Driving circuit for display apparatus, and method of driving display apparatus

• US 5,594,463 A
• Filed: 07/12/1994
• Issued: 01/14/1997
• Est. Priority Date: 07/19/1993
• Status: Expired due to Term

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Sakamoto, Mitsunao
• Primary Examiner(s): SARAS, STEVEN J
• Application Number:
  US08/273,816
• Time in Patent Office: 917 Days
• Field of Search: 345/36, 345/37, 345/76, 345/77, 345/78, 345/101
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• 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 2310/0272 Details of drivers for data electrodes, the drivers communicating data to the pixels by means of a current
• CPC Class Codes: G09G 2310/0275 Details 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
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/3216 using a passive matrix

Abstract

A display apparatus has a display panel, which is provided with a plurality of scanning electrodes and a plurality of signal electrodes arranged in a matrix shape, and a plurality of EL elements connected to the scanning electrodes and the signal electrodes at intersections thereof. A driving circuit for the display apparatus is provided with: a driving device for supplying a constant current driving signal to the signal electrodes in correspondence with an input signal, to drive the display panel; a detection device for detecting a voltage drop in a forward direction of the EL element, and outputting a detection signal which indicates the detected voltage drop; and a control device for controlling voltage, which is supplied to the driving device, to have a predetermined voltage value in correspondence with the detection signal from the detection device.

Claims

1. A driving circuit for a display apparatus having a display panel, which comprises a plurality of scanning electrodes and a plurality of signal electrodes arranged in a matrix shape, and a plurality of EL (Electroluminescence) elements connected to the scanning electrodes and the signal electrodes at intersections thereof, said driving circuit comprising:

a driving means for supplying a constant current driving signal to said signal electrodes in correspondence with an input signal, to drive said display panel;

a detection means for detecting a voltage drop in a forward direction of the EL element, and outputting a detection signal which indicates the detected voltage drop;

a control means for controlling voltage, which is supplied to said driving means, to have a predetermined voltage value for maintaining said driving means with respect to said EL elements in an initial usage condition and controlling the voltage to have an increased voltage value larger than the predetermined voltage value for compensating a voltage drop component of said EL elements due to degradation of said EL elements with respect to said EL elements in a used condition, in correspondence with the detection signal from said detection means; and

a temperature detection means for detecting a temperature of said display panel, said control means correcting the detected voltage drop of the detection signal on the basis of the detected temperature.

2. A driving circuit according to claim 1, wherein said control means checks whether the detected temperature exceeds an upper limit temperature of said display panel or not, and controls said driving means to decrease the current value of the constant current driving signal if the detected temperature exceeds the upper limit.

3. A driving circuit according to claim 1, wherein a detection terminal is installed to at least one of the signal electrodes and the scanning electrodes, where the voltage drop is detected by said detection means.

4. A driving circuit according to claim 3 wherein said detection terminal is installed to at least one of the signal electrode and the scanning electrode corresponding to a central portion of a picture plane of said display panel.

5. A driving circuit according to claim 1, wherein said control means controls the voltage to have a low voltage value when the detection means detects a small voltage drop, and controls the voltage to have a high voltage value when the detection means detects a large voltage drop.

6. A driving circuit for a display apparatus having a display panel, which comprises a plurality of scanning electrodes and a plurality of signal electrodes arranged in a matrix shape, and a plurality of EL (Electroluminescence) elements connected to the scanning electrodes and the signal electrodes at intersections thereof, said driving circuit comprising:

a driving means for supplying a constant current driving signal to said signal electrodes in correspondence with an input signal, to drive said display panel;

a detection means for detecting a voltage drop in a forward direction of the EL element, and outputting a detection signal which indicates the detected voltage drop;

a control means for controlling the constant current driving signal, which is supplied from said driving means, to have a predetermined current value for maintaining said EL elements with respect to said EL elements in an initial usage condition and controlling the constant current driving signal to have an increased current value larger than the predetermined current value for keeping the luminance of said EL elements constant by compensating a voltage drop component of said EL elements due to degradation of said EL elements with respect to said EL elements in a used condition, in correspondence with the detection signal from said detection means; and

a temperature detection means for detecting a temperature of said display panel, said control means correcting the detected voltage drop of the detection signal on the basis of the detected temperature.

7. A driving circuit according to claim 6, wherein said control means checks whether the detected temperature exceeds an upper limit temperature of said display panel or not, and controls said driving means to decrease the current value of the constant current driving signal if the detected temperature exceeds the upper limit.

8. A driving circuit according to claim 6, wherein a detection terminal is installed to at least one of the signal electrodes and the scanning electrodes, where the voltage drop is detected by said detection means.

9. A driving circuit according to claim 8 wherein said detection terminal is installed to at least one of the signal electrode and the scanning electrode corresponding to a central portion of a picture plane of said display panel.

10. A driving circuit according to claim 6, wherein said control means controls the constant current driving signal to have a low current value when the detection means detects a small voltage drop, and controls the constant current driving signal to have a high current value when the detection means detects a large voltage drop.

11. A method of driving a display apparatus having a display panel, which comprises a plurality of scanning electrodes and a plurality of signal electrodes arranged in a matrix shape, and a plurality of EL (Electroluminescence) elements connected to the scanning electrodes and the signal electrodes at intersections thereof, said method comprising the steps of:

supplying a constant current driving signal to said signal electrodes in correspondence with an input signal, to drive said display panel by a driving device;

detecting a voltage drop in a forward direction of the EL element, and outputting a detection signal which indicates the detected voltage drop;

controlling voltage, which is supplied to said driving device, to have a predetermined voltage value for maintaining said driving device with respect to said EL elements in an initial usage condition and controlling the voltage to have an increased voltage value larger than the predetermined voltage value for compensating a voltage drop component of said EL elements due to degradation of said EL elements with respect to said EL elements in a used condition, in correspondence with the detection signal;

detecting a temperature of said display panel; and

correcting the detected voltage drop of the detection signal on the basis of the detected temperature.

12. A method according to claim 11, wherein, in the controlling step, it is checks whether the detected temperature exceeds an upper limit temperature of said display panel or not, and the current value of the constant current driving signal is decreased if the detected temperature exceeds the upper limit.

13. A method according to claim 11, wherein, in the controlling step, the voltage is controlled to have a low voltage value when a small voltage drop is detected in the detecting step, and the voltage is controlled to have a high voltage value when a large voltage drop is detected in the detecting step.

14. A method of driving a display apparatus having a display panel, which comprises a plurality of scanning electrodes and a plurality of signal electrodes arranged in a matrix shape, and a plurality of EL (Electroluminescence) elements connected to the scanning electrodes and the signal electrodes at intersections thereof, said method comprising the steps of:

supplying a constant current driving signal to said signal electrodes in correspondence with an input signal, to drive said display panel;

detecting a voltage drop in a forward direction of the EL element, and outputting a detection signal which indicates the detected voltage drop;

controlling the constant current driving signal to have a predetermined current value for maintaining said EL elements with respect to said EL elements in an initial usage condition and controlling the constant current driving signal to have an increased current value larger than the predetermined current value for keeping the luminance of said EL elements constant by compensating a voltage drop component of said EL elements due to degradation of said EL elements with respect to said EL elements in a used condition, in correspondence with the detection signal;

detecting a temperature of said display panel; and

correcting the detected voltage drop of the detection signal on the basis of the detected temperature.

15. A method according to claim 14, wherein, in the controlling step, it is checks whether the detected temperature exceeds an upper limit temperature of said display panel or not, and the current value of the constant current driving signal is decreased if the detected temperature exceeds the upper limit.

16. A method according to claim 14, wherein, in the controlling step, the constant current driving signal is controlled to have a low current value when a small voltage drop is detected in the detecting step, and the constant current driving signal is controlled to have a high current value when a large voltage drop is detected in the detecting step.