CA2687477A1 - Stable current source for system integration to display substrate - Google Patents

Stable current source for system integration to display substrate Download PDF

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Publication number
CA2687477A1
CA2687477A1 CA2687477A CA2687477A CA2687477A1 CA 2687477 A1 CA2687477 A1 CA 2687477A1 CA 2687477 A CA2687477 A CA 2687477A CA 2687477 A CA2687477 A CA 2687477A CA 2687477 A1 CA2687477 A1 CA 2687477A1
Authority
CA
Canada
Prior art keywords
current
output
display substrate
current source
circuit
Prior art date
Legal status (The legal status 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 status listed.)
Abandoned
Application number
CA2687477A
Other languages
French (fr)
Inventor
G. Reza Chaji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ignis Innovation Inc
Original Assignee
Ignis Innovation Inc
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 Ignis Innovation Inc filed Critical Ignis Innovation Inc
Priority to CA2687477A priority Critical patent/CA2687477A1/en
Priority claimed from US12/944,488 external-priority patent/US8283967B2/en
Publication of CA2687477A1 publication Critical patent/CA2687477A1/en
Application status is Abandoned legal-status Critical

Links

Classifications

    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00Aspects of the constitution of display devices
    • G09G2300/04Structural and physical details of display devices
    • G09G2300/0404Matrix technologies
    • G09G2300/0408Integration of the drivers onto the display substrate
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00Command of the display device
    • G09G2310/02Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0264Details of driving circuits
    • G09G2310/0275Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00Command of the display device
    • G09G2310/02Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0264Details of driving circuits
    • G09G2310/0278Details of driving circuits arranged to drive both scan and data electrodes

Abstract

Disclosed is a technique to implement stable and high output impedance current sources based on single device,

Description

FIELD OF THE INVENTION

The present invention generally relates to drive a display particularly light emitting displays.
SUMMARY OF INVENTION

The disclosed technique enables integration of different peripheral circuitry onto display substrates using a single device.

ADVANTAGES
The new techniques can enable implementation of high output impendence current source and current sink based on single device architectures. Because of the reduced circuit complexity, a higher density integration can be achieved on the display substrate reducing the cost of drivers.

This technique can be applied to different fabrication technology including but not limited to poly-silicon, amorphous silicon, organic semiconductor, metal oxide, and conventional CMOS.
Also, the embodiments presented in this discloser are only examples and can be modified by different circuit techniques such as complimentary circuit concepts.

Most backplane technologies offer only one type of thin film transistors (TFT), either p-type or n-type. Thus, the device-type limitation needs to be overcome by some circuit technique in order to enable integration of more useful circuitry onto the display substrate which can lead to better performance and lower cost. The main circuit blocks for driving active matrix organic light emitting diodes are current sources (or sinks) and voltage to current convertors.

For example, p-type devices have been used in conventional current mirror and current sources since the source terminal of at least one TFT is fixed (e.g. VDD). The current output is coming through the drain and so change in the output line will only affect the drain voltage. As a result, the output current will stay constant despite change in the line voltage (leading to high output resistance current sources). On the other hand, if a p-type TFT is used for current sink, the source of the TFT will be connected to the output line. Thus, any change in the output voltage due to variation in the output load, we affect the gate-source voltage directly.
Consequently, the output current will not be constant for different loads. To overcome this issue, a circuit design technique is needed to control the effect of source voltage variability on the output current.

Figure 1 shows an embodiment of a current sink using only p-type devices.
During the calibration cycle, CAL is low and so T2, T4 and T5 are ON while T6 is OFF. As a result, the current adjusts the voltage at node A to allow all the current to pass through Ti and T3. After calibration, CAL is high and ACS is low; thus, T6 is ON and a negative polarity current is applied through T6. Here, the storage capacitor along with the source degenerate effect (between Ti and T3) preserves the copied current, thus providing very high output impedance. The signal diagram of the current sink operation is shown in Fig. 2.

Figure 3 shows the simulation result for the output current of the current sink presented in Fig. 1 as function of output voltage. Despite using p-type device, the output current is significantly stable despite the change in the output voltage.

Also, the output current is highly uniform despite the high level of non-uniformity in the backplanes (normally caused by process-induced effects). Figure 4 shows a parameter variation in a typical poly-Si process which is used for the simulation and analysis results. Figure 5 highlights the Mont Carlo simulation results. Here, over 12% variation in mobility and 30%
variation in the threshold voltage (VT) is considered, however, the output current variation is less than I%.

Figure 6 shows another embodiment of the current source. The operation of this circuit is the same as the one shown in Fig. 1.

The circuit shown in Figure 1 and 5 can be used to develop more complex circuit and system blocks. Figure 7 shows the use of this circuit in a voltage to current convertor. During the calibration, CAL is low and a VB4 is applied to node B. Here, the current of TI-T3-T5 branch is adjusted to allow VB4 at node B (see Fig. 8). As a result, a current correlated to VB3 and VB4 will pass through lout.

Fig 1 shows a current sink embodiment using p-type TFTs.
Fig 2 shows the signal diagram for driving the circuit shown in Fig. 1.
Fig 3 displays the output current of the circuit in Fig. I versus the output voltage.
Fig 4 demonstrates parameter variation used in a typical poly-Si process.
Fig 5 highlights the output current uniformity of the circuit demonstrated in Fig 1.
Fig 6 shows another embodiment of the current sink using p-type TFTs.
Fig 7 shows a voltage-to-current convertor based on the circuit shown in Fig.
1.
Fig 8 shows the signal diagram for driving the circuit in Fig. 7.

Claims

CA2687477A 2009-12-07 2009-12-07 Stable current source for system integration to display substrate Abandoned CA2687477A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA2687477A CA2687477A1 (en) 2009-12-07 2009-12-07 Stable current source for system integration to display substrate

Applications Claiming Priority (14)

Application Number Priority Date Filing Date Title
CA2687477A CA2687477A1 (en) 2009-12-07 2009-12-07 Stable current source for system integration to display substrate
US12/944,488 US8283967B2 (en) 2009-11-12 2010-11-11 Stable current source for system integration to display substrate
US12/944,477 US8497828B2 (en) 2009-11-12 2010-11-11 Sharing switch TFTS in pixel circuits
US12/944,491 US8633873B2 (en) 2009-11-12 2010-11-11 Stable fast programming scheme for displays
CN201080056457.4A CN102656621B (en) 2009-11-12 2010-11-12 Effective programming and fast calibration scheme for a light emitting display and a constant current source / sink for the light emitting display
EP20120174463 EP2506242A3 (en) 2009-11-12 2010-11-12 Efficient programming and fast calibration schemes for light-emitting displays and stable current source/sinks for the same
EP20100829593 EP2499633A4 (en) 2009-11-12 2010-11-12 Efficient programming and fast calibration schemes for light-emitting displays and stable current source/sinks for the same
PCT/IB2010/002898 WO2011058428A1 (en) 2009-11-12 2010-11-12 Efficient programming and fast calibration schemes for light-emitting displays and stable current source/sinks for the same
JP2012538429A JP2013511061A (en) 2009-11-12 2010-11-12 Efficient programming and fast calibration for light-emitting displays and their stable current sources and sinks
EP20120174465 EP2509062A1 (en) 2009-11-12 2010-11-12 Efficient programming and fast calibration schemes for light-emitting displays and stable current source/sinks for the same
US14/132,840 US9030506B2 (en) 2009-11-12 2013-12-18 Stable fast programming scheme for displays
US14/699,752 US9818376B2 (en) 2009-11-12 2015-04-29 Stable fast programming scheme for displays
JP2016072396A JP6488254B2 (en) 2009-11-12 2016-03-31 Efficient programming and fast calibration for light-emitting displays and their stable current sources and sinks
US15/783,802 US20180040300A1 (en) 2009-11-12 2017-10-13 Stable fast programming scheme for displays

Publications (1)

Publication Number Publication Date
CA2687477A1 true CA2687477A1 (en) 2011-06-07

Family

ID=44144918

Family Applications (1)

Application Number Title Priority Date Filing Date
CA2687477A Abandoned CA2687477A1 (en) 2009-12-07 2009-12-07 Stable current source for system integration to display substrate

Country Status (1)

Country Link
CA (1) CA2687477A1 (en)

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