WO2004019310A2 - Display device - Google Patents

Display device Download PDF

Info

Publication number
WO2004019310A2
WO2004019310A2 PCT/IB2003/003277 IB0303277W WO2004019310A2 WO 2004019310 A2 WO2004019310 A2 WO 2004019310A2 IB 0303277 W IB0303277 W IB 0303277W WO 2004019310 A2 WO2004019310 A2 WO 2004019310A2
Authority
WO
WIPO (PCT)
Prior art keywords
current
current path
coupled
control amplifier
display device
Prior art date
Application number
PCT/IB2003/003277
Other languages
French (fr)
Other versions
WO2004019310A3 (en
Inventor
Adrianus Sempel
Pieter J. Snijder
Remco Los
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Priority to AU2003247108A priority Critical patent/AU2003247108A1/en
Priority to JP2004530422A priority patent/JP2005536771A/en
Priority to EP03792541A priority patent/EP1532610A2/en
Priority to US10/525,141 priority patent/US20050285821A1/en
Publication of WO2004019310A2 publication Critical patent/WO2004019310A2/en
Publication of WO2004019310A3 publication Critical patent/WO2004019310A3/en

Links

Classifications

    • 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
    • G09G3/2007—Display of intermediate tones
    • G09G3/2011—Display of intermediate tones by amplitude modulation
    • 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
    • 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
    • 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]
    • G09G3/3216—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 a passive matrix
    • 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]
    • G09G3/3275—Details of drivers for data electrodes
    • G09G3/3283—Details of drivers for data electrodes in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving
    • 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
    • G09G3/3233—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 with pixel circuitry controlling the current through the light-emitting element
    • G09G3/3241—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 with pixel circuitry controlling the current through the light-emitting element the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror

Definitions

  • the invention relates to a display device comprising at least one picture element and a display driver device comprising a driving transistor to be connected in series with the picture element.
  • Such display devices are increasingly based on electroluminescence-based semiconducting organic materials, also known as light emitting diodes (polyLEDs or
  • the display devices may either luminesce via segmented pixels (or fixed patterns) but also display by means of a matrix pattern is possible.
  • the adjustment of the diode current generally determines the intensity of the light to be emitted by the pixels.
  • Suitable fields of application of the display devices are, for example, mobile telephones, organizers, etc.
  • a display device of the type described in the opening paragraph is described in USP 6.014.119.
  • the current through a LED is adjusted by means of current control.
  • a current driver comprising a bipolar transistor and a resistor is provided as part of a driving circuit.
  • MOS- or TFT- transistors may be used.
  • the current has to be substantially constant for a certain gray value. This is the reason why the transistors are used in the constant current region.
  • a high drain-source voltage or emittor -collector voltage in the case of bipolar transistors
  • the high drain-source voltage or emittor -collector voltage in the case of bipolar transistors
  • the display driver comprises means for monitoring and controlling the current in said first current path.
  • a controlling connection of the driving transistor is coupled to an output of a control amplifier each of the input connections of the control amplifier being coupled to the first and second current path respectively.
  • the control amplifier By comparing the currents in the first and second current path the control amplifier now forces the current in the first current path to draw a certain current, while the drain-source voltage (compliance voltage) may be lower than necessary for use in the saturation region. This leads to lower power dissipation.
  • the control amplifier can be realized in many different ways as known in the art (comparators, differential amplifiers, etc.).
  • suitable for active driving the current in the first current path is controlled by charge control e.g. by a charge stored by means of a current having passed in a second circuitry part.
  • Figure 1 shows diagrammatically a display device according to the invention
  • Figure 2 shows a part of a display driver device
  • Figure 3 shows a first embodiment of a display driver device according to the invention
  • Figure 4 shows transistor characteristics of the transistors used in the embodiments of Figures 2, 3 while Figures 5 and 6 shows further embodiments of a display driver device according to the invention and
  • Fig. 1 shows diagrammatically an equivalent circuit diagram of a part of a display device 1 according to the invention.
  • This display device comprises a matrix of (P) LEDs or (O) LEDs 4 with n rows (1, 2, ..., n) and m columns (1, 2, ..., m).
  • This device further comprises a row selection circuit 6 and a data register 5.
  • the selection of a row takes place by means of the row selection circuit 6 via the lines 3, in this example by providing them with the required selection voltage (passive addressing).
  • the current source 10 which may be considered to be an ideal current source, is switched on by means of the data register 5, for example via (not shown) switches.
  • the value of the current is determined by the contents of the data register and is supplied to the LEDs 4 via data lines 2.
  • the current switch 10 maybe of a simple type comprising just one transistor and one resistor. As explained in the introduction, to make the bias of the transistor less sensitive to variations in the drain voltage due to variations in for instance the forward characteristics of the pixel diodes or the supply voltage of the driver, the high drain-source, needed then, increases power dissipation.
  • Figure 2 shows a known device comprising a first current path (transistor 19 and LED 4).
  • the current I 0 flows in the LED 4 and determines the light intensity of the picture element.
  • the dashed line 21 schematically depicts the display area in Figure 2.
  • a second current path comprises a current source (a transistor 11 and a resistor 22) and a current mirror input stage, comprising a diode, realized by short-circuiting the gate terminal 14 and the drain terminal 15 of transistor 13 (and if necessary a further resistor 23).
  • a voltage on gate terminal 16 determines the current 1; in this second current path. Since the transistors 13, 19 (together with the resistor 23, and if necessary a further resistor 24) may be considered as a current mirror the current I 0 in the first current path is coupled to the current I, in a ratio, which ratio is determined by the k-factors of both transistors.
  • N ⁇ s Ncom the drive voltage (N gs - Nth, N th : threshold voltage) of transistor 19 has to be small.
  • a resistor 23, 24 may be incorporated as is shown by dashed lines.
  • FIG 3 shows a preferred embodiment of a device according to the invention comprising a first current path (transistor 19 and LED 4) again.
  • the current I 0 flows in the LED 4 and determines the light intensity of the picture element.
  • the dashed line 21 schematically depicts the display area in Figure 2.
  • the first and second current paths are now coupled to each other via the control amplifier 25.
  • the control amplifier 25 measures the output current l 0 via resistor 24(R 2 ), and compares it via the voltage over resistor 24 to the current I; as measured via resistor 23 (Rij.
  • the invention is applicable to both active and passive devices, matrix and segmented display devices.
  • active matrices as shown in Figure 5, which represents a single (sub)picture element, extra switches, such as (TFT) switches 28, 29, 30, 33 and 35 are used to select the picture element and charge an extra capacitor 26.
  • TFT time division multiple access
  • transistor 19 and switches 28 and 29 are conducting as determined by selection line 2.
  • the circuitry comprising resistor 24, capacitor 26, transistor 19 and switches 28 and 29 determines current path, which is controlled by data input 8 to define a current L; ata .
  • Capacitor 26 is charged to a voltage determined by the voltage across resistor 24. After selection (during a hold period), switches 28, 29, 35 are non-conducting, while the switches 30, 33 now are conducting. The charge remaining on capacitor 26 now controls the control amplifier 25 in such a way that the feedback mechanism maintains the current in current source 19,24 (and consequently in the LED 4 at I data .
  • the extra (TFT) switches 28, 29, and 31 are used to select the picture element and charge the extra capacitor 26.
  • both transistor 19 and switches 28 and 29 are conducting again as determined by selection line 8.
  • the circuitry comprising resistor 24, capacitor 26, transistor 19 and switches 28 and 29 again determines a current path, which is controlled by selection line 2 to define a current L ata again via data input 8 and charge capacitor 26.
  • both switches 28, 29 are non-conducting, while the switch 31 now connects capacitor 26 to control amplifier 25 (positive input).
  • the charge remaining on capacitor 26 controls the control amplifier 25 again in a similar way as in the previous example.
  • the protective scope of the invention is not limited to the embodiments described. Instead of measuring the currents I 0 and Iiin the first embodiment, fractions of these currents can be measured.
  • the invention is also applicable to field emission devices and other devices based on current driving.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Control Of El Displays (AREA)
  • Amplifiers (AREA)

Abstract

In a driver for a luminescent display feedback techniques, in particular techniques using a control amplifier (25), are used to reduce the power supply voltage.

Description

Display device
The invention relates to a display device comprising at least one picture element and a display driver device comprising a driving transistor to be connected in series with the picture element.
Such display devices are increasingly based on electroluminescence-based semiconducting organic materials, also known as light emitting diodes (polyLEDs or
OLEDs). The display devices may either luminesce via segmented pixels (or fixed patterns) but also display by means of a matrix pattern is possible. The adjustment of the diode current generally determines the intensity of the light to be emitted by the pixels.
Suitable fields of application of the display devices are, for example, mobile telephones, organizers, etc.
A display device of the type described in the opening paragraph is described in USP 6.014.119. In said document, the current through a LED is adjusted by means of current control. For each column of pixels in a matrix of luminescent pixels a current driver comprising a bipolar transistor and a resistor is provided as part of a driving circuit. In stead of the bipolar transistors MOS- or TFT- transistors may be used.
To obtain reproducible gray scales the current has to be substantially constant for a certain gray value. This is the reason why the transistors are used in the constant current region. In this case a high drain-source voltage (or emittor -collector voltage in the case of bipolar transistors) is used. This makes the bias of the transistor less sensitive to variations in the drain voltage due to variations in for instance the forward characteristics of the pixel diodes or the supply voltage of the driver. On the other hand the high drain-source voltage (or emittor -collector voltage in the case of bipolar transistors) increases power dissipation.
It is, inter alia, an object of the present invention to provide a display device of the type described in the opening paragraph in which the power dissipation due to the drain- source voltage (compliance voltage) adds to a lesser extent to the total power dissipation. To this end in a display device according to the invention the display driver comprises means for monitoring and controlling the current in said first current path.
In a preferred embodiment a controlling connection of the driving transistor is coupled to an output of a control amplifier each of the input connections of the control amplifier being coupled to the first and second current path respectively. By comparing the currents in the first and second current path the control amplifier now forces the current in the first current path to draw a certain current, while the drain-source voltage (compliance voltage) may be lower than necessary for use in the saturation region. This leads to lower power dissipation. The control amplifier can be realized in many different ways as known in the art (comparators, differential amplifiers, etc.).
In a further embodiment, suitable for active driving the current in the first current path is controlled by charge control e.g. by a charge stored by means of a current having passed in a second circuitry part.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. In the drawings:
Figure 1 shows diagrammatically a display device according to the invention, Figure 2 shows a part of a display driver device,
Figure 3 shows a first embodiment of a display driver device according to the invention,
Figure 4 shows transistor characteristics of the transistors used in the embodiments of Figures 2, 3 while Figures 5 and 6 shows further embodiments of a display driver device according to the invention and
The Figures are diagrammatic; corresponding components are generally denoted by the same reference numerals.
Fig. 1 shows diagrammatically an equivalent circuit diagram of a part of a display device 1 according to the invention. This display device comprises a matrix of (P) LEDs or (O) LEDs 4 with n rows (1, 2, ..., n) and m columns (1, 2, ..., m). This device further comprises a row selection circuit 6 and a data register 5. Externally presented information 7, for example, a video signal, is processed in a processing unit 8 which, dependent on the information to be displayed, charges the separate parts 5-1, ..., 5-n of the data register 5 via lines 9.
The selection of a row takes place by means of the row selection circuit 6 via the lines 3, in this example by providing them with the required selection voltage (passive addressing).
Writing data takes place in that, during selection, the current source 10, which may be considered to be an ideal current source, is switched on by means of the data register 5, for example via (not shown) switches. The value of the current is determined by the contents of the data register and is supplied to the LEDs 4 via data lines 2.
The current switch 10 maybe of a simple type comprising just one transistor and one resistor. As explained in the introduction, to make the bias of the transistor less sensitive to variations in the drain voltage due to variations in for instance the forward characteristics of the pixel diodes or the supply voltage of the driver, the high drain-source, needed then, increases power dissipation.
Figure 2 shows a known device comprising a first current path (transistor 19 and LED 4). The current I0 flows in the LED 4 and determines the light intensity of the picture element. The dashed line 21 schematically depicts the display area in Figure 2.
A second current path comprises a current source (a transistor 11 and a resistor 22) and a current mirror input stage, comprising a diode, realized by short-circuiting the gate terminal 14 and the drain terminal 15 of transistor 13 (and if necessary a further resistor 23). A voltage on gate terminal 16 determines the current 1; in this second current path. Since the transistors 13, 19 (together with the resistor 23, and if necessary a further resistor 24) may be considered as a current mirror the current I0 in the first current path is coupled to the current I, in a ratio, which ratio is determined by the k-factors of both transistors. In order to reduce the required drain-source voltage (compliance voltage) Nαs = Ncom the drive voltage (Ngs - Nth, Nth : threshold voltage) of transistor 19 has to be small. In both current paths a resistor 23, 24 may be incorporated as is shown by dashed lines.
Using transistors, which have a large k- factor, increases the required area of the integrated driving circuit, since the required chip area is proportional with k ~ W/l.
Figure 3 shows a preferred embodiment of a device according to the invention comprising a first current path (transistor 19 and LED 4) again. The current I0 flows in the LED 4 and determines the light intensity of the picture element. The dashed line 21 schematically depicts the display area in Figure 2. The first and second current paths are now coupled to each other via the control amplifier 25. The control amplifier 25 measures the output current l0 via resistor 24(R2), and compares it via the voltage over resistor 24 to the current I; as measured via resistor 23 (Rij. The control amplifier 25 then forces the output transistor 19 to draw lo = li .( Ri / R2) by control of Ngs . So the current l0 in the first current path is coupled to the current Ij in a ratio(Rι / R ).
This feedback allows a large Ngs value. This is shown in relation with Figure 4. When used at the edge of saturation for I0 the V S value is biased at point x. Due to the feedback mechanism at this (maximum) value for I0the Ngs value is biased, if necessary, at a Id - Nds curve related to a Nds value for a much higher I0 (e.g. at point y) without going into the saturation region, so the higher drain-source voltage (compliance voltage) for this higher I0 has not to be taken into account when designing the driver.
So this feedback mechanism allows larger Ngs values. As a result lower k - values are possible and consequently a lower dissipation and smaller chip area are obtained. The invention is applicable to both active and passive devices, matrix and segmented display devices. In one type of active matrices as shown in Figure 5, which represents a single (sub)picture element, extra switches, such as (TFT) switches 28, 29, 30, 33 and 35 are used to select the picture element and charge an extra capacitor 26. During selection both transistor 19 and switches 28 and 29 are conducting as determined by selection line 2. The circuitry comprising resistor 24, capacitor 26, transistor 19 and switches 28 and 29 determines current path, which is controlled by data input 8 to define a current L;ata. Capacitor 26 is charged to a voltage determined by the voltage across resistor 24. After selection (during a hold period), switches 28, 29, 35 are non-conducting, while the switches 30, 33 now are conducting. The charge remaining on capacitor 26 now controls the control amplifier 25 in such a way that the feedback mechanism maintains the current in current source 19,24 (and consequently in the LED 4 at Idata.
In the embodiment of Figure 6, which represents a single (sub)picture element again, the extra (TFT) switches 28, 29, and 31 are used to select the picture element and charge the extra capacitor 26. During selection both transistor 19 and switches 28 and 29 are conducting again as determined by selection line 8. The circuitry comprising resistor 24, capacitor 26, transistor 19 and switches 28 and 29 again determines a current path, which is controlled by selection line 2 to define a current Lata again via data input 8 and charge capacitor 26. After selection (during a hold period), both switches 28, 29 are non-conducting, while the switch 31 now connects capacitor 26 to control amplifier 25 (positive input). The charge remaining on capacitor 26 controls the control amplifier 25 again in a similar way as in the previous example.
The protective scope of the invention is not limited to the embodiments described. Instead of measuring the currents I0 and Iiin the first embodiment, fractions of these currents can be measured.
The invention is also applicable to field emission devices and other devices based on current driving.
The invention resides in each and every novel characteristic feature and each and every combination of features. Reference numerals in the claims do not limit the protective scope of these claims. The use of the verb "to comprise" and its conjugations does not exclude the presence of elements other than those stated in the claims. The use of the article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS:
1. A display device comprising at least one picture element and a display driver device comprising a driving transistor to be connected in series with the picture element in a first current path, the display driver comprising means for monitoring and controlling the current in said first current path.
2. A display device as claimed in Claim 1 in which in operation the current in the first current path is controlled by a current simultaneously passing in a second current path.
3. A display device as claimed in Claim 2 a controlling connection of the driving transistor being coupled to an output of a control amplifier each of the input connections of the control amplifier being coupled to the first and second current path respectively.
4. A display device as claimed in Claim 2 the driving transistor being a field effect transistor, the gate connection being the controlling connection.
5. A display device as claimed in Claim 1 which in operation the current in the first current path is controlled by a charge stored by means of a current having passed in a second circuitry part.
6. A display device as claimed in Claim 5 a controlling connection of the driving transistor being coupled to an output of a control amplifier one of the input connections of the control amplifier being coupled to a capacitor storing the control charge.
7. A display device as claimed in Claim 5 a controlling connection of the driving transistor being coupled to an output of a control amplifier the input connections of the control amplifier being coupled to the capacitor storing the control charge and the first current path respectively.
8. A display device as claimed in Claim 1 the picture element being a luminescent element and the first current determining the luminescence of the luminescent element.
9. A display driver device comprising a driving transistor for driving a picture element via first current path the first current path being controllable by the current in a second current path related to an input data value for the picture, a controlling connection of the driving transistor being coupled to an output of a control amplifier each of the input connections of the control amplifier being coupled to the first and second current path respectively.
10. A display driver device as claimed in Claim 9 the driving transistor being a field effect transistor, the gate connection being the controlling connection
11. A display driver device as claimed in Claim 9 the second current path comprising a current source.
12. A display driver device comprising a driving transistor for driving a picture element via a first current path in which in operation the current in the first current path is controlled by a charge stored by means of a current having passed in a second circuitry part.
13. A display driver device as claimed in Claim 12 a controlling connection of the driving transistor being coupled to an output of a control amplifier one of the input connections of the control amplifier being coupled to a capacitor storing the control charge.
PCT/IB2003/003277 2002-08-21 2003-07-18 Display device WO2004019310A2 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
AU2003247108A AU2003247108A1 (en) 2002-08-21 2003-07-18 Display device
JP2004530422A JP2005536771A (en) 2002-08-21 2003-07-18 Display device
EP03792541A EP1532610A2 (en) 2002-08-21 2003-07-18 Display device
US10/525,141 US20050285821A1 (en) 2002-08-21 2003-07-18 Display device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP02078455.9 2002-08-21
EP02078455 2002-08-21

Publications (2)

Publication Number Publication Date
WO2004019310A2 true WO2004019310A2 (en) 2004-03-04
WO2004019310A3 WO2004019310A3 (en) 2004-04-22

Family

ID=31896923

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2003/003277 WO2004019310A2 (en) 2002-08-21 2003-07-18 Display device

Country Status (8)

Country Link
US (1) US20050285821A1 (en)
EP (1) EP1532610A2 (en)
JP (1) JP2005536771A (en)
KR (1) KR20050058355A (en)
CN (1) CN100419837C (en)
AU (1) AU2003247108A1 (en)
TW (1) TWM250271U (en)
WO (1) WO2004019310A2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1793367A3 (en) * 2005-12-02 2009-08-26 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device
US7995012B2 (en) * 2005-12-27 2011-08-09 Semiconductor Energy Laboratory Co., Ltd. Light emitting device
US7583034B2 (en) * 2006-09-26 2009-09-01 Semiconductor Components Industries, L.L.C. LED controller and method therefor
WO2019008624A1 (en) * 2017-07-03 2019-01-10 シャープ株式会社 Display device and pixel circuit thereof

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5723950A (en) * 1996-06-10 1998-03-03 Motorola Pre-charge driver for light emitting devices and method
US5886474A (en) * 1995-10-13 1999-03-23 Sony Corporation Luminescent device having drive-current controlled pixels and method therefor
US5923308A (en) * 1996-11-12 1999-07-13 Motorola, Inc. Array of leds with active pull down shadow canceling circuitry
US5949194A (en) * 1996-05-16 1999-09-07 Fuji Electric Co., Ltd. Display element drive method
EP1164565A1 (en) * 1999-10-20 2001-12-19 TDK Corporation Constant-current device, display device, and method for driving the same

Family Cites Families (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60198872A (en) * 1984-03-23 1985-10-08 Seiko Instr & Electronics Ltd Mos integrated circuit for led driving
JPS61156198A (en) * 1984-12-28 1986-07-15 富士通株式会社 Light emitting cotnroller for display
JPH01255371A (en) * 1988-04-05 1989-10-12 Fujitsu Ltd System for driving light emitting diode
JPH02218183A (en) * 1989-02-17 1990-08-30 Mitsubishi Electric Corp Mos integrated circuit for driving led
WO1996036959A2 (en) * 1995-05-19 1996-11-21 Philips Electronics N.V. Display device
JP3688757B2 (en) * 1995-06-29 2005-08-31 Ｔｄｋ株式会社 Image display device and driving method thereof
JP3636777B2 (en) * 1995-07-04 2005-04-06 Ｔｄｋ株式会社 Image display device
US5990629A (en) * 1997-01-28 1999-11-23 Casio Computer Co., Ltd. Electroluminescent display device and a driving method thereof
US6310589B1 (en) * 1997-05-29 2001-10-30 Nec Corporation Driving circuit for organic thin film EL elements
US6097360A (en) * 1998-03-19 2000-08-01 Holloman; Charles J Analog driver for LED or similar display element
JPH11272223A (en) * 1998-03-26 1999-10-08 Toyota Motor Corp Power unit for light emissive display
GB9812742D0 (en) * 1998-06-12 1998-08-12 Philips Electronics Nv Active matrix electroluminescent display devices
JP2000081608A (en) * 1998-06-29 2000-03-21 Sanyo Electric Co Ltd Liquid crystal display device with light condensing mechanism
DE19930661A1 (en) * 1999-07-02 2001-01-18 Siemens Ag Transmitter
JP4376385B2 (en) * 1999-11-15 2009-12-02 富士通株式会社 Light emitting element drive circuit
US6528951B2 (en) * 2000-06-13 2003-03-04 Semiconductor Energy Laboratory Co., Ltd. Display device
JP2002040988A (en) * 2000-07-24 2002-02-08 Canon Electronics Inc Driving device for organic el elements
GB2367414A (en) * 2000-09-28 2002-04-03 Seiko Epson Corp Display device using TFT's
JP2002156944A (en) * 2000-11-21 2002-05-31 Canon Inc Light emitting element drive circuit
JP3757797B2 (en) * 2001-01-09 2006-03-22 株式会社日立製作所 Organic LED display and driving method thereof
US6717559B2 (en) * 2001-01-16 2004-04-06 Visteon Global Technologies, Inc. Temperature compensated parallel LED drive circuit
JP3819723B2 (en) * 2001-03-30 2006-09-13 株式会社日立製作所 Display device and driving method thereof
US6847171B2 (en) * 2001-12-21 2005-01-25 Seiko Epson Corporation Organic electroluminescent device compensated pixel driver circuit
JP3887229B2 (en) * 2001-12-28 2007-02-28 沖電気工業株式会社 Driving circuit for current-driven display device
US6841947B2 (en) * 2002-05-14 2005-01-11 Garmin At, Inc. Systems and methods for controlling brightness of an avionics display

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5886474A (en) * 1995-10-13 1999-03-23 Sony Corporation Luminescent device having drive-current controlled pixels and method therefor
US5949194A (en) * 1996-05-16 1999-09-07 Fuji Electric Co., Ltd. Display element drive method
US5723950A (en) * 1996-06-10 1998-03-03 Motorola Pre-charge driver for light emitting devices and method
US5923308A (en) * 1996-11-12 1999-07-13 Motorola, Inc. Array of leds with active pull down shadow canceling circuitry
EP1164565A1 (en) * 1999-10-20 2001-12-19 TDK Corporation Constant-current device, display device, and method for driving the same

Also Published As

Publication number Publication date
TWM250271U (en) 2004-11-11
JP2005536771A (en) 2005-12-02
CN100419837C (en) 2008-09-17
US20050285821A1 (en) 2005-12-29
AU2003247108A8 (en) 2004-03-11
WO2004019310A3 (en) 2004-04-22
CN1689062A (en) 2005-10-26
KR20050058355A (en) 2005-06-16
EP1532610A2 (en) 2005-05-25
AU2003247108A1 (en) 2004-03-11

Similar Documents

Publication Publication Date Title
US7817149B2 (en) Semiconductor circuits for driving current-driven display and display
KR100580956B1 (en) Active matrix drive circuit
US6756951B1 (en) Display apparatus and driving circuit of display panel
TWI428890B (en) Pixel circuit and display panel with ir-drop compensation function
US7319444B2 (en) Pixel circuit, electro-optical device, and electronic apparatus
US20010052606A1 (en) Display device
US7589701B2 (en) Systems and methods for driving a display device and interrupting a feedback
KR20030011715A (en) Providing of programming current to pixel
US7071905B1 (en) Active matrix display with light emitting diodes
US6867551B2 (en) Light-emission drive circuit for organic electroluminescence element and display device
US7215307B2 (en) Drive unit of self-luminous device with degradation detection function
US6509690B2 (en) Display device
KR20160069986A (en) Display device and displaying method of the same, and programing method of the same
US6870322B1 (en) Organic EL display device having adjustable offset voltage
US6946799B2 (en) Drive circuit
US7417605B2 (en) Electronic circuit, electronic device, and electronic apparatus
JP2006523322A (en) Display device and method for sparking display pixels of such a device
US20050285821A1 (en) Display device
JP2006251515A (en) Display device
US20090079670A1 (en) Display device
JP4556814B2 (en) Device, device driving method, and electronic apparatus
KR100659968B1 (en) Light emitting device and method of driving the same
KR100757563B1 (en) Organic electroluminescent device for preventing cross-talk phenomenon and method of driving the same

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 2003792541

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 2004530422

Country of ref document: JP

WWE Wipo information: entry into national phase

Ref document number: 10525141

Country of ref document: US

WWE Wipo information: entry into national phase

Ref document number: 20038196352

Country of ref document: CN

Ref document number: 1020057002769

Country of ref document: KR

WWP Wipo information: published in national office

Ref document number: 2003792541

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 1020057002769

Country of ref document: KR