Title: Matrix display device, matrix display driving method, and matrix display driver circuit
Abstract: A display device comprises a plurality of first to fourth switching elements. On the basis of control signals from the drive control circuit, the common line is brought to the selected state when the common line is connected to the low-voltage portion for common lines by turning on the first switching element and turning off the second switching element; the common line is brought to the non-selected state when the common line is brought to the high-impedance state by turning off both the first and second switching elements; the data line is brought to the selected state when the data line is connected to the high-voltage portion for data lines by turning off the third switching element and turning on the fourth switching element; and the data line is brought to the non-selected state when the data line is connected to the low-voltage portion for data lines by turning on the third switching element and turning off the fourth switching element.
Patent Number: 7,012,587 Issued on 03/14/2006 to Satoh, et al.
| Inventors:
|
Satoh; Shinichi (Tokyo, JP);
Fukuzako; Shinichi (Kanagawa, JP);
Kashiwada; Junji (Tokyo, JP);
Kokuda; Kenji (Saitama, JP)
|
| Assignee:
|
Oki Electric Industry Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
172979 |
| Filed:
|
June 18, 2002 |
Foreign Application Priority Data
| Aug 30, 2001[JP] | 2001/260918 |
| Current U.S. Class: |
345/82 |
| Current Intern'l Class: |
G09G 3/32 (20060101) |
| Field of Search: |
345/76,77,79-80,87-89,100,204,82,55,96
327/94,111
315/169.1,169.3,169.4
|
References Cited [Referenced By]
U.S. Patent Documents
| 4652872 | Mar., 1987 | Fujita.
| |
| 4967100 | Oct., 1990 | Okutsu et al.
| |
| 5517207 | May., 1996 | Kawada et al.
| |
| 5838289 | Nov., 1998 | Saito et al.
| |
| 6323851 | Nov., 2001 | Nakanishi.
| |
| 6847193 | Jan., 2005 | Sakuragi.
| |
| Foreign Patent Documents |
| 11143429 | May., 1999 | JP.
| |
| 11305728 | Nov., 1999 | JP.
| |
Primary Examiner: Nguyen; Chanh
Attorney, Agent or Firm: Rabin & Berdo, P.C.
Claims
What is claimed is:
1. A display device comprising:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state of said n first switching elements;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at a displaying state, the selected
one of said n common lines being kept at a selected state, the selected one of
said m data lines being kept at a selected state;
said display device further comprising:
a drive control circuit which controls turn-on and turn-off of said n first switching
elements, said n second switching elements, said m third switching elements, and
said m fourth switching elements in each scan period including a display period
in which the display elements are selectively brought to the displaying state and
a discharge period in which electrical charge stored in the display elements is discharged;
wherein on the basis of control signals from said drive control circuit,
said common line is brought to the selected state when said common line is connected
to said low-voltage portion for common lines by turning on said first switching
element and turning off said second switching element;
said common line is brought to a non-selected state when said common line is
brought to a high-impedance state by turning off both said first switching element
and said second switching element;
said data line is brought to the selected state when said data line is connected
to said high-voltage portion for data lines by turning off said third switching
element and turning on said fourth switching element; and
said data line is brought to the non-selected state when said data line is connected
to said low-voltage portion for data lines by turning on said third switching element
and turning off said fourth switching element.
2. The display device according to claim 1, wherein in the discharge period,
said n common lines are brought to the high-impedance state by turning off both
said n first switching elements and said n second switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and by turning off said m fourth switching elements.
3. The display device according to claim 1, wherein in the discharge period,
said n common lines are connected to said high-voltage portion for common lines
by turning off said n first switching elements and turning on said n second switching
elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
4. The display device according to claim 1, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and by turning off said n second
switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
5. The display device according to claim 1, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and turning off said n second switching elements;
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching
elements immediately before a start point of the discharge period;
a state, in which said m data lines are connected to said low-voltage portion
for data lines, is maintained until immediately after an end point of the discharge
period; and
the data line to be selected immediately after the end point of the discharge
period is connected to said high-voltage portion for data lines by turning off
said third switching element and turning on said fourth switching element of the
data line to be selected.
6. The display device according to claim 1, further comprising:
a common line power-supply circuit which sets said high-voltage portion for common
lines to the common line power-supply voltage; and
a data-line power-supply circuit which sets said high-voltage portion for data
lines to the data-line power-supply voltage;
said low-voltage portion for common lines being connected to ground, said low-voltage
portion for data lines being connected to ground.
7. The display device according to claim 1, further comprising:
a common line power-supply circuit which sets said high-voltage portion for common
lines to the common line power-supply voltage;
a data-line power-supply circuit which sets said high-voltage portion for data
lines to the data-line power-supply voltage; and
an intermediate-voltage portion which sets said low-voltage portion for data
lines to an intermediate voltage which is higher than the ground voltage and lower
than the voltage of said high-voltage portion for data lines;
said low-voltage portion for common lines being connected to ground.
8. A display device comprising:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at displaying state, the selected
one of said n common lines being kept at selected state, the selected one of said
m data lines being kept at selected state;
said display device further comprising:
an intermediate-voltage portion which sets at least either said high-voltage
portion for common lines or said low-voltage portion for data lines to an intermediate
voltage which is higher than the ground voltage and lower than the common line
power-supply voltage and data-line power-supply voltage; and
a drive control circuit which controls the turn-on and turn-off of said n first
switching elements, said n second switching elements, said m third switching elements,
and said m fourth switching elements in each scan period including a display period
in which display elements are selectively brought to the displaying state and a
discharge period in which the charge stored in the display elements is discharged;
wherein on the basis of control signals from said drive control circuit,
said common line is brought to the selected state when said common line is connected
to said low-voltage portion for common lines by turning on said first switching
element and turning off said second switching element;
said common line is brought to non-selected state when said common line is connected
to said high-voltage portion for common lines by turning off said first switching
element and turning on said second switching element;
said data line is brought to the selected state when said data line is connected
to said high-voltage portion for data lines by turning off said third switching
element and turning on said fourth switching element; and
said data line is brought to the non-selected state when said data line is connected
to said low-voltage portion for data lines by turning on said third switching element
and by turning off said fourth switching element.
9. The display device according to claim 8, wherein said high-voltage portion
for common lines is set to an intermediate voltage which is higher than the ground
voltage and lower than the common line power-supply voltage, and said low-voltage
portion for data lines is set to an intermediate voltage which is higher than the
ground voltage and lower than the data-line power-supply voltage.
10. The display device according to claim 1, wherein
a pair of said first switching element and said second switching element connected
to the same common line is configured by a CMOS circuit; and
a pair of said third switching element and said fourth switching element connected
to the same data line is configured by a CMOS circuit.
11. The display device according to claim 1, wherein the common line power-supply
voltage of said high-voltage portion for common lines is set to a voltage lower
than the data-line power-supply voltage of said high-voltage portion for data lines.
12. A method of driving a display device, wherein said display device comprises:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at displaying state, the selected
one of said n common lines being kept at selected state, the selected one of said
m data lines being kept at selected state;
said method comprising:
controlling the turn-on and turn-off of said n first switching elements, said
n second switching elements, said m third switching elements, and said m fourth
switching elements in each scan period including a display period in which the
display elements are selectively brought to the displaying state and a discharge
period in which electrical charge stored in the display elements is discharged;
turning on said first switching element and turning off said second switching
element to connect said common line to said low-voltage portion for common lines
when said common line is brought to the selected state;
turning off both said first switching element and said second switching element
to bring said common line to high-impedance state when said common line is brought
to non-selected state;
turning off said third switching element and turning on said fourth switching
element to connect said data line to said high-voltage portion for data lines when
said data line is brought to the selected state; and
turning on said third switching element and turning off said fourth switching
element to connect said data line to said low-voltage portion for data lines when
said data line is brought to the non-selected state.
13. The method according to claim 12, wherein in the discharge period,
said n common lines are brought to the high-impedance state by turning off both
said n first switching elements and said n second switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and by turning off said m fourth switching elements.
14. The method according to claim 12, wherein in the discharge period,
said n common lines are connected to said high-voltage portion for common lines
by turning off said n first switching elements and turning on said n second switching
elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
15. The method according to claim 12, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and by turning off said n second
switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
16. The method according to claim 12, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and turning off said n second switching elements;
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching
elements immediately before a start point of the discharge period;
a state, in which said m data lines are connected to said low-voltage portion
for data lines, is maintained until immediately after an end point of the discharge
period; and
the data line to be selected immediately after the end point of the discharge
period is connected to said high-voltage portion for data lines by turning off
said third switching element and turning on said fourth switching element of the
data line to be selected.
17. The method according to claim 12, wherein
said low-voltage portion for common lines is connected to ground; and
said low-voltage portion for data lines is connected to ground.
18. The method according to claim 12, wherein
said low-voltage portion for common lines is connected to ground; and
said low-voltage portion for data lines is connected to an intermediate voltage
which is higher than the ground voltage and lower than the voltage of said high-voltage
portion for data lines.
19. A method of driving a display device, wherein said display device comprises:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at displaying state, the selected
one of said n common lines being kept at selected state, the selected one of said
m data lines being kept at selected state;
said method comprising:
controlling the turn-on and turn-off of said n first switching elements, said
n second switching elements, said m third switching elements, and said m fourth
switching elements in each scan period including a display period in which the
display elements are selectively brought to the displaying state and a discharge
period in which electrical charge stored in the display elements is discharged;
setting at least either said high-voltage portion for common lines or said low-voltage
portion for data lines to an intermediate voltage which is higher than the ground
voltage and lower than the common line power-supply voltage and data-line power-supply voltage;
turning on said first switching element and turning off said second switching
element to connect said common line to said low-voltage portion for common lines
when said common line is brought to the selected state;
turning off said first switching element and turning on said second switching
element to connect said common line to said high-voltage portion for common lines
when said common line is brought to non-selected state;
turning off said third switching element and turning on said fourth switching
element to connect said data line to said high-voltage portion for data lines when
said data line is brought to the selected state; and
turning on said third switching element and by turning off said fourth switching
element to connect said data line to said low-voltage portion for data lines when
said data line is brought to the non-selected state.
20. The method according to claim 19, wherein said high-voltage portion for common
lines is set to an intermediate voltage which is higher than the ground voltage
and lower than the common line power-supply voltage, and said low-voltage portion
for data lines is set to an intermediate voltage which is higher than the ground
voltage and lower than the data-line power-supply voltage.
21. The method according to claim 12, wherein
a pair of said first switching element and said second switching element connected
to the same common line is configured by a CMOS circuit; and
a pair of said third switching element and said fourth switching element connected
to the same data line is configured by a CMOS circuit.
22. The method according to claim 12, wherein the common line power-supply voltage
of said high-voltage portion for common lines is set to a voltage lower than the
data-line power-supply voltage of said high-voltage portion for data lines.
23. A driver circuit of a display device, wherein said display device comprises:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at displaying state, the selected
one of said n common lines being kept at selected state, the selected one of said
m data lines being kept at selected state;
said driver circuit controls the turn-on and turn-off of said n first switching
elements, said n second switching elements, said m third switching elements, and
said m fourth switching elements in each scan period including a display period
in which the display elements are selectively brought to the displaying state and
a discharge period in which electrical charge stored in the display elements is discharged;
wherein on the basis of control signals from said driver circuit,
said common line is brought to the selected state when said common line is connected
to said low-voltage portion for common lines by turning on said first switching
element and turning off said second switching element;
said common line is brought to a non-selected state when said common line is
brought to a high-impedance state by turning off both said first switching element
and said second switching element;
said data line is brought to the selected state when said data line is connected
to said high-voltage portion for data lines by turning off said third switching
element and turning on said fourth switching element; and
said data line is brought to the non-selected state when said data line is connected
to said low-voltage portion for data lines by turning on said third switching element
and turning off said fourth switching element.
24. The driver circuit according to claim 23, wherein in the discharge period,
said n common lines are brought to the high-impedance state by turning off both
said n first switching elements and said n second switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and by turning off said m fourth switching elements.
25. The driver circuit according to claim 23, wherein in the discharge period,
said n common lines are connected to said high-voltage portion for common lines
by turning off said n first switching elements and turning on said n second switching
elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
26. The driver circuit according to claim 23, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and by turning off said n second
switching elements; and
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching elements.
27. The driver circuit according to claim 23, wherein in the discharge period,
said n common lines are connected to said low-voltage portion for common lines
by turning on said n first switching elements and turning off said n second switching elements;
said m data lines are connected to said low-voltage portion for data lines by
turning on said m third switching elements and turning off said m fourth switching
elements immediately before a start point of the discharge period;
a state, in which said m data lines are connected to said low-voltage portion
for data lines, is maintained until immediately after an end point of the discharge
period; and
the data line to be selected immediately after the end point of the discharge
period is connected to said high-voltage portion for data lines by turning off
said third switching element and turning on said fourth switching element of the
data line to be selected.
28. The driver circuit according to claim 23, wherein
said low-voltage portion for common lines is connected to ground; and
said low-voltage portion for data lines is connected to ground.
29. The driver circuit according to claim 23, wherein
said low-voltage portion for common lines is connected to ground; and
said low-voltage portion for data lines is connected to an intermediate voltage
which is higher than the ground voltage and lower than the voltage of said high-voltage
portion for data lines.
30. A driver circuit of a display device, wherein said display device comprises:
n common lines arranged in rows, where n is a positive integer;
m data lines arranged in columns, where m is a positive integer;
n×m display elements positioned at intersections of said n common lines
and said m data lines;
a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
common lines;
a low-voltage portion for data lines;
a high-voltage portion for data lines, which supplies a data-line power-supply
voltage that is higher than a voltage supplied by said low-voltage portion for
data lines;
n first switching elements which are respectively connected to said n common
lines and connect said common lines to said low-voltage portion for common lines
during ON state;
n second switching elements which are respectively connected to said n common
lines and connect said common lines to said high-voltage portion for common lines
during ON state of said n second switching elements;
m third switching elements which are respectively connected to said m data lines
and connect said data lines to said low-voltage portion for data lines during ON
state of said m third switching elements; and
m fourth switching elements which are respectively connected to said m data lines
and connect said data lines to said high-voltage portion for data lines during
ON state of said m fourth switching elements;
the display element at an intersection of a selected one of said n common lines
and a selected one of said m data lines being kept at displaying state, the selected
one of said n common lines being kept at selected state, the selected one of said
m data lines being kept at selected state;
wherein said driver circuit controls the turn-on and turn-off of said n first
switching elements, said n second switching elements, said m third switching elements,
and said m fourth switching elements in each scan period including a display period
in which the display elements are selectively brought to the displaying state and
a discharge period in which electrical charge stored in the display elements is discharged;
wherein on the basis of control signals from said drive control circuit,
said common line is brought to the selected state when said common line is connected
to said low-voltage portion for common lines by turning on said first switching
element and turning off said second switching element;
said common line is brought to non-selected state when said common line is connected
to said high-voltage portion for common lines by turning off said first switching
element and turning on said second switching element;
said data line is brought to the selected state when said data line is connected
to said high-voltage portion for data lines by turning off said third switching
element and turning on said fourth switching element; and
said data line is brought to the non-selected state when said data line is connected
to said low-voltage portion for data lines by turning on said third switching element
and by turning off said fourth switching element.
31. The driver circuit according to claim 30, wherein said high-voltage portion
for common lines is set to an intermediate voltage which is higher than the ground
voltage and lower than the common line power-supply voltage, and said low-voltage
portion for data lines is set to an intermediate voltage which is higher than the
ground voltage and lower than the data-line power-supply voltage.
32. The driver circuit according to claim 23, wherein
a pair of said first switching element and said second switching element connected
to the same common line is configured by a CMOS circuit; and
a pair of said third switching element and said fourth switching element connected
to the same data line is configured by a CMOS circuit.
33. The driver circuit according to claim 23, wherein the common line power-supply
voltage of said high-voltage portion for common lines is set to a voltage lower
than the data-line power-supply voltage of said high-voltage portion for data lines.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a dot-matrix display device such as an organic
electroluminescence (EL) display device, a method of driving the display device,
and a driver circuit of the display device.
FIG. 29 is a circuit diagram showing a conventional organic EL display device.
As shown in FIG. 29, the conventional display device has n common lines (namely,
scan lines) COM
1 to COM
n arranged in rows, m data lines SEG
1
to SEG
m arranged in columns, and n×m EL elements PE
1,1
to PE
m,n that are disposed at the intersections of the common
lines and the data lines. In addition, the display device has switching elements
SW
C1 to SW
Cn which connect the common lines COM
1 to
COM
n to either the ground-voltage portion GND (voltage V
G)
or the high-voltage portion
20 for common lines (common line power-supply
voltage V
C), switching elements SW
S1 to SW
Sm which
connect the data lines SEG
1 to SEG
m to either the ground-voltage
portion GND (voltage V
G) or the high-voltage portion
30 for data
lines (data-line power-supply voltage V
S), and a drive control circuit
10 which controls the switching elements SW
C1 to SW
Cn and
SW
S1 to SW
Sm. In FIG. 29, a reference
11 denotes a
constant-current output circuit.
FIG. 30 is a waveform diagram showing the operation of the display device of
FIG. 29. As shown in FIG. 30, the display device selects the common lines one after
another, brings the selected common line to the ground voltage V
G, and
brings the non-selected common lines to the common line power-supply voltage V
C
(reverse-bias voltage), during each display period P
2 included in each
scan period P
0. During the display period P
2, selected data
lines are brought to the data-line power-supply voltage V
S, and non-selected
data lines are brought to the ground voltage V
G, on the basis of the
signal input to the drive control circuit
10. During the display period
P
2 time point t
2 to t
3) shown in FIG. 30, the
data line SEG
1 is selected, so that the current I
1 flows
through the EL element PE
1,1, thereby bringing the EL element PE
1,1
to the light-emitting state, as shown in FIG. 29.
In addition, as shown in FIG. 30, the display device brings all the common lines
COM
1 to COM
n and data lines SEG
1 to SEG
m
to the ground voltage V
G during the discharge period P
1 included
in the scan period P
0. During the discharge period P
1, the
charge stored in the common lines COM
1 to COM
n and data lines
SEG
1 to SEG
m are discharged.
When bringing the EL element PE
1,1 into the displaying state, for
instance, the conventional display device as described above forms a current path
passing the EL element PE
1,1 (the high-voltage portion
30 for
data lines, the switching element SW
S1, the data line SEG
1,
the selected EL element PE
1,1, the common line COM
1, the
switching element SW
C1, and the ground-voltage portion GND in this order).
In this type of display device, however, a current path passing a non-light-emitting
EL element (for instance, the high-voltage portion
30 for data lines, the
switching element SW
S1, the data line SEG
1, the non-selected
EL elements PE
1,2 to PE
1,n, the non-selected common lines
COM
2 to COM
n, the switching elements SW
C2 to SW
Cn,
and the ground-voltage portion GND in this order), through which no current should
flow, is instantaneously formed at a time point t
1 or t
2,
for instance, and a shoot-through current (that is, "shoot-through current via
non-selected EL elements") flows, resulting in a waste of power. Moreover, if the
switching elements SW
C1 to SW
Cn are configured as CMOS circuits,
a current path passing a CMOS circuit (the high-voltage portion
20 for common
lines, the PMOS transistor, the NMOS transistor, and the ground-voltage portion
GND in this order) is instantaneously formed at a reversal of the CMOS circuit,
causing a shoot-through current (that is, "shoot-through current of CMOS circuit")
to flow, resulting in a waste of power.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide such a display device that
power consumption can be reduced by reducing the shoot-through current incident
to turn-on or turn-off of a switching element, a method of driving the display
device, and a driver circuit of the display device.
According to an aspect of the present invention, a display device comprises:
n common lines arranged in rows, where n is a positive integer; m data lines arranged
in columns, where m is a positive integer; n×m display elements positioned
at intersections of the n common lines and the m data lines; a low-voltage portion
for common lines; a high-voltage portion for common lines, which supplies a common
line power-supply voltage that is higher than a voltage supplied by the low-voltage
portion for common lines; a low-voltage portion for data lines; a high-voltage
portion for data lines, which supplies a data-line power-supply voltage that is
higher than a voltage supplied by the low-voltage portion for data lines; n first
switching elements which are respectively connected to the n common lines and connect
the common lines to the low-voltage portion for common lines during ON state of
the n first switching elements; n second switching elements which are respectively
connected to the n common lines and connect the common lines to the high-voltage
portion for common lines during ON state of the n second switching elements; m
third switching elements which are respectively connected to the m data lines and
connect the data lines to the low-voltage portion for data lines during ON state
of the m third switching elements; and m fourth switching elements which are respectively
connected to the m data lines and connect the data lines to the high-voltage portion
for data lines during ON state of the m fourth switching elements. The display
element at an intersection of a selected one of the n common lines and a selected
one of the m data lines is kept at a displaying state, the selected one of the
n common lines being kept at a selected state, the selected one of the m data lines
being kept at a selected state. The display device further comprises a drive control
circuit which controls turn-on and turn-off of the n first switching elements,
the n second switching elements, the m third switching elements, and the m fourth
switching elements in each scan period including a display period in which the
display elements are selectively brought to the displaying state and a discharge
period in which electrical charge stored in the display elements is discharged.
On the basis of control signals from the drive control circuit, the common line
is brought to the selected state when the common line is connected to the low-voltage
portion for common lines by turning on the first switching element and turning
off the second switching element; the common line is brought to a non-selected
state when the common line is brought to a high-impedance state by turning off
both the first switching element and the second switching element; the data line
is brought to the selected state when the data line is connected to the high-voltage
portion for data lines by turning off the third switching element and turning on
the fourth switching element; and the data line is brought to the non-selected
state when the data line is connected to the low-voltage portion for data lines
by turning on the third switching element and turning off the fourth switching element.
The display device eliminates the reversal of switching elements for common lines
by bringing non-selected common lines to a high impedance (Hi-Z) state. Accordingly,
the shoot-through current of the common line switching elements does not flow,
which results in reduced power consumption.
Further, the display device may be controlled in such a way that in the
discharge period, the n common lines are brought to the high-impedance state by
turning off both the n first switching elements and the n second switching elements,
and the m data lines are connected to the low-voltage portion for data lines by
turning on the m third switching elements and by turning off the m fourth switching elements.
The display device brings the common lines to the Hi-Z state in the discharge
period, so that the shoot-through current via non-selected display elements, which
flows from the high-voltage portion for data lines through the data-line switching
elements, non-selected display elements, and common line switching elements, can
be eliminated, resulting in reduced power consumption.
Furthermore, the display device may be controlled in such a way that
in the discharge period, the n common lines are connected to the high-voltage portion
for common lines by turning off the n first switching elements and turning on the
n second switching elements, and the m data lines are connected to the low-voltage
portion for data lines by turning on the m third switching elements and turning
off the m fourth switching elements.
The display device brings the common lines to the common line power-supply voltage
in the discharge period, so that the shoot-through current through non-selected
display elements, which flows from the high-voltage portion for data lines through
data-line switching elements, non-selected display elements, and common line switching
elements, can be eliminated, resulting in reduced power consumption.
Moreover, the display device may be controlled in such a way that in the
discharge period, the n common lines are connected to the low-voltage portion for
common lines by turning on the n first switching elements and by turning off the
n second switching elements, and the m data lines are connected to the low-voltage
portion for data lines by turning on the m third switching elements and turning
off the m fourth switching elements.
In addition, the display device may be controlled in such a way that in the discharge
period, the n common lines are connected to the low-voltage portion for common
lines by turning on the n first switching elements and turning off the n second
switching elements, the m data lines are connected to the low-voltage portion for
data lines by turning on the m third switching elements and turning off the m fourth
switching elements immediately before a start point of the discharge period, a
state, in which the m data lines are connected to the low-voltage portion for data
lines, is maintained until immediately after an end point of the discharge period,
and the data line to be selected immediately after the end point of the discharge
period is connected to the high-voltage portion for data lines by turning off the
third switching element and turning on the fourth switching element of the data
line to be selected.
The display device causes the reversal of switching elements for data lines to
occur while the common lines are in the Hi-Z state, so that the shoot-through current
through non-selected display elements does not flow, resulting in reduced power consumption.
Further, the display device may further comprise: a common line power-supply
circuit which sets the high-voltage portion for common lines to the common line
power-supply voltage; and a data-line power-supply circuit which sets the high-voltage
portion for data lines to the data-line power-supply voltage, the low-voltage portion
for common lines being connected to ground, the low-voltage portion for data lines
being connected to ground.
Furthermore, the display device may further comprise: a common line
power-supply circuit which sets the high-voltage portion for common lines to the
common line power-supply voltage; a data-line power-supply circuit which sets the
high-voltage portion for data lines to the data-line power-supply voltage; and
an intermediate-voltage portion which sets the low-voltage portion for data lines
to an intermediate voltage which is higher than the ground voltage and lower than
the voltage of the high-voltage portion for data lines, the low-voltage portion
for common lines being connected to ground.
In the display device, non-selected data lines are held to an intermediate voltage,
so that the voltage difference from the data-line power-supply voltage of selected
data lines decreases, resulting in reduced shoot-through current of switching elements
for data lines. The display device can also reduce the difference between the voltage
of selected or non-selected data line and the voltage in the discharge period,
resulting in fast light-emitting response.
According to another aspect of the present invention, a display device
comprises: n common lines arranged in rows, where n is a positive integer; m data
lines arranged in columns, where m is a positive integer; n×m display elements
positioned at intersections of the n common lines and the m data lines; a low-voltage
portion for common lines; a high-voltage portion for common lines, which supplies
a common line power-supply voltage that is higher than a voltage supplied by the
low-voltage portion for common lines; a low-voltage portion for data lines; a high-voltage
portion for data lines, which supplies a data-line power-supply voltage that is
higher than a voltage supplied by the low-voltage portion for data lines; n first
switching elements which are respectively connected to the n common lines and connect
the common lines to the low-voltage portion for common lines during ON state; n
second switching elements which are respectively connected to the n common lines
and connect the common lines to the high-voltage portion for common lines during
ON state of the n second switching elements; m third switching elements which are
respectively connected to the m data lines and connect the data lines to the low-voltage
portion for data lines during ON state of the m third switching elements; and m
fourth switching elements which are respectively connected to the m data lines
and connect the data lines to the high-voltage portion for data lines during ON
state of the m fourth switching elements, The display element at an intersection
of a selected one of the n common lines and a selected one of the m data lines
is kept at displaying state, the selected one of the n common lines being kept
at selected state, the selected one of the m data lines being kept at selected
state. The display device further comprises: an intermediate-voltage portion which
sets at least either the high-voltage portion for common lines or the low-voltage
portion for data lines to an intermediate voltage which is higher than the ground
voltage and lower than the common line power-supply voltage and data-line power-supply
voltage; and a drive control circuit which controls the turn-on and turn-off of
then first switching elements, then second switching elements, the m third switching
elements, and the m fourth switching elements in each scan period including a display
period in which display elements are selectively brought to the displaying state
and a discharge period in which the charge stored in the display elements is discharged.
On the basis of control signals from the drive control circuit, the common line
is brought to the selected state when the common line is connected to the low-voltage
portion for common lines by turning on the first switching element and turning
off the second switching element; the common line is brought to non-selected state
when the common line is connected to the high-voltage portion for common lines
by turning off the first switching element and turning on the second switching
element; the data line is brought to the selected state when the data line is connected
to the high-voltage portion for data lines by turning off the third switching element
and turning on the fourth switching element; and the data line is brought to the
non-selected state when the data line is connected to the low-voltage portion for
data lines by turning on the third switching element and by turning off the fourth
switching element.
In the display device, non-selected data lines or non-selected common lines are
held to an intermediate voltage, so that the shoot-through current of the switching
elements can be reduced. The display device can also reduce the difference between
the voltage of selected or non-selected data line and common line and the voltage
in the discharge period, resulting in fast light-emitting response.
Further, the display device may be controlled in such a way that the high-voltage
portion for common lines is set to an intermediate voltage which is higher than
the ground voltage and lower than the common line power-supply voltage, and the
low-voltage portion for data lines is set to an intermediate voltage which is higher
than the ground voltage and lower than the data-line power-supply voltage.
Furthermore, the display device may be controlled in such a way that
a pair of the first switching element and the second switching element connected
to the same common line is configured by a CMOS circuit, and a pair of the third
switching element and the fourth switching element connected to the same data line
is configured by a CMOS circuit.
Moreover, the display device may be controlled in such a way that the common
line power-supply voltage of the high-voltage portion for common lines is set to
a voltage lower than the data-line power-supply voltage of the high-voltage portion
for data lines.
The display device holds the common line power-supply voltage lower than the
data-line power-supply voltage, so that the low common line power-supply voltage
results in reduced power consumption.
According to yet another aspect of the present invention, a method is used
for driving a display device, wherein the display device comprises: n common lines
arranged in rows, where n is a positive integer; m data lines arranged in columns,
where m is a positive integer; n×m display elements positioned at intersections
of the n common lines and the m data lines; a low-voltage portion for common lines;
a high-voltage portion for common lines, which supplies a common line power-supply
voltage that is higher than a voltage supplied by the low-voltage portion for common
lines; a low-voltage portion for data lines; a high-voltage portion for data lines,
which supplies a data-line power-supply voltage that is higher than a voltage supplied
by the low-voltage portion for data lines; n first switching elements which are
respectively connected to the n common lines and connect the common lines to the
low-voltage portion for common lines during ON state; n second switching elements
which are respectively connected to the n common lines and connect the common lines
to the high-voltage portion for common lines during ON state of the n second switching
elements; m third switching elements which are respectively connected to the m
data lines and connect the data lines to the low-voltage portion for data lines
during ON state of the m third switching elements; and m fourth switching elements
which are respectively connected to the m data lines and connect the data lines
to the high-voltage portion for data lines during ON state of the m fourth switching
elements; the display element at an intersection of a selected one of the n common
lines and a selected one of the m data lines being kept at displaying state, the
selected one of the n common lines being kept at selected state, the selected one
of the m data lines being kept at selected state. The method comprises: controlling
the turn-on and turn-off of the n first switching elements, the n second switching
elements, the m third switching elements, and the m fourth switching elements in
each scan period including a display period in which the display elements are selectively
brought to the displaying state and a discharge period in which electrical charge
stored in the display elements is discharged; turning on the first switching element
and turning off the second switching element to connect the common line to the
low-voltage portion for common lines when the common line is brought to the selected
state; turning off both the first switching element and the second switching element
to bring the common line to high-impedance state when the common line is brought
to non-selected state; turning off the third switching element and turning on the
fourth switching element to connect the data line to the high-voltage portion for
data lines when the data line is brought to the selected state; and turning on
the third switching element and turning off the fourth switching element to connect
the data line to the low-voltage portion for data lines when the data line is brought
to the non-selected state.
According to yet another aspect of the present invention, a method is used
for driving a display device, wherein the display a device comprises: n common
lines arranged in rows, where n is a positive integer; m data lines arranged in
columns, where m is a positive integer; n×m display elements positioned at
intersections of the n common lines and the m data lines; a low-voltage portion
for common lines; a high-voltage portion for common lines, which supplies a common
line power-supply voltage that is higher than a voltage supplied by the low-voltage
portion for common lines; a low-voltage portion for data lines; a high-voltage
portion for data lines, which supplies a data-line power-supply voltage that is
higher than a voltage supplied by the low-voltage portion for data lines; n first
switching elements which are respectively connected to the n common lines and connect
the common lines to the low-voltage portion for common lines during ON state; n
second switching elements which are respectively connected to the n common lines
and connect the common lines to the high-voltage portion for common lines during
ON state of the n second switching elements; m third switching elements which are
respectively connected to the m data lines and connect the data lines to the low-voltage
portion for data lines during ON state of the m third switching elements; and m
fourth switching elements which are respectively connected to the m data lines
and connect the data lines to the high-voltage portion for data lines during ON
state of the m fourth switching elements; the display element at an intersection
of a selected one of the n common lines and a selected one of the m data lines
being kept at displaying state, the selected one of the n common lines being kept
at selected state, the selected one of the m data lines being kept at selected
state. The method comprises: controlling the turn-on and turn-off of the n first
switching elements, the n second switching elements, the m third switching elements,
and the m fourth switching elements in each scan period including a display period
in which the display elements are selectively brought to the displaying state and
a discharge period in which electrical charge stored in the display elements is
discharged; setting at least either the high-voltage portion for common lines or
the low-voltage portion for data lines to an intermediate voltage which is higher
than the ground voltage and lower than the common line power-supply voltage and
data-line power-supply voltage; turning on the first switching element and turning
off the second switching element to connect the common line to the low-voltage
portion for common lines when the common line is brought to the selected state;
turning off the first switching element and turning on the second switching element
to connect the common line to the high-voltage portion for common lines when the
common line is brought to non-selected state; turning off the third switching element
and turning on the fourth switching element to connect the data line to the high-voltage
portion for data lines when the data line is brought to the selected state; and
turning on the third switching element and by turning off the fourth switching
element to connect the data line to the low-voltage portion for data lines when
the data line is brought to the non-selected state.
According to yet another aspect of the present
