Information
-
Patent Grant
-
6392627
-
Patent Number
6,392,627
-
Date Filed
Monday, February 22, 199925 years ago
-
Date Issued
Tuesday, May 21, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Rader, Fishman & Grauer PLLC
- Kananen, Esq.; Ronald P.
-
CPC
-
US Classifications
Field of Search
US
- 345 92
- 345 99
- 345 98
- 345 100
- 345 211
- 345 212
- 345 210
- 345 204
- 345 205
- 327 291
- 327 333
- 377 69
- 377 75
- 377 77
- 377 81
- 377 76
-
International Classifications
-
Abstract
An output buffer is composed of first and second CMOS inverters that are connected to each other in cascade, a level conversion circuit for converting the low-voltage-side potential of output voltages of the first and second CMOS inverters to a potential that is lower than the low-voltage-side potential, and a third CMOS inverter provided downstream of the level conversion circuit. Since the level conversion circuit has a current mirror circuit configuration, the power consumption in the level conversion circuit is made small.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device (hereinafter referred to as LCD) and a driver circuit thereof. In particular, the invention relates to an active matrix LCD in which a number of pixels that are arranged two-dimensionally in matrix form are sequentially selected on a pixel-by-pixel basis, and to a vertical driver circuit thereof.
Among driving methods of an active matrix LCD are a 1H inversion driving method and a dot inversion driving method. In the 1H inversion driving method, the polarity of video signals applied to respective pixels is inverted every 1H (H: horizontal period) with respect to a common voltage VCOM. In the dot inversion driving method, the polarities of video signals applied to adjacent pixels (dots) are inverted alternately.
Selection is made between the above two driving methods in accordance with an intended use. The 1H inversion driving method is mainly used in small-size LCDs. By combining the 1H inversion driving method with a common inversion driving method in which a common voltage VCOM that is applied to opposed electrodes of liquid crystal cells of the respective pixels is inverted every 1H, reduction in voltage and power consumption is attained in a source driver (i.e., a horizontal driver circuit) and hence in the active matrix LCD.
The common inversion driving method, which is useful for reduction in voltage and power consumption, is widely used in medium-size LCDs (about 12 inches). In the common inversion driving method, the output voltage of a scan driver (vertical driver circuit) needs to have a negative low-voltage-side potential. The reason will be explained below with reference to
FIG. 1
(equivalent circuit of a pixel section) and
FIG. 2
(waveforms).
Assume that VCOMc represents the center potential of a common voltage VCOM and Vcom represents its amplitude, and that the common voltage VCOM is inverted every 1H in the following manner:
CVOM=VCOMc
±(1/2)
Vcom
In this case, a voltage VA that is held at node A is shifted by
Δ
VA=±(
Cs+CLC
)
Vcom/
(
Cs+CLC+Cp
)
where Cs is the capacitance value of an auxiliary capacitor
101
, CLC is the capacitance value of a liquid crystal cell
102
, and Cp is the capacitance value of a parasitic capacitance at node A of a pixel transistor
103
.
If the potential VA at node A has become lower than the potential of a scanning line (gate line)
104
and the pixel transistor
103
has been turned on, the holding potential VA at node A is varied and a bright spot or the like possibly occurs. Therefore, so that the pixel transistor
103
is never turned on in a non-selection period, it is necessary that the output voltage of the scan driver have a negative low-voltage-side potential.
FIG. 3
shows an example of a conventional scan driver that outputs a negative low-voltage-side potential. Specifically,
FIG. 3
shows the configuration of an output stage of a certain row of the scan driver.
In the output stage of this conventional scan driver, assume a case where the low-voltage-side potential of the scan driver is set at −4 V. For example, four CMOS inverters
111
-
114
are connected to each other in cascade. For example, +15 V is commonly applied to the respective stages of the CMOS inverters
111
-
114
as a positive-side power source voltage vdd. On the other hand, −1 V, −2 V, −3 V, and −4 V are applied to the respective stages of the CMOS inverters
111
-
114
as negative-side power source voltages vss, vss
1
, vss
2
, and vss
3
. That is, negative voltages are applied so as to increase in absolute value step by step in such a range that the transistors of each stage is not turned on completely.
However, in the conventional scan driver having the above configuration, since the negative-side power source voltages for the first to fourth CMOS inverters
111
-
114
are so set as to decrease in order, the negative-side power source voltage for a certain stage is necessarily lower than that for the preceding stage and hence a through-current (DC current) flows through the second and following CMOS inverters
112
-
114
. This causes a problem of large current consumption. In particular, the through-current and hence the current consumption increase as the absolute values of the negative-side power source voltages increase.
The amplitude of a final output voltage vout is determined by the on-resistance ratio between the PMOS transistor and the NMOS transistor of the fourth-stage CMOS inverter
114
. This causes another problem that the high-voltage-side potential of the output voltage vout drops from +15 V by ΔV.
FIG. 4
shows waveforms of the positive-side power source voltage vdd, the negative-side power source voltages vss, vss
1
, vss
2
, and vss
3
, and output voltages va, vb, vc, and vout of the respective CMOS inverters
111
-
114
.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems in the art, and an object of the invention is therefore to provide an LCD and a corresponding driver circuit that can reduce voltages and power consumption particularly in the case of accommodating common inversion driving.
According to the invention, in an LCD having a pixel section in which a plurality of pixels are arranged two-dimensionally in matrix form and a plurality of scanning lines are arranged for respective rows, and a driver circuit that sequentially outputs scanning pulses to the respective scanning lines, the driver circuit comprises, in an output stage, a level conversion circuit having a current mirror circuit configuration for shifting at least one of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses.
In the LCD or the driver circuit having the above configuration, the level conversion circuit for shifting the potential of an output voltage as a scanning pulse has a current mirror circuit configuration. Since current flows through the level conversion circuit only during a certain duty period of an input pulse, the power consumption in the level conversion circuit is made small.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an equivalent circuit diagram of a pixel section;
FIG. 2
is a waveform diagram showing behavior of a pixel potential in a common inversion operation;
FIG. 3
is a circuit diagram of an example of a conventional scan driver;
FIG. 4
is a waveform diagram showing an operation of the conventional scan driver of
FIG. 3
;
FIG. 5
schematically shows the configuration of an example of an active matrix LCD to which the present invention is applied;
FIGS. 6A and 6B
show waveforms of 1H inversion driving and a combination of 1H inversion driving and common inversion driving, respectively;
FIG. 7
is a block diagram showing an example configuration of a scan driver;
FIG. 8
is a circuit diagram of an output buffer according to a first embodiment of the invention;
FIG. 9
is a waveform diagram showing the operation of the output buffer of
FIG. 8
;
FIG. 10
is a circuit diagram of an output buffer according to a second embodiment of the invention; and
FIG. 11
is a waveform diagram showing the operation of the output buffer of FIG.
10
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings.
FIG. 5
schematically shows the configuration of an example of an active matrix LCD to which the invention is applied, in which a combination of 1H inversion and common inversion is employed as a driving method.
As shown in
FIG. 5
, pixels
13
are provided at crossing portions of plural rows of scanning lines
11
and plural columns of signal lines
12
. Each pixel
13
is composed of a pixel transistor (e.g., a thin-film transistor)
14
whose gate electrode and source electrode are connected to a scanning line
11
and a signal line
12
, respectively, a liquid crystal cell
15
whose pixel electrode is connected to the drain electrode of the pixel transistor
14
, and an auxiliary capacitor
16
, where one of the electrodes of the auxiliary capacitor
16
is connected to the drain electrode of the pixel transistor
14
.
Opposite electrodes of the respective liquid crystal cells
15
are connected to each other so as to be common to the pixels
13
. Similarly, the other electrodes (second electrodes) of the respective auxiliary capacitors
16
are connected to each other via CS lines
17
so as to be common to the pixels
13
. As shown in
FIG. 6B
, a common voltage VCOM that is inverted every 1H is supplied from a voltage source
18
to the opposed electrodes of the respective liquid crystal cells
15
and the second electrodes of the respective auxiliary capacitors
16
.
To sequentially select, on a pixel-by-pixel basis, from a number of pixels
13
that are arranged two-dimensionally, a scan driver
19
and a source driver
20
are provided as a vertical driver circuit and a horizontal driver circuit, respectively. The scan driver
19
selects pixels
13
on a row-by-row basis sequentially scanning the pixels
13
by applying scanning pulses to the respective scanning lines
11
for each vertical period (each field period).
On the other hand, the source driver
20
performs sequential sampling on an input video signal for each horizontal period (1H) and writes sampled video signals to pixels
13
of a row selected by the scan driver
19
. As shown in
FIG. 6A
, the polarity of a video signal that is input to the source driver
20
is inverted every 1H with respect to the common voltage VCOM.
Since the liquid crystal cells
15
are driven in an AC-like manner by using the 1H inversion driving method in the above manner, the polarities of voltages applied to the liquid crystal cells
15
of the respective pixels
13
are inverted every line, whereby deterioration of the liquid crystal cells
15
can be prevented. In this 1H inversion driving method, since the polarity of a video signal is inverted every
1
H, as seen from the waveform of
FIG. 6A
, a voltage source of at least 2 Vp is needed in the source driver
20
, where Vp is a voltage necessary for a gradation control of the liquid crystal cells
15
.
Where the above
1
H inversion driving method is combined with the common inversion driving method, the common voltage VCOM is also inverted every
1
H as seen from the waveform of FIG.
6
B. Therefore, a voltage source in the source driver
20
may be one that provides a voltage Vp in the lowest case, which makes it possible to reduce voltages and power consumption in the source driver
20
while securing the advantage of the
1
H inversion driving method as it is.
In the LCD having the above configuration, a driver circuit according to the invention is applied to the scan driver
19
, and more specifically, to its output stage. For example, as shown in
FIG. 7
, the scan driver
19
is composed of n stages of shift registers
21
-
1
to
21
-n (n: the number of rows of the pixel section) and output buffers
22
-
1
to
22
-n that are provided on the output side of the respective shift registers
21
-
1
to
21
-n and supply scanning pulses sequentially to n respective scanning lines
11
-
1
to
11
-n. The invention is applied to each of the output buffers
22
-
1
to
22
-n. Specific embodiments will be described below.
FIG. 8
is a circuit diagram showing an output buffer of a certain stage of the scan driver
19
according to a first embodiment of the invention. This output buffer is composed of first and second CMOS inverters
31
and
32
that are connected to each other in a cascade formation, a level conversion circuit
33
for shifting a low-voltage-side potential vss of output voltages of the CMOS inverters
31
and
32
to a potential vss
1
that is lower than vss, and a third CMOS inverter
34
that is provided downstream from the level conversion circuit
33
.
The first CMOS inverter
31
is composed of a PMOS transistor Qp
11
, whose source is connected to a positive-side voltage source vdd, and an NMOS transistor Qn
11
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
11
and whose source is connected to a first negative-side voltage source vss. Similarly, the second CMOS inverter
32
is composed of a PMOS transistor Qp
12
, whose source is connected to the positive-side voltage source vdd and an NMOS transistor Qn
12
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
12
and whose source is connected to the first negative-side voltage source vss.
The level conversion circuit
33
has a current mirror circuit configuration. That is, the source of a PMOS transistor Qp
13
is connected to the positive-side voltage source vdd and its gate is connected to an output node b of the second CMOS inverter
32
. The source of a PMOS transistor Qp
14
is connected to the positive-side voltage source vdd and its gate is connected to an output node a of the first CMOS inverter
31
. The drain of an NMOS transistor Qn
13
is connected to the drain of the PMOS transistor Qp
13
and its source is connected to a second negative-side voltage source vss
1
(<vss). The drain of a diode-connected NMOS transistor Qn
14
is connected to the drain of the PMOS transistor Qp
14
, its gate is connected to the gate of the NMOS transistor Qn
13
, and its source is connected to the second negative-side voltage source vss
1
.
The third CMOS inverter
34
is composed of a PMOS transistor Qp
15
whose source is connected to the positive-side voltage source vdd and an NMOS transistor Qn
15
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
15
and whose source is connected to the second negative-side voltage source vss
1
. The input end of the third CMOS inverter
34
, that is, the gate common connection point of the PMOS transistor Qp
15
and the NMOS transistor Qn
15
is connected to an output node c of the level conversion circuit
33
, that is, the drain common connection point of the PMOS transistor Qp
13
and the NMOS transistor Qn
13
.
In the above-configured output buffer according to the first embodiment, a voltage vdd−vss, which defines the dynamic range of output voltages va and vb of the first and second CMOS inverters
31
and
32
, respectively, can have a small amplitude that is sufficient to turn on the PMOS transistors Qp
13
and Qp
14
of the level conversion circuit
33
, for example, a small amplitude of about Vth+α where Vth is the threshold voltage of the transistors Qp
13
and Qp
14
. In other words, the level conversion circuit
33
can operate even if the output voltages va and vb of the first and second CMOS inverters
31
and
32
have a small amplitude of about Vth+α.
An input pulse vin of this output buffer is set so that a pulse in which the low-voltage-side duty is smaller than the high-voltage-side duty is input to the level conversion circuit
33
as a gate input pulse to the PMOS transistor Qp
14
. As a result, during the long high-voltage-side duty period of a gate input pulse being input to the PMOS transistor Qp
14
, the PMOS transistor Qp
14
is in a non-conductive state and no current flows through the NMOS transistors Qn
14
and Qn
13
. Only during the short low-voltage-side duty period of the gate input pulse, the PMOS transistor Qp
14
is in a conductive state and current flows through the NMOS transistors Qn
14
and Qn
13
. That is, current flows through the level conversion circuit
33
only during a short period, and hence the power consumption is small.
The low-voltage-side potential of the output node c of the level conversion circuit
33
is defined by the second negative-side power source voltage vss
1
, that is, the source potential of the NMOS transistor Qn
13
, when it is rendered conductive as a result of a current flow due to turning-on of the PMOS transistor Qp
14
. For example, assume a case that the positive-side power source voltage vdd is +5 V, the first negative-side power source voltage vss is 0 V, and the second negative-side power source voltage vss
1
is −4 V. In this case, the level conversion circuit
33
converts an input voltage to an output voltage vc whose high-voltage-side potential is fixed at +5 V and low-voltage-side potential is solely shifted from 0 V to −4 V. The voltage vc is inverted by the third CMOS inverter
34
and becomes an output voltage vout.
FIG. 9
shows waveforms of the output voltages va, vb, vc, and vout.
As described above, in the output buffer according to the first embodiment, the level conversion circuit
33
for shifting the low-voltage-side potential of an output voltage to the negative side is a current mirror circuit. Therefore, current flows through the level conversion circuit
33
only during the low-voltage-side duty period of an input pulse and hence the power consumption can be reduced. In particular, if an input pulse is such that the low-voltage-side duty is smaller than the high-voltage-side duty, current flows through the level conversion circuit
33
only during the short low-voltage-side duty period, whereby the power consumption can further be reduced.
FIG. 10
is a circuit diagram showing an output buffer of according to a second embodiment of the invention. This output buffer is composed of first and second CMOS inverters
41
and
42
that are connected to each other in a cascade formation, a first level conversion circuit
43
for shifting a low-voltage-side potential vss of output voltages of the CMOS inverters
41
and
42
to a potential vss
1
that is lower than vss, a third CMOS inverter
44
that is provided downstream of the level conversion circuit
43
, and a second level conversion circuit
45
for shifting a high-voltage-side potential vdd of an output voltage of the third CMOS inverter
44
to a potential vdd
1
that is higher than vdd.
The first CMOS inverter
41
is composed of a PMOS transistor Qp
21
whose source is connected to a first positive-side voltage source vdd and an NMOS transistor Qn
21
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
21
and whose source is connected to a first negative-side voltage source vss. Similarly, the second CMOS inverter
42
is composed of a PMOS transistor Qp
22
whose source is connected to the first positive-side voltage source vdd and an NMOS transistor Qn
22
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
22
and whose source is connected to the first negative-side voltage source vss.
The first level conversion circuit
43
has a current mirror circuit configuration. That is, the source of a PMOS transistor Qp
23
is connected to the first positive-side voltage source vdd and its gate is connected to an output node b of the second CMOS inverter
42
. The source of a PMOS transistor Qp
24
is connected to the first positive-side voltage source vdd and its gate is connected to an output node a of the first CMOS inverter
41
. The drain of an NMOS transistor Qn
23
is connected to the drain of the PMOS transistor Qp
23
and its source is connected to a second negative-side voltage source vss
1
(<vss). The drain of a diode-connected NMOS transistor Qn
24
is connected to the drain of the PMOS transistor Qp
24
, its gate is connected to the gate of the NMOS transistor Qn
23
, and its source is connected to the second negative-side voltage source vss
1
.
The third CMOS inverter
44
is composed of a PMOS transistor Qp
25
whose source is connected to the first positive-side voltage source vdd and an NMOS transistor Qn
25
whose drain and gate are connected to the drain and gate, respectively, of the PMOS transistor Qp
25
and whose source is connected to the second negative-side voltage source vss
1
. The input end of the third CMOS inverter
44
, that is, the gate common connection point of the PMOS transistor Qp
25
and the NMOS transistor Qn
25
is connected to an output node c of the first level conversion circuit
43
, that is, the drain common connection point of the PMOS transistor Qp
23
and the NMOS transistor Qn
23
.
The second level conversion circuit
45
has a current mirror configuration. That is, the source of a diode-connected PMOS transistor Qp
26
is connected to a second positive-side voltage source vdd
1
(>vdd). The source of a PMOS transistor Qp
27
is connected to the second positive-side voltage source vdd
1
and its gate is connected to the gate of the PMOS transistor Qp
26
. The drain of an NMOS transistor Qn
26
is connected to the drain of the PMOS transistor Qp
26
, its gate is connected to an output node d of the third CMOS inverter
44
, and its source is connected to the second negative-side voltage source vss
1
. The drain of an NMOS transistor Qn
27
is connected to the drain of the PMOS transistor Qp
27
, its gate is connected to the output node c of the first level conversion circuit
43
, and its source is connected to the second negative-side voltage source vss
1
.
In the above-configured output buffer according to the second embodiment, as in the case of the first embodiment, a voltage vdd-vss, which defines the dynamic range of output voltages va and vb of the first and second CMOS inverters
41
and
42
, respectively, can have a small amplitude that is sufficient to turn on the PMOS transistors Qp
23
and Qp
24
of the first level conversion circuit
43
. The level conversion circuit
43
can operate even with such a small amplitude.
An input pulse vin of this output buffer is set so that a pulse in which the low-voltage-side duty is smaller than the high-voltage-side duty is input to the first level conversion circuit
43
as a gate input pulse to the PMOS transistor Qp
24
. As a result, only during the short low-voltage-side duty period, the PMOS transistor Qp
24
is in a conductive state and current flows through the NMOS transistors Qn
24
and Qn
23
. That is, current flows through the level conversion circuit
43
only during a short period.
The low-voltage-side potential of the output node c of the first level conversion circuit
43
is defined by the second negative-side power source voltage vss
1
that is the source potential of the NMOS transistor Qn
23
when it is rendered conductive as a result of a current flow due to turning-on of the PMOS transistor Qp
24
. For example, assume a case where the first positive-side power source voltage vdd is +5 V, the first negative-side power source voltage vss is 0 V, and the second negative-side power source voltage vss
1
is −4 V. In this case, the level conversion circuit
43
converts an input voltage to a voltage vc whose high-voltage-side potential is fixed at +5 V and low-voltage-side potential has solely been shifted from 0 V to −4 V.
The voltage vc whose low-voltage-side potential has been converted from vss to vss
1
is inverted by the third CMOS inverter
44
and becomes a voltage vd that has the same amplitude as the voltage vc. Then, in the second level conversion circuit
45
, when the voltage vd is applied to the gate of the NMOS transistor Qn
26
, the NMOS transistor Qn
26
is kept conductive during the high-voltage-side duty period of the voltage vd to draw current from the PMOS transistor Qp
27
. When the PMOS transistor Qp
27
is turned on as a result, the high-voltage-side potential of an output voltage vout is defined by the second positive-side power source voltage vdd
1
which is the source potential of the PMOS transistor Qp
27
.
For example, assume that the second positive-side power source voltage vdd
1
is +15 V. In this case, the second level conversion circuit
45
produces a voltage vout whose low-voltage-side potential is fixed at −4 V and high-voltage-side potential has been shifted from +5 V to +15 V. That is, by virtue of the level conversion functions of the first and second level conversion circuits
43
and
45
, the input voltage vin having an amplitude ranging from 0 V to +5 V is level-converted to the output voltage vout having an amplitude ranging from −4 V to +15 V.
FIG. 11
shows waveforms of the output voltages va, vb, vc, vd and vout.
As described above, in the output buffer according to the second embodiment, both the first level conversion circuit
43
for shifting the low-voltage-side potential of an output voltage to the negative side and the second level conversion circuit
45
for shifting the high-voltage-side potential of the output voltage to the positive side is a current mirror circuit. Therefore, current flows through the first and second level conversion circuits
43
and
45
only during the low-voltage-side duty period of an input pulse, and hence the power consumption can be reduced and an output voltage having an even larger amplitude can be obtained.
The above-embodiments are directed to the case where in the active matrix LCD using the common inversion driving method, at least the low-voltage-side potential of an output voltage of the scan driver
19
is shifted to the negative side to make the low-voltage-side potential of the output voltage even lower than the negative-side power source voltage vss of the data transfer section (n-stages of shift registers) of the scan driver
19
. However, the invention is not limited to such a case and can be applied to an output buffer having a configuration where only the high-voltage-side potential of an output voltage is shifted to the positive side.
As described above, the above-configured output buffers according to the above embodiments can reduce the power consumption. Therefore, by using either of those output buffers as the output buffer of the scan driver
19
of the active matrix LCD shown in
FIG. 5
, the power consumption in the scan driver
19
and hence in the entire LCD can be reduced particularly in what is called a driver circuit integration type active matrix LCD, in which driver circuits are formed on the same substrate as a pixel section.
Further, because the output buffer is capable of easily producing an output pulse of a large dynamic range from an input pulse of a small dynamic range, the output buffer of each embodiment facilitates the designing of an LCD panel. In addition, since an input pulse having a small amplitude of, for example, about 2.7 V can be used satisfactorily, the power source voltage can be reduced in the data transfer section (n stages of shift registers) of the scan driver
19
and the driving system upstream of the data transfer section.
In active matrix LCDs, the substrate on which driver circuits and a pixel section are formed integrally may be either a transparent substrate, such as a glass substrate or a silicon substrate.
As described above, according to the invention, in an LCD and its driver circuit, a level conversion circuit having a current mirror circuit configuration for shifting at least one of the low-voltage-side potential or the high-voltage-side potential of a scanning pulse is provided in the output stage of the driver circuit. Since current flows through the level conversion circuit only during a certain duty period of an input pulse, the power consumption in the level conversion circuit is made small. Therefore, the power consumption in the LCD and the driver circuit can be reduced.
Claims
- 1. A liquid crystal display device comprising:pixel section in which a plurality of pixels are arranged two-dimensionally in matrix form and a plurality of scanning lines are arranged for respective rows; and a driver circuit for sequentially outputting scanning pulses to the respective scanning lines, the driver circuit having a current mirror circuit configuration for shifting at least one of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver circuit, wherein the driver circuit comprises: a buffer circuit that operates on a first positive-side power source voltage and a first negative-side power source voltage; and a level shift circuit that operated on the first positive-side power source voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage.
- 2. The liquid crystal display device according to claim 1, wherein the driver circuit is formed on the same substrate as the pixel section.
- 3. A liquid crystal display device comprising:a pixel section in which a plurality of pixels are arranged two-dimensionally in matrix form and a plurality of scanning lines are arranged for respective rows; and a driver circuit for sequentially outputting scanning pulses to the respective scanning lines, the driver circuit having a current mirror circuit configuration for shifting at least one of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver circuit, wherein the driver circuit comprises: a buffer circuit that operates on a first positive-side power source voltage and a first negative-side power source voltage; a first level shift circuit that operates on the first positive-side power source voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage; and a second level shift circuit that operates on a second positive-side power source voltage that is higher than the first positive-side power source voltage and the second negative-side power source voltage, and shifts a high-voltage potential of an output voltage of the first level shift circuit to the second positive-side power source voltage.
- 4. The liquid crystal display device according to claim 3, wherein the driver circuit is formed on the same substrate as the pixel section.
- 5. A driver circuit of a liquid display device having a pixel section in which a plurality of pixels are arranged two-dimensionally in matrix form and a plurality of scanning lines are arranged for respective rows, wherein:the driver circuit that sequentially outputs a scanning pulses to the respective scanning lines comprises, in an output stage, a level conversion circuit having a current mirror circuit configuration for shifting at least one of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver circuit,and further comprising: a buffer circuit that operates on a first positive-side power source voltage and a first negative-side power source voltage; and a level shifts circuit that operates on the first positive-side power source voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage.
- 6. A driver circuit of a liquid display device having a pixel section in which a plurality of pixels are arranged two-dimensionally in matrix form and a plurality of scanning lines are arranged for respective rows, wherein:the driver circuit that sequentially outputs a scanning pulses to the respective scanning lines comprises, in an output stage, a level conversion circuit having a current mirror circuit configuration for shifting at least one of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver circuit, and further comprising: a buffer circuit that operates on a first positive-side power source voltage and a first negative-side power source voltage; a first level shift circuit that operates on the first positive-side power voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage; and a second level shift circuit that operates on a second positive-side power source voltage that is higher than the first positive-side power source voltage and the second negative-side power source voltage, and shifts a high-voltage-side potential of an output voltage of the first level shift circuit to the second positive-side power source voltage.
- 7. A display device comprising:a pixel section in which a plurality of pixels are arranged in matrix from and a plurality of scanning lines are arranged for respective rows; and a driver configuration for sequentially outputting scanning pulses to the respective scanning lines, the driver circuit comprising, in an output stage, a level conversion circuit having a current mirror configuration for shifting at least on of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver, wherein the driver circuit comprises: a buffer circuit that operates on a first positive-side power source voltage and a first negative-side power source voltage; and a level shift circuit that operated on the first positive power source voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage.
- 8. The liquid crystal display device according to claim 7, wherein the driver circuit is formed on the same substrate as the pixel section.
- 9. A display device comprising:a pixel section in which a plurality of pixels are arranged in matrix from and a plurality of scanning lines are arranged for respective rows; and a driver configuration for sequentially outputting scanning pulses to the respective scanning lines, the driver circuit comprising, in an output stage, a level conversion circuit having a current mirror configuration for shifting at least on of a low-voltage-side potential and a high-voltage-side potential of the scanning pulses, wherein the driver circuit shifts the low-voltage-side potential of the scanning pulse to a potential that is lower than a negative-side power source voltage of a data transfer section of the driver circuit, wherein the driver circuit comprises: a buffer circuit that operates on a first positive-side power source voltage and a first negative power source voltage; a first level shift circuit that operates on the first positive-side power source voltage and a second negative-side power source voltage that is lower than the first negative-side power source voltage, and shifts a low-voltage-side potential of an output voltage of the buffer circuit to the second negative-side power source voltage; and a second level shift circuit that operates on a second positive-side power source voltage that is higher than the first positive-side power source voltage and the second negative-side power source voltage, and shifts a high-voltage-side potential of an output of the first level circuit to the second positive-side power source.
- 10. The liquid crystal display device according to claim 9, wherein the driver circuit is formed on the same substrate as the pixel section.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-043082 |
Feb 1998 |
JP |
|
US Referenced Citations (5)