JP2003280609A - Liquid crystal display device and its fluctuating power supply level shifter ic therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the characteristics of a level shifter which converts a control signal from a system power supply system into a fluctuating power supply system. <P>SOLUTION: For a scanning electrode driving IC of a p type semiconductor substrate, a fluctuating power supply level shifter IC is manufactured with an n type semiconductor substrate. Consequently, characteristics at low voltages can be improved and the level shifter IC is formed in the same chip as the fluctuating power source generating circuit to decrease the number of components, reduce the mounting area, and lower the price. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit (hereinafter referred to as an IC) of a liquid crystal display device, and more specifically, to a circuit configuration of a liquid crystal display device using an oscillating power supply, generation of the oscillating power supply and generation of signals. The present invention relates to the structure of an IC that performs a level shifter.

[0002]

2. Description of the Related Art A liquid crystal display device used as a display medium for a portable device or the like is required to have a small outer shape and a large screen. Driving method in which the signal electrode is driven with a low voltage waveform and a selection pulse is applied to the scanning electrode (ortho-preshko
The technique: APT) requires a high breakdown voltage for driving the scan electrodes. Generally, the chip area of the scan electrode driving IC is proportional to the square of its withstand voltage. If the breakdown voltage is halved, the chip area becomes ¼. Therefore, an oscillating power supply method is used that is capable of APT driving while reducing the power supply voltage applied to the scan electrodes by half.

A liquid crystal display device in which a scan electrode driving IC is driven by this oscillating power supply method will be described with reference to FIGS.

FIG. 4 is a block diagram of a conventional liquid crystal display device. The graphic control IC 403 exchanges image data and control signals with a microcomputer 405 (hereinafter, referred to as CPU) on a system board which is an external circuit when viewed from the liquid crystal display device. The signal electrode drive IC 401 and the scan electrode drive IC 402 are driven by the image data and the control signal to display the liquid crystal panel 406.

The graphic control IC 403 outputs image data and control signals to the signal electrode drive IC 401, and outputs a control signal 407 to the scan electrode drive IC 402. Further, the AC signal DF is output to the power supply circuit 404.

The power supply circuit 404 is a signal electrode driving IC 40.
The DC voltage VSEG as the liquid crystal drive voltage and the intermediate voltage VM are output to the first unit 1, and the swing power source VD is supplied to the scan electrode drive IC 402.
Outputs D, VCC, and VSS.

FIG. 5 is a waveform diagram of the oscillating power supply generated in the power supply circuit 404. The oscillating power supply VDD is a square wave that is inverted and synchronized with the alternating signal DF from the graphic controller, the high level is the DC voltage VDH, and the low level is the DC voltage VSEG. The oscillating power supply VSS is a square wave inverted and synchronized with the alternating signal DF from the graphic controller, the high level is the DC voltage VSL, and the low level is the DC voltage VSH. The oscillating power supply VCC is a square wave that is inverted and synchronized with the alternating signal DF from the graphic controller, the high level is a DC voltage VDL, and the low level is a voltage higher by VDL than the DC voltage VSH.

The oscillating power supply method is to drive an IC with the oscillating power supply VDD and the oscillating power supply VSS.

FIG. 6 is an electrode drive waveform diagram of a liquid crystal display device using an oscillating power supply system. In FIG. 6, the power source VM is an intermediate voltage between the DC voltage VDH and the DC voltage VSH. DC voltage VS
EG and DC voltage VSL are upper and lower liquid crystal drive voltages applied to the signal electrodes. It should be noted that the symbols in FIG. 6 that are the same as those in FIG. 5 will not be described.

When driving an arbitrary pixel (m, n) on the liquid crystal panel, the output waveform from the scan electrode driving IC 402 is COMn and the output waveform from the signal electrode driving IC 401 is SEGm. When the waveform COMn is selected, the pulse of the voltage VDH is generated in the first field f1 and the pulse of the voltage VSH is generated in the second field f2. A waveform SEGm corresponding to display data is output from the signal electrode driving IC 401. COMn-SEGm
The composite waveform of becomes the drive waveform of the pixel (m, n), and the transmittance of the liquid crystal is determined by the execution voltage value thereof.

At this time, assuming that the potential difference between the voltage VDH and the voltage VSL (or the voltage VSEG and the voltage VSH) is VH, the voltage of the scan electrode driving IC of the scan electrode driving IC can be applied to the pixel although the voltage is almost twice the voltage VH. The withstand voltage may be the voltage VH. In other words, the oscillating power supply can drive the scan electrode IC with a voltage that is approximately half the voltage applied to the pixel, and as a result, the chip area of the scan electrode drive IC is 1
It becomes / 4.

In the scan electrode driving IC 402, the control logic circuit operates between the swing power supply VCC and the swing power supply VSS. That is, a level shifter for converting the control signal from the graphic control IC 403 operating with the system power supply VDL / VSL into the swing power supply system VCC / VSS is built in. FIG. 7 is a circuit diagram of this level shifter, and FIG. 8 is a waveform diagram of this level shifter.

The operation of the level shifter will be described with reference to FIG. The high level of the control signal DF and the signal IN is the DC voltage VDL of the system power supply, and the low level is the DC voltage VSL of the system ground. This signal IN is first converted into a signal LEV1 whose high level is the system power supply voltage VDL and whose low level is the ground swing power supply VSS in the amplification stage in the level shifter. Next, the signal LEV1 is converted into a signal OUT whose high level becomes the swing power supply VCC for logic and whose low level becomes the swing power supply VSS for ground. The signal IN of the system power supply system is level-shifted to the signal OUT of the oscillating power supply system by the above two-stage conversion. Since the potential difference between the oscillating power supply VCC and the oscillating power supply VSS is about 3 V, the control system of the scan electrode driving IC 402 can be configured by a low voltage circuit.

Next, the circuit configuration of the level shifter will be described with reference to FIG. Transistors 701, 702, 7
The amplification stage is composed of 03, 704, 705 and 706, the waveform shaping stage is composed of inverters 711 and 712, and the step-down stage is composed of transistors 707, 708, 709 and 710. The output buffer circuit is omitted because it is not necessary for explaining the operation of the level shifter.

The level shifter of the oscillating power supply system is different in circuit from a general level shifter. In a general level shifter, a signal is input to a two-stage inverter that also serves for waveform shaping and acquisition of an inverted signal, the waveform shaped signal and the inverted signal are input to a differential amplifier, and the voltage-converted output is output from this. It has gained. In FIG. 7, the inverters 711, 71
2 and the transistors 707, 708, 709, and 710. However, in the case of level shifting to the swing power supply system, there is a circumstance that a two-stage inverter cannot be made in the input stage because the silicon substrate of the scan electrode driving IC swings. In the conventional example, since the semiconductor substrate is a P-type, when an inverter is arranged in the input stage, the substrate of the N-channel transistor in the inverter becomes the oscillation power supply VSS. Therefore, the substrate voltage of the N-channel transistor deviates from the system ground voltage VSL during the period when the oscillating power supply VSS drops, and the system power supply voltage VDL and the system ground voltage VS
The input inverter that operates between L causes a malfunction. For this reason, the input stage in FIG. 7 does not have a two-stage inverter that combines waveform shaping and inverted signal acquisition.

In FIG. 7, the inverted signal is not obtained, but the signal IN is input to the source of the transistor 704.
When the signal IN is at a high level, the transistor 701 is off and the transistor 704 is on. As a result, the output signal LEV1 of the amplification stage becomes the voltage VDL. On the contrary, when the signal IN is low level, the transistor 701 is on and the transistor 704 is off, and the output signal LE
V1 becomes equal to the swing power supply VSS. Transistor 70
2, 705 are inserted for current limitation, and the transistors 703, 706 are normal active loads. The inverters 711, 712 and the step-down stage (composed of transistors 707, 708, 709, 710) in the latter stage have the same configuration as the above-mentioned general level shifter.

FIG. 3 is a block diagram of a conventional oscillatory power supply generation circuit. The power supplies are the system power supply VDL, the system ground VSL, and the power supply VSEG input from the outside, and the input signal is the alternating signal DF.

The gate of the transistor 301 is driven by the clock signal LCK output from the boost control circuit 302.

The n-type transistor has a gate-source voltage Vgs, a drain-source voltage Vds, and a threshold voltage V.
If th, the state of the n-type transistor is Vds>
A saturation region is shown when Vgs-Vth, and Vgs <Vth
When it becomes the interception area. Usually, it is said that the transistor turns on when the transistor is in the saturation region state, and turns off when the transistor is in the cutoff region state.

By turning on / off the transistor 301, the connection between the coil 303 connected to the drain side and the system ground VSL is controlled. Coil 303
A counter electromotive force is generated at the moment when the transistor 301 is turned off. This is rectified by the diode 304 and the capacitor 305.

A high voltage VHH is obtained by repeating on / off of the transistor 301. When the high voltage VHH is raised above a predetermined value, the clock signal LCK from the boost control circuit 302 stops. The step-up control circuit 302 compares the voltage value obtained by dividing the high voltage VHH by the variable resistor 306 with the potential difference between the reference voltage source in the step-up control circuit 302, and as a result, is built in the step-up control circuit 302 for the clock signal LCK. It controls the oscillation / stop of the existing oscillator.

That is, the high voltage VHH is applied to the variable resistor 306.
When the voltage value divided by is lower than the reference voltage value set by the boost control circuit 302, the oscillator in the boost control circuit operates and outputs the clock signal LCK. On the contrary, when the voltage value obtained by dividing the high voltage VHH by the variable resistor 306 is higher than the reference voltage value set by the boost control circuit 302, the oscillator in the boost control circuit is stopped and the clock signal LCK is output at low level. Become.

The above is the description of the booster circuit.

Next, the oscillating power supply generation circuit will be described.

The first-stage normal rotation level shifter 307 converts the alternating signal DF output from the graphic controller (not shown) into a high voltage VHH signal and a ground VSL signal. The inversion level shifter 308 in the next stage voltage-converts the signal output from the first-stage level shifter 307 into signals of the voltage VHH and the voltage VSEG, and the positive swing power supply VDD.
Output as.

The negative swing power supply VSS is output by a clamp circuit composed of a switching element 309 and a capacitor 310. That is, the DC component of the oscillation power supply VSS is given by the switching element 309 being short-circuited to the ground VSL when the AC signal DF is at a low level,
The AC component is obtained by removing the DC component from the swing power supply VDD by the capacitor 310. Where capacitor 3
11, the diode 312, and the resistor 313 are AC signals DF
Is level-converted for the switching element 309.

Similarly, the oscillating power supply VCC is output by a clamp circuit composed of a switching element 314 and a capacitor 315. That is, the DC component of the oscillating power supply VCC is given by the switching element 314 being short-circuited with the system power supply VDL when the alternating signal DF is at a low level, and the AC component is supplied from the oscillating power supply VSS to the capacitor 31.
In FIG. 5, the DC component is removed.

In addition to the reference voltage source and the oscillator, the boost control circuit 302 has a temperature compensation circuit, a contrast adjustment circuit, and a frequency control circuit built therein.

[0029]

However, since the power supply circuit including the oscillating power supply generation circuit has a complicated potential level, it is difficult to make it into an IC, and it is composed of many external elements. Therefore, there is a problem that the mounting area and the number of parts are increased.

Further, in the scan electrode driving IC having the P-type semiconductor substrate, since the substrate of the N-channel transistor is the oscillating power supply VSS, the buffer for waveform shaping cannot be inserted in the input stage. Therefore, in the above-described example, the input signal is connected to the source of the transistor of the amplification stage of the level shifter, and the potential of the source is changed to control the on / off of the transistor. However, the input signal has many resistance elements such as an output resistance on the signal output side, a wiring resistance outside the IC, an input protection resistance of the scan electrode driving IC, and a wiring resistance inside the scan electrode driving IC. When trying to turn on the P-channel transistor of the amplification stage by source control, there is a problem that the drain level of the N-channel transistor, which becomes a load, cannot be sufficiently raised due to this resistance element. In particular, this tendency was remarkable in the low voltage region where the transistor itself becomes a resistance element.

SO in which independent elements are formed on an insulating substrate
In an IC having an I (Silicon On Insulator) structure, it is possible to incorporate all of the above circuits having a complicated power supply system. However, in SOI, the unit price is higher than that of an IC using a normal semiconductor substrate due to the unit cost of the substrate and the length of the manufacturing process. Therefore, in the IC having the above-mentioned circuit configuration, if the IC chip area becomes large, there arises a problem of high cost.

A first object of the present invention is to improve the characteristics of the level shifter which converts the control signal from the system power supply system to the swing power supply system.

A second object of the present invention is to provide a liquid crystal display device having an oscillating power supply system which is low in price and has a reduced number of parts, by using the oscillating power supply level shifter IC for achieving the first object. Is.

[0034]

In order to achieve the above object, a liquid crystal display device according to the present invention has a scanning electrode on one substrate and a signal electrode on the other substrate. In the liquid crystal display device in which the signal electrodes are respectively driven by the scan electrode driving IC and the signal electrode driving IC, the swing power supply generation circuit that supplies power to the scan electrode driving IC is
An oscillating power supply is used as a power supply, and an oscillating power supply level shifter IC that shifts and outputs the level of an input signal and a plurality of elements are provided. A semiconductor substrate type of the oscillating power supply level shifter IC and the scan electrode driving IC Different types of semiconductor substrates are used, and the output of the oscillating power supply level shifter IC is input to the scan electrode driving IC.

Further, the oscillating power supply level shifter IC of the liquid crystal display device according to the present invention has scan electrodes on one substrate and signal electrodes on the other substrate, and the scan electrodes and the signal electrodes are respectively scanned. Electrode drive IC and signal electrode drive I
A level shifter IC for a liquid crystal display device driven by C has a clock input terminal, a swing power supply input terminal, and a swing power supply level shifter IC, and inputs a swing power supply to the swing power supply input terminal to input a signal. It is characterized by shifting the level of and outputting.

Further, the oscillating power supply level shifter IC of the liquid crystal display device according to the present invention is characterized by using an n-type semiconductor substrate.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a liquid crystal display device according to the present embodiment, FIG. 2 is a configuration diagram of an oscillating power supply level shifter IC, and FIG. 9 is a circuit diagram of a level shifter section in the oscillating power supply level shifter IC.

In FIG. 1, the graphic control IC 103 exchanges image data and control signals with the CPU 105 on the system board which is an external circuit when viewed from the liquid crystal display device. The signal electrode drive IC 101 and the scan electrode drive IC 102 are driven by the image data and the control signal to display the liquid crystal panel 106. Here, a p-type is used for the semiconductor substrate of the scan electrode driving IC 102.

The graphic control IC 103 outputs image data and control signals to the signal electrode drive IC 101, and outputs control signals for driving scan electrodes and AC signals 107 to the swing power supply and level shifter circuit 104.

Oscillating power supply and level shifter circuit 104
The operating power supplies are the system power supply VDL and the system ground VSL. The DC voltage VSEG and the intermediate voltage VM as the liquid crystal drive voltage are output to the signal electrode drive IC 101, and the swing power supplies VDD, VCC, VS are output to the scan electrode drive IC 102.
The level-shifted control signal 108 is output to S, VM and the swing power supply system.

The signal electrode driving IC 101 has a power source of the system power source VDL and system ground VSL, and a CPU
A voltage is applied to the liquid crystal panel according to the display data and control signal output from the device. The applied voltages VSEG and VM at this time are input from the oscillating power supply and the level shifter circuit 104.

In the scan electrode driving IC 102, in addition to the system power source VDL and the system ground VSL, the swing power source and level shifter circuit 104 drives the swing power source VDD,
The control signals 108 of VSS, VCC, the DC power supply VM, and the swing power supply system are input.

The oscillating power supply and level shifter circuit 104 is an oscillating power supply level shifter IC on an n-type semiconductor substrate.
And an external element. Details are shown in FIG.

Oscillating power supply level shifter IC 201 of FIG.
Has a function of a booster circuit, a swing power supply generation circuit, and a level shifter circuit.

The booster circuit is composed of the swing power supply level shifter IC2.
01, the transistor 204, the diode 206, the coil 205 of the external element, the capacitor 207, and the resistor 2
03 and a boost control circuit 202.

The transistor 204 has at its gate terminal a clock inversion signal LCK output from the boost control circuit 202.
Works with B.

The p-type transistor has a gate-source voltage Vgs, a drain-source voltage Vds, and a threshold voltage V.
If th, the state of the p-type transistor is Vds <V
When gs-Vth, the saturation region is shown, and when Vgs> Vth, the cutoff region is shown. Usually, it is said that the transistor turns on when the transistor is in the saturation region state, and turns off when the transistor is in the cutoff region state.

The gate voltage of the transistor 204 can control the connection between the coil 205 connected to the drain side and the system power supply VDL. In the coil 205, a negative counter electromotive force is generated at the moment when the transistor 204 is turned off. This is connected to the capacitor 20 via the diode 206.
The high voltage VLL on the negative side is obtained by rectifying at 7.

The value obtained by dividing the high voltage VLL by the resistor 203 is input to the step-up control circuit 202, and the clock inversion signal LCK is input.
The output of B is controlled to form a feedback loop.

That is, the swing power supply level shifter IC 201
When the voltage value obtained by dividing the negative high voltage VLL output by the resistor 203 is higher than the reference voltage value set by the boost control circuit 202, the oscillator in the boost control circuit operates and outputs the clock inversion signal LCKB. . On the contrary, the voltage value obtained by dividing the low voltage VLL by the variable resistor 203 is the boost control circuit 20.
When it is lower than the reference voltage value set in 2, the oscillator in the boost control circuit is stopped and the clock inversion signal LCKB becomes a high level output.

The oscillating power supply generation circuit is an oscillating power supply IC 201.
Inversion level shifter 208, switching element 20 in
9. Inverter 216 and external element capacitor 210,
212, 213, switching element 211, resistor 21
4 and the diode 215.

The inversion level shifter 208 converts the AC signal DF output from the signal electrode driving IC 101 into a signal of the system power supply VDL and a high voltage VLL, and outputs it as the swing power supply VCC.

The negative swing power supply VSS is output by a clamp circuit composed of a switching element 209 and a capacitor 210. That is, the DC component of the oscillating power supply VSS is given by the switching element 209 being short-circuited to the ground VSL when the alternating signal DF is at a low level,
The AC component is obtained by removing the DC component from the oscillating power supply VCC by the capacitor 210.

Similarly, the positive swing power supply VDD is output by the clamp circuit composed of the switching element 211 and the capacitor 212. That is, the swing power supply VDD
As for the DC component of the
The signal obtained by inverting F by the inverter 216 is given by short-circuiting with the system power supply VDL at the time of high level, and the AC component is obtained by removing the DC component from the oscillating power supply VSS by the capacitor 212. Here, the capacitor 213,
The diode 215 and the resistor 214 level-convert the alternating signal DF for the switching element 211.

Next, the level shifter circuit 217 is shown in FIG.
Will be described in detail with reference to FIG. In FIG. 8, the signal LEV1 is reread as the signal LEV.

The level shifter circuit 217 includes an inverter 9
11, 912, a first waveform shaping stage, transistors 901, 902, 903, 904, 905, and 906; a second waveform shaping stage including inverters 913 and 914; and transistors 907, 908, and 909.
It consists of a step-down stage consisting of. The input / output protection circuit is omitted because it is not necessary for explaining the operation of the level shifter.

The level shifter circuit 217 has all the p-channel transistors 901 and 9 because the semiconductor substrate is n-type.
04, 907 and inverters 911, 912, 91
P-channel transistor in 3,914 (not shown)
The substrate is a DC voltage VDL of the system power supply.

In the first waveform shaping stage, the inverter 9
Substrates 11 and 912 on the n-channel transistor side have the system ground voltage VSL. Signal IN
Is input to the inverter 911, and this inverted signal is connected to the gates of the transistors 904 and 906. The waveform-shaped signal output from the inverter 912 is connected to the gates of the transistors 901 and 903.

In the amplification stage, the substrates of the n-channel transistors 902, 903, 905 and 906 are the swing power supply VSS. Transistors 902 and 905 are active loads and have their gates and drains interlocked. Transistors 903, 90
6 is for current limitation.

In the second waveform shaping stage, the inverter 9
The substrates of the n-channel transistors 13 and 914 are the swing power supply VSS for ground. The output signal LEV of the amplification stage is input to the inverter 913, and this inverted signal is connected to the gates of the transistors 907 and 909. The waveform-shaped signal output from the inverter 914 is connected to the gate of the transistor 908.

N-channel transistor 9 in the step-down stage
The substrates 08 and 909 are the swing power supply VSS for ground. Transistors 907 and 908 are transmission gates (also called analog switches)
One end is connected to the swing power supply VCC, and the other end is connected to the drain of the transistor 909.

The input signal IN is supplied to the inverters 911 and 91.
At 2, the generation of the inverted signal and the waveform shaping are performed. With the inverted signal and the waveform shaping signal, the transistor 904 is turned off when the transistor 901 is on, and the transistor 904 is turned on when the transistor 901 is off. When the signal IN is low level, the transistor 904 is turned off, and the output LEV of the amplification stage is the swing power supply VSS.
Becomes When the signal IN is at high level, the transistor 9
04 is turned on and the output LEV of the amplification stage is the system power supply VD.
It becomes L. The signal LEV is subjected to generation of an inverted signal and waveform shaping by the inverters 913 and 914. When the signal LEV is at a low level (voltage of the oscillating power supply VSS), the transistors 907 and 908 are turned off and the transistor 909 is turned on, so that the output signal OUT of the level shifter becomes the oscillating power supply VSS. On the contrary, when the signal LEV is at high level (DC voltage VDL of system power supply), the transistor 90
Since 7, 908 turn on and the transistor 909 turns off, the output signal OUT of the level shifter becomes the swing power supply VCC.

As described above, each level shifter in the level shifter circuit 217 converts the system power supply system signal IN into the swing power supply system signal OUT. Since the control signal of the scan electrode driving IC includes a start signal, a clock signal, a polarity control signal, a reset signal, and a display control signal,
The level shifter circuit 218 includes five level shifters.

As described above, the oscillating power supply level shifter IC201 of this embodiment has the reference power supply of the IC as VDL.
Type semiconductor substrate is adopted. As a result, with respect to the scan electrode driving IC on the p-type semiconductor substrate, it is possible to boost the voltage and generate the oscillating power supply only by the oscillating power supply level shifter IC 201 of this embodiment and some external components. A liquid crystal display device was realized.

Further, the power supply of the swing power supply level shifter IC 201 is the system power supply VDL and the ground VSL inputted from the outside, but there was no problem in the characteristic of the level shifter even during the low voltage operation. Further, the boosting control can be performed only by the clock inversion signal LCK, so that the control is easy.

In FIG. 2 used in the embodiment, the boost control circuit 202 and the resistor 203 are independently provided, but this is for convenience of description, and in this embodiment, the signal of FIG. 1 is used. It is built in the electrode drive IC 101.

In addition to the reference voltage source and the oscillator, the step-up control circuit 202 has a temperature compensation circuit and a contrast adjustment circuit built therein, and command control is possible.

Further, in the embodiment, as a switching element, an FET (Field Effect Transistor) is used.
However, a diode or the like may be used.

Further, in the embodiment, the booster circuit is described as the switching regulator system, but other system such as a charge pump type booster circuit may be used.

Further, in the embodiment, the oscillating power supply level shifter IC and the liquid crystal panel are separated, but the signal electrode driving I
It may be mounted on the liquid crystal panel as in the case of C and the scan electrode driving IC.

In addition, the CPU (Center) used in the embodiment is
al Processing unit. The power source in () is omitted because it is outside the scope of the present invention.

[0072]

By using the swing power supply level shifter IC and the n-type substrate used in the liquid crystal display device of the present invention, the swing power supply for driving the p-type scan electrode driving IC can be supplied. Since this oscillating power supply level shifter IC is an n-type semiconductor substrate, when the semiconductor substrate is set as the system power supply, various circuits that operate on the negative power supply can be built. In other words, the oscillating power supply level shifter IC, which operates with a negative voltage with the system power supply as the ground, is inserted into the circuit configured with the positive voltage with respect to the system ground. With this, the generation of the high voltage on the negative side, the two oscillating power supplies, and the level shifter circuit were completed. As a result, the external parts are I
Only the coil that cannot be converted to C, the large-capacity capacitor, and the positive side clamp circuit parts are used. As described above, the oscillating power supply level shifter IC has a small area in a general substrate process, and thus the cost is significantly reduced. Further, the characteristics at the time of low voltage operation were improved as compared with the level shifter made of the p-type semiconductor substrate. As is clear from the above description, the present invention has an effect that a system having a good low voltage characteristic can be realized with a reduced number of parts and a low price.

[Brief description of drawings]

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an oscillating power supply and a level shifter circuit according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional oscillatory power supply generation circuit.

FIG. 4 is a block diagram of a conventional liquid crystal display device.

FIG. 5 is a waveform diagram of a swing power supply.

FIG. 6 is an electrode drive waveform diagram in an oscillating power supply system.

FIG. 7 is a circuit diagram of a conventional level shifter.

FIG. 8 is a waveform diagram of a conventional level shifter.

FIG. 9 is a circuit diagram of a level shifter according to an embodiment of the present invention.

[Explanation of symbols]

101, 401 Signal electrode drive IC 102, 402 Scan electrode drive IC 103, 403 Graphic control IC 104 Oscillation power supply and level shifter circuit 105, 405 CPU 106, 406 Liquid crystal panel 107 Logic power supply system control signal 108 Oscillation power supply system control signal 201 Oscillating power supply level shifter IC 202 Boost control circuit 203 Variable resistance 204 Transistor 205 Coil 206, 215 Diode 207, 210, 212, 213 Capacitor 208 Inversion level shifter 209, 211 Switching element 214 Resistor 215 Diode 216 Inverter 217 Level shifter circuit 301 Transistor 302 Boost control Circuit 303 Coil 304, 312, 312 Diodes 305, 310, 311, 315 Capacitor 306 Variable resistance 30 Forward level shifter 308 Inverting level shifter 309, 314 Switching element 313 Resistor 404 Power supply circuit 407 Control signals 701-710 Transistors 711, 712 Inverters 901-910 Transistors 911-914 Inverter VDD Oscillation power supply VCC Oscillation power supply VDL System power supply VSL System ground VM Intermediate power supply

Claims (3)

[Claims] 1. A liquid crystal display device having scan electrodes on one substrate and signal electrodes on the other substrate, the scan electrodes and the signal electrodes being driven by a scan electrode driving IC and a signal electrode driving IC, respectively. In the above, the oscillating power supply generation circuit for supplying power to the scan electrode driving IC uses an oscillating power supply as a power supply, and includes an oscillating power supply level shifter IC for shifting and outputting the level of an input signal, and a plurality of elements. And a semiconductor substrate type of the swing power supply level shifter IC and a semiconductor substrate type of the scan electrode drive IC are different from each other, and an output of the swing power supply level shifter IC is input to the scan electrode drive IC. Liquid crystal display device. 2. A liquid crystal display device having scan electrodes on one substrate and signal electrodes on the other substrate, the scan electrodes and the signal electrodes being driven by a scan electrode driving IC and a signal electrode driving IC, respectively. Of the level shifter IC, which has a clock input terminal, an oscillating power supply input terminal, and an oscillating power supply level shifter IC, inputs the oscillating power supply to the oscillating power supply input terminal, shifts the level of the input signal, and outputs it. An oscillating power supply level shifter I for a liquid crystal display device, characterized in that
C. 3. The oscillating power supply level shifter IC of a liquid crystal display device according to claim 2, wherein the oscillating power supply level shifter IC uses an n-type semiconductor substrate.