Source: http://www.google.com/patents/US7230614?dq=Patent+number:+5706654
Timestamp: 2016-05-02 11:51:28
Document Index: 719882447

Matched Legal Cases: ['arts 201', 'arts 201', 'arts 201', 'art 201', 'art 201', 'art 30', 'arts 201', 'art 201', 'art 20', 'art 30', 'art 30', 'arts 202', 'arts 202', 'arts 202', 'arts 202', 'art 202', 'art 202', 'art 30', 'art 202', 'art 20', 'art 30', 'art 30', 'art 60', 'art 60', 'art 60', 'art 80', 'art 60', 'art 60', 'art 20', 'art 30']

Patent US7230614 - Circuit for driving display - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThe present invention relates to a display, and more particularly, to circuit for driving a display of a low power consumption. For the purpose, the circuit includes a light emitting display of current driven type having a plurality of column electrode lines arranged in a column direction, a plurality...http://www.google.com/patents/US7230614?utm_source=gb-gplus-sharePatent US7230614 - Circuit for driving displayAdvanced Patent SearchPublication numberUS7230614 B2Publication typeGrantApplication numberUS 10/151,928Publication dateJun 12, 2007Filing dateMay 22, 2002Priority dateMay 22, 2001Fee statusPaidAlso published asCN1462993A, CN100397457C, EP1262948A2, EP1262948A3, US20020175884Publication number10151928, 151928, US 7230614 B2, US 7230614B2, US-B2-7230614, US7230614 B2, US7230614B2InventorsHak Su Kim, Minho Lee, Young-wan Cho, Seung-Tae KimOriginal AssigneeLg Electronics Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (15), Non-Patent Citations (2), Referenced by (1), Classifications (18), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetCircuit for driving display
US 7230614 B2Abstract
The present invention relates to a display, and more particularly, to circuit for driving a display of a low power consumption. For the purpose, the circuit includes a light emitting display of current driven type having a plurality of column electrode lines arranged in a column direction, a plurality of row electrode lines arranged perpendicular to the column electrode lines, and a matrix of pixels at crossing points of the column electrode lines and the row electrode lines, a power source part, a column driving circuit connected to the column electrode lines formed in the column direction for supplying/discharging a current to/from the column electrode lines, for driving the light emitting display of current driven type, and an electric transformer for, when the current supplied to the column electrode lines is discharged, recovering the current discharged from the column electrode lines and re-supplying a recovered current to the power source part.
The foregoing display has smaller power consumption in comparison to the CRT, no distortion at edge parts, and permits to fabricate an extra thin display. Moreover, the foregoing display permits fabrication of a large sized screen because it is robust in comparison to the LCD and has a wider angle of view owing to self-luminescence and a good responsive characteristics, has a wide range of service temperature of −40�–+70�, permits to select a wide variety of colors without restraints, and is operative even with a voltage as low as 15V.
Accordingly, the present invention is directed to circuit and method for driving a display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
FIGS. 11–13 illustrate examples showing a connection of a switch and a diode with the voltage transforming part.
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 2 illustrates a power saving circuit for a display of current driven type in accordance with a first preferred embodiment of the present invention.
In the meantime, there are N organic EL driving parts 201 a–201N each including one element of the data driving part, a light emitting device a light emission state of which is fixed depending on a voltage applied to the scan driving part corresponding to the element of the data driving part, and one element of the data sink part which eliminates a trapped charge from an anode line of the light emitting device.
A system of each of the organic EL driving parts 201 a–201N is identical to FIG. 1, except that one side of each of the N data sink parts is connected to the ground through the transformer 10 b in common.
A source of the NMOSs of the data sink part in each of the organic EL driving parts 201 a–201N is connected to ground through the primary side coil of the transformer 10 b, and a source of the scan driving part is in general connected to the ground, directly.
In FIG. 2, for convenience of explanation, a part at which a drain of the NMOS of the data sink part in the first organic EL driving part 201 a and an anode of the organic EL are connected is represent with ‘A’, a part at which a drain of the NMOS of the data sink part in the Nth organic EL driving part 201N and the anode of the organic EL are connected is represent with ‘N’, and a part at which the source of the NMOS of the N data sink parts and the primary side coil of the transformer 10 b is represented with ‘B’.
An output node part of the transformer is represented with ‘C’, and a part at which the cathode of the diode 40 b and the power source part 30 are connected is represented with ‘P’. A signal provided to the data driving part in the organic EL driving parts 201 a–201N and a signal provided to the data sink part are identical. Therefore, the data driving part and the data sink part are operative oppositely. That is, if the data driving part is turned on, the data sink part is turned off, and vice versa.
If the data driving part is turned on, a current is made to flow from the constant current source to the light emitting device, to make the light emitting device to emit a light, and if the data driving part is turned off, a voltage (for an example, a voltage at ‘A’) on the anode of the light emitting device is provided to the primary side coil of the transformer 10 b through the data sink part.
The operation of the power saving circuit for the display of a current driven type of the present invention will be explained in detail, with reference to the attached drawings. FIG. 3 illustrates operation waveforms at various parts in FIG. 2, wherein Data1–DataN in FIGS. 3A and 3B represent examples of signals provided to the data driving parts, and Data1_B–DataN_B in FIGS. 3C and 3D represent examples of signals provided to the data sink parts.
For an example, if a signal provided to the data driving part in the first organic EL driving part 201 a is low, the PMOS in the data driving part is turned on such that a high voltage (i.e., the Vdd) is applied to the ‘A’ point as shown in FIG. 3E.
That is, in correspondence to the variation of the Data1–DataN signals, waveforms at points ‘A’–‘N’ vary as shown in FIGS. 3E, and 3F at the anode line of the light emitting device. Waveforms at the anode line are varied with a slight time delay.
If the NMOS of the data sink part is turned on, a voltage at the ‘A’ point is provided to the primary side coil of the transformer 10 b through the NMOS.
The voltage charged at the primary side of the transformer 10 b is induced at the secondary side coil in proportion to the winding ratio. That is, a current at the primary side of the transformer 10 b is transferred to the secondary side in proportion to the winding ratio 1:M of the transformer 10 b. A voltage at ‘B’ part at which one sides of all of the N NMOSs of the data sink part are connected thereto increases in proportion to a number of the data sink parts. That is, an intensity of the current flowing in the primary side coil of the transformer 10 b varies with the voltage at the ‘B’ point, and the voltage varies in proportion to the intensity of the current.
This variation of voltage causes to increase a voltage at ‘C’ point having an output part of the transformer 10 b connected thereto. That is, the voltage at ‘C’ point increases in proportion to the voltage at ‘B’ point and the winding ratio as shown in FIG. 3H. According to the variation, a desired level of voltage at ‘P’ point provided through the controlling part 20 b and the diode 40 b can be obtained from a voltage provided to the transformer 10 b as shown in FIG. 3I.
When the voltage at ‘P’ point turns on the diode 40 b, the power source part 30 provides power source voltages required for various parts (for an example, Vdd) from the voltage received through the diode 40 b, and provides to the required parts. That is, by recovering and using the power consumed at the data sink to the maximum, the power source part 30 can reduce a total power of entire system.
There are N organic EL driving parts 202 a–202M each inclusive of a light emitting device for emitting a light as the constant current source is turned on/off, a scan driving part connected to a cathode of the light emitting device, and a scan controlling part connected to a cathode of the light emitting device for prevention of cross talk of the light emitting device.
Systems of the organic EL driving parts 202 a–202M are identical to FIG. 1, except that one side of the scan driving part is connected to ground through the transformer 10 c. That is, the scan driving part includes M NMOSs each driven by a scan signal, the scan controlling part includes M PMOSs each driven by a scan_B signal, and both a drain of each NMOS of the scan driving part and a source of each PMOS of the scan controlling part are connected to a cathode of one of the light emitting devices.
Signals provided to the scan driving part and the scan controlling part of each of the organic EL driving parts 202 a–202M are the same. Therefore, the scan driving part and the scan controlling part are operative oppositely. That is, if the scan driving part is turned on, the scan controlling part is turned off, and vice versa.
Sources of the M NMOSs of the scan driving part in each of the organic EL driving parts 202 a–202M are connected to the primary side coil of the transformer 10 c in common. Therefore, if the scan driving part is turned on and the scan controlling part is turned off, a voltage on a cathode of the light emitting device connected to one of the M scan driving parts, which is turned on, is provided to the primary side coil of the transformer 10 c through the scan driving part.
In FIG. 4, for convenience of explanation, a part at which a cathode of the light emitting device in the first organic EL driving part 202 a, a drain of the scan driving part, and a source of the scan controlling part are connected in common is represented with ‘AC’, a cathode of the light emitting device of an Mth organic EL driving part 202M, a drain of the scan driving part, and a source of the scan controlling part are connected in common is represented with ‘MC’, and a part at which sources of the NMOSs of the M scan driving parts, and the primary side coil of the transformer 10 c are connected is represented with ‘BC’.
An output node part of the transformer is represented with ‘CC’, and a part at which a cathode of the diode 40 c and the power source part 30 are connected is represented with ‘PC’.
The operation of the foregoing power saving circuit for a display of a current driven type of the present invention will be explained in detail, with reference to the attached drawings. FIGS. 5A–5J illustrate operation waveforms at various parts in FIG. 4, wherein scan1–scanM in FIGS. 5A and 5B illustrate examples of signals provided to respective scan driving parts, and scan1_B and scanM_B in FIGS. 5C and 5D illustrate examples of signals provided to respective scan controlling parts.
For an example, if a scan signal provided to the scan driving part in the first organic EL driving part 202 a is turned from low to high, the NMOS of the scan driving part is turned on, and the PMOS of the scan controlling part is turned off. When the NMOS of the scan driving part is turned on, a voltage on the cathode of the light emitting device, i.e., a voltage at ‘AC’ point is pulled down as shown in FIG. 5F, which is provided to the primary side coil in the transformer through the scan driving part.
In correspondence to changes of the scan1–scanN signals, a signal waveform is changed at a cathode line in the light emitting device as ‘AC’ to ‘MC’ waveforms in FIGS. 5F–5G.
In this instance, since a resistance of the transformer 10 c is very small, a voltage at ‘BC’ point drops almost to a ground level as shown in FIG. 5H. Then, the voltage charged at the primary side of the transformer 10 c is induced at the secondary side coil in proportion to the winding ratio. That is, a current at the primary side of the transformer 10 c is transferred to the secondary side in proportion to a winding ratio 1:M of the transformer 10 c. A voltage at the point ‘BC’ to which one sides of all NMOSs of the N data sink part are connected increases in proportion to a number of turned on data sink parts. That is, an intensity of the current to the primary side coil of the transformer 10 c varies with the voltage at the point ‘BC’, and the voltage varies with the intensity of the current. This variation of the voltage causes a voltage at the point ‘CC’ the output part of the transformer 10 c is connected thereto to increase, too.
That is, as shown in FIG. 5I, the voltage at the point ‘CC’ increases in proportion to the voltage at the point ‘BC’ and the winding ratio, leading a voltage at the point ‘PC’ through the controlling part 20 c and the diode 40 c higher than the voltage to the transformer 10 c as shown in FIG. 5J.
Then, the voltage at the point ‘BC’ turns on the diode 40 c, so that the power source part 30 provides power source voltages (for examples, Vdd and Vpp) required for different parts from the voltage received through the diode 40 c, and provides to relevant parts. That is, the power source part 30 recovers, and re-uses the power wasted at the scan driving part to the maximum, to reduce a power for the entire system.
Referring to FIG. 6, the driving circuit for a display includes a data driver 60 d having a power source Vdd for applying a voltage to elements, a data driving part (data 1–data N) of N PMOSs each for controlling a current from the power source to an anode on an light emitting device part 60 in response to a data signal applied respectively, a data sink part (data 1_B–data N_B) of N NMOSs connected to the anode for making a voltage conductive, which is discharged from an anode of a device as at least one device (data line) in the data driving part is turned off, a scan driver 70 d having a scan driving part (scan 1–scan M) for making the light emitting device part to emit light in correspondence to the data line in response to the scan signal applied respectively, a scan controlling part (scan 1_B–scan M_B) for applying an inverse voltage to the scan driving part for prevention of cross talk of the light emitting device part 60, and a refresh part (Ref1–RefM) 71 d connected to a cathode of the light emitting device part 60 between the scan driving part and the controlling part for making a voltage conductive, which is discharged from a cathode of a device as at least one device (scan line) of the scan driving part is turned on, and a voltage transforming part 80 d connected between the data sink part and the refresh part for recovering the voltage discharged through the data sink part and/or the refresh part.
In the data sink part, source terminals of the data 1_B–data N_B, N sink elements, are connected into one and therefrom connected to an input of the transformer 10 d. Ref1–refM, refresh elements, are respectively connected between the M scan 1–scan M in the scan driving part and the scan 1_B–scan M_B, inverse voltage elements in the scan controlling part. Drain terminals of the ref1–refM are respectively connected to cathodes of the light emitting device part 60, and source terminals thereof are connected into one and, therefrom, connected to an input of the transformer 10 d. Accordingly, it is made that much current flows to the input of the transformer during a refresh time period.
Referring to FIGS. 7 and 8, parts represented with ‘T’ are refresh periods, during which the controller (not shown) controls such that all data lines and all scan lines are connected to ground, for having low signals. The data line represents one of elements of the data driving part, which has N data lines. The scan line represents one of elements of the scan driving part, which has N scan lines.
Referring to FIG. 7, when data signals, such as data 1–data N, are applied to the data lines, elements of the data sink part in correspondence to the lines, and connected to anodes of the light emitting devices in common are operative opposite to the data lines. However, corresponding signal waveforms are identical as shown in data 1_B and data N_B.
In this instance, all the data lines are grounded, and turned off during the ‘T’ time period, which is the refresh time period.
In correspondence to the signal waveforms of the data 1–data N, signal waveforms of A-1–A_N at respective anodes are as shown in FIG. 7. It can be noted that the signal waveforms of A-1–A_N vary with a slight time delays.
Elements in the scan controlling part in correspondence to the scan lines are operative opposite to the scan lines. However, corresponding signal waveforms are identical as shown in scan 1_B–scan M_B. The scan lines are also grounded during the ‘T’ time period, and turned off.
In correspondence to variation of the scan 1–scan M, waveforms of the B_1–B_M at respective cathodes vary as shown in FIG. 8. The waveforms of the B_1–B_M are also varied with a slight time delays.
Thus, upon dropping the data signals and the scan signals applied to the data driving part and the scan driving part to the ground utilizing the refresh time period ‘T’, a responsive time period can be shortened substantially, and the current required for an entire operation can be reduced substantially.
One is a method in which a power consumption is reduced, which is occurred as the data signals on the data lines are dropped from high signals to ground during the ‘T’ time period, the refresh time period, and turned to the high signals again at a time point the refresh time period ends.
The other is a method in which a power consumption is reduced, which is occurred as the scan signals on the scan lines are dropped from high signals to ground during the ‘T’ time period, the refresh time period, and turned to the high signals again at a time point the refresh time period ends.
Therefore, since there is much current flowing during the refresh time period, the source terminals of the data 1_B–data N_B, the N sink elements, are connected together, and therefrom connected to the input of the transformer 10 d. The ref1–refM, refresh elements, are respectively connected between the scan1–scanM, M scan driving circuits and scan 1_B–scan M_B, inverse voltage elements in the scan controlling part. Drain terminals of the ref1–refM are connected to cathodes of the light emitting device part 60 respectively, and source terminals of the ref1–refM are connected together, and therefrom to the input of the transformer 10 d. Therefore, there is much current flowing to the input of the transformer 10 d during the moment of refresh time period. That is, a current with a waveform of ‘CD’ part shown in FIGS. 7 and 8 in common is applied.
The momentary current flowing thus forms a flow of charge at an output terminal having a winding ratio of 1:M in the transformer 10 d. That is, the output terminal becomes to have a waveform of ‘DD’ part shown in FIGS. 7 and 8 in common, and provides a certain voltage to the controlling part 20 d connected to the next stage.
The voltage formed to a certain level under the control of the controller 20 d is applied to the power source part 30 of entire system through the diode 40 d. That is, the voltage has a waveform of a ‘PD’ part shown in FIGS. 7 and 8 in common.
That is, at least one of the N data sink parts (or scan driving parts) is turned on, an anode voltage (a voltage as point ‘A’–‘N’) of a relevant light emitting device is charged to the coil 401 through a relevant data sink part.
FIGS. 11–13 illustrate examples showing a connection of a switch and a diode with the voltage transforming part. That is, FIGS. 11–13 illustrate circuits showing exemplary applications in which a diode 110 a is connected to a connection part of the voltage transforming part, so that a voltage caused by an electromotive force generated at an inductor gives no influence to other circuit, or switch devices 111 a, 112 a, and 113 a are connected to the connection part of the voltage transforming part for stable operation and noise reduction of the voltage transforming part.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4594589Aug 27, 1982Jun 10, 1986Sharp Kabushiki KaishaMethod and circuit for driving electroluminescent display panels with a stepwise driving voltageUS5714968Aug 8, 1995Feb 3, 1998Nec CorporationCurrent-dependent light-emitting element drive circuit for use in active matrix display deviceUS5770923Oct 22, 1996Jun 23, 1998Norand CorporationPower supply for an electroluminescent panel or the likeUS5838289 *Sep 26, 1995Nov 17, 1998Nippondenso Co., Ltd.EL display driver and system using floating charge transfers to reduce power consumptionUS5852426 *Mar 21, 1996Dec 22, 1998Vivid Semiconductor, Inc.Power-saving circuit and method for driving liquid crystal displayUS5943030Nov 25, 1996Aug 24, 1999Nec CorporationDisplay panel driving circuitUS6028573 *Sep 17, 1996Feb 22, 2000Hitachi, Ltd.Driving method and apparatus for display deviceUS6229506Apr 22, 1998May 8, 2001Sarnoff CorporationActive matrix light emitting diode pixel structure and concomitant methodUS6559603 *Sep 10, 2001May 6, 2003Pioneer CorporationDriving apparatus for driving display panelEP0274380A2Jan 5, 1988Jul 13, 1988Sharp Kabushiki KaishaDriving circuit for thin film EL display deviceEP0377956A1Nov 20, 1989Jul 18, 1990United Technologies CorporationRow drive for EL panels and the like with transformer couplingJP2000148093A Title not availableJPH09146490A Title not availableJPH11338416A Title not availableJPS59167492A Title not available* Cited by examinerNon-Patent CitationsReference1Higgins ML: "High-quality Electroluminescent Display for a Personal Workstation," Hewlett-Packard Journal, Hewlett-Packard Co. Palo Alto, US, vol. 36, No. 10, Oct. 1, 1995, pp. 12-17.2Japanese Office Action dated Sep. 7, 2005.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS20140203725 *Jan 18, 2013Jul 24, 2014Chyng Hong Electronic Co.Power circuit of a vacuum fluorescent display having neither transformer nor electromagnetic interference* Cited by examinerClassifications U.S. Classification345/211, 345/209International ClassificationH05B33/08, H01L27/32, G09F9/30, G09G3/20, G09G3/30, G09G5/00, G09G3/32, H01L51/50Cooperative ClassificationG09G2330/04, G09G2310/0256, G09G3/3233, G09G2310/0262, G09G2300/0809, G09G2330/024, G09G2320/043European ClassificationG09G3/32A8CLegal EventsDateCodeEventDescriptionMay 22, 2002ASAssignmentOwner name: LG ELECTRONICS INC., KOREA, REPUBLIC OFFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KIM, HAK SU;LEE, MINHO;CHO, YOUNG-WAN;AND OTHERS;REEL/FRAME:012926/0520Effective date: 20020521Jun 9, 2008ASAssignmentOwner name: LG DISPLAY CO., LTD., KOREA, REPUBLIC OFFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LG ELECTRONICS INC.;REEL/FRAME:021090/0886Effective date: 20080404Owner name: LG DISPLAY CO., LTD.,KOREA, REPUBLIC OFFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LG ELECTRONICS INC.;REEL/FRAME:021090/0886Effective date: 20080404Oct 21, 2010FPAYFee paymentYear of fee payment: 4Dec 11, 2014FPAYFee paymentYear of fee payment: 8RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services