U.S. patent application number 09/886029 was filed with the patent office on 2002-03-07 for shift register and driving circuit of lcd using the same.
Invention is credited to Kwon, Oh-Jong, Park, Dong-Won, Park, Jin-Ho.
Application Number | 20020027545 09/886029 |
Document ID | / |
Family ID | 19678403 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020027545 |
Kind Code |
A1 |
Park, Jin-Ho ; et
al. |
March 7, 2002 |
Shift register and driving circuit of LCD using the same
Abstract
A shift register is provided, which adopts a shift operation
delay for each memory device, or a data conversion control system
through the estimation of conversion of data storage state. A
driver circuit of LCD is provided, which adopts such a shift
register, to thereby prevent instantaneous increase of electric
power consumption while preventing EMI. Accordingly, shift
registers operate as being sequentially delayed for each memory
device or data conversion is minimized, thus preventing
instantaneous excessive consumption of electric power.
Inventors: |
Park, Jin-Ho; (Suwon,
KR) ; Park, Dong-Won; (Seongnam, KR) ; Kwon,
Oh-Jong; (Suwon, KR) |
Correspondence
Address: |
HOWREY SIMON ARNOLD & WHITE LLP
BOX 34
1299 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Family ID: |
19678403 |
Appl. No.: |
09/886029 |
Filed: |
June 22, 2001 |
Current U.S.
Class: |
345/98 |
Current CPC
Class: |
G09G 3/3674 20130101;
G09G 2330/021 20130101; G09G 3/3685 20130101 |
Class at
Publication: |
345/98 |
International
Class: |
G09G 003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2000 |
KR |
2000-40942 |
Claims
What is claimed is:
1. A shift register, comprising: memory devices formed in a shape
of an m-row.times.n-column matrix and shifting data synchronized
with a clock signal; a clock signal delay unit for gradually
delaying the clock signal applied to said memory devices starting
from an (m)th row memory device that outputs data toward rows of
memory device where data are input; and a data delay unit for
delaying the data for a delay time of a clock signal applied to an
input side memory device and outputting the result.
2. A shift register according to claim 1, wherein said clock signal
delay unit is configured such that delay portions for delaying the
clock signal are one-to-one matched to (m-1)th row, (m-2)th row, .
. . 1st row memory devices, and said delay portions output the
clock signal with delay time increased in order of (m-I )th row,
(m-2)th row, . . . 1st row.
3. A shift register according to claim 2, wherein the delay
portions output delay time of t, 2t, . . . (m'11)t.
4. A shift register, comprising: memory devices formed in a shape
of an m-row.times.n-column matrix and shifting data synchronized
with a clock signal; a first switching unit that selectively
inverts n-bit data in accordance with a first switching control
signal and inputs the inverted data to a first row memory device of
each column of said memory devices; a second switching unit that
selectively inverts n-bit data shifted by said memory devices and
output to each column of (m)th row in accordance with a second
switching control signal and outputs the inverted data; a shift
comparing unit that outputs a flag signal while outputting a first
switching control signal to said first switching unit when data
state of the first row memory devices changes, by utilizing n-bit
data being input to said first switching unit and output data of
the first row memory device included in said memory devices; and a
shift comparing shift register having m-numbers of memory devices
arranged in line and that shifts the flag signal output from said
shift comparing unit to be synchronized with shift of said memory
devices and outputs a second control signal to said second
switching unit.
5. A shift register according to claim 4, wherein said first
switching unit and said second switching unit have switching logic
corresponding one-to-one to each row of said memory devices, and
the switching logic selectively outputs input data and inverted
data thereof in accordance with state of the first switching
control signal and the second switching control signal.
6. A shift register according to claim 4, wherein said shift
comparing unit comprises: exclusive OR gates for performing
exclusive OR sum of n-bit data to be input to said first switching
unit and output data of the first row memory device to said memory
device, and outputting the result; a logical combination unit for
logically combining outputs of said exclusive OR gates, and
outputting a logic high level as said first switching control
signal and a flag signal to be applied to said shift comparing
shift register, when a pair of output data and input data of first
row memory device is higher than a predetermined number.
7. A shift register according to claim 6, wherein the number
determined by said logical combination unit is larger than half of
the number of the first row memory device.
8. A driver circuit of liquid crystal display for driving a liquid
crystal panel by generating data, gradation voltage, gate voltage,
and column/scan control signals in accordance with an image signal
input from a predetermined image supply source, the driver circuit
having at each unit thereof for processing data, a shift register,
the shift register comprising: memory devices formed in a shape of
an m-row.times.n-column matrix and shifting data as being
synchronized data with a clock signal; a clock signal delay unit
for gradually delaying the clock signal applied to said memory
devices starting from an (m)th row memory device which outputs data
toward rows of memory device when data are input; and a data delay
unit that delays the data for a delay time of a clock signal
applied to an input side memory device and outputting the
result.
9. A shift register according to claim 8, wherein said clock signal
delay unit is configured such that delay portions for delaying the
clock signal are one-to-one matched to (m-1)th row, (m-2)th row, .
. . 1st row memory devices, and said delay portions output the
clock signal with delay time increased in order of (m-1)th row,
(m-2)th row, . . . 1 st row.
10. A shift register according to claim 9, wherein the delay
portions output delay time of t, 2t, . . . (m-1)t.
11. A shift register according to claim 8, wherein the shift
register is used in a controller.
12. A shift register according to claim 8, wherein the shift
register is used in column driver ICs.
13. A shift register according to claim 8, wherein the shift
register is used in scan driver ICs.
14. A shift register in a driver circuit of liquid crystal display
for driving a liquid crystal panel by generating data, gradation
voltage, gate voltage, and column/scan control signals in
accordance with an image signal input from an image source,
comprising: memory devices formed in a shape of an
m-row.times.n-column matrix and shifting data synchronized with a
clock signal; a first switching unit that selectively inverts n-bit
data in accordance with a first switching control signal and inputs
the inverted data to a first row memory device of each column of
said memory devices; a second switching unit that selectively
inverts n-bit data shifted by said memory devices and output to
each column of (m)th row in accordance with a second switching
control signal and outputs the inverted data; a shift comparing
unit that outputs a flag signal while outputting a first switching
control signal to said first switching unit when data state of the
first row memory devices changes, by utilizing n-bit data being
input to said first switching unit and output data of the first row
memory device included in said memory device; and a shift comparing
shift register having m-numbers of memory devices arranged in line
and that shifts the flag signal output from said shift comparing
unit to be synchronized with shift of said memory devices and
outputs a second control signal to said second switching unit.
15. A shift register according to claim 14, wherein said first
switching unit and said second switching unit have switching logic
corresponding one-to-one to each row of said memory devices, and
the switching logic selectively outputs input data and inverted
data thereof in accordance with state of the first switching
control signal and the second switching control signal.
16. A shift register according to claim 14, wherein said shift
comparing unit comprises: exclusive OR gates for performing
exclusive OR sum of n-bit data to be input to said first switching
unit and output data of the first row memory device to said memory
device, and outputting the result; a logical combination unit for
logically combining outputs of said exclusive OR gates, and
outputting a logic high level as said first switching control
signal and a flag signal to be applied to said shift comparing
shift register, when a pair of output data and input data of first
row contained in said memory devices is higher than a predetermined
number.
17. A shift register according to claim 16, wherein the number
determined by said logical combination unit is larger than half of
the number of the first row memory device.
18. A shift register according to claim 14, wherein the shift
register is used in a controller.
19. A shift register according to claim 14, wherein the shift
register is used in column driver ICs.
20. A shift register according to claim 14, wherein the shift
register is used in scan driver ICs.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention in general relates to a shift register
and a driver circuit of liquid crystal display adopting the shift
register, and more particularly, to a shift register that adopts a
shift delay for each memory device, or a data conversion control
system through the estimation of conversion of data storage state.
The present invention further relates to a driver circuit of LCD
adopting such a shift register, which can prevent instantaneous
increase of electric power consumption as well as EMI
(electromagnetic interference) occurrence.
[0003] 2. Description of the Related Art
[0004] A shift register is a logic circuit having memory devices
such as flip flop or latch arranged in line so as to sequentially
shift input data between memory devices and stores predetermined
amount of data.
[0005] Typically, shift registers have been widely used in a
digital circuitry for processing digital data in a variety of
fields. Specifically, shift registers are employed for timing
controllers and driver ICs to drive an LCD that has been widely
used as a flat panel display device. In such a case, a shift
register is used for generating a control signal or delaying data
for a predetermined time period.
[0006] A conventional shift register is configured such that data
stored in the entire register can be simultaneously shifted in a
direction at a rising time of clock, and data input/output is
determined in accordance with a first-in first-out principle.
[0007] In detail, as for the shift register for processing 4-bit
data, data D0, D1, D2, D3 are shifted for each of memory devices
sequentially from the data input initially and move in a direction,
and such data shift is synchronized with a clock. In addition,
outputs D0, D1, D2 and D3 are output in the same order as they are
input.
[0008] To perform such an operation, a large amount of current is
required to be supplied to a logic circuit instantaneously for
driving a shift register since the shift register is synchronized
with clocks during such an operation and each of memory devices
operates at the same time. This consumes a large amount of power
instantaneously while producing EMI.
[0009] This phenomenon is fortified when the data stored in the
shift register change the state significantly. More specifically, a
large amount of electric power is required when a memory device
changes logic 0 or logic 1 so as to perform shift operation
synchronized with a clock signal. The increased number of shift
registers requiring the state change requires low power consumption
and decreased EMI.
SUMMARY OF THE INVENTION
[0010] Therefore, it is an object of the present invention to
reduce instantaneous power fluctuation caused during an operation
of shift register and EMI by adjusting the timing of operation of
each of memory devices arranged in line in the shift register.
[0011] It is another object of the present invention to check in
advance the shift state of data being applied to a shift register
that is configured as a matrix so as to process predetermined bits
of data, and reduce cases of operation of shift register, to
thereby reduce power consumption and EMI caused by a large number
of shift registers operating at the same time.
[0012] It is still another object of the present invention to
improve configuration of a shift register which constitutes
components for driving a flat panel display in such a manner that a
plurality of shift registers are prevented from being operated at
the same time, to 5 thereby reduce power consumption and EMI.
[0013] To accomplish the above objects of the present invention,
there is provided a shift register including memory devices formed
of an m-row.times.n-column matrix and shifting data synchronized
with a clock signal; a clock signal delay unit for gradually
delaying the clock signal applied to the memory devices starting
from an m-row memory device that outputs data toward rows of memory
device to which data is being input; and a data delay unit for
delaying the data to have delay time identical with the delay time
of a clock signal applied to an input side memory device and
outputting the result. Preferably, the clock signal delay unit has
delay portions that delay the clock signal. The delay portions are
one-to-one matched to m-1 row, m-2 row, . . 1 row memory devices.
It is preferable that the delay portions output the clock signal
with delay time increased in the order of m-1 row, m-2 row, . . . 1
row.
[0014] To accomplish the above object of the present invention,
there is provided a shift register including memory devices formed
of an m-row.times.n-column matrix and shifting data synchronized
with a clock signal; a first switching unit for selectively
inverting n-bit 20 data in accordance with a first switching
control signal and inputting the inverted data to a first row
memory device of each column that constitutes memory device; a
second switching unit for selectively inverting n-bit data shifted
by memory devices and output to each column of m-row in accordance
with a second switching control signal and outputting the inverted
data; a shift comparing unit for outputting a flag signal while
outputting a first switching control signal to the first switching
unit upon occurrence of change to the data stored state of memory
devices arranged in the first row, by utilizing n-bit data being
input to the first switching unit and the output data of the first
row included in the memory devices; and a shift comparing shift
register having m-numbers of memory devices arranged in line and
shifting the flag signal output from the shift comparing unit to be
synchronized with the shift of the memory devices and outputting a
second control signal to the second switching unit.
[0015] A driver circuit of LCD according to the present invention
has each unit for generating data, gradation voltage, gate voltage
and column/scan control signal for driving LCD by using an image
signal applied from a predetermined image supply source, and a
shift register is applied to each unit for processing data.
[0016] As a shift register constituting the above-described LCD,
one of shift registers described above can be selected, and
thus-selected shift register is adopted to one or more devices of a
controller, or column or scan driver ICs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Additional features and advantages of the present invention
will be made apparent from the following detailed description of a
preferred embodiment, which proceeds with reference to the
accompanying drawings, in which:
[0018] FIG. 1 is a block diagram illustrating an LCD and driver
circuit according to the present invention;
[0019] FIG. 2 is a block diagram illustrating a shift register
according to an embodiment of the present invention;
[0020] FIG. 3 is a timing chart illustrating the operation of the
shift register shown in FIG. 2;
[0021] FIG. 4 is a block diagram illustrating a shift register
according to another embodiment of the present invention; and
[0022] FIG. 5 is a detailed circuit diagram of the shift comparing
unit of the shift register shown in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention will be explained in more detail with
reference to the attached drawings.
[0024] Referring to FIG. 1, driving circuit of LCD includes a
controller 10, column driver ICs 20 and scan driver ICs 18, each of
which adopts a shift register.
[0025] The driver circuit of LCD is configured as follows.
[0026] A plurality of bits of color data and control signal are
transmitted from a predetermined image supply source such as a main
body of computer or an image transmitting device, and input to the
controller 10.
[0027] A power supply unit 12 is arranged to supply constant
voltages required for the operation of the controller 10, a
gradation generating unit 14 and a gate voltage generating unit 16.
The gate voltage generating unit 16 is arranged to supply voltages
to scan driver ICs 18 so as to generate turn on/off voltages, and
the gradation generating unit is arranged to supply gradation
voltages to the column driver ICs 20.
[0028] The controller 10 generates control signals by using a shift
register arranged therein with logic, and determines timing format
while delaying data. As a result, column control signals and data
output from the controller 10 are distributed to column driver ICs
20, and scan control signals are output as being distributed to
scan driver ICs 18.
[0029] In addition, column driver ICs 20 generate a column signal
by utilizing data, column control signals and gradation voltage,
and applies the generated signal to a liquid crystal panel 22,
while scan driver ICs 18 generate a scan control signal by
utilizing a scan control signal and voltages applied from the gate
voltage generating unit 16 and applies the generated signal to the
liquid crystal panel 22. The liquid crystal panel 22 then performs
an optical shutter function, while forming an image.
[0030] In the above-described scheme, the controller 10, column
driver ICs 20 and scan driver ICs 18 have shift registers
incorporated therein. FIG. 2 illustrates a shift register adopted
to such configuration. The shift register illustrated in FIG. 2 is
for storing 4-bit data being input in serial, wherein D flip flop
is employed as a memory device.
[0031] Referring to FIG. 2, D flip flops M0, M2, M2, M3 are
connected in line in so as to transmit data according to the order
of their arrangement. D flip flop M0 has an input terminal provided
with a delay unit 30 connected thereto, and the other D flip flops
M1, M2, M3 have clock signal input terminals CLK1, CLK2, CLK3
provided with delay units 32, 34, 36 respectively connected
thereto.
[0032] Here, the delay unit 36 has delay time "t" set therein, the
delay unit 34 has delay time "2t" set therein, and the other delay
units 30, 32 have delay time "3t" set therein.
[0033] Accordingly, clock signals are input to D flip flop M3
through clock signal input terminal CLK4 without delay time, D flip
flop M2 through clock signal input terminal CLK3 with delay time of
"t", D flip flop M1 through clock signal input terminal CLK2 with
delay time of "2t", and D flip flop M1 through clock signal input
terminal CLK1 with delay time of "3t". The data is delayed for "3t"
time by the delay unit 30 and input the input terminal of D flip
flop M0.
[0034] As a result, D flip flop M3 is firstly synchronized with the
clock signal and outputs 5 data, then D flip flop M2 is
synchronized with clock signal with delay time of "t" and outputs
data which is stored in D flip flop M3.
[0035] D flip flop M2 which operates with time delay of "t" stores
data of D flip flop M1 which is synchronized and output with time
delay of "t" after operation of data output. D flip flop M1 which
operates with time delay of "2t" stores data of D flip flop M0
which is synchronized and output with time delay of "t" after
operation of data output. D flip flop M0 stores 1-bit data which is
delayed by "3t" through the delay unit 30.
[0036] The above-described configuration of D flip flop that starts
output side operation prior to the input side operation is to
output data of D flip flop with stability and to store safely the
data being shifted and input.
[0037] As shown in FIG. 3, clock signals for each of D flip flops
are input to D flip flops M2, M1, M0, delayed as long as "t", "2t",
"3t", respectively, when reference is made to the clock signal
applied to D flip flop M3. The data applied to D flip flop M0 is
delayed "3t" so as to correspond to the time of applying clock
signal.
[0038] Accordingly, each of D flip flops, i.e., memory devices,
operates with time difference arranged therebetween, and have
different timings of power requirement for operation. This
configuration does not require a large amount of current at the
same time.
[0039] As a consequence, instantaneous power consumption can be
reduced, while at the same time reducing EMI caused by the supply
of instantaneous large amount of current.
[0040] The above-described configuration of shift register
employing delay units illustrated and explained with reference to
FIGS. 2 and 3, can be also applied to m.times.n matrix
configuration.
[0041] The shift register of m.times.n matrix configuration
minimizes shifting by checking the state of data being shifted, to
thereby decrease instantaneous power consumption and EMI, as shown
in FIGS. 4 and 5.
[0042] FIG. 4 illustrates 4.times.4 matrix structured shift
register, wherein D flip flops M00, M01-M15 as memory devices
constituting the shift register are arranged in matrix.
[0043] The first column of the matrix consists of D flip flops M00,
M01, M02, M03, the second column of the matrix consists of D flip
flops M04, M05, M06, M07, the third column of the matrix consists
of D flip flops M08, M09, M10, M1, and fourth column of the matrix
consists of D flip flops M12, M13, M14, M15.
[0044] D flip flops M00, M04, M08, M12 constituting the first row
have input terminals with switching logics 40, 42, 44, 46,
respectively. Switching logics 40, 42, 44, 46 classifies input data
D00, D10, D20, D30 into positive and negative, and selectively
outputs the data to the corresponding D flip flop by a first
switching control signal.
[0045] D flip flops M03, M07, M11, M15 constituting the fourth row
have output terminals with switching logics 50, 52, 54, 56,
respectively. Switching logics 50, 52, 54, 56 classifies data
output from D flip flops M03, M07, M11, M15 into positive and
negative, and selectively outputs data D01, D11, D21, D31 by a
second switching control signal.
[0046] Data D02, D12, D22, D32 obtained by dividing data D00, D10,
D20, D30 and output D03, D13, D23, D33 of D flip flops M00, M04,
M08, M12 of the first row are input to the shift comparing unit 60.
The shift comparing unit 60 applies, as the first switching control
signal, the result of processing the input data using the logic
process configured as shown in FIG. 5, to switching logics 40, 42,
44, 46, and at the same time inputting a flag signal to the input
terminal of D flip flop MFO.
[0047] To shift the flag signal, D flip flops MF0, MF1, MF2, MF3 of
the counts same as those of column of matrix, constitute a column.
D flip flops MF0, MF1, MF2, MF3 are shift comparing shift
registers. The flag signal is shifted passing through D flip flops
MF0, MF1, MF2, MF3, and input as the second switching control
signal of switching logics 50, 52, 54, 56.
[0048] Each of D flip flops M00, M01 -M15, MF0, MF1, MF2, MF3 is
applied with a clock signal CLK for operation of flip flops.
[0049] The shift comparing unit 60 consists of exclusive OR gates
70, 72, 74, 76 and a logical combination unit(80).
[0050] In detail, the exclusive OR gate 70 obtains exclusive
logical sum S0 of data D02 and D03, the exclusive OR gate 72
obtains exclusive logical sum S1 of data D12 and D13, the exclusive
OR gate 74 obtains exclusive logical sum S2 of data D22 and D23,
and the exclusive OR gate 76 obtains exclusive logical sum S3 of
data D3 2 and D33.
[0051] The logical combination unit 80 consists of four AND gates
82, 84, 86, 88 and an OR gate 90 for logically summing outputs of
the four AND gates. The AND gate 82 obtains product of exclusive
logical sums S0, S1, S2. The AND gate 84 obtains product of
exclusive logical sums S0, S1, S3. The AND gate 86 obtains product
of exclusive logical sums SO, S2, S3. And the AND gate 88 obtains
product of exclusive logical sums S1, S2, S3.
[0052] Outputs of AND gates 82, 84, 86, 88 are logically summed in
the OR gate 90, and input to switching logics 40, 42, 44, 46 and D
flip flop MF0, as a first switching control signal and a flag
signal, respectively.
[0053] Under the assumption that data "0000" is stored in D flip
flops M00, M04, M08, M12 of the first row, respectively, and data
to be input D00, D10, D20, D30 is "1111", D flip flops M00, M04,
M08, M12 of the first row shift, when clock signal CLK is input,
the stored data "0000" to D flip flops M01, M05, M09, M13 of the
second row and store new data "1111". However, in this case, all of
D flip flops M00, M04, M08, M12 of the first row shift require
current supply for converting from logic "0" to "1". If D flip
flops constituting the matrix perform the above-described data
conversion in their entirety, a significant amount of instantaneous
power supply is needed.
[0054] In the first embodiment of the present invention, data D02,
D12, D22, D32 which are divided from the data to be input to the
first row, and data D03, D13, D23, D33 output from D flip flops
constituting the first row are compared in the shift comparing unit
60. This prevents data conversion that may require huge volume of
power supply.
[0055] In other words, the exclusive OR gate 70 compares input data
and output data of D flip flop M00, and outputs logic "0" if they
are the same, and logic "1" if two data if they are different. The
other exclusive OR gates 72, 74, 76 compare input data and output
data of D flip flops M04, M08, M12, and outputs "0" or "1" as a
logic result.
1TABLE 1 AND AND AND S0 S1 S2 S3 gate(84) gate(86) gate(88) 0 0 0 0
0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 1 0 0 0 0 1 0 0 0 0 0 0 1 0
1 0 0 0 0 1 1 0 0 0 0 0 1 1 1 0 0 1 1 0 0 0 0 0 0 1 0 0 1 0 0 0 1 0
1 0 0 0 0 1 0 1 1 0 1 0 1 1 0 0 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1
1 1 1 1 1 1
[0056] Each of exclusive OR gates 70, 72, 74, 76 have outputs S0,
S1, S2, S3 as shown in Table 1, and AND gates 82, 84, 86, 88
accordingly have outputs as shown in Table 1. In other words, AND
gates 82, 84, 86, 88 output logic "1" when input data and output
data of D flip flops D00, D04, D08, D12 of the first row are
compared and a change is found in the set state. Then, the OR gate
90 outputs a first switching control signal and a flag signal as
logic "1".
[0057] Switching logics 40, 42, 44, 46 inverts the state of input
data and outputs the result to D flip flop M00, M04, M08, M12, when
the first switching control signal is fed from the shift comparing
unit 60 as logic "1". Then, the flag signal for recognizing
conversion of data for corresponding row is input to D flip flop
MF0 constituting the shift comparing shift register. The flag
signal to be stored in D flip flop MF1 is synchronized with clock
CLK and shifted like other data stored in D flip flops D00, D04,
D08, D12 of the first row.
[0058] When data state change is estimated in three or more D flip
flops of each row, the data being input is converted and stored in
the corresponding D flip flop, and the corresponding flag is
stored. In this manner, data conversion of flip flops can be
maintained minimum, while at the same time reducing instantaneous
power supply, preventing the occurrence of EMI.
[0059] When thus-stored data and flag are shifted, D flip flops
M03, M07, M11, M15 of the last row output data, and the flag signal
is output from the last D flip flop of the shift comparing shift
register.
[0060] The flag signal output from D flip flop MF3 is a second
switching control signal, and is input to switching logics 50, 52,
54, 56.
[0061] Therefore, switching logics 50, 52, 54, 56 invert data
output from D flip flops M03, M07, M11, M15 constituting the last
row of the shift register and output data D01, D11, D21, D31 when
the flag signal, i.e., the second switching control signal, is
applied as logic "1".
[0062] When data is stored as "0000" to D flip flops M00, M04, M08,
M12 of the first row and data D00, D10, D20, D30 are input as
"1111", switching logics 40, 42, 44, 46 invert the state of data
D00, D10, D20, D30 and input "0000" to D flip flops M00, M04, M08,
M12. Here, the flag signal generated together with the first
switching control signal applied to switching logics 40, 42, 44,
46, is stored in D flip flop MFO of the shift comparing shift
register.
[0063] When such data and flag signal are synchronized with the
clock signal, gradually shifted, output from D flip flops M03, M07,
M11, M15 of the last row, and input to switching logics 50, 52, 54,
56, data of logic "0000" is inverted into the original state "1111"
by the second switching control signal output from D flip flop MF3
of the shift comparing shift register.
[0064] The above-described shift register can be employed for
controllers, column driver ICs, and scan driver ICs of LCD with
configuration shown in FIG. 1. By a method of checking and
estimating delayed or input data and shifted data, a phenomenon
where a large amount of power is instantaneously supplied to shift
registers arranged within controllers, column driver ICs and scan
driver ICs, can be prevented while at the same time preventing the
occurrence of EMI.
[0065] The present invention has an advantage in that shift
registers operate as being sequentially delayed for each memory
device or data conversion is minimized, thus preventing
instantaneous excessive supply of electric power. With the shift
register of the present invention adopted to components of LCD, EMI
problem can be solved.
* * * * *