TWI807573B - Light-emitting diode display panel and control method thereof - Google Patents

Abstract

A light-emitting diode display panel and a control method thereof are 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 the brightness corresponding to the first to a-th gray scale values. A second driving current and a second driving frequency are used to generate the brightness corresponding to the a+1-th to (2^M-1)-th gray scale values. The first driving current is smaller than the second driving current, or the first driving frequency is higher than the second driving frequency.

Description

Light-emitting diode display panel and control method thereof

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.

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 display resolution (number of bits) decreases, and the discrimination at low gray levels is poor. If the number of scans is reduced to increase the resolution of the display, the number of driver chips used will increase, and the cost will also increase.

In order not to increase the number of driver chips used, how to improve the discrimination of low gray levels without increasing the resolution has become an important research and development direction in the industry.

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

According to an aspect of the present disclosure, a method for controlling a light emitting diode display panel is provided. The light emitting diode display panel has ^2M grayscale 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 1st-a grayscale values. A second driving current and a second driving frequency are used to generate brightness corresponding to the a+ ^1-2M -1th gray scale value. 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 ^2Mth gray scale values. The LED 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 and 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 the brightness corresponding to the 1st~a grayscale value with the first driving current and the first driving frequency, and generate the brightness corresponding to the a+1~ ^2M -1th grayscale value with the second driving current and the second driving frequency. 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 and other aspects of the present disclosure, the following specific embodiments are described in detail in conjunction with the attached drawings as follows:

100: LED display panel

110: Source drive circuit

111: Current switching circuit

1111: the first current generator

1112: second current generator

1113: multiplexer

112: Frequency switching circuit

1121: the first frequency generator

1122: second frequency generator

1123: multiplexer

113: control circuit

114: Displacement temporary storage circuit

115: temporary memory

116: Scrambling circuit

117: output buffer circuit

118: Regulating circuit

119: Bit counting control circuit

120: Scan driving circuit

130: light emitting diode

a,b,n,x: value

CS1: The first control signal

CS2: Second control signal

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

GCLK1: the first driving frequency

GCLK2: Second drive frequency

GP: segment difference

Igain1: the first driving 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

FIG. 1 is a graph showing the relationship between gray scale value and brightness according to an embodiment.

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

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

FIG. 4 shows the relationship between the driving signal and the scanning signal according to an embodiment.

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

Figure 6 shows the comparison of three Gamma 2.2 curves.

FIG. 7 shows the distribution of Gamma values according to the curve CV12 and the curve CV13 in FIG. 6 .

Please refer to FIG. 1 , which shows the relationship between gray scale value and brightness according to an embodiment. As shown by the curve CV1 in FIG. 1 , before adjustment, the grayscale value and brightness have a linear relationship, for example. When the number of bits is M, there are 2 ^M gray scale values in total. The brightness corresponding to the 1st grayscale value to the ath grayscale value is relatively high, which makes the discrimination between the 1st grayscale value and the ath grayscale value poor.

In one embodiment, as shown by the curve CV2, the present technology reduces the brightness of the first grayscale value to the ath grayscale value, so that the brightness corresponding to the first grayscale value to the ath grayscale value becomes lower, so as to improve the discrimination between the first grayscale value and the ath grayscale value.

For example, with the a-th grayscale value as the boundary, for the 1st-a grayscale values, the first driving current Igain1 and the first driving frequency GCLK1 are used to generate brightness corresponding to the 1st-a grayscale values. For the a+1~ ^2M -1th grayscale value, the brightness corresponding to the a+1~ ^2M −1th grayscale value is generated by the second driving current Igain2 and the second driving frequency GCLK2. The following three ways can reduce the luminance corresponding to the 1st to a gray scale values: (1) the first driving current Igain1 is smaller than the second driving 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 prevent the curve CV2 from forming a gap GP between the a-th gray scale value and the a+1-th gray scale value, as shown in the curve CV3, the technology further connects the brightness corresponding to the a+1-th gray-scale value and the brightness corresponding to the a-th gray-scale value. That is to say, this technology can control the PWM width corresponding to the brightness of 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 ath grayscale value.

In addition, in order to allow high grayscale values to be supplemented with proper brightness, this technology increases the range of brightness change from the bth grayscale value onwards.

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

As shown in the curve CV3 of FIG. 1, for the 1st-a grayscale values, the first driving current Igain1 and the first driving frequency GCLK1 are used, and the PWM width increase rate is controlled to 1T. For the a+1~b-th grayscale values, the second driving current Igain2 and the second driving frequency GCLK2 are used, and the PWM width increase rate is controlled to 1T. For the b+1~ ^2M -1th grayscale value, the second driving current Igain2 and the second driving frequency GCLK2 are used, and the PWM width increase rate is controlled to 2T.

Please refer to Table 2 below, which illustrates the gray scale value with 13 bits and its corresponding brightness control. In the example in Table 2 below, M is 13, a is 255, b is 7947, and n is 12.

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

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, with the 7947th grayscale value as the boundary, for the 1st~7947th grayscale value, the PWM width increase rate is controlled to 1T, so as to generate the brightness corresponding to the 1st~7947th grayscale value. For the 7948th to 8191st grayscale values, the increase rate of the PWM width is controlled to 2T to generate brightness corresponding to the 7948th to 8191st grayscale values.

Please refer to FIG. 2 , which shows a light emitting diode display panel 100 according to an embodiment. The LED display panel 100 includes a source driver circuit (source driver circuit) 110 , a scan driver circuit (scan driver circuit) 120 and several 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 in columns L1 , L2 , L3 , . . . .

Please refer to FIG. 3 , which shows a block diagram of a source driving circuit 110 according to an embodiment. The source drive circuit 110 includes a current switching circuit 111, a frequency switching circuit 112, a control circuit 113, a displacement temporary storage circuit (Shift Register) 114, a temporary storage memory 115, a scrambler circuit (Scrambler) 116, an output buffer circuit (Output Buffer) 117, and a regulation circuit (Regulator) 118 and a bit count control circuit (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 end of the multiplexer 1113 is connected to the first current generator 1111 and the second current generator 1112 , and the output end of the multiplexer 1113 is connected to the regulating circuit 118 . The first current generator 1111 is used to generate a first driving current Igain1, and the second current generator 1112 is used to generate a 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 to generate the first driving frequency GCLK1, and the second frequency generator 1122 is used to generate the second driving frequency GCLK2.

After receiving the value a and the value n, the control circuit 113 calculates the value b (shown in FIG. 1 ) according to the value a and the value n. For example, the control circuit 113 can be calculated according to the following formula (1): b=2 ^M -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 gray scale.

The multiplexer 1113 selects to output 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 to output 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 the relationship between the driving signal S1 and the scanning signal S2 according to an embodiment. The scan signal S2 turns on the light emitting diodes of each row in sequence. During the switching process, there will be a 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 between 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 in Figure 3 as an example. In step S110, the control circuit 113 obtains the value a and the value n, and calculates the value b according to the value a and the value n.

Next, in step S120 , the control circuit 113 receives a display signal, and the display signal intends to display the xth gray scale value.

Then, in step S130, the control circuit 113 judges whether the value x is less than or equal to the value a. If the value x is less than or equal to the value a, go to step S140; if the value x is greater than the 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 through The second control signal CS2 controls the frequency switching circuit 112 to switch to the second driving frequency GCLK2.

After step S140, the flow goes to step S160. In step S160 , the control circuit 113 controls the PWM width corresponding to the luminance of the xth gray scale value to be xT. For example, please refer to Table 1, the PWM width of the brightness of the 1st grayscale value is 1T; the PWM width of the brightness of the 2nd 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;

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

In step S180 , the control circuit 113 controls the PWM width corresponding to the brightness of the x-th gray scale 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 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 PWM width of the brightness of the 7947th grayscale value is 7703T([7945-(255+1)+1 2] T).

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

According to the above-mentioned control method of the light-emitting diode display panel 100, the present technology reduces the brightness of the 1st~a grayscale values, so that the brightness corresponding to the 1st~a grayscale values becomes lower, so as to improve the discrimination of the 1st~a grayscale values. Furthermore, the luminance corresponding to the a+1th grayscale value and the luminance corresponding to the ath grayscale value are connected. In addition, the high gray-scale values starting from the b-th gray-scale value can be supplemented with proper brightness.

Please refer to Figure 6, which shows the comparison of three Gamma 2.2 curves. Curve CV11 is a standard Gamma 2.2 curve, curve CV12 is a Gamma 2.2 curve that does not implement the control method of the present technology, and curve CV13 is a Gamma 2.2 curve that implements the control method of the present technology. It can be seen from the enlarged diagram of the low gray scale that the curve CV12 has no discrimination, while the curve CV13 obviously improves the discrimination and is closer to the curve CV11. It can be seen from the enlarged illustration of the 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 the distribution of Gamma values according to the curve CV12 and the curve CV13 in 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 Fig. 7 that the Gamma value of the curve CV23 is closer to 2.2 than that of the curve CV22.

That is to say, through the technologies of the above-mentioned embodiments, the light-emitting diode 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 embodiments, it is not intended to limit the present disclosure. Those with ordinary knowledge in the technical field to which this disclosure belongs may make various changes and modifications without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure should be defined by the scope of the appended patent application.

110: Source drive circuit

111: Current switching circuit

1111: the first current generator

1112: second current generator

1113: multiplexer

112: Frequency switching circuit

1121: the first frequency generator

1122: second frequency generator

1123: multiplexer

113: control circuit

114: Displacement temporary storage circuit

115: temporary memory

116: Scrambling circuit

117: output buffer circuit

118: Regulating circuit

119: Bit counting control circuit

a, n: value

CS1: The first control signal

CS2: Second control signal

GCLK1: the first driving frequency

GCLK2: Second drive frequency

Igain1: the first driving current

Igain2: the second driving current

OUT1-OUTm: output terminal

Claims (14)

A control method of a light-emitting diode display panel, the light-emitting diode display panel has ^2M grayscale values, the control method comprising: using a first driving current and a first driving frequency to generate brightness corresponding to the 1st-a grayscale value; and using a second driving current and a second driving frequency to generate brightness corresponding to the a+1~ ^2M -1 grayscale 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. The method for controlling a light emitting diode display panel as described in Claim 1, wherein the first driving current and the second driving current, the first driving frequency and the second driving frequency are switched during a non-display time. The method for controlling a light-emitting diode display panel as described in Claim 1, further comprising: controlling the PWM width increasing rate of the first driving current or the second driving current T to generate brightness corresponding to the 1st to b grayscale values, b>a; and controlling the PWM width increasing rate of the second driving current to 2T to generate brightness corresponding to the b+1~ ^2M -1th grayscale value. The method for controlling a light-emitting diode display panel as described in Claim 3, wherein the second driving current corresponding to the luminance of the a+1th gray scale value The PWM width is nT, and the brightness corresponding to the a+1th grayscale value is substantially equal to the brightness corresponding to the ath grayscale value. The method for controlling a light-emitting diode display panel according to Claim 3, wherein b=2 ^M -1-(a+1)+n. The control method of the light-emitting diode display panel as described in Claim 3, wherein when x is between a+1~b, the PWM width of the second driving current corresponding to the brightness of the xth gray scale value is [x-(a+1)+n]T. The control method of the light-emitting diode display panel as described in Claim 3, wherein when x is between b+1~ ^2M -1, the PWM width of the second drive current corresponding to the brightness of the xth grayscale value is [x-(a+1)+n+(xb)]T. A light emitting diode display panel, the light emitting diode display panel has a second^mThe light-emitting diode display panel includes: a source driving circuit, including: a current switching circuit, used to switch between a first driving current or a second driving current; a frequency switching circuit, used for switching between a first driving frequency or a second driving frequency; and a control circuit, 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 first to a gray scale values with the first driving current and the first driving frequency, and use the second driving frequency The dynamic current and the second driving frequency are generated corresponding to the first a+1~2^m- luminance of 1-level 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. The light emitting diode display panel as described in 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. In the light-emitting diode display panel as described in Claim 8, the control circuit is further used to control the increase rate of the PWM width of the first drive current or the second drive current T to generate brightness corresponding to the 1st to b gray scale values, and to control the PWM width increase rate of the second drive current to 2T to generate brightness corresponding to the b+1 to ^2M -1 gray scale value. The light-emitting diode display panel as described in Claim 10, wherein the PWM width adjustment circuit controls the PWM width of the second driving current corresponding to the brightness of the a+1th grayscale value to be nT, and the brightness corresponding to the a+1th grayscale value is substantially equal to the brightness corresponding to the ath grayscale value. The light-emitting diode display panel according to claim 10, wherein b=2 ^M -1-(a+1)+n. The light-emitting diode display panel as described in Claim 10, wherein when x is between a+1~b, the PWM width adjustment circuit controls the PWM width of the second driving current corresponding to the brightness of the x-th grayscale value to be [x-(a+1)+n]T. The light-emitting diode display panel as described in Claim 10, wherein when x is between b+1~ ^2M -1, the PWM width adjustment circuit controls the PWM width of the second drive current corresponding to the brightness of the x-th grayscale value to be [x-(a+1)+n+(xb)]T.

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