JP5153331B2 - Active matrix image display device and control method thereof - Google Patents

Description

The present invention relates to a display device, a display control circuit, and an image display method. More particularly, the present invention relates to an active matrix image display device. Active matrix image display device
Each light source is periodically addressable by the value of the display signal, said value representing a plurality of light sources which form an array of light sources arranged in rows and columns representing display data for the image period ,
A light source connected in series with each light source of the array, forming a series of modulators, having a source, drain and gate, capable of conducting drain current, greater than the trip threshold voltage of said modulator; A current modulator for supplying power to the light emitting source with a voltage between one of the equal drain and source and the gate;
A charge storage capacitor capable of maintaining a control voltage at the gate of each modulator during the image period;
A selection means capable of selecting light sources in one and the same row, and-an output connected to one of the respective terminals in series of the light sources in said column, and an inverting input (-), a non-inverting input (+) And means for supplying power to the light source having at least one operational amplifier having an output and controlling a corresponding regulating device, each column having an output to the regulating device Means for driving the light emission of the light emitting source, which is connectable to the gates of the adjusting devices of the row when the connected light emitting source is selected and applies the control voltage to the gates;

  Image display devices are widely used in all kinds of applications such as automobiles, digital cameras, or mobile phones.

  There is known a display device in which a light emission source is formed based on an organic light emitting cell, such as an OLED (organic light emitting diode) display device.

  In particular, passive matrix OLED display devices are already widely available on the market. However, passive matrix OLED display devices consume a large amount of electrical energy and have a short lifetime.

  Active matrix OLED display devices have integrated electronics and have many advantages such as low power consumption, high resolution, video rate compatibility, and longer lifetime than passive matrix OLED display devices.

  Conventionally, active matrix OLED display devices have an active matrix formed especially by an array of light emitting sources. Each light emitting source is associated with a pixel or sub-pixel of the image to be displayed and is addressed by an array of column electrodes and row electrodes via an addressing circuit.

  The addressing circuit has in particular a current regulator. The current regulator can drive the current passing through the light source and thus the brightness of each pixel or sub-pixel of the display device.

  In an active matrix, these current regulators are thin film transistors (TFTs) made from polysilicon by low temperature polysilicon (LTPS) technology based on an amorphous silicon layer. However, this technique introduces a local spatial variation in the trip threshold voltage between these transistors. Such variations are due to the fact that the bonding and size of silicon particles is not well controllable during the crystallization stage of amorphous silicon (Si-a) to polysilicon (Poly-Si).

  As a result, TFT transistors that are powered by the same supply voltage and controlled by the same display current or voltage produce currents of different strengths. Furthermore, the trip threshold voltage of the thin film transistor tends to change non-uniformly with time.

  Also, since the light emitting source emits light intensity that is directly proportional to the current passing through the light emitting source, the non-uniformity of the trip threshold of these transistors causes unevenness in the brightness of the display device having such transistors. This results in a difference between the luminance levels and apparent visual discomfort for the user.

  In order to limit this discomfort, various circuits have been proposed to compensate for the trip threshold voltage.

  For example, Patent Document 1 describes a display device having a compensation circuit. The compensation circuit has an operational amplifier. The output of the operational amplifier is connected to the gate of the regulator, and the non-inverting input of the operational amplifier is connected in series with the anode of each light source in one and the same column and is associated with the light source. Does not have.

However, this device is extremely complex. This device in particular requires the control of a large number of switches.
EP 1340019

  An object of the present invention is to realize a simple display device.

  For this purpose, an object of the present invention is an active matrix image display device, wherein one of a non-inverting input and an inverting input of an operational amplifier is connected to an output of a power supply means, and one of the light emitting sources is selected. In this case, an active matrix image display device is characterized in that a feedback loop of the operational amplifier is formed together with the gate of the adjusting device connected to the output of the operational amplifier.

  Therefore, when compared with the pixel circuit described in Patent Document 1 cited above, the input of the operational amplifier is not connected to the series common terminal of the light source-regulator, but the light source-regulator series terminal. Connected to one of these.

  The present invention can therefore command the current to supply power to the light sources in each column to supply power to the light sources at least during the addressing period of the light sources. An advantage of the present invention is that this instruction is executed without measuring this current.

  Each light source is periodically addressed multiple times for each image in each image to be displayed or according to the display scheme used.

  According to particular embodiments, the device has one or more of the following features.

  One of the terminals in series of the light emitting source-regulating device of the column is connected to the output of the power supply means and corresponds to the drain or source of the regulating device.

The output of the operational amplifier 35 produces a control signal V _c that depends on the display signals V _{data 22} , V _{data 23} and the trip threshold voltage V _th of the adjusting device 26 connected to the selected light source 22, 23, 24. Supply. The control signal V _c can charge the capacitor 30.

  One of the non-inverting input (+) and the inverting input (−) of the operational amplifier is connected to the output and can receive a signal that depends on the value of the display signal. The value of the display signal is for addressing the light source selected from the column.

  According to a first main variant, the power supply means further comprises a drive signal generator. The drive signal generator continuously supplies discontinuous power to each of the light sources in a column by supplying a drive signal to one of the series terminals of the light source-regulator corresponding to the light source. Suitable for The drive signal depends on the value of the display signal, the value of the display signal being for addressing to a light emitting source selected from the column. Therefore, the drive signal generator supplies power to the light emitting source one after another only during the addressing period of the light emitting source.

  The power supply means therefore generally further comprises a holding signal generator. The function of the holding signal generator is to supply power to the light sources in the column outside the addressing phase of the light sources. Such an apparatus requires switching means for toggling the power supply of the light source between the drive signal generator and the hold signal generator. In practice, therefore, there are generally two additional switches in each addressing circuit. One connects the light source-regulator series of the circuit to an address generator during the addressing phase. The other is to connect the light source-regulator series in series to the holding signal generator outside the addressing stage.

  As described above, the output of the drive signal generator is connected to one of the non-inverting input (+) and the inverting input (−) of the operational amplifier. During the column addressing only, the same output is also connected to the corresponding light source-regulator series terminal via a switch closed for addressing.

  The drive signal generator includes a display voltage generator and a resistive element connected in series. The voltage generator is also suitable for generating a voltage that depends on the value of the display signal. The value of the display signal is for addressing the light source selected from the column.

  The resistance may be an internal resistance of a voltage generator.

  Due to the series resistance, the value of the current flowing through the resistor, and thus the light source, does not depend on the trip threshold voltage of the regulator associated with the light source during the light source addressing period. The value of the current is therefore, on the one hand, proportional to the difference between the value of the display signal and the value of the voltage applied to the non-inverting input of the operational amplifier and the other one of the inverting input. On the other hand, the value of the current is inversely proportional to the resistance value of the resistive element.

  According to a second preferred main variant, the power supply means comprises a drive signal generator. The drive signal generator can continuously supply power to the entire set of column light sources by supplying one identical drive signal to one of the series terminals of the column light source-regulator. It is. The drive signal depends on the sum of the values of the display signals that are pre-addressed and currently addressed for the entire set of light sources in the column during the image period. Advantageously, the additional holding signal generator required in the first main variant described above is not necessary.

  The drive signal generator includes a display voltage generator and a resistive element connected in series. The voltage generator is also suitable for generating a voltage that depends on the sum of the values of display signals that are pre-addressed and currently addressed across the set of light sources in the column during the current image period. .

  The resistance may be an internal resistance of a voltage generator. Due to the series resistance, the value of the current flowing through the resistor, and thus the light source, does not depend on the trip threshold voltage of the regulator associated with the light source. The value of the current is therefore, on the one hand, proportional to the difference between the sum of the values of the display signal and the voltage value applied to the non-inverting input of the operational amplifier and the other one of the inverting input. On the other hand, the value of the current is inversely proportional to the resistance value of the resistive element.

  The second main variant does not have any switching means between the output of the power supply means and the series light-emitting source-adjustment device terminals. Advantageously, the addressing circuit of the light source is simple compared to the first main variant. This is because it is not necessary to alternately switch one of the series terminals of the light source-conditioning device between the different drive signal generators as required in the first main variant.

  The output of the drive signal generator is connected on the one hand to one of the non-inverting input (+) and the inverting input (-) of the operational amplifier, on the other hand, without the intermediate switch, in series with the light source-conditioning device. Connected to the corresponding terminal.

  The voltage generator is connected to the resistive element and supplies a drive current obtained based on the following relationship.

ここで、Ｒは抵抗性要素である。
Ｖ_{ｒｅｆ ｎ}は、発光源ｎと関連付けられた基準電圧である。
Ｖ_{ｄａｔａ ｎ}は、発光源ｎにアドレス指定されたディスプレイ電圧の値である。
Ｐは、列内の発光源の総数である。

Here, R is a resistive element.
V _{ref n} is a reference voltage associated with the light source n.
V _{data n} is the value of the display voltage addressed to the light source n.
P is the total number of light sources in the column.

  The driving means further includes a reference signal generator capable of supplying a reference signal to the other one of the inverting input (−) and the non-inverting input (+) of the operational amplifier.

  Each light source exhibits individual electrical and / or optical properties. The value of each reference signal depends on the electrical and / or optical characteristics.

  Each light source is associated with a color light emission. The reference signal can be adjusted according to the color assigned to the selected light source.

  A given white color is usually labeled with a white chromaticity coordinate. With the present invention, the colored performance of the device can be easily optimized. Also, aging differences between the light emitting sources can be compensated.

  The light sources are grouped into a plurality of adjacent light sources that are each suitable for emitting different colors. For each of the plurality of light sources, the reference signal is the plurality of light sources such that addressing of the light sources by one identical display signal value causes the white light emission by the plurality of light sources. Assigned to various light sources.

  The drive means further comprises data storage means capable of storing display signal values addressed to each light source during an image period.

The subject of the invention is also a method of an active matrix image display device. Active matrix image display device
Each light source is periodically addressable by the value of the display signal, the value of the display signal forming an array of light sources arranged in rows and columns representing the data of the display during the image period Multiple light emitting sources,
One of the drains or sources of each regulator is connected in series to the light source of the array and has two terminals; a current regulator with source, drain and gate, forming a series of regulators;
A selection means capable of selecting the light source of the row;
A charge storage capacitor capable of maintaining a control voltage at the gate of each adjustment device during the image period;
-Means for driving the light emission of the light source of the column comprising at least one operational amplifier having an inverting input, a non-inverting input and an output;
The method
Sending a selection signal (V _select ) to the row of light emitting sources by the selection means;
Applying a drive signal (I) to one of the series terminals of the light source of the column by means of the drive means; and a control signal (V _c ) by the drive means to the selected light emission. Applying to the gate of each regulator connected to a source, the method comprising:
The non-inverting input and the inverting input of the operational amplifier connected to the output of the power supply means of the light source and with the gate of the regulator connected to the output of the operational amplifier and the row of the light source selected And a step of forming a feedback loop of the operational amplifier.

  According to an embodiment, the method has the property that the drive signal depends on the sum of the values of the display signals addressed to the entire set of light sources in the column during the image period.

  The invention will be better understood with reference to the following description and figures, given by way of non-limiting example only.

  FIG. 1 shows an image display device according to the invention. The image display device has an active matrix 1 driven by the control means 2.

  As is known, the active matrix 1 has a plurality of addressing circuits 3, 4, 5, 6. Each addressing circuit is associated with a light source (not shown) and is distributed according to rows and columns.

  The active matrix control means 2 includes a control system 7, a selection control circuit 8 and an addressing control circuit 10.

  The control system 7 is capable of receiving an image display signal, processes the image display signal (eg, decodes and decompresses the image display signal), provides a synchronization signal to the selection control circuit 8, and addresses the display signal. This is supplied to the designated control circuit 10.

The selection control circuit 8 is connected to the plurality of row electrodes 14 and 15. Each row electrode is associated with a row of light emitting sources. When receiving the synchronization signal, the circuit 8 is suitable for continuously generating the selection pulse V _select at each row electrode 14. First, the circuit 8 sequentially selects the entire set of the addressing circuits 3 and 6 in the row at the scanning frequency corresponding to the image period. The selection pulse V _select is logical data for selecting a light emission source.

  The addressing control circuit 10 is connected to a plurality of column electrodes 16 and 17 and a plurality of drive electrodes 18 and 19. Each row electrode and drive electrode is associated with a column 21A, 21B of light emitting sources. The address designation control circuit 10 includes a plurality of address designation drive units 20A and 20B. Each addressing drive unit is capable of addressing and power to the addressing circuits 3, 4, 5, 6 in the columns 21A, 21B via the column electrodes 16, 17 and the drive electrodes 18, 19. Can be supplied.

  Row electrodes 14, 15, column electrodes 16, 17 and drive electrodes 18, 19 select, address, and power a particular addressing circuit of the set of circuits 3, 4, 5, 6 of the display device, respectively. Makes it possible to supply.

Therefore, by selecting only the row electrodes 14 of the display device, and by activating the transmittable drive unit 20A of the control voltage V _c to the electrode 16 and the driving current I of the column 21A to the electrode 18, the row electrodes 14 and the circuit 3 which is the intersection of the electrodes 16 and 18 in that column of the light source 21A are activated. At the same time, other circuits 4,. . . 5 is activated.

  FIG. 2 shows the light emitting sources 22, 23, 24. Each light-emitting source is similar to the addressing driver 20A in the light-emitting source column 21A and the selection control circuit 8 in the addressing circuits 3, 4, 5, and 6, and the addressing circuit for the pixel set in the light-emitting source column 21A. 3, 4, 5.

  The light emitting sources 22, 23, and 24 of the display device are organic light emitting diodes. The light emission sources 22, 23, and 24 have an anode and a cathode. The structure of these diodes is “conventional”. That is, the anode is in the lower layer, which is the substrate side, and the cathode is in the upper layer.

  These light sources emit light that is directly proportional to the current passing through them. Each light source constitutes a basic pixel. These basic pixels have the same characteristics (same color light emission) as in the case of a monochrome screen, or constitute three sets of red, green and blue in the case of a color screen.

  Within the scope of the present invention, the set of light sources 22, 23, 24 in a row is associated with sub-pixels of the same color. Three adjacent rows of light sources are sequentially associated with red, green and blue. The bias voltage required for the same value of current to flow through the light sources 22, 23, 24 depends on the current-voltage characteristics of these light sources, and in particular is associated with the light sources 22, 23, 24 in each column. It changes according to the color of the subpixel.

  Since the addressing circuits 3, 4 and 5 of the active matrix 1 are the same, only the circuit 3 will be described in detail.

  The circuit 3 includes a current modulator 26, a switch 28 composed of a transistor, a storage capacitor 29, and a power supply electrode 30.

The current adjusting device 26 and the switch 28 are thin films based on a technique using polysilicon (Poly-Si), amorphous silicon (a-Si), or single crystal silicon (μc-Si) deposited as a thin film layer on a glass substrate. It is a transistor. Such a component has three electrodes. That is, the drain electrode and the source electrode, and a gate electrode control voltage V _c is applied. A modulated current called a drain current flows between the drain electrode and the source electrode.

  The source of the modulation device 26 is connected to the anode of the light source 22, and the modulation device 26 and the light source 22 are connected in series. One of the serial terminals 31, that is, here the drain of the modulation device 26 is connected to the drive electrode 18. The gate of the modulation device 26 is connected to the first terminal of the capacitor 29 on the one hand, and connected to the current transmission electrode (drain or source) of the switch 28 via the electric wire 33 on the other hand. The other current transmission electrode (drain or source) of the switch 28 is connected to the column electrode 16. The gate of the switch 28 is connected to the row electrode 14. The second terminal of each capacitor 29 in the set of circuits 3, 4, and 5 in the column 21 </ b> A is connected to the power supply electrode 30. Finally, each other terminal 32 in series of the modulator-light source, that is, here the cathode of the light source 22 is connected to the power supply electrode 34. The two power electrodes 30 and 24 may be connected to the same potential together by a conductor (not shown).

  The modulation device 26 shown in FIG. 2 is n-type. That is, during operation, the drain current of the modulation device 26 flows between the drain and the source. It should be noted that such a device can also be used to drive a p-type TFT having a diode of conventional structure, as shown in FIG.

  Capacitor 29 is placed between the gate and source of modulator 26, and a substantially constant control voltage is applied to the gate of modulator 26 for a time interval corresponding to image periods T1, T2. Maintain the brightness of the light source during the period.

  The power supply electrode 30 can provide the voltage necessary to bias one of the terminals of the capacitor 29 to a desired potential, as is known in the art.

A driver 20A is applied to compensate for the trip threshold voltage _Vth of each regulator 26 in the set of addressing circuits 3, 4, 5 in column 21A in a feedback loop as described below, and column 21A of light emitting sources. Electric power is supplied to the light emission sources 22, 23, and 24.

  For this purpose, the drive unit 20A includes an operational amplifier 35 having an inverting input −, a non-inverting input +, and an output. The output of the amplifier 35 is connected to the column electrode 16. The non-inverting input + of the amplifier 35 is connected to the drive electrode 18 and reliably supplies power to the light emitting sources of the column via a regulator associated with them. Accordingly, the non-inverting input + is simultaneously connected to the anodes of the light emitting sources 22, 23, and 24 in the column 21A via the modulation device 26 associated with the anode.

  Therefore, the feedback loop of the amplifier 35 comprises the addressing circuits 3, 4, 5 of the light source column 21A by the drive electrode 18, the modulator-light source series terminal 31, the modulator device 26, the line 33 and the column electrode 16. Formed each time the switch 28 is closed. It should be noted that the series terminal 31 of the modulator-light source that forms part of the feedback loop is one of the drains or sources of this series regulator in the embodiment shown in FIGS. It corresponds to one.

The amplifier 35 is operable with feedback and thus compensates for the trip threshold voltage _Vth of each modulator 26 of the addressing circuits 3, 4, 5 of the light source column 21A, as will be described below. Is possible.

Furthermore, the drive unit 20A can be addressed and can be powered by the drive current I to the light emitting sources 22, 23, 24 of the column 21A. This current I depends on the sum of the values of the display voltages V _{data 22} , V _{data 23} , V _{data 24} addressed to the light emitting sources 22, 23, 24 of this column 21A.

  For this purpose, the drive unit 20 </ b> A includes a drive current generator 36 and a reference voltage generator 38. The drive current generator 36 and the reference voltage generator 38 are connected to the non-inverting input + and the inverting input − of the amplifier 35, respectively.

  The current generator 36 is formed by a variable voltage generator 39 connected in series with the resistor 40. The drive electrode 18 is connected to the output of the resistor 40, the node 42 and thus forms one of the outputs of the current generator 36.

The generator 39 is a variable voltage generator. The voltage of the generator 39 changes according to the values of the display signals V _{data 22} and V _{data 23} . The values of the display signals V _{data 22} , V _{data 23} are for addressing the light sources 22, 23 as will be explained in the following description.

The generator 38 is a generator adapted to supply a reference voltage that is fixed during the setting of the display device and is unique to each column. As a variant, it is also possible to use a variable voltage generator. The type of reference voltage follows the column 21A of the light source to be addressed. This will be clarified in the following description.
The output of the generator 38 is connected to the inverting input − of the amplifier 35, optionally via a resistor 44. The resistor 44 is not absolutely necessary for the operation of the drive unit 20A. Resistor 44 simply has the advantageous function of balancing between the two inputs of operational amplifier 35.

  Also optionally, the capacitor 46 is connected between the inverting input − of the amplifier 35 and the output of the amplifier 35. Resistor 44 and capacitor 46 constitute a compensation array that can advantageously improve the accuracy and stability of the circuit.

  The drive unit 20 </ b> A also includes a data storage means 48 and a control module 50 for the generators 38 and 39.

The storage means 48 has a database 52. The database 52 on the one hand stores the values of the display signals V _{data 22} , V _{data 23} addressed to each light source 22, 23 in the column 21 A during the previous image period T 1, on the other hand, the value is Stores data identifying or indicating the addressed light sources 22, 23.

  These storage means 48 also have a directory 54 for storing reference voltage values to be associated with the set of light sources in column 21A. This value depends on the colors associated with the light sources 22 and 23 in the column 21A, red, green or blue.

  Light sources associated with different colors exhibit different current-voltage characteristics as can be seen in FIG. Therefore, it is necessary to apply different voltages to the terminals of the red light source and the blue light source to obtain the same luminance and the same value of current passing through these light sources.

  Here, the reference voltage value of the directory 54 in each column is fixed according to the color of the light source in the column 21A. This process is performed at the factory during the setting of the display device performed prior to shipment. These reference values are defined to compensate for variations between the current-voltage electrical and / or emission characteristics of the various light sources of the device, as described below.

In general, there are three different reference voltage values since these characteristics mainly depend on the color of the emission of the light source. The first value V _{ref. R} is common to the set of red emission sources in the first column. The second value V _{ref. G} is common to the set of green emission sources in the second column. And the third value V _{ref. B} is common to the set of blue emission sources in the third column. According to a more complex variant, these reference voltage values are specific to each column of light sources, and even if the various columns of light sources have the same emission color, the current-voltage electrical current between them. Compensates for variations in characteristics and / or emission characteristics.

Only when the display signal V _data addressed to the light source is greater than the reference voltage V _ref associated with the light source, current can flow through the light source. In order to avoid having to use an excessively high value display signal, it is desirable to determine the lowest possible reference voltage value while setting up the display device and at the same time obtain the desired compensation.

  The control module 50 is connected to the storage means 48, retrieves the information of the means and records it in the means.

  Furthermore, the module 50 can receive display signals transmitted by the system 7 and control the generators 38 and 39 according to the information stored in the signals and storage means 48.

  In operation, the circuits 8 and 10 can sequentially address, supply and select a set of light sources 22, 23, 24 of the matrix 1.

  When the power is turned on, at the start of the first image frame T1, during the stage 60 shown in FIG. 3, the drive unit 20A and the circuit 8 control the lighting of the first light source 22 in the column 21A. This stage 60 has stages 62 to 69.

During step 62, circuit 8 generates a _select pulse V _{select 22} at electrode 14. This pulse is shown in FIG. 4 and can close the switch 28.

  At the same time, during step 64, module 50 queries directory 54 to determine the reference voltage associated with the light source 22 column. This reference voltage depends in particular on the color of the subpixels associated with the light source 22, 23, 24 of the column.

During step 66, module 50 controls generator 38. Therefore generator 38 supplies a reference voltage _{V ref 21A} for the constant and has a value equal to _{V ref a,} column 21A emission source.

At the same time, during the step 68, module 50, from the control system 7, the identifier of the light emitting source 22 to the display voltage V _{data 22} to be addressed value V _a and the light emitting source 22 addressed associated with the value Or receive location. The module 50 then records in the database 52 this value Va and the identifier of the light source to which that value is addressed.

At the same time, during stage 69, module 50 controls generator 39. Thus, as shown in FIG. 6, the generator 39 generates the value V _a of the display voltage V _{data 22} to be addressed to the light source 22.

The generator 38 therefore provides a reference voltage value V _{ref 21A} equal to V _{ref a} to the inverting input − of the amplifier 35. At the same time, as shown in FIG. 6, the generator 39 applies a voltage V _{data 22} equal to V _a to the resistor 40. The voltage _{V a} produces a drive current I _{= I 22.} The drive current I is taken into the drain of the adjusting device 26 via the drive electrode 18. This drive current I = I ₂₂ is shown in FIG. 7 and is determined by the following relationship.

ここで、Ｖ_ａは、生成器３９により生成されるディスプレイ電圧Ｖ_{ｄａｔａ ２２}の値である。Ｖ_{ｒｅｆ ａ}は、生成器３８により生成される基準電圧値である。そしてＲは、抵抗４０の値である。留意すべき点は、任意の抵抗４４が、電流の計算に入っていないことである。これは、少なくとも駆動電流Ｉ_２２に関しては、如何なる有意な電流も当該抵抗を通じて流れないためである。

Here, V _a is a value of the display voltage V _{data 22} generated by the generator 39. V _{ref a} is a reference voltage value generated by the generator 38. R is the value of the resistor 40. It should be noted that any resistor 44 is not included in the current calculation. This is because at least for the drive current I ₂₂ , no significant current flows through the resistor.

By considering that the modulation device 26 of the circuit 3 connected in series to the first light source 22 operates in the saturation mode (V _gs −V _th <V _ds ) of the modulation device, the modulation device is The drain current passing therethrough is equal to the drive current I and has the following relationship.

ここで、Ｉ_２２は、変調装置２６を通過するドレイン電流である。Ｖ_ｇｓは、変調装置２６のゲート及びソースの間の電圧である。ｋは、変調装置２６の固有の特性に依存する定数である。Ｖ_ｔｈは、変調装置２６のトリップスレッショルド電圧である。そしてＶ_ｄｓは、変調装置２６のドレイン及びソースの間の電圧である。

Here, I ₂₂ is a drain current passing through the modulation device 26. V _gs is the voltage between the gate and source of the modulator 26. k is a constant that depends on the specific characteristics of the modulator 26. V _th is the trip threshold voltage of the modulator 26. V _ds is a voltage between the drain and the source of the modulation device 26.

Due to the feedback loop of the present invention, the potential difference between the inverting input − and the non-inverting input + in the amplifier 35 disappears. The voltage at node 42 is therefore equal to V _{ref a} . The amplifier 35 therefore supplies the control voltage V _c to the gate of the modulator 26. The value of the control voltage V _c is automatically adjusted so that the current I = (V _a −V _{ref a} ) / R flows through the series modulation device 26 and the light source 22. Therefore, the current I is independent of the trip threshold voltage V _th of the modulator device 26. Compensation of the trip threshold voltage of the light source 22 of the device is thus obtained directly without measuring the current passing through the light source.

The value V _gs is automatically estimated from the value of the control voltage V _c .

The value of the control voltage V _c depends not only on the display signal V _{data 22} of the light source and the reference voltage V _{ref a} associated with the light source, but also on the trip threshold voltage V _th of the modulator 26.

When the value V _a of the display voltage V _{data 22} is applied by the generator 39, the voltage V _{ref a} is applied by the generator 38, so that the trip threshold voltage V _th is specific to the configuration characteristics of the modulator 26. As such, the control voltage V _c applied to the gate of the modulator 26 is adapted and modulated by the amplifier 35 to compensate for the trip threshold voltage V _th of the modulator.

Thus, the control voltage V _{c at} the output of the amplifier 35 accurately adapts to the voltage required to address the light source 22 with the value V _a of the display voltage V _{data 22} . Further, the control voltage V _c is adapted regardless of the value of the trip threshold voltage V _th of the adjusting device 26 and even if the voltage changes with time.

This control voltage V _c is then maintained at the gate of the modulator 26 by the capacitor 29 for the remainder of the image period. At the same time, the switch 28 of the circuit 3 is opened again as is known in the art.

  During stage 70, the second light source 23 in row 21A is lit. Step 70 includes steps 72-79.

During step 72, the circuit 8 supplies a selection pulse V _{select 23} to the row electrode 15 as shown in FIG.

During step 74, the module 50 determines the reference voltage V _{ref 21A} associated with the column of light sources 23 by querying the storage means 48. Since the light emitting source 23 is in the same column as the light emitting source 22, and thus these light emitting sources are associated with the same color, the value V _{ref a} of the reference voltage V _{ref 21 A} is the first light emitting source 22. _Is equal to the value V _{ref a of} the reference voltage V _{ref 22} generated during the addressing.

During step 76, module 50 controls reference generator 38. Thus, the reference generator 38 generates the voltage V _{ref a} determined during step 74.

At the same time, during step 77, the module 50 receives from the control system 7 the value V _b of the display voltage V _{data 23} to be addressed to the light source 23, as shown in FIG. The identifier or position of the emitted light source 23 is received.

During step 78, module 50, advance in the same column of the light emitting source 22 to the addressed display voltage _{V data 22} value _{V a} and the display voltage _{V data 23} to be addressed in the next light emitting source 23 The value _Vb is added up.

Next, during step 79, module 50 controls generator 39. The generator 39 therefore supplies _a display voltage equal to the voltage value calculated during step 78, ie V _a + V _b .

Accordingly, the new drive current is I = I ₂₃ + I ₂₂ , shown in FIG. 9, flows through the resistor R and the drive electrode 18, and is determined by the following equation. The common point of the resistor R and the drive electrode 18 is connected to the non-inverting input + of the amplifier 35.

発光源２２の発光に必要な電流Ｉ_２２＝（Ｖ_{ｄａｔａ ２２}−Ｖ_{ｒｅｆ ａ}）／Ｒは、変調装置２６に電力を供給し続ける。特に、同一の制御電圧Ｖ_ｃは、回路３のスイッチ２８が開かれているので、増幅器３５によってではなく、キャパシター２９により、第１の回路３の変調装置２６のゲートにおいて維持される。この電圧Ｖ_ｃは、段階６０の間に設定された強度に等しくなるよう、発光源２２に電力を供給する電流の強度を指示する。

The current I ₂₂ = (V _{data 22} −V _{ref a} ) / R required for light emission from the light source 22 continues to supply power to the modulator 26. In particular, the same control voltage V _c is maintained at the gate of the modulator 26 of the first circuit 3 by the capacitor 29 rather than by the amplifier 35 because the switch 28 of the circuit 3 is open. This voltage V _c indicates the intensity of the current supplying power to the light emitting source 22 to be equal to the intensity set during step 60.

The remaining current I ₂₃ = I−I ₂₂ = V _{data 23} / R of the drive electrode 18 supplies power to the adjusting device 26 of the second circuit 4.

Since the switch 28 of the circuit 4 is closed during the stage 72, the column electrode 16, the amplifier 35, the drive electrode 18, the modulator-light source series terminal 31, the regulator 26 of the second circuit 4, and The line 33 of the second circuit 4 forms a new feedback loop for the amplifier 35. Therefore, the control voltage V _c exiting the amplifier 35 compensates for the trip threshold voltage V _th of the adjusting device 26 of the second circuit 4 as described above.

The display device addressing method according to the invention is similar to steps 72-79 by addressing the entire set of light sources 22, 23, 24 in column 21A during the same first image frame of period T1. This step is continued for each addressing circuit 3, 4, 5 in column 21A. In particular, database 52 then displays the p-value V _data.V of the display voltage addressed to each light source in column 21A during this first image frame _{. n} . Module 50 also controls generator 39 such that generation 39 provides the following display voltage.

駆動電極１８を通過する駆動電流Ｉは、従って次の一般的な関係により定められる。

The drive current I passing through the drive electrode 18 is thus determined by the following general relationship:

ここで、
Ｉは、駆動部２０Ａにより生成される駆動電流であり、駆動電極１８を通じて流れる。
Ｉ_ｎは、発光源ｎを通じて流れる電流である。
Ｖ_{ｄａｔａ ｎ}は、発光源ｎにアドレス指定された画像ディスプレイ電圧の値である。
Ｖ_{ｒｅｆ ２１Ａ}は、列２１Ａの発光源に関連付けられた基準電圧の値である。
ｐは、列２１Ａ内の発光源の数である。

here,
I is a drive current generated by the drive unit 20 </ b> A and flows through the drive electrode 18.
I _n is the current flowing through the light emitting source n.
V _{data n} is the value of the image display voltage addressed to the light source n.
V _{ref 21A} is the value of the reference voltage associated with the light source in column 21A.
p is the number of light emitting sources in column 21A.

  After the image period T1, the entire set of light sources 22, 23, 24 in column 21A is illuminated according to the display voltage representing the image data to be displayed by that light source. Circuit 3 is also addressed a second time during stage 80. This stage 80 includes stages 82 to 89.

Steps 82, 84, 86, 87, 88 and 89 are identical to steps 62, 64, 66, 68 and 69, respectively, and will not be described again. In this second addressing of circuit 3, these stages are adapted and the module 50
- from the database 52 receives the value _{V a} of the display voltage _{V data 22} in advance addressed to emission source 22 during the previous image frame, and the light emitting source 22 to be addressed display voltage V _{'data Twenty-} two new values V ′ _a are received from the system 7 and recorded in the database 52 instead of the old values V _a .
Subtract the old value V _a from the sum shown below and add the new value V ′ _a .

次に、モジュール５０は、生成器３９を制御する。従って生成器３９は、次に示す和の計算された新たな値に等しいディスプレイ電圧を供給する。

Next, the module 50 controls the generator 39. Therefore, the generator 39 supplies a display voltage equal to the calculated new value of the following sum:

回路４の第２のアドレス指定は、同様の方法で実行される。画像期間Ｔ２の後、列２１Ａの発光源２２、２３、２４のセット全体は、当該発光源により表示されるべき新たな画像データを表すディスプレイ電圧に応じて発光される。

The second addressing of the circuit 4 is performed in a similar manner. After the image period T2, the entire set of light sources 22, 23, 24 in row 21A is illuminated according to a display voltage representing new image data to be displayed by the light source.

  The other image frame then follows the previous image frame. For example, the image frame T2 follows the image frame T1.

In an exemplary embodiment of the invention, as shown in FIG. _6, the value of the reference voltage is equal to _{V ref a V ref 22} has an inverting input of the amplifier 35 - is applied to, and equal to _{V a} display voltage V The value of _{data 22} is addressed to the light source 22 during the image period T1. The value of the voltage V _a during the new image period T2, continues to be addressed.

  Accordingly, the following sum is not changed during the second image period T2.

また前の画像期間Ｔ１の間に回路３のキャパシター２９により格納された電荷は、変更されない。

Also, the charge stored by the capacitor 29 of the circuit 3 during the previous image period T1 is not changed.

Similarly, during the lighting phase of the second light source 23 (not shown in FIG. 3), the value of the display voltage addressed to the light source 23 is V _b during the first and previous image periods T3. (FIG. 6) and zero during the next image period T4.

Therefore, the following sum is simply reduced by the value _Vdata .

従って、回路４のキャパシター２９に蓄積された全電荷は、除去される。また従って、値Ｖ_ｄａｔａは、点灯していないダイオードの特性である、ゼロ電位を示す。

Accordingly, all charges accumulated in the capacitor 29 of the circuit 4 are removed. Accordingly, the value V _data indicates zero potential, which is a characteristic of a diode that is not lit.

  Advantageously, it can be seen that this device and method of the display allows the initialization phase to be avoided before setting up the addressing circuits 3, 4, 5.

Advantageously, a reference voltage applied to one of the inputs of the amplifier 35 and a reference voltage specific to each column of light sources, or a reference voltage applied to a group of columns, here different color groups, is advantageous. In particular, it is possible to reduce the power consumption of the display device. In particular, the reference voltage value is not only in such a way as to compensate for variations in the electrical and / or emission characteristics of the light sources of the various columns, but in such a way as to obtain the lowest possible average value of the reference voltage in each column. If selected, the value _{Vdata of the} display signal is shifted and reduced accordingly. As a result, the power to be generated by the power generator 39 is reduced.

  In the case of an OLED display device having the conventional structure of FIG. 2, the anodes of the light sources 22, 23 form an interface for the active matrix 1 (diode having a “conventional” structure). The drain (if n-type) or source (if p-type) of the modulation device 26 is thus connected to the drive electrode 18. The cathodes of the light emission sources 22 and 23 are connected to the electrode 34. The drive electrode 18 is therefore connected to the node 42. At node 42, one of the outputs of power supply means 36 and the non-inverting input + of amplifier 35 are brought together.

  However, as shown in FIG. 11, the invention also applies to a display device having a so-called inverse structure in which the cathode of the light emitting source forms an interface for the active matrix. The drain (if p-type) or source (if n-type) of the modulation device 26 is thus connected to the drive electrode 18. The anodes of the light sources 22 and 23 are connected to the electrode 34. The drive electrode 18 is connected to the node 42. At node 42, one of the outputs of the power supply means 36 and in this case the inverting input − of the amplifier 35 are brought together. This circuit is much more stable than the circuit described with reference to a diode having a conventional structure. Advantageously, any resistor 44 or balancing and / or compensation capacitor 46 is no longer necessary. The display signal therefore corresponds to a negative voltage. Also, the diode current is “drawn” from the power electrode 34.

  As a variant, the generator 38 can change the reference voltage according to the aging of the light source, or can lower the reference voltage in the low power consumption mode.

  As a variant, a reference voltage is associated with each column of light emitting sources. In this case, the storage means 48 has a database capable of storing a reference voltage value to be applied to each column of light emitting sources. The driver 50 is suitable for searching the reference voltage value to be applied to the inverting input − of the amplifier 35 through this database according to the identifier or position of the column of the light source.

According to the present invention, the difference (V _{ref x} −V _{ref y} ) is determined in such a way as to compensate for the difference in the electrical and / or emission characteristics of the various columns of the light source while setting up the device before shipment. It is desirable.

  The part of the display device according to the third variant is shown in FIG.

  The electronic components of this display device are the same as the electronic components of the display device shown in FIG. 2, and are denoted by the same reference numerals.

  This display device has an addressing circuit 103. The address designation circuit 103 is connected to the address designation drive unit 20A on the one hand via the column electrode 16 and on the other hand via the selection circuit 8 via the row electrode 14.

  The circuit 103 is suitable for addressing the light source 22 and supplying power. The cathode of the light emission source 22 is connected to the power supply electrode 34.

  The circuit 103 includes a current modulator 26, a switch 28 including a transistor, a storage capacitor 29, and a ground electrode 110.

  The drain of the modulation device 26 is connected to the anode of the light source 22, and the modulation device 26 and the light source 22 are connected in series. The gate of the modulation device 26 is connected to the first terminal of the capacitor 29 on the one hand, and connected to the current transmission electrode (drain or source) of the switch 28 via the electric wire 33 on the other hand. The other current transmission electrode (drain or source) of the switch 28 is connected to the column electrode 16. The gate of the switch 28 is connected to the row electrode 14. A second terminal of the capacitor 29 is connected to the ground electrode 110. The gate of the modulation device 26 is connected to the drain of the switch 108 on the one hand, and connected to the current transmission electrode (drain or source) of the switch 106 via the electric wire 33 on the other hand. The source of the switch 108 is connected to the ground electrode 110. The gate of the switch 108 is connected to the row electrode 14. The other current transmission electrode (drain or source) of the switch 106 is connected to the column electrode 18. The gate of the switch 106 is connected to the row electrode 14.

  The drive unit 20A is partially shown. The drive unit 20A has the same elements as the drive unit shown in FIG. 2 and operates in the same manner.

  The drive electrode 18 is connected to the inverting input of the operational amplifier 35 and the resistor 40.

  The gate of the column electrode 16 is connected to the output of the operational amplifier 35.

The driver 20A continuously supplies discontinuous power to each of the light emission sources 22 of the circuit 103, and supplies a current I ₂₁ to one of the series terminals of the light emission source 22-modulator 26, thereby providing a column. Suitable for addressing 21A.

  The non-inverting input of operational amplifier 35 is suitable for receiving a reference voltage for light emitting source 22 in column 21A. The value of the reference voltage depends on the color of the subpixel associated with the light source 22 in the column.

A display voltage V _data to be addressed to the light source 22 is applied to the resistor 40. This voltage generates a drive current that is applied to the current transfer electrode of the switch 106.

  During the refresh period of the addressing circuit 103, the row electrode 14 is in a logic state 0, so that the switches 28 and 106 are closed and the switch 108 is open.

The feedback loop of the amplifier 35 is formed by the drive electrode 18, the switch 106, the modulation device 26 and the switch 28. This feedback loop stabilizes the current I _{21 A} through the drive electrode 18. Therefore, the current satisfies the following formula.
I _21A = (V _21A −V _ref ) / R
The trip threshold voltage at the gate of modulator 26 is compensated independently of the characteristics of modulator 26 by amplifier 35 operating in feedback mode.

  The voltage at the gate of modulator 26 is then stored in capacitor 29.

During the accumulation period of current I _{21 A} , the row electrode 14 switches to a logic state 1 so that the switches 28 and 106 are open and the switch 108 is closed.

  Advantageously, the voltage at the drain, source and date electrodes of the modulator 26 does not change during the transition from the refresh period to the accumulation period. Accordingly, the same current flows through the light emitting source 22 during the transition from the refresh period to the accumulation period.

  Advantageously, this device according to the third embodiment of the invention finally allows the current flowing through the light source 22 to be controllable. The current flowing through the light source 22 creates a detailed grid scale, uniform light intensity, and low noise, even on a high resolution screen.

  Advantageously, the time required to set up the display device is short compared to a display device without feedback.

  Advantageously, the display device allows a large dispersion of the characteristics and in particular the threshold voltage of the modulator device 26.

1 is a schematic view of a display device according to the present invention. FIG. 2 is a schematic view of a portion of the display device shown in FIG. 1. It is a chart figure which shows the step of the control method by this invention. 4 is a graph showing time characteristics of a selection voltage applied to a selection electrode of a first addressing circuit of a display device according to the present invention. 6 is a graph showing time characteristics of a selection voltage applied to a selection electrode of a second addressing circuit of a display device according to the present invention. FIG. 4 represents the time characteristics of the display voltage generated by the drive signal generator for addressing in different consecutive addressing circuits of one and the same column of the display device according to the invention, in particular in the first and second circuits. It is a graph. It is a graph showing the time characteristic of the drain current which flows through the modulation apparatus of a 1st addressing circuit. 4 is a graph showing a time characteristic of a drain current flowing through a modulation device of a second addressing circuit of a display device according to the present invention. 4 is a graph illustrating a time characteristic of a driving current generated by a driving unit of a display device according to the present invention. FIG. 3 is a schematic view of a first variant embodiment of the portion of the display device shown in FIG. 2. FIG. 6 is a schematic view of a second variant embodiment of the part of the display device shown in FIG. 2. 4 is a graph having curves representing the current passing through various light sources of a display device according to the present invention as a function of the voltage applied to the terminals of the light sources. FIG. 6 is a schematic view of a third variant embodiment of the portion of the display device shown in FIG. 2.

Claims (13)

An active matrix image display device comprising:
A plurality of light emitting sources forming an array of light emitting sources distributed in rows and columns, each light emitting source being periodically addressable by a value of a display signal, said value being an image A plurality of light emitting sources representing data of the display of the period;
-A light source-a current modulator connected in series with each light source of the array to form a set of current modulators, having a source, drain and gate and supplying power to the light source A current modulation device in which a drain current is passed so that a voltage between one of the drain and source and the gate is equal to or higher than a trip threshold voltage of the current modulation device;
A charge storage capacitor capable of maintaining a control voltage at the gate of each current modulator during the image period;
A selection means capable of selecting light sources in the same row;
Means for driving the light emission of the light source, each column having an output connected to one of the respective terminals of the light source- current modulator set of the column for supplying power to the light source Light-emission driving means for controlling adjustable power supply means and at least one operational amplifier for controlling a corresponding current modulator and having an inverting input, a non-inverting input, and an output; When a light emission source connected to the current modulator is selected, it can be connected to the gate of each current modulator in the column so as to apply the control voltage to the gate;
A non-inverting input and an inverting input of the operational amplifier so as to form a feedback loop of the operational amplifier together with the gate of the current modulator connected to the output of the operational amplifier when one of the light emitting sources is selected. one of the is connected to the output of the adjustable power supply means, said adjustable power supply means, said during the image period, the variable voltage generator for supplying continuous power to the entire set of the origination source of the column An active matrix image display device , wherein the voltage of the variable voltage generator varies as a function of the value of the display signal . One of the terminals of each of the light emitting source- current modulation device pairs in the column is connected to the output of the adjustable power supply means and corresponds to the drain or source of the current modulation device, The apparatus of claim 1. One of the non-inverting input and the inverting input of the operational amplifier is connected to the output of the adjustable power supply means and can receive a signal depending on the value of the display signal, the value from the column Device according to claim 1 or 2, characterized in that it is for addressing a selected light source. The variable voltage generator is continuous across the entire set of light sources in the column by providing the same drive signal to one of the respective terminals of the light source- current modulator set in the column. to supply power, the driving signal depends on the sum of the values of said column light emitter display signal currently addressed to the entire set of between pre addressed and the image period, wherein Item 4. The apparatus according to any one of Items 1 to 3. The drive generator has a display voltage generator and a resistive element connected in series, and the voltage generator is suitable for generating a voltage that depends on a sum of values of the display signal, the value 5. The apparatus of claim 4 , wherein is currently addressed to the entire set of light emitters in a column during a pre-addressed and image period. 6. A device according to claim 5 , characterized in that it does not have any switching means between the output of the adjustable power supply means and each terminal of the light source- current modulator set of the column. The display voltage generator is connected to the resistive element and has the following relationship:

Supply the drive current obtained on the basis of
R is a resistive element;
V _ref is the reference voltage associated with light source n, and V _{data n} is the value of the display voltage addressed to light source n, and P is the total number of light sources in the column. A device according to claim 5 or 6 , characterized in that Said drive means is characterized by further having an inverting input and non-inverting reference generator capable of supplying a reference signal to one of the inputs of the operational amplifier, according to any one of claims 1 to 7 Equipment. 9. A device according to claim 8 , characterized in that each light source exhibits an individual electrical and / or optical characteristic and the value of each reference signal depends on the electrical and / or optical characteristic. 10. Apparatus according to claim 8 or 9 , characterized in that each light source is associated with a color light emission and the reference signal is modifiable according to the color assigned to the selected light source. . The light sources are grouped into a plurality of adjacent light sources suitable for emitting different colors, and for each of the plurality of light sources, the reference signal is applied to various light sources of the plurality of light sources. 10. A device according to claim 8 or 9 , characterized in that addressing of the light source by means of two identical display signal values is assigned to cause white light emission by the plurality of light sources. It said driving means during the image period, characterized by further comprising a data storage means capable of storing the value of the display signal that is addressed to each of the light sources, according to any one of claims 1 to 11 Equipment. A control method for an active matrix image display device, comprising:
The active matrix image display device includes:
A plurality of light emitting sources forming an array of light emitting sources distributed in rows and columns, each light emitting source being periodically addressable by a value of a display signal, said value being an image period A plurality of light sources representing the display data of
One of the drain or source of each current modulator is connected in series with the light source of the array so as to form a light source- current modulator having a source, drain and gate and having two terminals. A current modulator;
A selection means capable of selecting the light source of the row;
A charge storage capacitor capable of maintaining a control voltage at the gate of each current modulator during the image period;
Means for supplying power to the light source, and means for driving the light emission of the light sources of the column, comprising at least one operational amplifier having an inverting input, a non-inverting input and an output,
The method
Sending by the selection means a selection signal to a row of light sources;
Applying a driving signal by said driving means to one of the respective terminals of the light-emitting source- current modulator set of columns;
Applying a control signal to the gate of each current modulator connected to the selected light source by the driving means;
The method
One of a non-inverting input and an inverting input of the operational amplifier connected to the output of the adjustable power supply means of the light-emitting source with the gate of the current modulator connected to the output of the operational amplifier And selecting a row of light emitting sources so as to form a feedback loop of the operational amplifier,
The method of controlling an active matrix image display device, wherein the drive signal depends on a sum of display signal values addressed to the entire set of light sources in the column during an image period.

Images