b according to the numerical value a and the numerical value n.

Next, in step S120, the control circuit 113 receives a display signal, and the display signal is to present an x-th grayscale value.

Then, in step S130, the control circuit 113 judges whether the numerical value x is less than or equal to the numerical value a. If the numerical value x is less than or equal to the numerical value a, go to step S140; if the numerical value x is greater than the numerical value a, go to step S150.

In step S140, the control circuit 113 controls the current switching circuit 111 to switch to the first driving current Igain1 through the first control signal CS1, and controls the frequency switching circuit 112 to switch to the first driving frequency GCLK1 through the second control signal CS2.

In step S150, the control circuit 113 controls the current switching circuit 111 to switch to the second driving current Igain2 through the first control signal CS1, and controls the frequency switching circuit 112 to switch to the second driving frequency GCLK2 through the second control signal CS2.

After step S140, the flow proceeds to step S160. In step S160, the control circuit 113 controls the PWM width of the luminance corresponding to the x-th grayscale value to be xT. For example, please refer to Table 1, the PWM width of the brightness of the first grayscale value is 1T; the PWM width of the brightness of the second grayscale value is 2T; the PWM width of the brightness of the 253rd grayscale value is 253T ; The PWM width of the brightness of the 254th grayscale value is 254T; the PWM width of the brightness of the 255th grayscale value is 255T.

In step S170, the control circuit 113 determines whether the numerical value x is less than or equal to the numerical value b. If the numerical value x is less than or equal to the numerical value b, go to step S180; if the numerical value x is greater than the numerical value b, go to step S190.

In step S180, the control circuit 113 controls the PWM width of the luminance corresponding to the x-th grayscale value to be [x-(a+1)+n]T. For example, the PWM width of the brightness of the 256th grayscale value is 12T([256-(255+1)+12]T); the PWM width of the brightness of the 257th grayscale value is 13T([257-( 255+1)+12]T); the PWM width of the brightness of the 258th grayscale value is 14T([258-(255+1)+12]T); the PWM width of the brightness of the 7945th grayscale value is 7701T([7945-(255+1)+12]T); the PWM width of the brightness of the 7946th grayscale value is 7702T([7945-(255+1)+12]T); the 7947th grayscale value The PWM width of the brightness is 7703T ([7945-(255+1)+12]T).

In step S190, the control circuit 113 controls the PWM width of the luminance corresponding to the x-th grayscale value to be [x-(a+1)+n+(x-b)]T. For example, the PWM width corresponding to the brightness of the 7948th grayscale value is 7705([7648-(255+1)+12+(7948-7947)]T); the brightness corresponding to the 7949th grayscale value The PWM width is 7707([7649-(255+1)+12+(7949-7947)]T); the PWM width corresponding to the brightness of the 8189th grayscale value is 8187([8189-(255+1) +12+(8189-7947)]T); the PWM width corresponding to the brightness of the 8190th grayscale value is 8189([8190-(255+1)+12+(8190-7947)]T); corresponding to The PWM width of the luminance of the 8191st grayscale value is 8191([8191-(255+1)+12+(8191-7947)]T).

According to the control method of the light-emitting diode display panel 100 described above, the present technology reduces the brightness of the grayscale values of the first to a levels, so that the brightness corresponding to the grayscale values of the first to a levels decreases, so as to improve the brightness of the grayscale values of the first to a levels Discrimination of grayscale values. And the brightness corresponding to the a+1-th grayscale value and the brightness corresponding to the a-th grayscale value are further connected. In addition, high gray-scale values from the b-th gray-scale value can be supplemented with due brightness.

Please refer to FIG. 6, which shows a comparison graph of three Gamma 2.2 curves. The curve CV11 is the standard Gamma 2.2 curve, the curve CV12 is the Gamma 2.2 curve without the control method of the present technology, and the curve CV13 is the Gamma 2.2 curve with the control method of the present technology. It can be seen from the enlarged illustration of low gray level that the curve CV12 has no discrimination, while the curve CV13 significantly improves the discrimination and is closer to the curve CV11. It can be seen from the enlarged illustration of high gray scale that the curve CV13 still has obvious discrimination and is close to the curve CV11.

Please refer to FIG. 7 , which shows a distribution diagram of Gamma values according to the curve CV12 and the curve CV13 of FIG. 6 . The curve CV22 represents the gamma value of the curve CV12, and the curve CV23 represents the gamma value of the curve CV13. It can be clearly seen from Figure 7 that the Gamma value of the curve CV23 is closer to 2.2 than the curve CV22.

That is to say, through the technology of the above-mentioned embodiments, the LED display panel 100 can perfectly present the display level of Gamma 2.2.

To sum up, although the present disclosure has been disclosed above with examples, it is not intended to limit the present disclosure. Those skilled in the art to which the present disclosure pertains can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure should be determined by what is defined by the claims.

Claims (14)

1. A control method of LED display panel having 2^MThe control method comprises the following steps:

generating brightness corresponding to 1 st-a gray scale values by using a first driving current and a first driving frequency; and

generating a second driving current and a second driving frequency corresponding to the (a +1) -2^M-a luminance of 1-step gray scale value, wherein the first driving current is smaller than the second driving current or the first driving frequency is higher than the second driving frequency.

2. The method according to claim 1, wherein the first and second driving currents, the first and second driving frequencies are switched during a non-display time.

3. The method of controlling a light emitting diode display panel of claim 1, further comprising:

controlling the PWM width increase rate to be T so as to generate brightness corresponding to 1 st-b-stage gray scale values, b > a; and

controlling the PWM width increase rate to be 2T to generate the pulse width corresponding to the (b +1) -2^M-a brightness of 1-step grey scale value.

4. The method of claim 3, wherein the PWM width of the luminance corresponding to the a +1 th gray scale value is nT, and the luminance corresponding to the a +1 th gray scale value is substantially equal to the luminance corresponding to the a th gray scale value.

5. The method of claim 3, wherein b-2^M-1-(a+1)+n。

6. The method of claim 3, wherein when x is between a +1 and b, the PWM width of the luminance corresponding to the x-th gray scale value is [ x- (a +1) + n ] T.

7. The method according to claim 3, wherein x is between b + 1-2^M-1, PWM width of luminance corresponding to x-th order gray scale value [ x- (a +1) + n + (x-b)]T。

8. A light emitting diode display panel having the 2 nd^MThe light emitting diode display panel comprises:

a source driver circuit, comprising:

a current switching circuit for switching between a first driving current and a second driving current;

a frequency switching circuit for switching between a first driving frequency and a second driving frequency; and

a control circuit connected to the current switching circuit and the frequency switching circuit for controlling the current switching circuit and the frequency switching circuit to generate brightness corresponding to 1-a gray scale values with the first drive current and the first drive frequency, and generate brightness corresponding to a + 1-2 with the second drive current and the second drive frequency^M-luminance of 1 gray level;

the first driving current is smaller than the second driving current or the first driving frequency is higher than the second driving frequency.

9. The led display panel of claim 8, wherein the current switching circuit switches the first driving current and the second driving current during a non-display time, and the frequency switching circuit switches the first driving frequency and the second driving frequency during the non-display time.

10. The LED display panel of claim 8, wherein the control circuit is further configured to control the PWM width increase rate to be T to generate a brightness corresponding to the 1 st-b gray scale values and to control the PWM width increase rate to be 2T to generate a brightness corresponding to the b +1 st-2 nd gray scale values^M-a brightness of 1-step grey scale value.

11. The led display panel of claim 10, wherein the PWM width adjustment circuit controls the PWM width of the luminance corresponding to the a +1 th gray scale value to be nT, the luminance corresponding to the a +1 th gray scale value being substantially equal to the luminance corresponding to the a th gray scale value.

12. The light emitting diode display panel of claim 10, wherein b-2^M-1-(a+1)+n。

13. The LED display panel of claim 10, wherein the PWM width adjustment circuit controls the PWM width of the luminance corresponding to the x-th gray scale value to be [ x- (a +1) + n ] T when x is between a +1 and b.

14. The light-emitting diode display panel of claim 10, wherein x is between b +1 and 2^M-1, the PWM width adjusting circuit controlling a PWM width of the luminance corresponding to the x-th gray scale value to be [ x- (a +1) + n + (x-b)]T。

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