Method of driving display panel and drive for carrying out same

• US 7,561,123 B2
• Filed: 09/25/2003
• Issued: 07/14/2009
• Est. Priority Date: 04/10/2003
• Status: Expired due to Fees

• Current Assignee: Oki Semiconductor Company Limited (ROHM Co., Ltd.)
• Original Assignee: Oki Semiconductor Company Limited (ROHM Co., Ltd.)
• Inventors: Satoh, Shinichi
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): Shapiro; Leonid
• Application Number:
  US10/669,446
• Publication Number:
  US 20040201554A1
• Time in Patent Office: 2,119 Days
• Field of Search: 345 76- 77, 345/204, 315/169.3
• US Class Current: 345/76
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

A drive of a display panel, according to the invention, comprises first switching means SEG_m for changing over between connection of the respective data lines SWsm to the side of respective variable current sources and connection thereof to a grounding side, second switching means SWc2 for changing over a potential of the respective scanning lines between a power supply potential V_C and a grounding potential, a drive control circuit for controlling the first switching means and second switching means correspondingly to input data, a comparison circuit provided in each of the data lines, for outputting a control signal by comparing a potential from a voltage regulator with a potential of the respective data lines, and a current control circuit for controlling a current of the variable current source provided in each of the data lines based on results of comparison executed by the respective comparison circuit.

Claims

1. A method of driving a display panel made up of (n×

m) display elements respectively disposed at different crossover points of a matrix formed of n rows of scanning lines and m columns of data lines, the method comprising variably controlling respective constant current values for driving the respective data lines,

wherein said variably controlling the constant current values is implemented by individually comparing a reference voltage with a voltage of each of the respective data lines as driven by the constant current values, using respective comparators each having a first input connected to the reference voltage and a second input connected to a respective one of the data lines, and

wherein said variably controlling the constant current values is further implemented by supplying a constant current to the data lines by respective first transistors, and by supplying an adjustment current to the data lines by respective second transistors responsive to control signals output from the comparators.

2. The method of driving a display panel according to claim 1, wherein the display elements are organic EL elements.

3. A drive of a display panel for driving (n×

m) display elements respectively disposed at different crossover points of a matrix formed of n rows of scanning lines and m columns of data lines, the display elements each having an anode connected to a respective one of the data lines and a cathode connected to a respective one of the scanning lines, the drive comprising;

first switching means for changing over between connection of the respective data lines to respective variable current sources and connection thereof to ground;

second switching means for changing over a potential of the respective scanning lines between a power supply potential and ground;

driving means for controlling the first switching means and second switching means responsive to input data;

comparison means respectively provided for each of the data lines, said comparison means each having a first input coupled to a respective one of the data lines and for outputting a control signal by comparing a reference voltage from a reference voltage generator with a potential of the respective one of the data lines; and

current control means for individually controlling respective current values flowing from the variable current sources to the respective data lines, based on respective results of comparison executed by the comparison means,

each of the variable current sources having a first transistor and a second transistor connected to the respective data lines, the first transistors supplying constant currents to the respective data lines, and the second transistors supplying adjustment currents to the respective data lines responsive to the control signals.

4. The drive of a display panel according to claim 3, wherein the comparison means detect a decrease in current of the respective variable current sources based on an increase in potential of the respective data lines to thereby control an increase of the current of the respective variable current sources, and detect an increase in the current of the respective variable current sources based on a drop in the potential of the respective data lines to thereby control a decrease of the current of the respective variable current sources.

5. The drive of a display panel according to claim 3, wherein the display elements are organic EL elements.

6. A drive of a display panel for driving (n×

m) display elements respectively disposed at respective crossover points of a matrix formed of n rows of scanning lines and m columns of data lines, the display elements each having an anode connected to a respective one of the data lines and a cathode connected to a respective one of the scanning lines, the drive comprising;

a first switching unit that changes over between connection of the respective data lines to respective variable current sources and connection thereof to ground;

a second switching unit that changes over a potential of the respective scanning lines between a power supply potential and ground;

a drive control circuit that controls the first switching unit and the second switching unit responsive to input data;

comparators respectively provided for each of the data lines, the comparators each having a first input coupled to a respective one of the data lines, the comparators each output control signals by comparing a reference voltage from a voltage regulator with a potential of the respective one of the data lines; and

current control circuits respectively provided for each of the data lines, the current control circuits individually control current values flowing from the respective variable current sources to the respective one of the data lines, based on respective results of comparison by the comparators,

each of the variable current sources having a first transistor and a second transistor connected to the respective data lines, the first transistors supplying constant currents to the respective data lines and the second transistors supplying adjustment currents to the respective data lines responsive to the control signals.

7. The drive of a display panel according to claim 6, wherein the comparators detect a decrease in the current of the respective variable current sources based on an increase in the potential of the respective data lines to thereby control an increase of the current of the respective variable current sources, and detect an increase in the current of the respective variable current sources based on a drop in the potential of the respective data lines to thereby control a decrease of the current of the respective variable current sources.