CN103021335B - OLED (organic light emitting diode) driving circuit, OLED display device and brightness adjusting method for OLED display device - Google Patents
OLED (organic light emitting diode) driving circuit, OLED display device and brightness adjusting method for OLED display device Download PDFInfo
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Abstract
The invention belongs to the field of display technology, and particularly relates to an OLED (organic light emitting diode) driving circuit, an OLED display device and a brightness adjusting method for the OLED display device. The OLED driving circuit comprises a control unit and a driving unit, the control unit is used for calculating the average brightness of a frame image according to all sub-image data of the frame image to be displayed, reversely adjusting brightness control signals for displaying sub-images of the frame image by taking the average brightness as reference brightness and transmitting the adjusted brightness control signals to the driving unit, and the driving unit is used for receiving the adjusted brightness control signals and driving an OLED according to the adjusted brightness control signals, so that the frame image is displayed according to the adjusted brightness. The OLED driving circuit has the advantages that overall power consumption of an OLED display panel is low, and image quality is improved.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to an OLED driving circuit, an OLED display device and a brightness adjusting method of the OLED display device.
Background
An OLED (Organic Light-Emitting Diode) Display device is an emerging flat panel Display device, and the OLED can self-emit Light without a backlight unit, compared to a Liquid Crystal Display (LCD), and thus, the OLED Display device is generally considered to have lower power consumption than the LCD.
The pixel unit in the OLED display device includes a plurality of pixel units arranged in a matrix form. The pixel units are classified into a Passive Matrix (PM) driving method and an Active Matrix (AM) driving method according to the driving method. AM-OLEDs are widely used because of their significant advantages in viewing angle, color reduction, power consumption, and response time.
In terms of driving mechanism, the AM-OLED is a matrix addressed circuit structure, and the circuit structure includes a Thin Film Transistor (TFT), and the TFT is connected to the sub-pixel unit (i.e., OLED). The driving signals comprise scanning signals for providing row gating for the pixel units and data signals (with display information) for providing column gating, the scanning signals and the data signals act on the TFT simultaneously, and the current of the OLED connected with the TFT is controlled by controlling the on-off of the TFT, so that the OLED can emit light within a controllable frame time to display an image to be displayed.
The tasks of the drive circuit include: a controlled current is supplied to drive the OLED and current continues to be supplied after an addressing period to ensure that each sub-pixel cell continues to emit light. As shown in fig. 1, a 2T1C driving circuit commonly used for a single OLED in the prior art includes a switching tube (switching) T1 (hereinafter referred to as T1), a driving tube (driving) T2 (hereinafter referred to as T2), and a storage (storing) capacitor Cs (hereinafter referred to as Cs). When the scanning line is selected, the row selection signal Vsel enables the T1 to be turned on, the data voltage Vdata charges the Cs through the T1, the voltage of the Cs controls the drain current of the T2, and the T2 starts to be turned on and stably works in a saturation region along with the gradual increase of the gate potential of the T2; when the scan line is not selected, T1 is turned off, the charge stored in Cs keeps the gate voltage of T2, and T2 keeps the on state, so that the OLED can be maintained in constant current control in one frame period, and the required driving current of the OLED is small, and the power consumption is low.
However, in the practical use process, when pictures with different brightness are displayed, the power consumption of the OLED display panel is found to be greatly different, for example: in a black picture or a low-darkness image, the OLED display panel consumes little power because all OLEDs do not operate or only a small number of OLEDs operate; when a white picture or a high-brightness image is displayed, all or most of the OLEDs are turned on, and the current flowing through the OLEDs is large, so that the power consumption of the OLED display panel is increased. Statistical data shows that when the OLED display device displays the same white picture or high-brightness image as the LCD, the power consumption of the OLED display panel is 4 times as high as that of the LCD.
In order to solve the problem of high power consumption of AM-OLED in white pictures or high-luminance images, chinese patent application No. 200610079980.4 proposes a solution, which controls the width of the scanning signal according to the number of gray level values of the displayed image or the brightness of the external environment, and adjusts the on-time and off-time of the OLED to achieve the purpose of reducing power consumption in white pictures or high-luminance images. However, in this scheme, the purpose of reducing power consumption is achieved by adjusting the on and off of the TFT, and the sudden on and off of the TFT easily causes the OLED display panel to have unstable image display due to unstable driving voltage, and even causes defects such as display screen jitter. Therefore, how to reduce the power consumption of the OLED display panel and ensure the stability of the image display is an urgent problem to be solved at present.
Disclosure of Invention
The present invention provides an OLED driving circuit, an OLED display device, and a method for adjusting the brightness of the display device, which are directed to solve the above-mentioned deficiencies in the prior art.
The technical scheme adopted for solving the technical problem of the invention is that the OLED drive circuit comprises a control unit and a drive unit, wherein:
the control unit is used for calculating the average brightness of a frame of image according to all sub-image data of the frame of image to be displayed, reversely adjusting the brightness control signal for displaying each sub-image of the frame of image by taking the average brightness as the reference brightness, and sending the adjusted brightness control signal to the driving unit;
and the driving unit receives the adjusted brightness control signal and drives the OLED according to the adjusted brightness control signal, so that the frame image is displayed according to the adjusted brightness.
Preferably, the reference luminance is obtained by counting gray scale values of sub-images of the frame image.
Preferably, when the luminance of the sub-image is greater than the reference luminance by a first preset range, the control unit decreases the luminance control signal of the OLED for displaying the sub-image by the first preset range accordingly.
Further preferably, the first preset range is 30% -50%, and the first preset range is 20% -40%.
Preferably, when the luminance of the sub-image is smaller than a second preset range of the reference luminance, the control unit increases the luminance control signal of the OLED for displaying the sub-image by the second preset range correspondingly.
Further preferably, the second preset range is 30% -50%, and the second preset range is 20% -40%.
Preferably, the driving unit includes a first driving unit and a second driving unit, and the first driving unit and/or the second driving unit transmit the adjusted brightness control signal to the OLED.
The first driving unit is provided with a plurality of gamma gray curves with different grades, calls the gamma gray curve with the corresponding grade according to the adjusted brightness control signal, and searches the gamma voltage corresponding to the gray grade value on the gamma gray curve, wherein the gamma voltage is used for driving the OLED.
The second driving unit comprises a DC/DC converter, the second driving unit adjusts the output voltage of the DC/DC converter according to the adjusted brightness control signal, and the output voltage is used for driving the OLED.
Preferably, the control unit transmits the luminance control signal to the second driving unit in a pulse width modulation mode that varies an output voltage of the DC/DC converter by adjusting a duty ratio of a pulse width.
It is also preferable that the control unit transmits the luminance control signal to the second driving unit in a serial control manner, a variable resistor is provided in the DC/DC converter, and the serial control manner changes the output voltage of the DC/DC converter by changing the resistance value of the variable resistor.
An OLED display device comprises the driving circuit and a plurality of pixel units, wherein each pixel unit comprises an OLED, and the OLED receives the adjusted brightness control signal output by the driving unit and realizes display.
A method for adjusting the brightness of an OLED display device comprises the following steps:
step S1) calculating the average brightness of a frame image to be displayed according to all sub-image data of the frame image, and adjusting the brightness control signal for displaying each sub-image of the frame image reversely by using the average brightness as the reference brightness;
step S2), the frame image is displayed with the adjusted brightness according to the adjusted brightness control signal.
Preferably, the reference luminance is obtained by counting gray scale values of sub-images of the frame image.
Preferably, when the luminance of the sub-image is greater than the reference luminance by the first preset range, the luminance control signal of the sub-image is correspondingly reduced by the first preset range.
Further preferably, the first preset range is 30% -50%, and the first preset range is 20% -40%.
Preferably, when the luminance of the sub-image is smaller than the second preset range of the reference luminance, the luminance control signal of the sub-image is correspondingly increased by the second preset range.
Further preferably, the second preset range is 30% -50%, and the second preset range is 20% -40%.
The invention has the beneficial effects that: the whole power consumption of the OLED display panel is reduced, and the picture quality is improved.
Drawings
FIG. 1 shows a prior art OLED pixel cell;
FIG. 2 is a schematic view of a gamma curve;
fig. 3 is a schematic structural diagram of an OLED display device in embodiment 1 of the present invention;
fig. 4A illustrates a method for obtaining an adjusted brightness control signal by using a pwm method according to embodiment 1 of the present invention;
FIG. 4B is a schematic diagram of a PWM square wave signal;
fig. 5 shows a method for obtaining an adjusted brightness control signal by using a serial control method in embodiment 2 of the present invention.
In the figure: 1-pixel unit; 2-a control unit; 3-a first drive unit; 4-a second drive unit.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the following describes an OLED driving circuit, an OLED display device, and a method for adjusting the brightness of the OLED display device in detail with reference to the accompanying drawings and the detailed description.
As shown in fig. 1, in the OLED driving circuit, since T2 stably operates in the saturation region when turned on, the saturation current is the current I flowing through the OLEDELObtaining the current I passing through the OLED according to a source-drain current formula of a TFT saturation regionELComprises the following steps:
IEL=1/2*K×(Vdata-Vdd-Vth)2…………（1）
in formula (1), K is a constant related to the structure of T2, Vdata is a voltage from the first driving unit, Vdd is a voltage from the second driving unit, and Vth is a threshold voltage of T2.
From equation (1), the current I through the OLEDELAnd is influenced by Vdata and Vdd. Wherein Vdata is a voltage signal (analog signal) corresponding to an image (digital signal) to be displayed, Vdd is a voltage supplied from a DC/DC converter, and a current I flowing through the OLEDELDetermine its luminous intensityAnd its power consumption.
It should be understood that, because the human eye's ability to recognize the brightness of light is not linear, the Video Electronics Standards Association (VESA) determines a gamma value curve according to the human eye characteristics, so that the designer working in display technology can make the gray-scale image displayed on the display panel become the display image most suitable for the human eye to watch according to the brightness level. However, since the gamma curve defined by VESA is defined in a darkroom (dark) environment, when the display panel is in a very dark environment, the same gray level (gray level) image is displayed, and the human eye can clearly distinguish the distinct and hierarchical gray levels, but when the display panel is in a very bright environment, the human eye cannot clearly distinguish the distinct gray levels from the similar gray level images, which results in the user's perception that the color brightness accuracy of the display panel is not sufficient, and the displayed image becomes more blurred.
In view of the above, the technical idea of the present invention is to change the current I flowing through the OLED by changing the magnitude of Vdata and/or Vdd according to equation (1)ELThat is, by appropriately reducing the value of Vdata and/or Vdd, the display luminance of the entire display panel is reduced, thereby achieving the purpose of reducing the power consumption of the display panel. In actual display, when the image to be displayed is high-brightness, because human eyes are insensitive to the brightness of the image, the proper reduction of the brightness of the image can not generate great visual influence on an observer and can not cause influence on the display effect.
An OLED drive circuit comprising a control unit and a drive unit, wherein:
the control unit is used for calculating the average brightness of a frame of image according to all sub-image data of the frame of image to be displayed, reversely adjusting the brightness control signal for displaying each sub-image of the frame of image by taking the average brightness as the reference brightness, and sending the adjusted brightness control signal to the driving unit;
and the driving unit receives the adjusted brightness control signal and drives the OLED according to the adjusted brightness control signal, so that the frame image is displayed according to the adjusted brightness.
An OLED display device comprises the driving circuit and a plurality of pixel units, wherein each pixel unit comprises an OLED, and the OLED receives the adjusted brightness control signal output by the driving unit and realizes display.
A method for adjusting the brightness of an OLED display device comprises the following steps:
step S1) calculating the average brightness of a frame image to be displayed according to all sub-image data of the frame image, and adjusting the brightness control signal for displaying each sub-image of the frame image reversely by using the average brightness as the reference brightness;
step S2), the frame image is displayed with the adjusted brightness according to the adjusted brightness control signal.
Example 1:
in this embodiment, the OLED display device includes an OLED driving circuit and a plurality of pixel units, each pixel unit includes an OLED, and the OLED receives the adjusted brightness control signal output by the driving unit and implements display. As shown in fig. 3, the OLED driving circuit includes a control unit 2 and a driving unit, wherein the driving unit includes a first driving unit 3 and a second driving unit 4, and the first driving unit 3 and the second driving unit 4 are respectively connected to the OLEDs. The image data of the image to be displayed in the OLED display device includes real-time video data, pre-stored images, graphic data, or other display information.
A method for adjusting the brightness of an OLED display device comprises the following steps:
step S1) calculating the average brightness of a frame image to be displayed according to all sub-image data of the frame image, and adjusting the brightness control signal for displaying each sub-image of the frame image reversely by using the average brightness as the reference brightness;
step S2), the frame image is displayed with the adjusted brightness according to the adjusted brightness control signal.
The control unit 2 calculates the average brightness of the frame image according to all sub-image data of the frame image to be displayed, reversely adjusts the brightness control signal for displaying each sub-image of the frame image by taking the average brightness as the reference brightness, and sends the adjusted brightness control signal to the driving unit. The image to be displayed comprises a plurality of sub-images, the reference brightness is obtained by counting the gray level values of the sub-images of the frame image, by taking 6-bit digital signals as an example, 64 gray level values are obtained, the gray level value of the sub-image is 111111 which is the highest brightness, the gray level value of the sub-image is 000000 which is the lowest brightness, and the reference brightness is obtained by calculating the arithmetic mean value of the gray level values of the sub-images. Of course, the reference luminance may also be calculated by using other statistical methods, for example, a method of calculating a weighted average, and in the method of calculating a weighted average, the weights of the high-luminance gray-level value and the low-luminance gray-level value may be set manually, which is not described herein again.
When the brightness of the sub-image is larger than the first preset range of the reference brightness, the control unit correspondingly reduces the brightness control signal of the OLED for displaying the sub-image by the first preset range; exemplarily, the following steps are carried out: the first preset range is 30% -50%, and the first preset range is 20% -40%.
Further, in order to reduce the image display brightness without losing details of a dark part and affecting the display effect, when the brightness of the sub-image is smaller than a second preset range of the reference brightness, the control unit correspondingly increases the brightness control signal of the OLED for displaying the sub-image by the second preset range; illustratively, the second predetermined range is 30% -50%, and the second predetermined range is 20% -40%. Specifically, the upper limit value and/or the lower limit value of the adjusted brightness range can be flexibly set according to actual needs. In this embodiment, the control unit is a CPU, an MCU, or an FPGA.
And the driving unit receives the adjusted brightness control signal and drives the OLED according to the adjusted brightness control signal, so that the frame image is displayed according to the adjusted brightness. The driving unit includes a first driving unit and a second driving unit, and the first driving unit and/or the second driving unit transmits a signal corresponding to the adjusted luminance to the OLED, so that the OLED displays a sub-image corresponding to the adjusted luminance.
Optionally, a plurality of gamma gray curves with different levels are set in the first driving unit, the first driving unit calls the gamma gray curve with the corresponding level according to the adjusted brightness control signal, and searches for the gamma voltage corresponding to the gray level value on the gamma gray curve, and the gamma voltage is transmitted to the OLED.
The first driving unit adopts a driving chip (driver IC), and a plurality of gamma gray curves with different grades are preset in the driving chip. The gamma curve is a special tone curve, which converts the image digital signal into the analog signal Vdata required by the display panel. The basic formula of gamma conversion is:
s=c(r/max gray(num))γ…………（2）
in the formula (2), c is a constant, r is a gray scale value (r ≧ 0), and num is the number of bits of the gray scale value (e.g., 2)5Bit, 26Bit or 28Bit), γ is the gamma value and s is the brightness level value.
As shown in fig. 2, in the gamma curve graph, the vertical axis is the brightness level of the image, the horizontal axis is the gray scale value, when the gamma value is equal to 1, the gamma curve is a straight line, which indicates that the input gray scale value and the output brightness are linearly related; whereas the gamma value for the display system is higher than 1, depending on the perceptual properties of the human eye for brightness.
In this embodiment, the driving chip retrieves a gamma curve corresponding to the adjusted brightness control signal according to the adjusted brightness control signal sent by the control unit. For example, as shown in fig. 2, when a gamma curve of γ =2.2 is used as a reference curve, a curve a for dimming the output is obtained if the adjusted luminance control signal is a luminance lowering signal, and a curve B for brightening the output is obtained if the adjusted luminance control signal is a luminance raising signal. For example, in fig. 2, when the preset gamma level in the driving unit corresponds to a gamma curve with γ =2.2, for the brightness at the point a of the gamma level value of 32 in fig. 2, the corresponding brightness control signal can be correspondingly adjusted to the brightness at the point b on the gamma curve with the gamma level corresponding to γ =3.0, so as to reduce the display brightness of the image.
Optionally, a gamma gray curve is set in the first driving unit, the first driving unit directly searches for a corresponding gamma voltage according to the adjusted brightness control signal, and the gamma voltage is transmitted to the OLED. Exemplarily, as shown in fig. 2, for the luminance of the point a having the gray level value of 32, the corresponding luminance control signal is adjusted to the luminance of the point c having the same gamma level.
The second driving unit comprises a DC/DC converter, and adjusts the output voltage of the DC/DC converter according to the adjusted brightness control signal to generate corresponding voltage signals of Vdd and Vss. For a PMOS TFT, Vdd passes to the source of OLED drive transistor T2, the drain of T2 is connected to the anode of the OLED, and Vss passes to the cathode of the OLED. That is, when the frame image is bright, the adjusted Vdd value is smaller than the relative Vdd value before adjustment; for example, when the luminance of the sub-image is greater than the reference luminance by a first preset range, the control unit correspondingly reduces the luminance control signal of the OLED for displaying the sub-image by the first preset range; exemplarily, the following steps are carried out: the first preset range is 30% -50%, and the first preset range is 20% -40%.
Further, in order to reduce the image display brightness and not lose the details of the dark portion, and not affect the display effect, when the frame image is dark, the Vdd value after adjustment is made larger than the Vdd value before relative adjustment. For example, when the luminance of the sub-image is smaller than a second preset range of the reference luminance, the control unit increases the luminance control signal of the OLED for displaying the sub-image by the second preset range correspondingly; illustratively, the second predetermined range is 30% -50%, and the second predetermined range is 20% -40%.
In this embodiment, the manner in which the control unit sends the luminance control signal to the second driving unit is a Pulse Width Modulation (PWM) manner, that is, the PWM manner changes the output voltage Vout of the DC/DC converter by adjusting the duty ratio d (duty ratio) of the Pulse Width, so as to change the Vdd voltage at T2 in the OLED display panel, and a specific circuit diagram is shown in fig. 4A, and a PWM square wave signal is shown in fig. 4B. In fig. 4B, the period of the PWM square wave signal is T, and the duty ratio D is the ratio of the time T0 when the signal is high to the period T. The output voltage Vout of the DC/DC converter is proportional to the duty cycle D of the PWM square wave, and the formula is as follows:
Vdd=Vout=D×Vin…………（3）
in formula (3), Vin is the Vdd value corresponding to the luminance before the adjustment of the frame image can be displayed, and the purpose of changing Vdd can be achieved by changing D.
In the case of a white screen or a high-luminance image, Vdata is kept constant, and the Vdd value, i.e., the size of the opening degree when the OLED driving transistor T2 is turned on, is reduced, but the current I flowing through each OLED may be made constantElThe brightness of the picture is relatively reduced, the power consumption of a single OLED is reduced, and the purpose of reducing the power consumption of the whole OLED display panel is achieved; vdata is kept unchanged in the case of a black picture or a low-darkness image, while the Vdd value is increased, i.e., equivalent to the OLED drive transistor T2 being turned onThe size of the opening is not changed, but the current I flowing through each OLED can be enabledELThe brightness of the picture is relatively improved, and the display effect of the OLED display panel is improved.
In this embodiment, the brightness of the image is adjusted by simultaneously adjusting the first driving unit and the second driving unit. Since the power consumption of the OLED is mainly determined by the current I flowing through the OLEDELWhen (Vdata-Vdd) is changed, the corresponding current I flowing through the OLED is induced according to equation (1)ELVaries in magnitude. However, when the adjusted (Vdata-Vdd) is reduced as a whole, the whole luminance is largely uniform when the frame image is displayed. The Vdd, Vdata, and the row select signal Vsel (the same as the control signal in the prior art) make the OLED continuously light up within a frame time, and display the frame image according to the adjusted brightness, thereby achieving the purpose of reducing the overall power consumption of the AM-OLED display panel and improving the picture quality.
Example 2:
the present embodiment is different from embodiment 1 in that the Vdd adjustment manner in the present embodiment is different from that in embodiment 1, in the present embodiment, the manner in which the control unit sends the luminance control signal to the second driving unit is a serial control manner, a rheostat is arranged in the DC/DC converter, and the serial control manner changes the output voltage of the DC/DC converter by changing the resistance value of the rheostat, and a specific circuit diagram is shown in fig. 5.
In fig. 5, the DC/DC converter includes a varistor, and the output of the varistor is Vdd. The brightness adjusting signal sent by the control unit to the DC/DC converter includes resistance information (e.g., ratio information) of the rheostat, and the second driving unit adjusts the resistance of the rheostat according to the resistance information of the rheostat to obtain different divided voltages, and the divided voltages are transmitted to the source of T2. In this embodiment, the value of the Vdd voltage is changed by changing the resistance value of the resistor R1, the output voltage Vdd of the varistor is proportional to the voltage division ratio, and the specific relationship is as follows:
vdd = Vout × voltage division ratio = Vout × [ R2/(R1 + R2) ] … … … … (4)
In the formula (4), R1 and R2 can be in an appropriate ratio according to the actually required voltage, and the voltage division ratio is determined by the luminance control signal of the control unit.
The structure of the OLED display device in this embodiment is the same as that in embodiment 1, and is not described herein again.
Example 3:
the present embodiment is different from embodiment 1 in that the present embodiment adjusts the brightness of an image only in a manner of adjusting the size of Vdata output in the first driving unit.
In this embodiment, the Vdata is adjusted in the same manner as in embodiment 1, that is, when the frame image is bright, the value of the Vdata after adjustment is smaller than the value of the Vdata before relative adjustment; when the frame image is darker, the Vdata value after adjustment is larger than the Vdata value before relative adjustment. Thus, according to equation (1), when Vdata changes, the current I flowing through the OLEDELIs in the same trend as Vdata. I.e., when Vdata is reduced, the corresponding IELIf the brightness of the image is reduced, and the overall power consumption of the OLED display panel is reduced; when Vdata is increased, the image screen brightness is increased and the screen quality is improved.
The structure of the OLED display device in this embodiment is the same as that in embodiment 1, and is not described herein again.
Example 4:
the present embodiment is different from embodiment 1 in that the present embodiment adjusts the luminance of an image only by adjusting the Vdd magnitude output in the second driving unit. In this control mode, the brightness of the same adjusted frame image will have the same trend of change.
In this embodiment, as the adjustment method of Vdd, any one of the pulse width modulation method in embodiment 1 and the serial control method in embodiment 2 can be adopted. In the present embodiment, Vdata is kept unchanged in the case of a white screen or a high-luminance image, and the Vdd value, i.e., the size equivalent to the opening degree when T2 is on, is reduced, but the current I flowing through each OLED may be made constantElThe brightness of the picture is relatively reduced, the power consumption of a single OLED is reduced, and the purpose of reducing the power consumption of the whole OLED display panel is achieved; vdata is kept unchanged in the case of a black picture or a low-darkness image, while the Vdd value, i.e., the value equivalent to the opening degree when T2 is turned on, is increased, but the current I flowing through each OLED can be made to be constantELThe brightness of the picture is relatively improved, and the display quality of the OLED display panel is improved.
The structure of the OLED display device in this embodiment is the same as that in embodiment 1, and is not described herein again.
Embodiments 1-4 adjust the voltage output from the driver chip and/or the DC/DC converter to T2 according to the statistical result of the gray scale value data of the image to be displayed, and compared with the prior art that the power consumption is reduced by controlling the turn-on or turn-off of the TFT to cause the display image to shake, the embodiments of the present invention do not need to turn on or turn off the TFT repeatedly, but adjust the brightness of the image by adjusting the size of Vdata and/or Vdd applied to the TFT, and avoid the display image shake while adjusting the brightness of the image, thereby reducing the power consumption of the display panel and improving the display quality of the OLED display panel.
Meanwhile, it should be understood that the brightness adjusting method of the OLED display device according to the present invention is not only applicable to the OLED pixel unit with the 2T1C structure analyzed in each embodiment, but also applicable to the OLED pixel unit with the improved 2T1C structure.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (17)
1. An OLED driving circuit comprises a control unit and a driving unit, and is characterized in that,
the control unit is used for calculating the average brightness of a frame of image according to all sub-image data of the frame of image to be displayed, reversely adjusting the brightness control signal for displaying each sub-image of the frame of image by taking the average brightness as the reference brightness, and sending the adjusted brightness control signal to the driving unit;
the driving unit receives the adjusted brightness control signal and drives the OLED according to the adjusted brightness control signal;
the driving unit comprises a first driving unit and a second driving unit, and the second driving unit transmits a Vdd signal to the OLED according to the adjusted brightness control signal; or,
the second driving unit transmits a Vdd signal to the OLED according to the adjusted brightness control signal, and the first driving unit also transmits a Vdata signal to the OLED according to the adjusted brightness control signal, so that the frame image is displayed according to the adjusted brightness.
2. The driving circuit according to claim 1, wherein the reference luminance is obtained by counting gray scale values of sub-images of the frame image.
3. The driving circuit according to claim 2, wherein when the luminance of the sub-image is greater than the reference luminance by a first preset range, the control unit decreases the luminance control signal of the OLED for displaying the sub-image by the first preset range accordingly.
4. The driving circuit according to claim 3, wherein the first predetermined range is 30% to 50%, and the first predetermined range is 20% to 40%.
5. The driving circuit according to claim 2, wherein when the luminance of the sub-image is smaller than the second preset range of the reference luminance, the control unit increases the luminance control signal of the OLED for displaying the sub-image by the second preset range accordingly.
6. The driving circuit according to claim 5, wherein the second predetermined range is 30% -50%, and the second predetermined range is 20% -40%.
7. The driving circuit according to claim 1, wherein a plurality of gamma gray curves with different levels are provided in the first driving unit, and the first driving unit calls the gamma gray curve with the corresponding level according to the adjusted brightness control signal and searches the gamma gray curve for a gamma voltage corresponding to the gray level, where the gamma voltage is used for driving the OLED.
8. The driving circuit according to claim 7, wherein the second driving unit includes a DC/DC converter therein, and the second driving unit adjusts an output voltage of the DC/DC converter according to the adjusted brightness control signal, the output voltage being used for driving the OLED.
9. The driving circuit according to claim 8, wherein the control unit sends the luminance control signal to the second driving unit in a pulse width modulation scheme that changes an output voltage of the DC/DC converter by adjusting a duty ratio of a pulse width.
10. The driving circuit according to claim 8, wherein the control unit sends the brightness control signal to the second driving unit in a serial control mode, a rheostat is disposed in the DC/DC converter, and the serial control mode changes the output voltage of the DC/DC converter by changing the resistance value of the rheostat.
11. An OLED display device comprising the driving circuit as claimed in any one of claims 1 to 10, further comprising a plurality of pixel units, each pixel unit including an OLED therein, wherein the OLED receives the adjusted brightness control signal outputted from the driving unit and implements display.
12. A method for adjusting the brightness of an OLED display device is characterized by comprising the following steps:
step S1) calculating the average brightness of a frame image to be displayed according to all sub-image data of the frame image, and adjusting the brightness control signal for displaying each sub-image of the frame image reversely by using the average brightness as the reference brightness;
step S2), receiving the adjusted brightness control signal, and transmitting a Vdd signal to the OLED according to the adjusted brightness control signal and the adjusted brightness control signal; or, transmitting a Vdd signal to the OLED according to the adjusted brightness control signal, and simultaneously transmitting a Vdata signal to the OLED according to the adjusted brightness control signal, so as to display the frame image with the adjusted brightness.
13. The method according to claim 12, wherein the reference luminance is obtained by counting gray scale values of sub-images of the frame image.
14. The method of claim 13, wherein when the luminance of the sub-image is greater than the reference luminance by a first predetermined range, the luminance control signal of the sub-image is correspondingly decreased by the first predetermined range.
15. The method according to claim 14, characterized in that said first preset range is 30% -50% and said first set range is 20% -40%.
16. The method of claim 13, wherein when the luminance of the sub-image is smaller than the second predetermined range of the reference luminance, the luminance control signal of the sub-image is increased by the second predetermined range accordingly.
17. The method according to claim 16, characterized in that said second preset range is 30% -50% and said second set range is 20% -40%.
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