Organic EL panel drive circuit and organic EL display device using the same drive circuit

• US 20050001795A1
• Filed: 05/28/2004
• Published: 01/06/2005
• Est. Priority Date: 06/06/2003
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Kitahara, Shinji
• Granted Patent: US 7,292,234 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• 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 resetting period of organic EL elements is divided to a discharge period for discharging residual charges of the organic EL elements and a precharge period for pre-charging the organic EL elements to predetermined potentials. First switch circuits provided for each of R (red), G (green) and B (blue) display colors are turned ON in the discharge period to discharge residual charges of the organic EL elements and second switch circuits provided for each of R, G and B display colors are turned ON in the precharge period to precharge the EL elements to a precharge potential lower than a light emission voltage of the organic EL elements. Values of finally set precharge voltages for R, G and B display colors are made different from each other.

Claims

1. An organic EL panel drive circuit for current-driving an organic EL panel through terminal pins thereof, which are provided correspondingly to R, G and B display colors, comprising:

at least three first switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminal pins and a first potential line at a first potential, for discharging residual chargers of organic EL elements having anodes connected to said terminal pins;

at least three second switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminals and a second potential line at a second potential, for setting said anodes of said organic EL elements to predetermined potentials lower than light emission potentials of said EL elements; and

a pulse generator circuit for generating pulses for turning said first switch circuits ON and then turning the first switch circuits and the second switch circuits OFF and ON within a predetermined time period, respectively.

2. The organic EL panel drive circuit as claimed in claim 1, wherein the predetermined time period is a resetting period, said pulses generated by said pulse generator circuit reset said organic EL elements to a constant voltage determined by said second potential and said first potential is lower than said second potential.

3. The organic EL panel drive circuit as claimed in claim 2, wherein each said pulse generated by said pulse generator circuit is composed of a first pulse and a second pulse, said first pulse functions to turn said first switch circuit ON and then OFF, said second pulse functions to turn said second switch circuit ON and then OFF in the resetting period, said first potential is ground potential and said second potential line is at a potential higher than ground potential.

4. The organic EL panel drive circuit as claimed in claim 3, wherein said resetting period has a discharge period and a precharge period for resetting the organic EL element to the constant voltage, a width of said first pulse corresponds to the discharge period and a width of said second pulse corresponds to the precharge period.

5. The organic EL panel drive circuit as claimed in claim 4, wherein said second potential line includes a potential line for R display color and a potential line for G or B display color, the potential of said second potential line for R display color is different from the potential of said second potential line for G or B display color.

6. The organic EL panel drive circuit as claimed in claim 5, further comprising a programmable voltage generator circuit for generating a programmable voltage corresponding to the potential of said second potential line for R or G or B display color, wherein the second potential for R display color and the second potentials for G and B display colors are different.

7. The organic EL panel drive circuit as claimed in claim 6, wherein said pulses generated by said pulse generator circuit are provided correspondingly to respective R, G and B display colors and the second potentials for R, G and B display colors are different.

8. The organic EL panel drive circuit as claimed in claim 6, wherein said pulse generator circuit sets said anodes to ground potential once by turning said first switch circuits ON by said first pulse, said width of said first pulse for R display color is less than said width of said first pulse for each of G and B display colors and said predetermined potential of said organic EL element for each of G and B display colors is lower than said predetermined potential of the organic EL element for R display color.

9. The organic EL panel drive circuit as claimed in claim 7, wherein said pulse generator circuit has a programmable pulse generator circuit for making the width of said pulse selectable and said width of said second pulse for R display color is larger than said width of said second pulse for each of G and B display colors.

10. An organic EL panel drive circuit for current-driving an organic EL panel through terminal pins thereof, which are provided correspondingly to R, G and B display colors, comprising:

at least three first switch circuits and provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminal pins and a first potential line at a first potential, for discharging residual chargers of organic EL elements having anodes connected to said terminal pins;

at least three second switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminals and a second potential line at a second potential, for setting said anodes of said organic EL elements to predetermined potentials lower than light emission potentials of said EL elements; and

a pulse generator circuit for generating pulses for turning said first switch circuits ON and then turning the first switch circuits and the second switch circuits OFF and ON within a predetermined time period, respectively, said pulses generated by said pulse generator circuit having widths, with which said predetermined potentials for at least two of the R, G and B display colors are made different, in order to regulate luminous intensities of R, G and B display colors for regulation of white balance.

11. The organic EL panel drive circuit as claimed in claim 10, wherein said predetermined time period is a resetting period, said pulses generated by said pulse generator circuit reset said organic EL elements to a constant voltage determined by said second potential and the potential of said first potential line is lower than the potential of said second potential line.

12. The organic EL panel drive circuit as claimed in claim 11, wherein each said pulses generated by said pulse generator circuit is composed of a first pulse and a second pulse, said first pulse functions to turn said first switch circuit ON and then OFF, said second pulse functions to turn said second switch circuit ON and then OFF in the resetting period, said first potential line is at ground potential and said second potential line is at potential higher than ground potential.

13. The organic EL panel drive circuit as claimed in claim 12, wherein said resetting period has a discharge period and a precharge period for resetting the organic EL element to the constant voltage, a width of said first pulse corresponds to the discharge period and a width of said second pulse corresponds to the precharge period.

14. The organic EL panel drive circuit claimed in claim 13, wherein said second potential line includes a potential line for R display color and a potential line for G or B display color, a potential of said potential line for R display color of said second potential line and a potential of said potential line for G or B display color of said second potential line are made different.

15. The organic EL panel drive circuit as claimed in claim 14, wherein said pulse generator circuit sets said anodes of said organic EL elements to ground potential once by turning said first switch circuit ON by said first pulse, said width of said first pulse for R display color is less than said width of said first pulse for each of G and B display colors and said predetermined potential of said organic EL elements for each of G and B display colors is lower than said predetermined potential of said organic EL elements for R display color.

16. The organic EL panel drive circuit as claimed in claim 15, further comprising a reference current generator circuit and a reference current forming circuit provided for each of the R, G and B display colors, wherein said second potential line is provided for each of the R, G and B display colors, said reference current forming circuits are responsive to reference currents generated by said reference current generator circuits and externally set data to form currents having values corresponding to the externally set data as drive currents to be supplied to said terminal pins or currents, which are bases of the drive currents and values of said drive currents generated by said reference current forming circuit are set correspondingly to the respective R, G and B display colors in order to perform luminance regulation to thereby obtain white balance.

17. An organic EL display device for current-driving an organic EL panel through terminal pins thereof, which are provided correspondingly to R, G and B display colors, comprising:

at least three first switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminal pins and a first potential line, for discharging residual chargers of organic EL elements having anodes connected to said terminal pins;

at least three second switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminals and a second potential line, for setting said anodes of said organic EL elements to predetermined potentials lower than light emission potentials of said EL elements; and

a pulse generator circuit for generating pulses for turning said first switch circuits ON and then turning the first switch circuits and the second switch circuits OFF and ON within a predetermined time period, respectively.

18. The organic EL display device as claimed in claim 17, wherein the predetermined time period is a resetting period, said pulses generated by said pulse generator circuit reset said organic EL elements to a constant voltage determined by said second potential and the potential of said first potential line is lower than the potential of said second potential line.

19. The organic EL display device as claimed in claim 18, wherein each said pulse generated by said pulse generator circuit is composed of a first pulse and a second pulse, said first pulse functions to turn said first switch circuit ON and then OFF, said second pulse functions to turn said second switch circuit ON and then OFF in the resetting period, said first potential line is at ground potential and said second potential line is at a potential higher than ground potential.

20. The organic EL display device as claimed in claim 19, wherein said resetting period has a discharge period and a precharge period for resetting the organic EL element to the constant voltage, a width of said first pulse corresponds to the discharge period and a width of said second pulse corresponds to the precharge period.

21. The organic EL display device as claimed in claim 20, wherein said second potential line includes a potential line for R display color and a potential line for G or B display color, a potential of said potential line for R display color of said second potential line and a potential of said potential line for G or B display color of said second potential line are different.

22. An organic EL display device for current-driving an organic EL panel through terminal pins thereof, which are provided correspondingly to respective R, G and B display colors, comprising:

at least three first switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminal pins and a first potential line, for discharging residual chargers of organic EL elements having anodes connected to said terminal pins;

at least three second switch circuits provided correspondingly to said terminal pins for R, G and B display colors and connected between said terminals and a second potential line, for setting said anodes of said organic EL elements to predetermined potentials lower than light emission potentials of said EL elements; and

a pulse generator circuit for generating pulses for turning said first switch circuits ON and then turning the first switch circuits and the second switch circuits OFF and ON within a predetermined time period, respectively, said pulse generator circuit generating said pulses having widths, with which said predetermined potentials for at least two of the R, G and B display colors are made different, in order to regulate luminous intensities of R, G and B display colors for regulation of white balance.

23. The organic EL display device as claimed in claim 22, wherein said predetermined time period is a resetting period having a discharge period and a precharge period for resetting the organic EL element to the constant voltage, said pulses generated by said pulse generator circuit reset said organic EL elements to a constant voltage determined by said second potential and the potential of said first potential line is lower than the potential of said second potential line.

24. The organic EL display device as claimed in claim 23, wherein each said pulse generated by said pulse generator circuit is composed of a first pulse and a second pulse, said first pulse has a first width for turning said first switch circuits ON and then OFF correspondingly to the discharge period, said second pulse has a second width for turning said second switch circuits ON and then OFF in the resetting period correspondingly to the precharge period, said first potential line is at ground potential and said second potential line is at a potential higher than ground potential.