U.S. patent application number 13/420452 was filed with the patent office on 2012-07-05 for data driver and display apparatus using the same including clock control circuit and shift register circuit.
This patent application is currently assigned to Renesas Electronics Corporation. Invention is credited to Kazuo Nakamura.
Application Number | 20120170706 13/420452 |
Document ID | / |
Family ID | 39497413 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120170706 |
Kind Code |
A1 |
Nakamura; Kazuo |
July 5, 2012 |
DATA DRIVER AND DISPLAY APPARATUS USING THE SAME INCLUDING CLOCK
CONTROL CIRCUIT AND SHIFT REGISTER CIRCUIT
Abstract
A circuit includes a first shift register configured to be reset
with a reset signal, to shift a first pulse signal and output the
shifted first pulse signal as a second pulse signal, and a second
shift register configured to be reset with the first pulse signal,
to shift the second pulse signal and to output the shifted second
pulse signal as a third pulse signal.
Inventors: |
Nakamura; Kazuo; (Shiga,
JP) |
Assignee: |
Renesas Electronics
Corporation
Kawasaki-shi
JP
|
Family ID: |
39497413 |
Appl. No.: |
13/420452 |
Filed: |
March 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11987860 |
Dec 5, 2007 |
|
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13420452 |
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Current U.S.
Class: |
377/64 |
Current CPC
Class: |
G11C 19/00 20130101;
G11C 19/28 20130101 |
Class at
Publication: |
377/64 |
International
Class: |
G11C 19/00 20060101
G11C019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2006 |
JP |
2006-330962 |
Claims
1. A circuit comprising: a first shift register configured to be
reset with a reset signal, to shift a first pulse signal and output
the shifted first pulse signal as a second pulse signal; and a
second shift register configured to be reset with the first pulse
signal, to shift the second pulse signal and to output the shifted
second pulse signal as a third pulse signal.
2. The circuit according to claim 1, further comprising a third
shift register configured to be reset with the second pulse signal,
to shift the third pulse signal and to output the shifted third
pulse signal.
3. A circuit comprising: a first shift register including a first
reset node, a first input node coupled to a first node and a first
output node coupled to a second node; and a second shift register
including a second reset node coupled to the first node, a second
input node coupled to the second node, and a second output node
coupled to a third node.
4. The circuit according to claim 3, further comprising a third
shift register including a third reset node coupled to the second
node, a third input node coupled to the third node, and a third
output node.
5. The circuit according to claim 4, further comprising a clock
control circuit including a first clock node coupled to the first
shift register, a second clock node coupled to the second shift
register and a third clock node coupled to the third shift
register.
6. The circuit according to claim 5, wherein the first shift
register is configured to be reset with a reset signal inputted to
the reset node and to shift a first pulse signal inputted to the
first node and output the shifted first pulse signal to the second
node as a second pulse signal, wherein the second shift register is
configured to be reset with the first pulse signal and to shift the
second pulse signal and output the shifted second pulse signal to
third node as a third pulse signal, and wherein the third shift
register is configured to be reset with the second pulse signal and
to shift the third pulse signal and output the shifted third pulse
signal as a fourth pulse signal.
7. The circuit according to claim 6, wherein the clock control
circuit is configured to start supplying a first clock signal
through the first clock node in response to the reset signal and to
stop supplying the first clock signal in response to the third
pulse signal.
8. The circuit according to claim 7, wherein the clock control
circuit is further configured to start supplying a second clock
signal through the second clock node in response to the first pulse
signal and to stop supplying the second clock signal in response to
the fourth pulse signal.
9. A semiconductor device, comprising: a first shift register
including a first reset node, a first input node coupled to a first
node and a first output node coupled to a second node; and a second
shift register including a second reset node coupled to the first
node, a second input node coupled to the second node and a second
output node coupled to a third node.
10. The semiconductor device according to claim 9, further
comprising a third shift register including a third reset node
coupled to the second node, a third input node coupled to the third
node and a third output node.
11. The semiconductor device according to claim 10, further
comprising a clock control circuit including a first clock node
coupled to the first shift register, a second clock node coupled to
the second shift register and a third clock node coupled to the
third shift register.
Description
[0001] The present application is a Continuation Application of
U.S. patent application Ser. No. 11/987,860 filed on Dec. 5, 2007,
which is based on Japanese Patent Application No. 2006-330962,
filed on Dec. 7, 2006, the entire contents of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a data driver and a display
apparatus for displaying a display data by using the data driver.
The present invention is based on Japanese Patent Application No.
2006-330962. The disclosure of the application is incorporated
herein by reference.
[0004] 2. Description of Related Art
[0005] Display apparatuses such as a TFT (Thin Film Transistor)
type liquid crystal display apparatus, a simple-matrix type liquid
crystal display apparatus, an electroluminescence (EL) display
apparatus, and a plasma display apparatus have been widely
used.
[0006] As an example of a conventional display apparatus, the TFT
type liquid crystal display apparatus will be described. FIG. 1
shows a configuration of the conventional TFT type liquid crystal
display apparatus 101. The display apparatus 101 includes a timing
controller 2, a gate driver 120, a data driver 130 and a liquid
crystal panel 10.
[0007] The liquid crystal panel 10 includes a plurality of pixels
11 which are arranged on a glass substrate 3 in a matrix. For
example, (m.times.n) pixels (m and n are integers of 2 or more) are
arranged on the glass substrate 3. Each of the (m.times.n) pixels
11 includes a thin film transistor (TFT) 12 and a pixel capacitor
15. The pixel capacitor 15 includes a pixel electrode and a counter
electrode opposite to the pixel electrode. The TFT 12 includes a
drain electrode 13, a source electrode 14 connected to the pixel
electrode, and a gate electrode 16.
[0008] The gate driver 120 is connected to one end of m gate lines
G1 to Gm. The data driver 130 is connected to one end of n data
lines D1 to Dn. The m gate lines G1 to Gm are connected to the gate
electrodes 16 of the TFTs 12 of the pixels 11 in m rows,
respectively. The n data lines D1 to Dn are connected to the drain
electrodes 13 of the TFTs 12 of the pixels 11 in n columns,
respectively.
[0009] The timing controller 2 supplies a gate clock signal GCLK to
the gate driver 120 to select and drive one of the gate lines in
one horizontal period. Also, the timing controller 2 supplies a
clock signal CLK and one-line display data DATA to the data driver
130. A data DATA for one horizontal line contains n display data
corresponding to the data lines D1 to Dn.
[0010] The data driver 130 outputs the n display data to the n data
lines D1 to Dn in accordance with the clock signal CLK. At this
time, the TFTs 12 of (1.times.n) pixels 11 corresponding to the
driven gate line and the n data lines D1 to D2 are turned on.
Therefore, the n display data are written to the pixel capacitors
15 of the (1.times.n) pixels 11, which are held until a next write
operation of display data. With this, the n display data are
displayed as the one-line display data DATA.
[0011] The data driver 130 includes K data driver circuits 130-1 to
130-K which are cascade-connected in this order for allowing
display of the n pixels. FIG. 2 shows a configuration of the data
driver circuit 130. It should be noted that "K" is an integer of 2
or more, which satisfies n/y (n>y, y is an integer of 2 or
more). Each of the K data driver circuits 130-1 to 130-K includes
an internal signal circuit 40, a shift register circuit 131, a data
register circuit 32, a latch circuit 33, a level shifter circuit
34, a digital/analog (D/A) converter circuit 35, a data output
circuit 36, and a gradation voltage generating circuit 37.
[0012] The internal signal circuit 40 is connected to the shift
register circuit 131. The shift register circuit 131 is connected
to the data register circuit 32, and the data register circuit 32
is connected to the latch circuit 33. The latch circuit 33 is
connected to the level shifter circuit 34, and the level shifter
circuit 34 is connected to the D/A converter circuit 35. The D/A
converter circuit 35 is connected to the data output circuit 36 and
the gradation voltage generating circuit 37. Y output buffers of
the data output circuit 36 are connected to y data lines D1 to Dy,
respectively.
[0013] The gradation voltage generating circuit 37 includes a
plurality of -correction resistance elements that are connected in
series as shown in FIG. 3. The gradation voltage generating circuit
37 divides a difference between reference voltages from a power
supply circuit (not shown) by the plurality of -correction
resistance elements to generate a plurality of gradation voltages.
For example, when a display of sixty-four gradation levels is
performed, the gradation voltage generating circuit 37 divides
reference voltages by sixty-three -correction resistance elements
R0 to R62, and generates positive-polarity gradation voltages. The
same is performed for negative-polarity gradation voltages.
[0014] The shift register circuit 131 includes y registers (not
shown), and the data register circuit 32 includes y registers (not
shown). The latch circuit 33 includes y latches (not shown), and
the level shifter circuit 34 includes y level shifters (not
shown).
[0015] The D/A converter circuit 35 includes y D/A converters (see
FIG. 4). The y D/A converters contain a P-type converters (PchDAC)
which output the positive-polarity gradation voltages and N-type
converters (NchDAC) which output the negative-polarity gradation
voltage. For example, of the above y D/A converters, odd-numbered
D/A converters are the PchDAC, and even-numbered D/A converters are
the NchDAC. The D/A converter circuit 35 further includes y
switching elements (see FIG. 4) for performing an inversion drive
in which the positive-polarity gradation voltage and the
negative-polarity gradation voltage are alternately applied to the
pixels 11. The data output circuit 36 includes y output buffers or
amplifiers (see FIG. 4).
[0016] The timing controller 2 supplies the clock signal CLK to the
K data driver circuits 130-1 to 130-K, supplies the one-line
display data DATA to the K data driver circuits 130-1 to 130-K in
one horizontal period, and supplies a shift pulse signal STH to the
data driver circuit 130-1 as a start pulse signal. The data driver
circuit 130-i outputs the y display data contained in the one-line
display data DATA to the y data lines D1 to Dy, respectively, in
response to the clock signal CLK and the shift pulse signal STH. It
should be noted that "i" is an integer that satisfies 1iK.
[0017] In this case, the internal signal circuit 40 of the data
driver circuit 130-1 generates a reset signal RESET and an internal
shift pulse signal ISTH that is delayed by a predetermined number
of clocks from the reset signal RESET, based on the shift pulse
signal STH supplied from the timing controller 2, and outputs those
signals to the shift register circuit 131. The y shift registers of
the shift register circuit 131 of the data driver circuit 130-i
(i=1, 2, . . . , K) are reset in response to the reset signal RESET
(will be described later).
[0018] In the data driver circuit 130-i (in this case, i=1, 2, . .
. , K-1), each of the y shift registers of the shift register
circuit 131 shifts the internal shift pulse signal ISTH in order in
synchronization with the clock signals CLK, and outputs the shifted
signal to the y data registers of the data register circuit 32. The
yth shift register of the shift register circuit 131 outputs the
internal shift pulse signal ISTH to the yth data register of the
data register circuit 32, and outputs it to the data driver circuit
130-(i+1) (in this case, i=1, 2, . . . , K-1). In the data driver
circuit 130-K, each of the y shift registers of the shift register
circuit 131 shifts the internal shift pulse signal ISTH in order in
synchronization with the clock signal CLK, and outputs the shifted
signal to the y data registers of the data register circuit 32.
[0019] In the data driver circuit 130-i, each of the y shift
registers acquires the y display data from the timing controller 2
in synchronization with the internal shift pulse signal ISTH from
the y shift registers of the shift register circuit 131, and
outputs them to the y latches of the latch circuit 33. The y
latches latch the y display data from the y data registers of the
data register circuit 32 at a same timing, and output them to the y
level shifters of the level shifter circuit 34. Each of the y level
shifters performs level-conversion on the y display data, and the y
level shifters output them to the y D/A converters of the D/A
converter circuit 35. The y D/A converters perform a digital/analog
conversion on the y display data outputted from the y level
shifters of the level shifter circuit 34. For example, as shown in
FIG. 4, each of the PchDACs serving as the odd-numbered (the 1st,
3rd, . . . , (y-1)th) D/A converters selects an output gradation
voltage from among the positive-polarity sixty-four gradation
voltages in accordance with the display data outputted from a
corresponding one of the odd-numbered (the 1st, 3rd, . . . ,
(y-1)th) level shifters, and outputs the selected voltage to a
corresponding one of the odd-numbered (the 1st, 3rd, . . . ,
(y-1)th) output buffers of the data output circuit 36 via a
corresponding one of the odd-numbered (the 1st, 3rd, . . . ,
(y-1)th) switching elements. Also, each of the NchDACs serving as
the even-numbered (the 2nd, 4th, . . . , yth) D/A converters
selects an output gradation voltage among the negative-polarity
sixty-four gradation voltages in accordance with the display data
outputted from a corresponding one of the even-numbered (the 2nd,
4th, . . . , yth) level shifters, and outputs the selected voltage
to a corresponding one of the even-numbered (the 2nd, 4th, . . . ,
yth) output buffers of the data output circuit 36 via a
corresponding one of the even-numbered (the 2nd, 4th, . . . , yth)
switching elements.
[0020] Meanwhile, for performing an inversion drive, as shown in
FIG. 4, each of the PchDACs serving as the odd-numbered (the 1st,
3rd, . . . , (y-1)th) D/A converters selects an output gradation
voltage among the positive-polarity gradation voltages of
sixty-four gradations in accordance with the display data outputted
from a corresponding one of the odd-numbered (the 1st, 3rd, . . . ,
(y-1)th) level shifters, and outputs the selected voltage to a
corresponding one of the even-numbered (the 2nd, 4th, . . . , yth)
output buffers of the data output circuit 36 via a corresponding
one of the odd-numbered (the 1st, 3rd, . . . , (y-1)th) switching
elements. Also, each of the NchDACs serving as the even-numbered
(the 2nd, 4th, . . . , yth) D/A converters selects an output
gradation voltage among the negative-polarity sixty-four gradation
voltages in accordance with the display data outputted from a
corresponding one of the even-numbered (the 2nd, 4th, . . . , yth)
level shifters, and outputs the selected voltage to a corresponding
one of the odd-numbered (the 1st, 3rd, . . . , (y-1)th) output
buffers of the data output circuit 36 via a corresponding one of
the even-numbered (the 2nd, 4th, . . . , yth) switching
elements.
[0021] As such, each of the above-described y D/A converters
outputs the y output gradation voltages to the y output buffers of
the data output circuit 36. The y output buffers output the y
display data from the D/A converter circuit 35 to the y data lines
D1 to Dy.
[0022] FIG. 5 shows a configuration of the shift register circuit
131 of the data driver circuit 130-i. The shift register circuit
131 of the data driver circuit 130-i is a 32-bit shift register
circuit (y=32), which includes eight 4-bit partial shift registers
SR1 to SR8 which are cascade-connected in this order. As shown in
FIG. 6, each of the eight partial shift registers SR1 to SR8
includes four synchronous D-type flip-flops (to be referred to as
flip-flops, hereinafter) F1 to F4 which are cascade-connected in
this order. Each of the four flip-flops F1 to F4 needs to be reset
(initialized) then is subjected to a normal operation, since an
output state thereof becomes unstable under circumstances, e.g.
immediately after a supply of a power source, and immediately after
the transfer direction of a bidirectional register is switched.
Therefore, each of the four flip-flops F1 to F4 has a reset input
(R), in addition to a clock input (C), a data input (D), and an
output (Q). Each output (Q) of the four flip-flops F1 to F4 is
connected to the above-described data register circuit 32.
[0023] The data input (D) of the flip-flop F1 of the partial shift
register SR1 of the data driver circuit 130-1 is connected to the
internal signal circuit 40 thereof, and the internal shift pulse
signal ISTH is supplied thereto. The output (Q) of the flip-flop F4
of the partial shift register SRj of the data driver circuit 130-i
is connected to the data input (D) of the flip-flop F1 of the
partial shift register SR(j+1) of the data driver circuit 130-i. It
should be noted that "j" is an integer that satisfies 1j7. The
output (Q) of the flip-flop F4 of the partial shift register SR8 of
the data driver circuit 130-i is connected to the data input (D) of
the partial shift register SR1 of the data driver circuit
130-(i+1). Each clock input (C) of the eight partial shift
registers SR1 to SR8 of the data driver circuit 130-i is connected
to the timing controller 2, and the clock signal CLK is supplied
thereto. Each reset input (R) of the eight partial shift registers
SR1 to SR8 of the data driver circuit 130-i is connected to the
internal signal circuit 40 thereof, and the reset signal RESET is
supplied thereto.
[0024] Now, among the K data driver circuits 130-1 to 130-K, an
operation of the shift register circuit 131 of the data driver
circuit 130-1 will be described. The timing controller 2 always
outputs the clock signal CLK to each of shift register circuits 131
of the K data driver circuits 130-1 to 130-K.
[0025] When resetting (initializing) the shift register circuits
131 of the K data driver circuits 130-1 to 130-K, the internal
signal circuit 40 of the data driver circuit 130-1 generates the
reset signal RESET and the internal shift pulse signal ISTH that is
delayed by a predetermined number of clocks from the reset signal
RESET based on the shift pulse signal STH supplied from the timing
controller 2, and outputs those signals to the shift register
circuit 131.
[0026] First, the internal signal circuit 40 of the data driver
circuit 130-1 outputs the reset signal RESET to the partial shift
registers SR1 to SR8 of the shift register circuit 131. The reset
signal RESET is in a high level. At this time, each of the partial
shift registers SR1 to SR8 is reset to an initial state in
accordance with the reset signal RESET. Then, the internal signal
circuit 40 of the data driver circuit 130-1 outputs the internal
shift pulse signal ISTH to the flip-flop F1 of the partial shift
register SR1 of the shift register circuit 131. The internal shift
pulse signal ISTH is in the high level. For example, the partial
shift register SRj outputs the internal shift pulse signal ISTH to
the data register circuit 32 in synchronization with the clock
signal CLK for four times, and outputs the internal shift pulse
signal ISTH (when being synchronized with the clock signal CLK for
four times) to the flip-flop F1 of the partial shift register
SR(j+1). The partial shift register SR8 outputs the internal shift
pulse signal ISTH outputted from the partial shift register SR7 to
the data register circuit 32 in synchronization with the clock
signal CLK for four times, and outputs the internal shift pulse
signal ISTH (when being synchronized with the clock signal CLK for
four times) to the flip-flop F1 of the partial shift register SR1
of the shift register circuit 131 of the data driver circuit 130-2.
However, in the above-described data driver 130 (K data driver
circuits 130-1 to 130-K), the eight partial shift registers SR1 to
SR8 of the shift register circuit 131 are reset simultaneously,
thereby causing following problems.
[0027] Recently, display apparatuses have been large-scaled to
display the display data in a larger screen, in which the number of
outputs of the display apparatus are increased. In accordance with
this, the number of elements is also increased in the data driver
130. When the eight partial shift registers SR1 to SR8 as the
elements operate simultaneously, an operation current (peak value)
at that time increases drastically, so that a supply voltage to be
supplied to the TFT type liquid crystal display apparatus 101
becomes fluctuated. This may cause malfunctions or may become a
factor for generating electromagnetic noise (EMI) in some
cases.
[0028] The same is true when the gate drover 120 includes the shift
register circuit 131.
[0029] In conjunction with the above description, Japanese Laid
Open Patent Application (JP-A-Showa 59-14195) discloses a
semiconductor apparatus in which the timings of reset are shifted.
This semiconductor apparatus includes a plurality of latch circuits
and delay circuits. In this publication, the delay circuits delay
reset signals so that the plurality of latch circuits are not reset
simultaneously.
[0030] A case is discussed where the technique disclosed in
Japanese Laid Open Patent Application (JP-A-Showa 59-14195) is
applied to the above-described shift register circuit 131. For
example, it is considered that the above delay circuit includes 8
delay sections, the 8 delay sections are connected to the eight
partial shift registers SR1 to SR8, respectively, and the plurality
of latch circuits are the eight partial shift registers SR1 to SR8.
In this case, a delay time when the 8 delay sections delay the
reset signals is referred to as 1st to 8th delay times. The 1st to
8th delay times are longer in this order. The 1st to 8th delay
sections delay the reset signals by the 1st to 8th delay time,
respectively, and outputs them to the partial shift registers SR1
to SR8. Each of the partial shift registers SR1 to SR8 executes a
reset operation based on a corresponding one of the reset signals
from the 8 delay sections.
[0031] However, in the technique disclosed in Japanese Laid Open
Patent Application (JP-A-Showa 59-14195), the reset signal is not
synchronized with the clock signal CLK. Thus, when the 8 delay
sections output the reset signals without synchronizing with the
clock signals CLK, the reset signals are outputted from the 8 delay
sections at the improper timings. The partial shift registers SR1
to SR8 perform the reset at the improper timings in response to the
reset signals from the 8 delay sections, respectively. Therefore,
when the internal shift pulse signal ISTH is supplied to the
partial shift register SR1 of the shift register circuit 131, the
internal shift pulse signal ISTH is outputted from the partial
shift register SR8 at an improper timing. As a result, the data
register circuit 32 cannot acquire the n display data from the
timing controller 2 in synchronization with the internal shift
pulse signal ISTH from the shift register circuit 131.
[0032] As described, it is desired that the partial shift registers
SR1 to SR8 do not perform reset operations simultaneously, while
performing the reset operations in synchronization with the clock
signal CLK.
SUMMARY OF THE INVENTION
[0033] In a first embodiment of the present invention, a data
driver circuit includes a shift register section including
flip-flops in cascade-connection and configured to shift a pulse
signal through the flip-flops in synchronization with a clock
signal, and a control circuit configured to receive a display data
in response to the shifted pulse signal from the shift register
section and to drive data lines of a display section based on
display data to display the display data on the display section.
The flip-flops are grouped in units of N (N is an integer of 2 or
more) flip-flops into M (M is an integer of 2 or more) partial
shift registers, and the shift register circuit is reset in units
of partial shift registers.
[0034] In a second embodiment of the present invention, a display
apparatus includes a display panel having gate lines, data lines,
and pixels arranged at intersections of the gate lines and the data
lines; a gate driver configured to drive the gate lines
sequentially; and a data driver configured to drive the data lines
based on display data in each of horizontal periods. The data
driver includes K (K is an integer of 2 or more) data driver
circuits which are cascade-connected. Each of the data driver
circuits includes a shift register section including flip-flops in
cascade-connection and configured to shift a pulse signal through
the flip-flops in synchronization with a clock signal, and a
control circuit configured to receive a corresponding portion of
the display data in response to the shifted pulse signal from the
shift register circuit and to drive corresponding ones of the data
lines based on the corresponding portion of the display data. The
flip-flops are grouped in units of N (N is an integer of 2 or more)
flip-flops into M (M is an integer of 2 or more) partial shift
registers, and the shift register circuit is reset in units of
partial shift registers.
[0035] In a third embodiment of the present invention, a shift
register circuit includes a clock control section configured to
generate a shift clock signal in synchronization to a clock signal;
and a shift register comprising flip-flops in cascade-connection
and configured to shift a pulse signal in synchronization with the
shift clock signal. The flip-flops are grouped in units of N (N is
an integer of 2 or more) flip-flops into M (M is an integer of 2 or
more) partial shift registers, and the shift register is reset in
units of partial shift registers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The above and other objects, advantages and features of the
present invention will be more apparent from the following
description of certain embodiments taken in conjunction with the
accompanying drawings, in which:
[0037] FIG. 1 is a block diagram showing a configuration of a
conventional TFT type liquid crystal display apparatus;
[0038] FIG. 2 is a block diagram showing a configuration of each of
data driver circuits used in a conventional data driver in the
conventional TFT type liquid crystal display apparatus;
[0039] FIG. 3 is a block diagram showing a configuration of a
gradation voltage generating circuit in the conventional TFT type
liquid crystal display apparatus;
[0040] FIG. 4 is a block diagram showing a configuration of a D/A
converter circuit and a data output circuit in the conventional TFT
type liquid crystal display apparatus;
[0041] FIG. 5 is a circuit diagram showing a configuration of a
shift register circuit in the conventional TFT type liquid crystal
display apparatus;
[0042] FIG. 6 is a circuit diagram showing a configuration of each
of eight partial shift registers in the conventional TFT type
liquid crystal display apparatus;
[0043] FIG. 7 is a block diagram showing a configuration of a
display apparatus of the present invention;
[0044] FIG. 8 is a block diagram showing a configuration of each of
data driver circuits according to an embodiment of the present
invention;
[0045] FIG. 9 is a circuit diagram showing a hardware configuration
of a shift register circuit of the data driver circuit in the
embodiment;
[0046] FIG. 10 is a circuit diagram showing a configuration of each
of eight partial shift registers in the exemplary embodiment;
and
[0047] FIGS. 11A and 11B are a timing chart showing an operation of
the shift register circuit and a clock control circuit of the data
driver circuit in the embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Hereinafter, a display apparatus to which a data driver of
the present invention is applied will be described in detail with
reference to the attached drawings. The present invention is
applied to a TFT (Thin Film Transistor) type liquid crystal display
apparatus, a simple-matrix type liquid crystal display apparatus,
an electroluminescence (EL) display apparatus, a plasma display
apparatus, and the like.
[0049] FIG. 7 is a block diagram showing a configuration of a TFT
type liquid crystal display apparatus 1 as the display apparatus of
the present invention. It should be noted that the same reference
numerals are assigned to the same or similar components in FIG. 1,
and their description will be omitted.
[0050] The TFT type liquid crystal display apparatus 1 includes a
timing controller 2, a gate driver 20 and a data driver 30, a
display section (liquid crystal panel) 10. The gate driver 20 is
connected to one end of the m gate lines G1-Gm. The data driver 30
is connected to one end of the n data lines D1 to Dn. The timing
controller 2 supplies a gate clock signal GCLK to the gate driver
20 to select one of the gate lines in one horizontal period. The
timing controller 2 supplies a clock signal CLK and data DATA for
one horizontal line to the data driver 30. The data DATA contains n
display data for the data lines D1 to Dn.
[0051] FIG. 8 is a block diagram showing a configuration of the
data driver 30. The data driver 30 includes K data driver circuits
30-1 to 30-K which are cascade-connected in this order to make a
display of the n pixels possible. It should be noted that "K" is an
integer of 2 or more, which satisfies n/y (n>y, y is an integer
of 2 or more). Each of the K data driver circuits 30-1 to 30-K of
the data driver 30 includes an internal signal circuit 40, a shift
register circuit 31, a clock control circuit 38, and a control
section 39. The control section 39 includes a data register circuit
32, a latch circuit 33, a level shifter circuit 34, a
digital/analog (D/A) converter circuit 35, a data output circuit
36, and a gradation voltage generating circuit 37.
[0052] The internal signal circuit 40 is connected to the shift
register 31 and the clock control circuit 38. The shift register 31
is connected to the data register circuit 32 and the clock control
circuit 38, and includes y shift registers (not shown). The timing
controller 2 supplies the clock signal CLK to the K data driver
circuits 30-1 to 30-K, supplies the data DATA for one horizontal
line to the K data driver circuits 30-1 to 30-K in one horizontal
period, and supplies a shift pulse signal STH to the data driver
circuit 30-1 as a start pulse signal. The data driver circuit 30-i
outputs the y data contained in the one-line display data DATA to y
data lines D1 to Dy, respectively, in response to the clock signal
CLK and the shift pulse signal STH. It should be noted that "i" is
an integer that satisfies 1iK. In this case, the internal signal
circuit 40-1 of the data driver circuit 30-1 generates a reset
signal RESET and an internal shift pulse signal ISTH that has been
delayed by a predetermined number of clocks from the reset signal
RESET based on the shift pulse signal STH supplied from the timing
controller 2, and outputs those signals to the shift register 31.
In response to the reset signal RESET, the y shift registers of the
shift register circuit 31 of the data driver circuit 30-i (i=1, 2,
. . . , K) are reset, as described later.
[0053] In the data driver circuit 30-i (in this case, i=1, 2, . . .
, K-1), the clock control circuit 38 outputs a transfer clock
signal CLK' to be described later to the shift register circuit 31
in synchronization with the clock signal CLK. Each of the y shift
registers of the shift register circuit 31 shifts the internal
shift pulse signal ISTH in order in synchronization with the
transfer clock signal CLK' from the clock control circuit 38, and
outputs the shifted signal to the y data registers of the data
register circuit 32. The shift registers of the shift register
circuit 31 output the internal shift pulse signal ISTH to the
control section 39, and output (cascade-outputs) it to the data
driver circuit 30-(i+1) (in this case, i=1, 2, . . . , K-1). In the
data driver circuit 30-K, each of the y shift registers of the
shift register circuit 31 shifts the internal shift pulse signal
ISTH in order in synchronization with the transfer clock signal
CLK', and outputs the shifted signal to a corresponding one of the
y data registers of the data register circuit 32. An operation of
the control section 39 (the data register circuit 32, the latch
circuit 33, the level shifter circuit 34, the D/A converter circuit
35, the data output circuit 36, and the gradation voltage
generating circuit 37) are the same as that of the TFT type liquid
crystal display apparatus 101 shown in FIG. 2.
[0054] FIG. 9 shows a hardware configuration of the shift register
circuit 31 of the data driver circuit 30-i. The shift register
circuit 31 of the data drier circuit 30-i is a (M.times.N)-bit
shift register, which includes M partial shift registers SR1 to SRM
which are cascade-connected in this order ("M" is an integer of 2
or more, and "N" is an integer of 1 or more (for example, M=8
(M=2.sup.3), and N=4 (N=2.sup.2))). The M partial shift registers
SR1 to SRM are N-bit shift registers.
[0055] As shown in FIG. 10, each of the M partial shift registers
SR1 to SRM includes N synchronous D-type flip-flops (to be referred
to as flip-flops simply, hereinafter) F1 to FN which are
cascade-connected in this order. Each of the N flip-flops F1 to FN
has a clock input (C), a data input (D), an output (Q), and a reset
input (R). The outputs (Q) of the N flip-flops F1 to FN are
connected to the above-described data register circuit 32. The data
input (D) of the flip-flop F1 of the partial shift register SR1 of
the data driver circuit 30-1 is connected to the internal signal
circuit 40, and the internal shift pulse signal ISTH is supplied
thereto. The output (Q) of the flip-flop FN of the partial shift
register SRj of the data driver circuit 30-i is connected to the
data input (D) of the flip-flop F1 of the partial shift register
SR(j+1) of the data driver circuit 30-i. It should be noted that
"j" is an integer that satisfies 1j(M-1). The output (Q) of the
flip-flop FN of the partial shift register SRM of the data driver
circuit 30-i is connected to the data input (D) of the partial
shift register SR1 of the data driver circuit 30-(i+1). The clock
inputs (C) of the M partial shift registers SR1 to SRM of the data
driver circuit 30 are connected to the clock control circuit 38,
and the 1st to Mth transfer clock signals are respectively supplied
thereto, as the transfer clock signal CLK'.
[0056] The reset input (R) of the partial shift register SR1 of the
data driver circuit 30-i is connected to the internal signal
circuit 40 thereof, and the reset signal RESET is supplied thereto.
The reset input (R) of the partial shift register SR(j+1) of the
data driver circuit 30-i is connected to the data input (D) of the
flip-flop F1 of the partial shift register SRj of the data driver
circuit 30-i, and the internal shift pulse signal ISTH is supplied
thereto as the reset signal RESET.
[0057] The timing controller 2 always outputs the clock signal CLK
to each of the clock control circuits 38 of the K data driver
circuits 30-1 to 30-K.
[0058] When resetting (initializing) the shift register circuits 31
of the K data driver circuits 30-1 to 30-K, the internal signal
circuit 40 of the data driver circuit 30-1 generates the reset
signal RESET and the internal shift pulse signal ISTH that has been
delayed by a predetermined number of clocks from the reset signal
RESET based on the shift pulse signal STH supplied from the timing
controller 2, and outputs those signals to the shift register
circuit 31-1.
[0059] First, the internal signal circuit 40 of the data driver
circuit 30-1 outputs the reset signal RESET to the partial shift
register SR1 and the clock control circuit 38 of the shift register
circuit 31-1. The reset signal RESET is in a high level. At this
time, the clock control circuit 38 of the data driver circuit 30-1
receives the reset signal RESET as a first transfer control signal
FF' from the internal signal circuit 40, and outputs the reset
signal RESET to the partial shift register SR1 in synchronization
with the clock signal CLK in accordance with the first transfer
control signal FF'. The partial shift register SR1 of the shift
register circuit 31 in the data driver circuit 30-1 is reset to an
initial state in accordance with the reset signal RESET from the
internal signal circuit 40.
[0060] Next, the internal signal circuit 40 of the data driver
circuit 30-1 outputs the internal shift pulse signal ISTH to the
flip-flop F1 of the partial shift register SR1 of the shift
register circuit 31-1, and outputs the internal shift pulse signal
ISTH to the partial shift register SR2 of the shift register
circuit 31-1 as the reset signal RESET. The internal shift pulse
signal ISTH is in the high level.
[0061] The partial shift register SRj receives the internal shift
pulse signal ISTH. At this time, the partial shift register SR(j+1)
is reset to an initial state while resetting a held signal, in
accordance with the internal shift pulse signal ISTH supplied to
the partial shift register SRj. The partial shift register SRj
outputs the internal shift pulse signal ISTH to the data register
circuit 32 in synchronization with the clock signal CLK for N
times, and outputs the internal shift pulse signal ISTH (when being
synchronized with the clock signal CLK for N times) to the
flip-flop F1 of the partial shift register SR(j+1) and the clock
control circuit 38.
[0062] The clock control circuit 38 receives the internal shift
pulse signal ISTH supplied to the partial shift register SRj as a
(j+1)th transfer control signal FF', and outputs the (j+1)th
transfer clock signal to the partial shift register SR(j+1) in
synchronization with the clock signal CLK in accordance with the
(j+1)th transfer control signal FF'. The clock control circuit 38
stops the output of the jth transfer clock signal when the internal
shift pulse signal ISTH is received from the partial shift register
SR(j+1). The partial shift register SRM of the data driver circuit
30-1 receives the internal shift pulse signal ISTH from the partial
shift register SR(M-1), and outputs it to the data register circuit
32 in synchronization with the Mth transfer clock signal for N
times. At the same time, the partial shift register SRM outputs the
internal shift pulse signal ISTH (when being synchronized with the
clock signal CLK N times) to the flip-flop F1 of the partial shift
register SR1 of the shift register circuit 31 of the data driver
circuit 30-2 and the clock control circuit 38 of the data driver
circuit 30-1.
[0063] Although being not shown, the clock control circuit 38
receives a signal, which has been delayed from an output of the
partial shift register SRM by N clocks of the clock signal CLK, as
the transfer control signal FF', and stops the output of the Mth
transfer clock signal in accordance with the transfer control
signal FF'.
[0064] Recently, a display apparatus has become large-scaled in
order to display the display data on a larger screen, in which the
number of outputs of the display apparatus is increased. In
accordance with this, the number of elements is also increased in
the data driver 30 of the TFT type liquid crystal display apparatus
1 according to the present invention. When the M partial shift
registers SR1 to SRM as the elements operate simultaneously, an
operation current (peak value) at that time increases drastically,
so that a supply voltage supplied to the TFT type liquid crystal
display apparatus 1 becomes fluctuated. This may cause malfunctions
or may become a factor for generating electromagnetic noise (EMI)
in some cases. The same is true when the gate driver 20 also
includes the shift register circuit 31.
[0065] However, in the data driver 30 (K data driver circuits 30-1
to 30-K) of the TFT type liquid crystal display apparatus 1
according to the present invention, the partial shift register
SR(j+1) of the shift register circuit 31 is reset in response to
the internal shift pulse signal ISTH supplied to the partial shift
register SRj (1j(M-1)). This internal shift pulse signal ISTH is
transferred as the reset signal RESET to the partial shift
registers SR1 to SRM successively in synchronization with the clock
signals CLK (first to Mth transfer clock signals). In this way,
each of the partial shift registers SR1 to SRM is reset
successively in synchronization with the clock signals CLK.
Therefore, the partial shift registers SR1 to SRM of the shift
register circuit 31 do not perform the reset operations
simultaneously, and the reset operation can be performed in
synchronization with the clock signal CLK (internal shift pulse
signal ISTH).
[0066] In the data driver 30 (K data driver circuits 30-1 to 30-K)
of the TFT type liquid crystal display apparatus 1 according to the
present invention, the reset signal RESET is synchronized with the
clock signal CLK. Thus, the partial shift registers SR1 to SRM are
reset at the proper timings in accordance with the signals RESET
from the internal signal circuit 40 and the partial shift registers
SR1 to SR(M-2), respectively. Therefore, when the internal shift
pulse signal ISTH is supplied to the partial shift register SR1 of
the shift register circuit 31, the internal shift pulse signal ISTH
is outputted from the partial shift register SRM at the proper
timing. As a result, the data register circuit 32 can acquire the n
display data from the timing controller 2 in synchronization with
the internal shift pulse signal ISTH from the shift register
circuit 31.
[0067] Further, in the data driver 30 (K data driver circuits 30-1
to 30-K) of the TFT type liquid crystal display apparatus 1
according to the present invention, the clock control circuit 38
controls the start and stop of the outputs of the 1st to Mth
transfer clock signals. Therefore, the shift register circuit 31
can output the internal shift pulse signal ISTH to the data
register circuit 32 at a more adequate timing.
[0068] Among the K data driver circuits 30-1 to 30-K, an operation
of the shift register circuit 31 and the clock circuit 38 of the
data driver circuit 30-1 will be described in detail. FIG. 11A and
FIG. 11B are timing charts showing the operation of the shift
register circuit 31. In this case, it is assumed here that "M" is
8, and "N" is 4.
[0069] Here, as shown in FIGS. 11A and 11B, the four flip-flops F1
to F4 in each of the partial shift registers SR1 to SR8 are
referred to as the flip-flops FF1 to FF32 by using sequential
numbers. Further, as shown in FIGS. 11A and 11B, the first to
eighth transfer clock signals are referred to as transfer clock
signals CLK0 to CLK7, respectively, as the transfer clock signals
CLK'.
[0070] First, in one horizontal period, the shift pulse signal STH
is supplied from the timing controller 2 to the internal signal
circuit 40 of the data driver circuit 30-1. At this time, the reset
signal RESET is supplied from the internal signal circuit 40 to the
partial shift register SR1 of the shift register circuit 31 and the
clock control circuit 38. The reset signal RESET is in the high
level. The clock control circuit 38 receives the reset signal RESET
from the internal signal circuit 40 as the first transfer control
signal FF', and outputs the transfer clock signal CLK0 as the first
transfer clock signal to the partial shift register SR1 in
synchronization with the clock signal CLK in accordance with the
first transfer control signal FF'. The partial shift register SR1
is reset in accordance with the reset signal RESET from the
internal signal circuit 40.
[0071] Then, the internal shift pulse signal ISTH is supplied from
the internal signal circuit 40 to the flip-flop FF1 of the partial
shift register SR1 of the shift register circuit 31, and the
internal shift pulse signal ISTH is supplied to the partial shift
register SR2 as the reset signal RESET. This internal shift pulse
signal ISTH is in the high level. The partial shift register SR1
receives the internal shift pulse signal ISTH from the internal
signal circuit 40. At this time, the partial shift register SR2 is
resets in accordance with the internal shift pulse signal ISTH
supplied to the partial shift register SR1. The partial shift
register SR1 outputs the internal shift pulse signal ISTH from the
internal signal circuit 40 to the data register circuit 32 in
synchronization with the transfer clock signal CLK0 for four times,
and outputs the internal shift pulse signal ISTH (when being
synchronized with the transfer clock signal CLK0 for four times) to
the flip-flop FF5 of the partial shift register SR2 and the clock
control circuit 38.
[0072] The clock control circuit 38 receives the internal shift
pulse signal ISTH supplied to the partial shift register SR1 as a
second transfer control signal FF', and outputs the transfer clock
signal CLK1 as the second transfer clock signal to the partial
shift register SR2 in synchronization with the clock signal CLK in
accordance with the second transfer control signal FF'. The partial
shift register SR2 receives the internal shift pulse signal ISTH
from the flip-flop FF4. At this time, the partial shift register
SR3 is reset in accordance with the internal shift pulse signal
ISTH supplied to the partial shift register SR2. The partial shift
register SR2 outputs the internal shift pulse signal ISTH from the
flip-flop FF4 to the data register circuit 32-1 in synchronization
with the transfer clock signal CLK1 for four times, and outputs the
internal shift pulse signal ISTH (when being synchronized with the
transfer clock signal CLK1 for four times) to the flip-flop FF9 of
the partial shift register SR3 and the clock control circuit 38.
The clock control circuit 38 receives the internal shift pulse
signal ISTH from the flip-flop FF4 of the partial shift register
SR1 as a third transfer control signal FF'. The clock control
circuit 38 outputs the transfer clock signal CLK2 as the third
transfer clock signal to the partial shift register SR3 in
synchronization with the clock signal CLK in accordance with the
third transfer control signal FF'. The partial shift register SR3
receives the internal shift pulse signal ISTH from the flip-flop
FF8. At this time, the partial shift register SR4 is reset in
accordance with the internal shift pulse signal ISTH supplied to
the partial shift register SR3.
[0073] The partial shift register SR3 shifts and outputs the
internal shift pulse signal ISTH from the flip-flop FF8 to the data
register circuit 32 in synchronization with the transfer clock
signal CLK2 for four times, and outputs the internal shift pulse
signal ISTH (when being synchronized with the transfer clock signal
CLK2 for four times) to the flip-flop FF13 of the partial shift
register SR4 and the clock control circuit 38. The clock control
circuit 38 receives the internal shift pulse signal ISTH from the
flip-flop FF8 of the partial shift register SR2 as a fourth
transfer control signal FF'. The clock control circuit 38 stops the
output of the transfer clock signal CLK0 and outputs the transfer
clock signal CLK3 as the fourth transfer clock signal to the
partial shift register SR4 in synchronization with the clock signal
CLK in accordance with the fourth transfer control signal FF'.
[0074] In the data driver circuit 30-1, the same operation is
repeated to the partial shift registers SR4 and the subsequent.
That is, the partial shift registers SR4 to SR8 of the data driver
circuit 30-1 receive the internal shift pulse signals ISTH from the
flip-flops FF12, FF16, FF20, FF24, and FF28, respectively. At this
time, each of the partial shift registers SR5 to SR8 is reset in
accordance with the internal shift pulse signal ISTH supplied to a
corresponding one of the partial shift registers SR4 to SR7. The
partial shift registers SR4 to SR8 output the internal shift pulse
signals ISTH from the flip-flops FF12, FF16, FF20, FF24, FF28 to
the data register circuit 32 in synchronization with the transfer
clock signals CLK3 to CLK7 for four times, respectively. Further,
the partial shift registers SR4 to SR7 output the internal shift
pulse signals ISTH (when being synchronized with the transfer clock
signal CLK3 to CLK6 for four times) to the flip-flops FF17, FF21,
FF25, FF29 of the partial shift registers SR5 to SR8 and the clock
control circuit 38, respectively.
[0075] The clock control circuit 38 receives the internal shift
pulse signals ISTH from the flip-flops FF12, FF16, FF20, FF24,
FF28, and FF36 of the partial shift registers SR3 to SR8 as fifth
to tenth transfer control signals FF'. The clock control circuit 38
stops the outputs of the transfer clock signals CLK1 to CLK6 in
accordance with the fifth to tenth transfer control signals FF'.
Further, the clock control circuit 38 outputs the transfer clock
signals CLK4 to CLK7 as the fifth to eighth transfer clock signals
to the partial shift registers SR5 to SR8 in synchronization with
the clock signal CLK in accordance with the fifth to eighth
transfer control signals FF'. Although not shown, the clock control
circuit 38 receives a signal, which has been delayed from an output
of the partial shift register SR8 by four clocks of the clock
signal CLK, for example, as the transfer control signal FF', and
stops the output of the transfer clock signal CLK7 in accordance
with the transfer control signal FF'.
[0076] As described above, in the data driver 30 (K data driver
circuits 30-1 to 30-K) of the TFT type liquid crystal display
apparatus 1 according to the present invention, the partial shift
register SR(j+1) of the shift register circuit 31 is reset in
accordance with the internal shift pulse signal ISTH supplied to
the partial shift register SRj (1j7). This internal shift pulse
signal ISTH is shifted and transferred as the reset signal RESET to
the partial shift registers SR1 to SR8 successively in
synchronization with the clock signals CLK (transfer clock signals
CLK0 to CLK7). In this way, each of the partial shift registers SR1
to SR8 is reset successively in synchronization with the clock
signals CLK. Therefore, the partial shift registers SR1 to SR8 of
the shift register circuit 31 do not perform the reset operations
simultaneously, and the reset can be performed in synchronization
with the clock signals CLK (internal shift pulse signals ISTH).
[0077] In the data driver 30 (K data driver circuits 30-1 to 30-K)
of the TFT type liquid crystal display apparatus 1 according to the
present invention, the reset signal RESET is synchronized with the
clock signal CLK. Thus, the partial shift registers SR1 to SR8 are
reset at the proper timings in accordance with the reset signals
RESET from the internal signal circuit 40, and the partial shift
registers SR1 to SR6, respectively. Therefore, when the internal
shift pulse signal ISTH is supplied to the partial shift register
SR1 of the shift register circuit 31, the internal shift pulse
signal ISTH is outputted from the partial shift register SR8 at the
proper timing. As a result, the data register circuit 32 can
acquire the n display data from the timing controller 2 in
synchronization with the internal shift pulse signal ISTH from the
shift register circuit 31.
[0078] Further, in the data driver 30 (K data driver circuits 30-1
to 30-K) of the TFT type liquid crystal display apparatus 1
according to the present invention, the clock control circuit 38
controls the start and stop of the outputs of the transfer clock
signals CLK0 to CLK7. Therefore, the shift register circuit 31 can
output the internal shift pulse signal ISTH to the data register
circuit 32 at a more proper timing.
* * * * *