Drive unit of self-luminous device with degradation detection function

• US 20040027320A1
• Filed: 04/14/2003
• Published: 02/12/2004
• Est. Priority Date: 04/15/2002
• Status: Active Grant

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Ochi, Hideo, Sakamoto, Tsuyoshi, Ishizuka, Shinichi, Tsuchida, Masami
• Granted Patent: US 7,215,307 B2
• Time in Patent Office: Days
• US Class Current: 345/84
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• 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 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/20 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
• CPC Class Codes: G09G 3/3216 using a passive matrix
• 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 unit which can prevent the decrease of the luminance of a self-luminous device due to degradation or a change is electric characteristic thereof. The drive unit has a semiconductor device having an electric characteristic almost the same as the that of the self-luminous device, and drives the semiconductor device in accordance with the frequency of light emission of the self-luminous device. The device generates a characteristic change detection signal indicating the degree of a change in an electric characteristic of the semiconductor device, and supplies the self-luminous device with a drive signal having a current level or a voltage level based on the characteristic change detection signal.

Claims

1. A drive unit for driving a self-luminous device to make said self-luminous device emit light, said drive unit comprising:

a semiconductor device having an electric characteristic substantially equal to an electric characteristic of said self-luminous device;

a driver for driving said semiconductor device in accordance with frequency of light emission from said self-luminous device;

a characteristic change detector for generating a characteristic change detection signal indicating degree of characteristic change in said semiconductor device; and

a drive signal supply device for supplying said self-luminous device with a drive signal having a current level or a voltage level based on said characteristic change detection signal.

2. The drive unit according to claim 1, wherein said driver comprises:

a switch device turned on in accordance with the frequency of light emission of said self-luminous device; and

a constant current supply device for supplying said semiconductor device with a constant current in a forward direction while said switch device is turned on.

3. The drive unit according to claim 1, wherein said characteristic change detector comprises a sample hold circuit, said sample hold circuit detecting a voltage across said semiconductor device as said characteristic change detection signal, in order to supply said drive signal supply device with said characteristic change detection signal, while said driver drives said self-luminous device, said sample hold circuit holding the voltage across said semiconductor device detected just before said self-luminous device is turned off, in order to supply said drive signal supply device with hold a voltage as said characteristic change detection signal, while said driver does not drive said self-luminous device.

4. The drive unit according to claim 3, wherein said drive signal supply device comprises:

a current supply circuit for outputting a reference current corresponding to an output voltage from said sample hold circuit; and

a current mirror circuit for supplying said self-luminous device with a current having a level being proportionate to the reference current output from said current supply circuit as said drive signal.

5. The drive unit according to claim 3, wherein said drive signal supply device comprises:

a booster circuit for boosting an output voltage from said sample hold circuit and outputting a boosted voltage to said drive signal supply device as a power source voltage;

a current supply circuit for outputting a reference current corresponding to the output voltage from said sample hold circuit;

a current mirror circuit for supplying said self-luminous device with a current having a level being proportionate to the reference current output from said current supply circuit as said drive signal.

6. The drive unit according to claim 3, wherein said drive signal supply device comprises:

an arithmetic part for performing a predetermined computation based on an output voltage from said sample hold circuit, and outputting a voltage in accordance with a result of the computation;

a current supply circuit for outputting reference current corresponding to the output voltage from said arithmetic part;

a current mirror circuit for supplying said self-luminous device with a current having a level being proportionate to the reference current output from said current supply circuit as said drive signal.

7. The drive unit according to claim 3, wherein said drive signal supply device comprises a circuit for applying a voltage having a level in accordance with an output voltage from said sample hold circuit to said self-luminous device as said drive signal.

8. The drive unit according to claim 1, wherein said self-luminous device is an organic electroluminescent device.

9. The drive unit according claim 1, wherein said semiconductor device is an organic electroluminescent device or an organic semiconductor.

10. The drive unit according to claim 1, wherein said drive signal supply device comprises a circuit for applying a voltage having a level in accordance with an output voltage from said sample hold circuit to a cathode driving circuit of said self-luminous device as a power supply voltage of said cathode driving circuit.

11. The drive unit according to claim 1, wherein said drive signal supply device comprises a circuit for applying a voltage having a level in accordance with an output voltage from said sample hold circuit to a cathode driving circuit of said self-luminous device as a second voltage applied through each of switches in said cathode driving circuit.