CN114170966B - Image display device and display method thereof - Google Patents
Image display device and display method thereof Download PDFInfo
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- CN114170966B CN114170966B CN202111504071.1A CN202111504071A CN114170966B CN 114170966 B CN114170966 B CN 114170966B CN 202111504071 A CN202111504071 A CN 202111504071A CN 114170966 B CN114170966 B CN 114170966B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/04—Maintaining the quality of display appearance
- G09G2320/041—Temperature compensation
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/04—Maintaining the quality of display appearance
- G09G2320/043—Preventing or counteracting the effects of ageing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
Abstract
The invention discloses an image display device and a display method thereof, wherein the device comprises the following components in turnA pixel circuit, a switching switch and a bias voltage generating circuit connected; the bias voltage generating circuit is used for generating bias voltage VB, the input end of the change-over switch is respectively connected with GND and the bias voltage VB, the output end of the change-over switch is connected with the pixel circuit for switching the GND and the bias voltage VB, and the input ends of the pixel circuit are respectively data signals V DATA The grid electrode is connected with the line scanning signal SELN and the output end of the switch, the output of the pixel circuit is connected with the anode of the OLED device and used for controlling the OLED device to emit light, and the bias voltage VB is used for improving the brightness of the OLED device. According to the invention, no additional transistor is added in the pixel, so that the maximum brightness of the OLED device can be improved under the condition of not changing the power supply voltage.
Description
Technical Field
The invention belongs to the technical field of micro display driving circuits, and particularly relates to an image display device and a display method thereof.
Background
The silicon-based OLED (Organic Light Emitting Diode) micro display is a novel micro display technology, and combines the display technology with the silicon-based integrated circuit technology. Compared with other micro-display technologies, the silicon-based OLED micro-display device has the advantages of active luminescence, high contrast ratio, high response speed, high resolution ratio and the like, and is widely applied to helmet display products and intelligent wearing products.
Fig. 1 is a 2T1C pixel circuit formed by a conventional N-type MOS transistor used in a silicon-based OLED micro-display chip, where MN1 is a driving transistor, MN2 is a switching transistor, and C is a capacitor. Data voltage V DATA The highest voltage value of the switch tube MN2 is limited by the threshold voltage of the switch tube MN2, so that the grid voltage of the drive tube can reach VDD-V TH，MN2 . The driving tube MN1 and the OLED form a source electrode following structure, and the anode voltage of the OLED can reach VDD-V at most TH，MN2 -V TH，MN1 I.e. the highest voltage of the OLED anode relative to the supply voltage VDD, loses the sum of the threshold voltages of the driving transistor MN1 and the switching transistor MN 2. While the OLED cathode voltage remains unchanged, the brightness of the OLED device is determined by the anode voltage, which means that the maximum brightness of the OLED microdisplay is limited.
If the OLED micro-display screen is required to achieve higher brightness, the power supply voltage of the pixel circuit has to be raised, and the reliability of the MOS transistor is affected by the rise of the power supply voltage, and the power consumption of the display is increased. If the P-type MOS tube and the switch tube MN1 are added to form a transmission gate structure, the voltage output to the grid electrode of the driving tube MN1 is not limited by the threshold voltage of the MOS tube, however, the addition of the PMOS tube occupies a larger area in a limited pixel space, so that the pixel size cannot be smaller, and the improvement of PPI (Pixels Per Inch) of the OLED micro-display screen is affected.
On the other hand, the luminance of the OLED light emitting device is greatly affected by temperature, and the higher the temperature, the greater the luminance. If the pixel circuit shown in fig. 1 is adopted, the brightness of the OLED micro-display will have a large difference at different temperatures, which affects the display effect.
Moreover, as the lighting time increases, the OLED device may undergo aging decay, and the internal resistance of the OLED device gradually increases. If the pixel circuit shown in fig. 1 is used, the current flowing through the OLED is gradually reduced due to the increase of the internal resistance of the OELD, and the brightness of the OLED microdisplay is reduced with the increase of the use time, so that the service life is limited.
Disclosure of Invention
The invention aims to: aiming at the problem that the brightness of an OLED device cannot be improved in the prior art, the invention discloses an image display device and a display method thereof, and the maximum brightness of the OLED device can be improved under the condition that the power supply voltage is not changed without adding an additional transistor in a pixel.
The technical scheme is as follows: in order to achieve the above object, the present invention adopts the following technical scheme.
An image display device includes a pixel circuit, a changeover switch and a bias voltage generating circuit which are connected in order; the bias voltage generating circuitThe input end of the change-over switch is respectively connected with the GND and the bias voltage VB, the output end is connected with the pixel circuit for switching the GND and the bias voltage VB, and the input of the pixel circuit is respectively a data signal V DATA The grid electrode is connected with the line scanning signal SELN and the output end of the switch, the output of the pixel circuit is connected with the anode of the OLED device in the effective display area and used for controlling the OLED device to emit light, and the bias voltage VB is used for providing anode voltage compensation of the OLED device and improving the brightness of the OLED device.
Preferably, the pixel circuit includes a driving tube MN1, a switching tube MN2, and a capacitor C, the drain of the switching tube MN2 is connected to the data signal V DATA The grid electrode of the switch tube MN2 is connected with the row scanning signal SELN, and the source electrode of the switch tube MN2 is connected with the upper polar plate of the capacitor C; the grid electrode of the driving tube MN1 is respectively connected with the source electrode of the switching tube MN2 and the upper polar plate of the capacitor C, the drain electrode of the driving tube MN1 is connected with a VDD voltage signal, the source electrode of the driving tube MN1 is connected with the anode of the OLED device, the lower polar plate of the capacitor C is connected with the change-over switch, and the grounding or bias voltage VB is controlled through the switch signal SW.
The bias voltage VB and the internal resistance of the OLED device change to form a positive correlation; when the internal resistance of the OLED device is reduced, the voltage value of the bias voltage VB is also reduced along with the reduction of the internal resistance, and the bias voltage VB is used for realizing the stable brightness of the OLED device when the internal resistance of the OLED device is changed.
Preferably, the change of the internal resistance of the OLED device is related to the ambient temperature and the aging degree of the device, the internal resistance of the OLED device decreases with the increase of the temperature, the internal resistance of the OLED device increases with the decrease of the temperature, and the internal resistance of the OLED device increases with the aging degree of the device.
Preferably, the bias voltage generating circuit is mainly generated by anode voltage of a redundant area OLED array, the redundant area OLED array is the same as the working environment and working time of the OLED device in the effective display area, and a light shielding layer is arranged above the redundant area OLED array and is used for shielding the redundant area OLED array from emitting light.
Preferably, the bias voltage generating circuit comprises a reference current source, a first redundant area OLED array, a second redundant area OLED arrayThe residual area OLED array, an adjusting tube MN3, an operational amplifier and a voltage dividing circuit; the reference current source supplies current to the first redundant area OLED array, and voltage VP is generated at the anode of the first redundant area OLED array; the drain electrode of the adjusting tube MN3 is connected with the power supply VDD, and the source electrode of the adjusting tube MN3 is connected with the anode of the second redundant area OLED array to generate voltage VN; VP and VN are input to an operational amplifier, which outputs a voltage V OP Controlling the output current of the adjusting tube MN3 to make VP and VN equal; operational amplifier output voltage V OP Is input to the voltage divider circuit to generate the bias voltage VB.
Preferably, the bias voltage VB is smaller than the gate voltage threshold voltage V of the driving transistor MN1 TH，MN1 。
An image display method applied to any one of the above image display devices, wherein the data signal V is generated within the effective period of the row scanning signal SELN DATA After the OLED device is transmitted to the pixel circuit, a switching signal SW in a change-over switch is controlled to be changed from a GND to a bias voltage VB, so that the highest voltage of the anode of the OLED device is raised to VB, and the maximum brightness of the OLED device is improved.
Preferably, the bias voltage VB and the internal resistance of the OLED device change to form a positive correlation; when the internal resistance of the OLED device is reduced, the voltage value of the bias voltage VB is reduced along with the reduction of the internal resistance, and the bias voltage VB controls the current of the OLED device to be unchanged, so that the brightness stability of the OLED device at different temperatures is realized.
The beneficial effects are that:
1. according to the invention, no additional transistor is added in the pixel, so that the maximum brightness of the OLED micro-display can be improved under the condition of not changing the power supply voltage;
2. according to the invention, through the bias voltage VB which is in positive correlation with the internal resistance change of the OLED device, the brightness stability of the OLED micro-display screen at different temperatures can be improved, and the brightness decay of the OLED micro-display screen after long-time use can be compensated.
Drawings
Fig. 1 is a conventional pixel circuit diagram of 2T 1C;
fig. 2 is a schematic diagram of an image display device of the present invention;
fig. 3 is a timing chart of the image display device of the present invention;
FIG. 4 is a schematic diagram of a redundant OLED array;
FIG. 5 is one embodiment of a voltage divider circuit;
fig. 6 is a schematic diagram of the general structure of a circuit applied in a silicon-based OLED driving chip according to the present invention.
Detailed Description
An image display device and a display method thereof according to the present invention will be further explained and illustrated with reference to the drawings and embodiments.
As shown in fig. 2, in one embodiment of the present invention, an image display apparatus includes a pixel circuit, a switch, and a bias voltage generating circuit connected in sequence, wherein a driving tube MN1, a switching tube MN2, and an adjusting tube MN3 in the pixel circuit are all N-type MOS tubes; the bias voltage generating circuit is used for generating bias voltage VB, the input end of the change-over switch is respectively connected with GND and the bias voltage VB, the output end of the change-over switch is connected with the pixel circuit for switching the GND and the bias voltage VB, and the input ends of the pixel circuit are respectively data signals V DATA The grid electrode is connected with the line scanning signal SELN and the output end of the switch, the output of the pixel circuit is connected with the anode of the OLED device in the effective display area and used for controlling the OLED device to emit light, and the bias voltage VB is used for providing anode voltage compensation of the OLED device and improving the brightness of the OLED device.
The bias voltage VB and the internal resistance of the OLED device change to form a positive correlation; when the internal resistance of the OLED device is reduced, the voltage value of the bias voltage VB is also reduced along with the reduction of the internal resistance, and the bias voltage VB is used for realizing the stable brightness of the OLED device when the internal resistance of the OLED device is changed. The change of the internal resistance of the OLED device is related to the ambient temperature and the aging degree of the device, the internal resistance of the OLED device is reduced along with the increase of the temperature, the internal resistance of the OLED device is increased along with the decrease of the temperature, and the internal resistance of the OLED device is increased along with the aging of the device.
The bias voltage generating circuit is mainly generated by anode voltages of the redundant area OLED array and the working ring of the OLED device in the effective display areaAnd a shading layer is arranged above the redundant area OLED array and used for shielding the redundant area OLED array from emitting light. The bias voltage generating circuit comprises a reference current source, a first redundant area OLED array, a second redundant area OLED array, an adjusting tube MN3, an operational amplifier and a voltage dividing circuit; the reference current source supplies current to the first redundant area OLED array, and voltage VP is generated at the anode of the first redundant area OLED array; the drain electrode of the adjusting tube MN3 is connected with the power supply VDD, and the source electrode of the adjusting tube MN3 is connected with the anode of the second redundant area OLED array to generate voltage VN; VP and VN are input to an operational amplifier, which outputs a voltage V OP Controlling the output current of the adjusting tube MN3 to make VP and VN equal; operational amplifier output voltage V OP Is input to the voltage divider circuit to generate the bias voltage VB.
In one embodiment, as shown in fig. 4, a redundant area and an effective display area are divided into a silicon-based OLED driving chip, and the redundant OLED array is arranged at the left side of the effective display area of the silicon-based OLED driving chip and divided into two areas with equal area: redundant area 1 and redundant area 2. The same OLED device as the active display area is fabricated in both redundant areas. A light shielding layer is covered over the redundant areas 1 and 2 to shield the OLED devices of the redundant areas from emitting light. The reference current source supplies current to the OLED devices (i.e. OLED x N) within the redundant area 1, generating a voltage VP at the anode of the OLED devices. The drain of the regulator MN3 is connected to the power supply VDD, and the source is connected to the anode of the OLED device (i.e., oled×n) in the redundant area 2, so as to generate the voltage VN. VP and VN are input to an operational amplifier, which outputs a voltage V OP The output current of the regulator MN3 is controlled. When VN is smaller than VP, the operational amplifier outputs high level to the grid electrode of the adjusting tube MN3, the output current of the adjusting tube MN3 is increased, and the voltage of VN is increased; when VN is greater than VP, the operational amplifier outputs low level to the grid of the adjusting tube MN3, the output current of the adjusting tube MN3 is reduced, and the voltage of VN is reduced. Therefore, the level of VN always remains equal to VP. Operational amplifier output voltage V OP Is input to the voltage divider circuit to generate the bias voltage VB.
FIG. 5 is an embodiment of a voltage divider circuit employing a resistive voltage divider structure, outputtingVoltage V B ＝[R B2 /(R B1 +R B2 )]*V OP By reacting R B1 The adjustment of the proportional coefficient of the voltage-dividing circuit can be realized, so that the bias voltage VB is kept in a reasonable range.
FIG. 6 is a schematic diagram showing a general circuit structure of the present invention applied to a silicon-based OLED driving chip, wherein the silicon-based OLED driving chip is provided with a redundancy area, an effective display area and a timing control module, the number of rows of OLED devices in the redundancy area and the effective display area is the same, the timing control module provides a row driving circuit and a column driving circuit for the OLED devices in the effective display area, wherein each row of OLED devices in the effective display area shares a row selection signal SELN in the row driving circuit, and each column of OLED devices in the effective display area shares a data signal V in the column driving circuit DATA All OLED devices in the effective display area are respectively provided with a pixel circuit in the invention, each row of OLED devices in the effective display area share a switch in the invention, and all the switches are connected with a bias voltage generating circuit in the invention, namely when the image display device is applied to a specific silicon-based OLED driving chip (the effective display area in the silicon-based OLED driving chip is n rows and m columns), n switches are corresponding to n pixel circuits. A bias voltage generating circuit is arranged in the silicon-based OLED driving chip to generate a global bias voltage VB. The switch is placed between the row driver circuit and the pixel array (i.e., all OLED devices in the active display area) for voltage switching of the capacitive lower plates of a row of pixels. The number of the change-over switches is equal to the total number of rows of the pixel array, and one change-over switch corresponds to one row of pixels. The control signal SW and the row selection signal SELN of the switch are generated by a row driving circuit in the chip. The switch control signal SW of each row is kept in synchronization with the row selection signal SELN of the row.
The pixel circuit comprises a driving tube MN1, a switching tube MN2 and a capacitor C, wherein the drain electrode of the switching tube MN2 is connected with a data signal V DATA The grid electrode of the switch tube MN2 is connected with the row scanning signal SELN, and the source electrode of the switch tube MN2 is connected with the upper polar plate of the capacitor C; the grid electrode of the driving tube MN1 is respectively connected withThe source of the switch tube MN2 is connected with the upper polar plate of the capacitor C, the drain of the driving tube MN1 is connected with the VDD voltage signal, and the source of the driving tube MN1 is connected with the anode of the OLED device.
The lower plate of the capacitor C is connected to a switch, and the ground or bias voltage VB is controlled by a switch signal SW. When the switch signal SW is set to '0', the lower plate of the capacitor C is grounded; when the switch signal SW is set to '1', the lower plate of the capacitor C is connected to the bias voltage VB. The switch signal SW and the row selection signal SELN are both generated by a timing control module in the silicon-based OLED driving chip.
The switch signal SW in the change-over switch is the data signal V DATA After the voltage is transmitted to the gate voltage of the driving tube MN1, the voltage of the lower polar plate of the control capacitor C is switched from the GND to the bias voltage VB, and then the gate voltage of the driving tube MN1 is raised by the VB in a capacitive coupling mode. The highest voltage at the anode of the OLED device thus also raises VB, and thus the maximum brightness of the OLED device is improved. On the other hand, by adjusting the proportionality coefficient of the voltage dividing circuit, the bias voltage VB is smaller than the gate voltage threshold voltage V of the driving transistor MN1 TH，MN1 The OLED micro-display screen can be ensured not to be started under the full black picture.
When the ambient temperature increases, the internal resistance of the OLED device decreases, and in order to maintain the current in the OLED device unchanged, the anode voltage VP of the OLED device driven by the reference current source decreases with the increase in temperature. Under the action of a negative feedback loop formed by the adjusting tube MN3, the OLED device and the operational amplifier, the output voltage V of the operational amplifier OP The output current of the regulator MN3 decreases to equalize VN and VP. Bias voltage VB is output voltage V of operational amplifier OP Generated by a voltage dividing circuit and output voltage V of an operational amplifier OP Proportional to the ratio. Therefore, the bias voltage VB has a negative temperature characteristic, and decreases with an increase in temperature.
The larger the voltage value of the bias voltage VB, the more the anode voltage of the OLED device rises, and the larger the magnitude of the luminance rise of the OLED light emitting device. Conversely, the smaller the voltage value of the bias voltage VB, the smaller the magnitude of the luminance improvement of the OLED light emitting device. At a high temperature, the voltage value of the bias voltage VB is smaller, and the anode voltage of the OLED light emitting device is raised to a smaller extent, so that the brightness of the OLED device at a high temperature is suppressed. At low temperature, the voltage value of the bias voltage VB is larger, and the anode voltage of the OLED light-emitting device is raised to a larger extent, so that the brightness of the OLED device at low temperature is raised to a larger extent. Therefore, the negative temperature characteristic of the bias voltage VB is helpful to realize the temperature compensation of the OLED device, so that the brightness stability of the OLED micro-display screen at different temperatures is improved.
In the case where the internal resistance of the OLED device increases due to aging, the anode voltage VP of the OLED device driven by the reference current source increases. Under the action of a negative feedback loop formed by the adjusting tube MN3, the OLED device and the operational amplifier, the output voltage V of the operational amplifier OP The output current of the regulator MN3 increases to keep VN and VP equal. Bias voltage VB and output voltage V of operational amplifier OP In proportion, the bias voltage VB increases with the aging of the OLED device. The bias voltage VB increases and the anode voltage of the OLED device increases. Accordingly, luminance decay of the OLED device after a long period of use can be compensated.
Fig. 3 is a timing diagram of a pixel circuit of the present invention. During the active period of the row scan signal SELN, the switch tube MN2 is turned on, and the data signal V DATA To the gate of the driving transistor MN1, at this time, the switching signal SW is set to '0', and the lower plate voltage of the capacitor C is grounded. Subsequently, the row scan signal SELN is set to '0', the switching transistor MN2 is turned off, the switching signal SW is set to '1', and the lower plate voltage of the control capacitor C is switched from GND to VB. Because the capacitor has the function of maintaining the voltage difference, the gate voltage of the driving transistor MN1 is increased by VB, i.e. the gate voltage of the driving transistor MN1 becomes V DATA +VB. Accordingly, the current flowing through the OLED device increases, and the maximum brightness of the OLED microdisplay is improved. The value range of the bias voltage VB is 0-V by adjusting the proportionality coefficient of the voltage dividing circuit TH，MN1 Make it smaller than the gate voltage threshold voltage V of the driving transistor MN1 TH，MN1 The OLED micro-display screen can be ensured not to be started under the full black picture.
The bias voltage VB is a voltage with negative temperature characteristics, namely the voltage value of the bias voltage VB is reduced along with the rise of temperature. The lifting amplitude of the grid voltage of the driving tube is reduced along with the temperature rise, and the highest voltage of the anode of the OLED device is also reduced along with the temperature rise, so that the condition that the brightness of the OLED micro-display screen is greatly influenced by the temperature is improved.
The bias voltage VB and the internal resistance change of the OLED device are in positive correlation. Under the condition that the internal resistance of the OLED device is reduced due to the increase of the ambient temperature, the voltage value of the bias voltage VB is reduced along with the increase of the temperature, and the anode voltage of the OLED device is also reduced along with the increase of the temperature, so that the condition that the brightness of the OLED micro-display screen is greatly influenced by the temperature is improved. Under the condition that the internal resistance of the OLED device is increased due to aging, the bias voltage VB is increased along with the aging of the OLED device, and the anode voltage of the OLED device is also increased, so that the brightness compensation of the OLED device after aging is realized.
The foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention. The invention is not related in part to the same as or can be practiced with the prior art.
Claims (6)
1. An image display device characterized by: the pixel circuit, the switching switch and the bias voltage generating circuit are sequentially connected; the bias voltage generating circuit is used for generating bias voltage VB, the input end of the change-over switch is respectively connected with GND and the bias voltage VB, the output end of the change-over switch is connected with the pixel circuit for switching the GND and the bias voltage VB, and the input ends of the pixel circuit are respectively data signals V DATA The grid electrode is connected with a line scanning signal SELN and a switching switch output end, the output of the pixel circuit is connected with the anode of the OLED device in the effective display area and used for controlling the OLED device to emit light, and the bias voltage VB is used for providing anode voltage compensation of the OLED device and improving the brightness of the OLED device;
the bias voltage generating circuit comprises a reference current source, a first redundant area OLED array, a second redundant areaThe OLED array, the adjusting tube MN3, the operational amplifier and the voltage dividing circuit; the reference current source supplies current to the first redundant area OLED array, and voltage VP is generated at the anode of the first redundant area OLED array; the drain electrode of the adjusting tube MN3 is connected with the power supply VDD, and the source electrode of the adjusting tube MN3 is connected with the anode of the second redundant area OLED array to generate voltage VN; VP and VN are input to an operational amplifier, which outputs a voltage V OP Controlling the output current of the adjusting tube MN3 to make VP and VN equal; operational amplifier output voltage V OP Inputting the voltage to a voltage dividing circuit to generate bias voltage VB;
the bias voltage VB and the internal resistance of the OLED device change to form a positive correlation; when the internal resistance of the OLED device is reduced, the voltage value of the bias voltage VB is also reduced along with the reduction of the internal resistance, and the bias voltage VB is used for realizing the stable brightness of the OLED device when the internal resistance of the OLED device is changed;
the change of the internal resistance of the OLED device is related to the ambient temperature and the ageing degree of the device, the internal resistance of the OLED device is reduced along with the increase of the temperature, the internal resistance of the OLED device is increased along with the decrease of the temperature, and the internal resistance of the OLED device is increased along with the ageing of the device.
2. An image display device according to claim 1, wherein the pixel circuit comprises a driving transistor MN1, a switching transistor MN2, and a capacitor C, the drain of the switching transistor MN2 being connected to the data signal V DATA The grid electrode of the switch tube MN2 is connected with the row scanning signal SELN, and the source electrode of the switch tube MN2 is connected with the upper polar plate of the capacitor C; the grid electrode of the driving tube MN1 is respectively connected with the source electrode of the switching tube MN2 and the upper polar plate of the capacitor C, the drain electrode of the driving tube MN1 is connected with a VDD voltage signal, the source electrode of the driving tube MN1 is connected with the anode of the OLED device, the lower polar plate of the capacitor C is connected with the change-over switch, and the grounding or bias voltage VB is controlled through the switch signal SW.
3. The image display device according to claim 1, wherein the bias voltage generating circuit is mainly generated by an anode voltage of a redundant area OLED array, the redundant area OLED array has the same working environment and working time as those of the OLED devices in the effective display area, and a light shielding layer is disposed above the redundant area OLED array for shielding the redundant area OLED array from emitting light.
4. An image display device according to claim 1, wherein the bias voltage VB is smaller than a gate voltage threshold voltage of the driving transistor MN1。
5. An image display method applied to an image display device according to any one of claims 1 to 4, characterized in that: during the active period of the row scanning signal SELN, the data signal V DATA After the OLED device is transmitted to the pixel circuit, a switching signal SW in a change-over switch is controlled to be changed from a GND to a bias voltage VB, so that the highest voltage of the anode of the OLED device is raised to VB, and the maximum brightness of the OLED device is improved.
6. The image display method according to claim 5, wherein the bias voltage VB is in positive correlation with the change in internal resistance of the OLED device; when the internal resistance of the OLED device is reduced, the voltage value of the bias voltage VB is reduced along with the reduction of the internal resistance, and the bias voltage VB controls the current of the OLED device to be unchanged, so that the brightness stability of the OLED device at different temperatures is realized.
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Citations (6)
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| CN114170966A (en) | 2022-03-11 |
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