Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-12-27
2003-03-18
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169300, C313S582000, C345S076000
Reexamination Certificate
active
06534925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic electroluminescence (EL) driving circuit and a passive matrix organic EL display device which can reduce power consumption occurring when a passive matrix organic EL display panel is operated.
The present application claims priority of Japanese Patent Application No. 2000-403533 filed on Dec. 28, 2000, which is hereby incorporated by reference.
2. Description of the Related Art
A passive matrix organic EL display panel is a display panel in which an organic EL element formed by stacking a thin film made up of an organic material and being a micro-light emitting unit containing no active element is placed on a substrate in a matrix form, requiring no backlight and now drawing the attention of people as a spontaneous light emitting type display device. The organic EL element, however, has a large problem. That is, since a parasitic capacity that a light emitting section has is structurally large at a time of a high-speed operation, a charging current of the organic EL element has to be reduced. To solve this problem, some technologies have been proposed (for example, in Japanese Laid-open Patent Application No. Hei 11-143429).
FIG. 6
is a diagram showing an example of configurations of a conventional passive matrix organic EL display device
100
.
FIG. 7
is a diagram showing a state of connection occurring at a time being different from a time shown in a case of the conventional passive matrix organic EL display device
100
in FIG.
6
.
FIG. 8
is a diagram showing another state of connection occurring at a time being different from the time shown in the case of the conventional passive matrix organic EL display device
100
in FIG.
6
.
The conventional passive matrix organic EL display device
100
, as shown in
FIG. 6
, chiefly includes a passive matrix organic EL display panel in which a plurality of organic EL elements E
11
, E
12
, E
13
, . . . , E
1
n, E
21
, E
22
, E
23
, . . . , E
2
n, E
31
, E
32
, E
33
, . . . , E
3
n, E
41
, E
42
, E
43
, . . . , E
4
n, . . . , Em
1
, Em
2
, Em
3
, . . . , and Emn is arranged in row and column direction and in a matrix form and in which one terminal of each of organic EL elements E
11
, E
12
, . . . , Emn is connected to each of a plurality of scanning lines R
1
, R
2
, R
3
, R
4
, . . . , and Rm for every row and another terminal of each of the organic EL elements E
11
, E
12
, . . . , Emn is connected to each of a plurality of data lines C
1
, C
2
, C
3
, . . . , and Cn for every column, horizontal driving change-over switches
11
,
12
,
13
,
14
, . . . ,
1
m placed on every scanning line R
1
, R
2
, . . . , Rm in each row, driving sources
21
,
22
,
23
, . . . ,
2
n placed in every data line C
1
, C
2
, Cn in each column, charging switches
31
,
32
,
33
, . . . ,
3
n placed in every data line C
1
, C
2
, . . . , Cn in each row, a voltage holding circuit
4
placed commonly on an output side of the charging switches
31
,
32
,
33
, . . . ,
3
n in each column, a first power source
5
and a second power source
6
.
The passive matrix organic EL display device
100
shown in
FIG. 6
is constructed in a matter that organic EL elements E
11
, E
12
, . . . , Emn each corresponding to one of three primary colors made up of red (R), green (G), and blue (B) colors are formed in a form of a strip of paper and the organic EL elements E
11
, E
12
, . . . , Emn each having a number corresponding to each of the three primary colors are arranged in a same area and in a same arrangement order and a plurality of sets each including three organic EL elements E
11
, E
12
, . . . , Emn each having a different color is arranged on a same substrate so that they make up an pixel for displaying full colors. In the description below, to simplify the explanation, a passive matrix organic EL display panel to display only one color out of the three colors is described.
Each of the organic EL elements E
11
, E
12
, . . . , Emn is made up of a diode DE forming a light emitting section and its parasitic capacitor CE and an anode-side terminal of each of the organic EL elements E
11
, E
12
, . . . , Emn is connected to each of data lines C
1
, C
2
, . . . , Cn and a cathode-side terminal of each of the organic EL elements E
11
, E
12
, . . . , Emn is connected to each of scanning lines R
1
, R
2
, R
3
, . . . , and Rm.
The scanning line R
1
, R
2
, . . . , Rm in each row is sequentially selected for every scanning cycle and the data line C
1
, C
2
, . . . , Cn in each column is sequentially selected in every scanning cycle. Each of the horizontal driving change-over switches
11
,
12
,
13
,
14
, . . . , and
1
m is, for example, a known semiconductor switch made up of a combination of a P (Positive)-type FET (Field Effect Transistor) and an N (Negative)-type FET, having “one-pole two-input” functions, that is, one port (pole) of the horizontal driving change-over switche
11
,
12
, . . . ,
1
m can be connected or switched sequentially to either of other two ports of the same horizontal driving change-over switch
11
,
12
, . . . ,
1
m and causes scanning lines R
1
, R
2
, . . . , Rm in each row to be connected to a ground when being selected and to be connected to a second power source
6
when being not connected. Each of the driving sources
21
,
22
,
23
, . . . , and
2
n feeds an amount of a current corresponding to luminous intensity of light to be emitted while being driven and does not feed the current while being not driven to the data lines C
1
, C
2
, . . . , Cn. Each of the charging switches
31
,
32
,
33
, . . . , and
3
n, in response to switching operation of the scanning line R
1
, R
2
, . . . , Rm on each row, connects a cathode-side terminal of each of the organic EL elements E
11
, E
12
, . . . , Emn, in parallel, to an anode-side of the voltage holding circuit
4
. The voltage holding circuit
4
includes a constant-voltage element DH made up of a Zener diode (ZD) and parallel capacitor CH having electrostatic capacity being equivalent to a sum of all organic EL elements E
11
, E
12
, . . . , Emn making up the passive matrix organic EL display panel and is adapted to hold a voltage on the anode side of all organic EL elements E
11
, E
12
, . . . , Emn at a fixed electric potential VH determined by the constant-voltage element DH when each of the charging switches
31
,
32
,
33
, . . . , and
3
n is turned ON due to grounding of the cathode-side terminal. The first power source
5
applies a voltage V
1
to each of driving sources. The second power source
6
applies a voltage V
2
to each of horizontal driving change-over switches
11
,
12
, . . . ,
1
m.
Operations of the conventional passive matrix organic EL display device
100
will be described by referring to
FIGS. 6
,
7
, and
8
.
FIG. 6
shows a state in which the scanning operation is switched from a scanning line R
1
in a first column to a scanning line R
2
in a second column and the scanning line R
2
is connected to a ground through the horizontal driving change-over switch
12
. At this point, cathodes of all organic EL elements being connected to the selected scanning line R
2
are connected to a ground. For example, when the data line C
2
is in a driving state and when a driving current is fed from the first power source
5
through the driving source
22
, in the organic EL element E
22
being connected between the data line C
2
and the scanning line R
2
and now shown by being circled by a broken line, the fed driving current causes the diode DE to emit light with intensity corresponding to an amount of the fed driving current and also causes the parasitic capacitor CE to be charged.
Each of the organic EL elements being connected to the selected scanning line R
2
and being connected to each of the data lines C
1
, C
3
, . . . , Cn but being not driven does not emit light, since each of corresponding driving sources
21
,
23
, . . . ,
2
n feeds the driving current to a degree which causes each of the organic EL elements to be a voltage le
NEC Corporation
Vu Jimmy T.
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