Electronic device and driving method thereof

• US 6,611,108 B2
• Filed: 04/25/2001
• Issued: 08/26/2003
• Est. Priority Date: 04/26/2000
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Lee, Wilson
• Application Number:
  US09/841,098
• Publication Number:
  US 20010035863A1
• Time in Patent Office: 853 Days
• Field of Search: 315/169--16, 345/60-72, 345/77, 345/78
• US Class Current: 315/169.3
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/78627 with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD

Abstract

A pixel is provided in which normal display of an image is possible even if a sustain period is shorter than an address period in a driving method combining digital gray scales and time gray scales, and in which operation can be compensated by changing the electric potential of a signal line even for a case in which the EL driver transistor becomes normally on due to deterioration. One of a source region and a drain region of an erasure TFT is connected to an electric current supply line, and the remaining one of the source region and the drain region is connected to a gate signal line. It is possible to change the voltage between a gate and a source of an EL driver TFT by changing the electric potential of the gate signal line so that the EL driver TFT is placed in a non-conducting state with certainty with this structure, even for cases in which the EL driver TFT becomes normally on due to a shift in the value of its threshold voltage.

Claims

1. A method of driving an electronic device, wherein:

one frame period has n subframe periods SF₁, SF₂, . . . , SF_n;

the n subframe periods each have address (write in) periods Ta₁, Ta₂, . . . , Ta_n, and sustain (turn on) periods Ts₁, Ts₂, . . . , Ts_n;

the address (write in) period and the sustain (turn on) period overlap in at least one subframe period among the n subframe periods; and

when ta_m>

ts_m+t_g is satisfied in a certain subframe period SF_m (where ta_m, is the length of the address (write in) period, ts_m is the length of the sustain (turn on) period and t_g is the length of one gate signal line selection period and 1≦

m≦

n), a non-display period exists in a period from the completion of the sustain (turn on) period SF_m of the subframe period SF_m, until the start of the address (write in) period Ta_m+1.

4. A method of driving an electronic device according to claim 1, wherein:

the EL driver transistor is placed in a non-conductive state in the non-display period by the reset transistor being conductive due to a signal input from a reset signal line driver circuit; and

during a period after the reset transistor returns to a non-conducting state, until write in of the next signal from the source signal line is preformed, the gate voltage of the EL driver transistor is maintained by the storage capacitor.

7. A method of driving an electronic device according to claim 1, wherein the EL element is turned off during the non-display period, irrespective of an image signal.

10. A method of driving an electronic device according to claim 1, wherein the gate voltage of the EL driver transistor in the non-display period is determined by the difference between the electric potential of the electric current supply line and the electric potential of a certain gate signal line in a non-selected state.

13. A method of driving an electronic device according to claim 1, wherein an electric potential lower than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non-selected state for a case in which the EL driver transistor has n-channel polarity.

16. A method of driving an electronic device according to claim 1, wherein an electric potential higher than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non-selected state for a case in which the EL driver transistor has p-channel polarity.

19. A method of driving an electronic device according to claim 1, wherein said electronic device is a device selected from the group consisting of:

an EL display, a video camera, a head-mounted, a DVD player, a personal computer, a portable telephone and a car audio system.

2. A method of driving an electronic device, wherein:

one frame period has n subframe periods SF₁, SF₂, . . . , SF_n;

the n subframe periods each have address (write in) periods Ta₁, Ta₂, . . . , Ta_n, and sustain (turn on) periods Ts₁, Ts₂, . . . , Ts_n;

the address (write in) period and the sustain (turn on) period overlap in at least one subframe period among the n subframe periods; and

when ta_n>

ts_n+t_g is satisfied in the subframe period SF_n of the number j frame (where ta_n is the length of the address (write in) period, ts_n is the length of the sustain (turn on) period and t_g is the length of one gate signal line selection period, and 0<

j, a non-display period exists in a period from the completion of the sustain (turn on) period Ts_n of the subframe period SF₁ of the number j frame, until the start of the address (write in) period Ta₁ of the subframe period SF₁ of the number j+1 frame.

5. A method of driving an electronic device according to claim 2, wherein:

the EL driver transistor is placed in a non-conductive state in the non-display period by the reset transistor being conductive due to a signal input from a reset signal line driver circuit; and

during a period after the reset transistor returns to a non-conducting state, until write in of the next signal from the source signal line is preformed, the gate voltage of the EL driver transistor is maintained by the storage capacitor.

8. A method of driving an electronic device according to claim 2, wherein the EL element is turned off during the non-display period, irrespective of an image signal.

11. A method of driving an electronic device according to claim 2, wherein the gate voltage of the EL driver transistor in the non-display period is determined by the difference between the electric potential of the electric current supply line and the electric potential of a certain gate signal line in a non-selected state.

12. A method of driving an electronic device according to claim 5, wherein the gate voltage of the EL driver transistor in the non-display period is determined by the difference between the electric potential of the electric current supply line and the electric potential of a certain gate signal line in a non-selected state.

14. A method of driving an electronic device according to claim 2 wherein an electric potential, lower than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non- elected state for a case in which the EL driver transistor has n-channel polarity.

17. A method of driving an electronic device according to claim 2, wherein an electric potential higher than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non-selected state for a case in which the EL driver transistor has p-channel polarity.

20. A method of driving an electronic device according to claim 2, wherein said electronic device is a device selected from the group consisting of:

an EL display, a video camera, a head-mounted, a DVD player, a personal computer, a portable telephone and a car audio system.

3. A method of driving an electronic device, wherein:

one frame period has n subframe periods SF₁, SF₂, . . . , Sf_n;

the n subframe periods each have address (write in) periods Ta₁, Ta₂, . . . , Ta_n, and sustain (turn on) periods Ts₁, Ts₂, . . . , Ts_n; and

when ta_k>

ts_k+tg is satisfied in a certain subframe period SF_k (1≦

k≦

n), where the length of the address (write in) period is taken as ta_k, the length of the sustain (turn on) period is taken as ts_k, and the length of one gate signal line selection period is taken as tg, and ta_k, ts_k, tg>

0, and if the length of a non-display period of SF_k is taken as tr_k (where tr_k>

0);

tr_k≧

ta_k−

(ts_k+tg) is always satisfied.

6. A method of driving an electronic device according to claim 3, wherein:

the EL driver transistor is placed in a non-conductive state in the non-display period by the reset transistor being conductive due to a signal input from a reset signal line driver circuit; and

during a period after the reset transistor returns to a non-conducting state, until write in of the next signal from the source signal line is preformed, the gate voltage of the EL driver transistor is maintained by the storage capacitor.

9. A method of driving an electronic device according to claim 3, wherein the EL element is turned off during the non-display period, irrespective of an image signal.

15. A method of driving an electronic device according to claim 3, wherein an electric potential lower than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non-selected state for a case in which the EL driver transistor has n-channel polarity.

18. A method of driving an electronic device according to claim 3, wherein an electric potential higher than the threshold voltage of the EL driver transistor, with respect to the electric potential of the electric current supply line, is inputted to the gate signal line in a non-selected state for a case in which the EL driver transistor has p-channel polarity.

21. A method of driving an electronic device according to claim 3, wherein said electronic device is a device selected from the group consisting of:

an EL display, a video camera, a head-mounted, a DVD player, a personal computer, a portable telephone and a car audio system.