EP1324304A1 - "Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige" - Google Patents

"Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige" Download PDF

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Publication number
EP1324304A1
EP1324304A1 EP01830810A EP01830810A EP1324304A1 EP 1324304 A1 EP1324304 A1 EP 1324304A1 EP 01830810 A EP01830810 A EP 01830810A EP 01830810 A EP01830810 A EP 01830810A EP 1324304 A1 EP1324304 A1 EP 1324304A1
Authority
EP
European Patent Office
Prior art keywords
voltage
terminal
supply system
supply
ctnk
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.)
Withdrawn
Application number
EP01830810A
Other languages
English (en)
French (fr)
Inventor
Leonardo Sala
Francesco Pulvirenti
Roberto Gariboldi
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.)
STMicroelectronics SRL
Dora SpA
Original Assignee
STMicroelectronics SRL
Dora SpA
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 STMicroelectronics SRL, Dora SpA filed Critical STMicroelectronics SRL
Priority to EP01830810A priority Critical patent/EP1324304A1/de
Publication of EP1324304A1 publication Critical patent/EP1324304A1/de
Withdrawn legal-status Critical Current

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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
    • G09G3/34—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 by control of light from an independent source
    • G09G3/36—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 by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3696—Generation of voltages supplied to electrode drivers
    • 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
    • G09G2330/023—Power management, e.g. power saving using energy recovery or conservation
    • 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
    • G09G3/34—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 by control of light from an independent source
    • G09G3/36—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 by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3622—Control of matrices with row and column drivers using a passive matrix

Definitions

  • the present invention refers to a supply system of the driving voltage generator of the rows and of the columns of a liquid crystals display.
  • the first voltage level is called Vlcd and it is directly proportional to the lighting threshold of the liquid crystal and to the square root of the number of the driven rows.
  • the other four voltage levels V2, V3, V4 and V5 are distributed between the Vlcd and GND voltages according to a law that depends on the square root of the number of the driven rows.
  • the voltages V2, V3, V4 and V5 tend to gather at the extreme supply values, that is the voltages V2 and V3 towards the voltage Vlcd while the voltages V4 and V5 towards the ground voltage GND.
  • the different voltage levels are applied to the rows and columns with alternate phase in order to cancel the direct component of the voltage applied to the display, harmful for the liquid crystal. More particularly, in a frame period, or part of it, the rows are driven between the voltages V5 and Vlcd, while in the following period the rows are driven between the voltages GND and V2, in the same way the columns are driven between the voltages GND and V4 and between the voltages V3 and Vlcd.
  • the voltage Vlcd is generated by a charging pump starting from the supply voltage Vdd, while the other four voltage levels V2, V3, V4 and V5 are obtained by intermediary dividers of Vlcd, and applied to voltage followers that work as buffer circuits, normally supplied between the voltages Vlcd and GND.
  • the US patent 6,201,522 describes a method for driving a liquid cristal display that includes a series of multiplexers coupled to the columns of the display.
  • the multiplexers couple selectively each of the columns to a capacity for a fraction of the driving period to discharge each of the pixel placed in the column. In the fraction of the remaining driving period the multiplexer couples to the column the driving voltage generators.
  • This solution requires that all the controller outputs coupled to the display, equal in number to the sum of the totality of the rows and the totality of the columns, have an additional capacitor, according to a "distributed" approach.
  • a supply system of the driving voltage generator of the rows and of the columns of a liquid crystals display comprising: a first terminal of a first supply voltage; a second terminal of a second supply voltage; a first generator circuit of a first prefixed voltage having a third terminal of a third supply voltage and a fourth terminal of a fourth supply voltage; a second generator circuit of a second prefixed voltage having a fifth terminal of a fifth supply voltage and a sixth terminal of a sixth supply voltage; characterized by further comprising an energy storage device coupled to said fourth and to said fifth terminal.
  • the present invention it is possible to provide the driving voltage generators with a charge reserve, so as to reduce the need to draw, where the supply of a current is requested, directly from the power supply.
  • charging tanks are equipped with a control circuit that assures the correct working of the generators towards the voltage variations of the charging tank.
  • an hysteresis has been introduced into such a control circuit.
  • the solution according to the present invention is applicable both to the driving method according to the technique denominated Improved Halt & Pleshko (IA& P), and according to the denominated technique Multi Row Addressing (MLA), but the application of other techniques is not excluded.
  • the supplying voltage Vdd supplies a positive charging pump 1, that provides in output the voltage Vddbis.
  • the voltage Vddbis supplies an operational amplifier OP1 that supplies a voltage Vlcd in output.
  • the voltage Vlcd is applied to a terminal of a variable resistance P1, the other terminal of P1 is connected to ground GND.
  • the cursor of the variable resistance P1 is connected to the negative terminal of the operational amplifier OP1.
  • a reference voltage Vref produced by a voltage generator 2 is connected to the positive terminal of the operational amplifier OP1.
  • the operational amplifier OP 1 produces a voltage Vlcd in output. This voltage Vlcd is applied to a resistance divider R1-R5 in turn connected to ground GND.
  • the positive inputs of the operational amplifiers denominated respectively OP2-OP5 are applied at the junction nodes between a resistance and another.
  • the negative terminals of the operational amplifiers OP2-OP5 are connected to the respective outputs of the operational amplifiers OP2-OP5, so as to constitute voltage followers.
  • the operational amplifiers OP2-OP5 produces respectively the voltages V2-V5 at their outputs.
  • the operational amplifiers OP2-OP5 in the embodiment of figure 1, are supplied between the voltages Vlcd and GND, alternatively they can be supplied by any suitable voltage.
  • the voltage generator 2 is designed so that it compensates the thermal variations and eventually other factors of the liquid crystal display.
  • figure 2 represents in a schematic way one part of a supply system of the driving voltage generator of the rows and of the columns of a liquid crystals display according to the present invention.
  • the supply voltage Vlcd and the ground voltage GND supply two circuits D3 and D4, that are schematic of one part of the circuits reported in figure 1, that produce respectively the driving voltages V3 and V4 in output.
  • the voltage Vlcd is applied to a supplying terminal of the circuit D3
  • the voltage GND is applied to a supplying terminal of the circuit D4
  • the other two supplying terminals of the circuits D3 and D4, connected in the known art of figure 1 respectively to ground and Vlcd, in this case are connected together and a capacitor Ctnk is connected to them too, with the function of storage energy device.
  • a control circuit CONT is connected to the capacitor Ctnk too, preferably, but not necessarily, supplied by the voltages Vlcd and GND.
  • the voltage of the capacitor Ctnk goes up beyond a prefixed upper activation threshold, it is brought again to an suitable value to the correct working of D3 by the control circuit Cont.
  • the characteristic distribution of the voltage levels of the rows and of the columns allows therefore to synthesize the following optimizations in the charge transfer.
  • the control circuit Cont keeps the voltage to the terminals of the capacitor Ctnk within an prefixed voltages range.
  • the prefixed voltages range is for instance comprised between the voltages V3-0,5V and V4+0,5V, and however must be so as to guarantee the right working of D3 and D4.
  • a terminal of the capacitors Ctnk1-Ctnk3 is connected respectively to the common terminals of D2-D3, D3-D4 and D4-D5, while the other terminal of the capacitors Ctnk1-Ctnk3 is preferably, but not necessarily, connected to ground GND, or any other supply terminal.
  • the control circuits Cont1-Cont4 check the voltages to the terminals of the capacitors Ctnk1-Ctnk3 respectively.
  • the upper supply voltage is the Vlcd, but they can be supplied with any other suitable voltage.
  • figure 4 represents a first embodiment of a supply system of the driving voltage generator of the rows and of the columns of a liquid crystals display according to the present invention.
  • the voltage Vtnk available on the capacitor Ctnk is applied to the negative input of the comparators C1 and C3 and to the positive input of the comparators C2 and C4.
  • the reference voltage Vth2 is applied to the positive input of the comparator C1
  • the reference voltage Vth1 is applied to the negative input of the comparator C2
  • the reference voltage Vtl1 is applied to the positive input of the comparator C3
  • the reference voltage Vtl2 is applied to the negative input of the comparator C4.
  • the outputs of the comparators C1-C4 are applied respectively to the inputs S and R of the flip-flop FF1 and FF2.
  • the output of the flip-flop FF1 controls a controlled switch IC2 connected between the terminal of the capacitor Ctnk and ground GND.
  • the output of the flip-flop FF2 controls a controlled switch IC1 connected between the terminal of the capacitor Ctnk and the voltage Vlcd.
  • V is the voltage difference we can have between the start and the stop of the frame, compatibly with the correct working of the control circuits
  • B is the bias that shows the spacing of the voltage levels of a given row number.
  • This sizing of the capacitor Ctnk that makes the function of charging tank in the particular embodiment of figure 4, allows of excluding, in absence of sudden display changes that can determine asymmetries in the capacitor charging and discharging, the intervention of the recovery circuit of the optimal situation that is the circuit Cont.
  • figure 5 represents a second embodiment of a supply system of the driving voltage generator of the rows and of the columns of a liquid crystals display according to the present invention.
  • the voltage Vtnk available at the capacitor Ctnk is applied to the positive input of the comparator C5 and to the negative input of the comparator C6; it is also applied to the anode of the diode DD1 whose cathode is applied to the output of the comparator C5, and to the cathode of the diode DD2 whose anode is applied to the output of the comparator C6.
  • the reference voltage Vth is applied to the negative input of the comparator C5, and the reference voltage Vtl is applied to the positive input of the comparator C6. Both the comparators C5 and C6 are supplied between Vlcd and ground GND.
  • both the diodes DD1 and DD2 are inversely biased and there is neither a contribution nor a subtraction of charge from the capacitor Ctnk. If instead the voltage Vtnk overcomes the reference voltage Vth the comparator C5 tries to reduce the output voltage, lowering the voltage of the cathode of the diode DD1 and carrying the diode DD1 in forward bias, which subtracts charges from the capacitor Ctnk and reducing the voltage on its terminals.
  • the comparator C6 tries to increase the output voltage, increasing the voltage of the anode of the diode DD2 and carrying the diode DD2 in direct biasing, that brings charge to the capacitor Ctnk and increasing the voltage at its terminals.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (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)
  • Liquid Crystal Display Device Control (AREA)
EP01830810A 2001-12-27 2001-12-27 "Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige" Withdrawn EP1324304A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP01830810A EP1324304A1 (de) 2001-12-27 2001-12-27 "Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige"

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP01830810A EP1324304A1 (de) 2001-12-27 2001-12-27 "Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige"

Publications (1)

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EP1324304A1 true EP1324304A1 (de) 2003-07-02

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EP01830810A Withdrawn EP1324304A1 (de) 2001-12-27 2001-12-27 "Stromversorgungssystem für Spannungsgenerator zur Ansteuerung der Zeilen und Spalten einer Flüssigkristallanzeige"

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005017869A1 (en) * 2003-08-18 2005-02-24 Koninklijke Philips Electronics N. V. Display device having reduced power consumption

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0391655A2 (de) * 1989-04-04 1990-10-10 Sharp Kabushiki Kaisha Ansteuerschaltung für ein Matrixanzeigegerät mit Flüssigkristallen
US4983931A (en) * 1989-06-29 1991-01-08 Nec Corporation CR-type oscillator circuit
JPH03251817A (ja) * 1990-03-01 1991-11-11 Hitachi Ltd 液晶駆動用電源回路
EP0735677A1 (de) * 1995-03-31 1996-10-02 Co.Ri.M.Me. Consorzio Per La Ricerca Sulla Microelettronica Nel Mezzogiorno Oszillatorschaltung mit einer versorgungsspannungsunabhängigen Oszillatorfrequenz
EP0756190A1 (de) * 1995-01-13 1997-01-29 Seiko Epson Corporation Stromversorgungsschaltung, stromversorgung für flüssigkristallanzeigevorrichtung und flüssigkristallanzeigevorrichtung
EP0772182A2 (de) * 1995-10-04 1997-05-07 Sharp Kabushiki Kaisha Vorrichtung zum Erzeugen von Anzeigesteuerspannungen
US5751278A (en) * 1990-08-10 1998-05-12 Sharp Kabushiki Kaisha Clocking method and apparatus for display device with calculation operation

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0391655A2 (de) * 1989-04-04 1990-10-10 Sharp Kabushiki Kaisha Ansteuerschaltung für ein Matrixanzeigegerät mit Flüssigkristallen
US4983931A (en) * 1989-06-29 1991-01-08 Nec Corporation CR-type oscillator circuit
JPH03251817A (ja) * 1990-03-01 1991-11-11 Hitachi Ltd 液晶駆動用電源回路
US5751278A (en) * 1990-08-10 1998-05-12 Sharp Kabushiki Kaisha Clocking method and apparatus for display device with calculation operation
EP0756190A1 (de) * 1995-01-13 1997-01-29 Seiko Epson Corporation Stromversorgungsschaltung, stromversorgung für flüssigkristallanzeigevorrichtung und flüssigkristallanzeigevorrichtung
EP0735677A1 (de) * 1995-03-31 1996-10-02 Co.Ri.M.Me. Consorzio Per La Ricerca Sulla Microelettronica Nel Mezzogiorno Oszillatorschaltung mit einer versorgungsspannungsunabhängigen Oszillatorfrequenz
EP0772182A2 (de) * 1995-10-04 1997-05-07 Sharp Kabushiki Kaisha Vorrichtung zum Erzeugen von Anzeigesteuerspannungen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 016, no. 050 (P - 1308) 7 February 1992 (1992-02-07) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005017869A1 (en) * 2003-08-18 2005-02-24 Koninklijke Philips Electronics N. V. Display device having reduced power consumption

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