JPH06318055A - Level shift circuit and high voltage driving circuit using it - Google Patents

Abstract

PURPOSE:To realize a level shift circuit provided with a function excepting the function converting from a first power source voltage to a second power source voltage and to realize a high voltage driving circuit using the level shift circuit. CONSTITUTION:In addition to a first and second switching elements (transistors 50-56), third and fourth switching elements (transistors 62, 64) are provided in series. The transistors 62, 64 are turned on/off by a prescribed control signal, and thus, the current path of the level shift circuit is conducted/interrupted. By such a constitution, a logic circuit arranged on the poststage of the level shift circuit is arranged on the preceding stage of the level shift circuit, and since the logic circuit is driven by a voltage for driving the logic circuit, the area of the circuit is reduced. Further, since the generation of a penetration current in the period when the voltage levels of the first and second input signals are inverted is prevented and a short circuit state in the current path is prevented, the performance of a display characteristic, etc., is improved, and the response operation of the level shift circuit is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level shift circuit for converting the voltage amplitude of an input signal from a first power supply voltage to a second power supply voltage and a high voltage drive circuit using this level shift circuit. is there.

[0002]

2. Description of the Related Art In a conventional level shift circuit, the voltage amplitudes of first and second input signals input in opposite phases from a first power supply voltage (E1) to a second power supply voltage (E2). It had no function other than converting to.

11A and 11B are circuit diagrams of conventional level shift circuits. This level shift circuit includes a transistor 15 that is the first and second switching elements.
0, (152), 154, (156) and transistors 158, 160. And the voltage amplitude is 0
~ E1 first input signal and a second input signal having a phase opposite to the first input signal are input to the gate electrodes of the transistors 150, (152), 154, and (156), respectively. . In addition, the transistors 158 and 16
The first and second output signals of the level shift circuit are input to the 0 gate electrode.

In the conventional level shift circuit, the voltage amplitudes of the first and second input signals having mutually opposite phases are changed from the first power supply voltage (E1) to the second power supply voltage (E
It was converted to 2). In the example of the level shift circuit shown in FIGS. 11A and 11B, both E1 and E2 are negative values, and E1> E2.

In the conventional level shift circuit, in addition to the first and second switching elements, the third and fourth switching elements which are turned on / off by a predetermined control signal are not provided. Therefore, it has no function other than the conversion from the power supply voltage E1 to E2, and therefore the conventional level shift circuit has the following problems.

[0006]

First, the first problem will be described.

FIG. 11C shows a truth table of this conventional level shift circuit. As shown in the figure,
In this conventional example, when input signals having opposite phases are input, the power supply voltage E1 is converted to E2. However, when both the first and second input signals have the same level, this level shift circuit does not operate normally. That is, in the circuits of FIGS. 11A and 11B, when the first and second input signals are both at H level (GND level), the first and second
Output signal is at the Z level (high impedance level), and both the first and second input signals are at the L level (E
In the case of (1 level), the current path of the level shift circuit becomes conductive and becomes inoperable.

Due to this drawback, the conventional level shift circuit is replaced with a high voltage drive circuit, for example, a liquid crystal drive circuit (ST, for example).
When applied to N, TFT, MIM liquid crystal drive circuits), multi-bit high voltage output drivers, etc., the following problems occur.

FIG. 12 shows an example in which the conventional level shift circuit is applied to a drive circuit for STN liquid crystal, for example. The data signal is input to the transistors 150 and 152 that are the first switching elements as the first input signal. Further, this data signal is inverted by the inverter 34 and input as the second input signal to the transistors 154 and 156 which are the second switching elements. Thereby, the voltage amplitude changes from GND to VSS (VSS is -5V) to GND to V5 (V5 is -30, for example).
V). Similarly, the AC signal is also input to the level shift circuit 32, and the voltage amplitude is converted from GND to VSS to GND to V5.

The output signals 45, 46, 44 of the level shift circuits 33, 35 thus level-shifted are
It is input to the logic circuit 170. This logic circuit 170
Is the NAND circuit 3 operating at the second power supply voltage V5.
7, 39 and NOR circuits 36 and 38. Then, a predetermined logical operation is performed in the logical circuit 170, and after the logical operation is completed, the output signals 172, 17
4, 176, 178 are Nch transistors 40, 4
3, and is input to the output drive circuit 180 including the Pch transistors 41 and 42. And the output drive circuit 1
In these transistors 40 to 43 in 80, output signals 172 to 178 of the logic circuit 170 are connected to the gate electrodes, and power sources V0, V2, V3, V5 (V0
>V2>V3> V5) are connected. The drain regions of the transistors 40 to 43 are commonly connected, and the commonly connected drain outputs are output to the respective liquid crystal elements as liquid crystal drive signals. With the above configuration, in this conventional liquid crystal drive circuit,
It becomes possible to convert a binary output into a quaternary output (V0, V2, V3, V5).

Now, in the liquid crystal drive circuit using the conventional level shift circuit, as shown in FIG.
It was necessary to arrange the logic circuit 170 composed of 6, 38 and the NAND circuits 37, 39 in the subsequent stage of the level shift circuit 33. The reason is as follows. That is, it is assumed that the logic circuit 170 is arranged in the previous stage of the level shift circuit 33 in the conventional example. Then, the output of the logic circuit 170 has four modes (HL, LH, HH, L
L), signals of the same level (HH level, LL level) may be input to the first and second switching elements (transistors 150 to 156) of the level shift circuit 33. However, in the conventional level shift circuit, as described in FIGS. 11A to 11C described above, normal operation is guaranteed when the same level signal is input to the first and second input signals. Was not done. Therefore, it is impossible to arrange the logic circuit 170 at the stage before the level shift circuit 33 in the conventional example, and as shown in FIG. 12, the logic circuit 170 is arranged at the stage after the level shift circuit 33. It was As a result, the NOR circuit 36 in the logic circuit 170 is inevitably generated.
38 and the NAND circuits 37 and 39 have a second power supply voltage V
It will be driven by 5.

However, the second power supply voltage V5 is also used as a liquid crystal driving voltage. Therefore, when the data signal or the alternating signal changes, the N
When a glitch occurs due to a through current generated in the OR circuits 36 and 38 and the NAND circuits 37 and 39, the glitch also greatly affects the liquid crystal driving voltage. In particular, these NOR circuits and NAND circuits are
Since four data lines are connected to all the data lines of the liquid crystal panel (for example, a total of 640 × 4 = 2560 in a liquid crystal panel of 200 × 640 dots), the influence is extremely large. Therefore, these glitches
The effective value of the voltage supplied to the liquid crystal display element is changed, and the display quality of the liquid crystal is extremely deteriorated.

The second power supply voltage V5 is, for example, −
It is a high voltage of 20 to -40V (or 20 to 40V). Therefore, the NOR circuits 36 and 38, the NAND circuit 3
It is also necessary that the transistors constituting 7, 39 are high breakdown voltage transistors. However, these high breakdown voltage transistors occupy an extremely large area for realizing the same driving capability as compared with the transistor operating at the first power supply voltage, for example, −5V (or 5V).

Further, when a semiconductor chip is laid out, it is necessary to dispose a so-called guard band having the same potential as the substrate around the source region of the transistor in order to maintain the potential of the substrate. These guard bands are
This is necessary in order to prevent latch-up, which tends to occur particularly when the drive voltage supplied to the source region becomes high. Therefore, in a high breakdown voltage transistor that needs to be driven at a higher voltage than an ordinary transistor, the occupied area of this guard band needs to be made extremely large.

As described above, a logic circuit composed of high breakdown voltage transistors is more likely to adversely affect the display characteristics and occupies a very large area than a logic circuit composed of ordinary transistors. Was becoming. Therefore, it is preferable that these logic circuits are not composed of high breakdown voltage transistors as much as possible from the viewpoint of improving the display characteristics or reducing the area of the semiconductor chip. However, as shown in FIG. 12, in the high voltage drive circuit to which the conventional level shift circuit is applied, these logic circuits 170 are used.
Need to be arranged in the subsequent stage of the level shift circuit 33.
Therefore, these logic circuits 170 inevitably have to be composed of high breakdown voltage transistors, and as a result, display characteristics deteriorate and the area of the semiconductor chip becomes large.

Next, the second problem will be described.

Circuit diagrams of FIGS. 11A and 11B and FIG.
As is clear from the truth table of (C), in the conventional level shift circuit, the voltage level inversion period of the first and second input signals, that is, the first and second input signals are changed from H, L level to L level. , H level, or when L, H level is changed to H, L level, the current path of the level shift circuit becomes conductive and a through current is generated. The generation of these shoot-through currents causes glitches in the high-voltage power supply, as described above, when these level shift circuits are applied to a high-voltage drive circuit, for example. And
The generation of these glitches has a great influence on the display characteristics of the liquid crystal. Also, in this way, the first and second
If the current path becomes conductive during the voltage level reversal period of the input signal, the response speed of the level shift circuit may slow down. To speed up this response speed,
Transistors 150, (152), 154, (156)
, Or the size of a transistor for driving an element to which the level shift circuit is connected, needs to be extremely large. However, this undesirably increases the area of the semiconductor chip.

Conventionally, for example, as a technique for reducing the through current, Japanese Patent Publication No. 4-30765 and Japanese Unexamined Patent Publication No. Hei.
There is a technique shown in -30765. These conventional technologies are
For example, the on resistance of a MOS transistor is used to form a resistor in the current path of the level shift circuit to reduce the through current. Therefore, although the through current can be reduced to some extent, the through current and the conductive state of the current path cannot be completely cut off.

However, when these level shift circuits are applied to high voltage drive circuits such as liquid crystal drive circuits and multi-bit high voltage output drivers, a large number of these level shift circuits are required. For example, a liquid crystal panel of 200 × 640 dots requires 640 level shift circuits. Therefore, even if a resistor can be inserted in the current path to reduce the through current to some extent, it still has a great influence on the display characteristics and the like. On the other hand, if the resistance value of the resistor inserted in the current path or the on-resistance value of the transistor is increased in order to further reduce the shoot-through current, then the response speed of the level shift circuit becomes slower. However, for example, in a liquid crystal panel or the like, it becomes necessary to operate the level shift circuit at high speed as the area of the liquid crystal panel increases or the resolution of the liquid crystal panel increases. Therefore, there has been a problem that it is not preferable to insert a resistor into the current path or an on-resistance of the transistor, which is an obstacle to increasing the response speed of the level shift circuit.

The present invention is intended to solve the above problems. An object of the present invention is to provide a level shift circuit with third and fourth switching elements which are turned on / off by a predetermined control signal. Realizes a level shift circuit having a function other than converting the voltage amplitude of the input signal from the first power supply voltage to the second power supply voltage, and also realizes a high voltage drive circuit using this level shift circuit. To do.

[0021]

In order to achieve the above object, a level shift circuit according to the present invention changes the voltage amplitude of first and second input signals from a first power supply voltage to a second power supply voltage. In the level shift circuit for converting, in addition to the first and second switching elements that are turned on / off by the first and second input signals, a third switching element is connected in series with the first switching element. A fourth switching element is provided in series with the second switching element, and the third and fourth switching elements are formed in accordance with the signal states of the first and second input signals. The control signal is turned on / off by the control signal, and conduction / cutoff of the current path is switched.

In this case, the third and fourth switching elements are turned off by the control signal when both the first and second input signals are at the upper level or both are at the lower level. The current path may be cut off.

Further, in this case, the third and fourth switching elements are turned off by the control signal during the voltage level inversion period of the first and second input signals, and the current path is cut off. Good.

The high-voltage drive circuit according to the present invention is a high-voltage drive circuit that generates a high-voltage drive signal for driving a predetermined element with the second power supply voltage, and performs a first logical operation by a predetermined logical operation. A logic circuit that forms a second input signal; a level shift circuit that converts the voltage amplitudes of the first and second input signals from a first power supply voltage to a second power supply voltage; An output drive circuit for forming the high voltage drive signal according to an output signal, wherein the level shift circuit has first and second switching elements which are turned on / off by the first and second input signals. A third switching element is provided in series with the first switching element, a fourth switching element is provided in series with the second switching element, and the third and fourth switching elements are provided. Quenching element, the first, it is in an OFF state by a predetermined control signal when the second input signal is in both in the case or both the lower level in the upper level,
The current path of the level shift circuit is cut off.

[0025]

According to the present invention, the current path of the level shift circuit can be turned on / off by turning on / off the third and fourth switching elements using a predetermined control signal. With this configuration, in the present invention, normal circuit operation can be guaranteed even if both the first and second input signals are at the same level. Therefore, signals of all modes can be input to the first and second input signals, and as a result, the logic circuit which is conventionally arranged at the subsequent stage of the level shift circuit
It is possible to dispose it in the previous stage of the level shift circuit.
Furthermore, according to the present invention, during the voltage level inversion period of the first and second input signals, the third and fourth switching elements are turned off by a predetermined control signal, thereby generating a through current and level shifting. It is possible to effectively prevent the current path of the circuit from being short-circuited.

[0026]

【Example】

 (1) First Example FIGS. 1A and 1B show a first example of the present invention.

As shown in FIGS. 1A and 1B, in the level shift circuit according to the first embodiment, the transistors 50, (52) and 5 serving as the first and second switching elements are provided.
4, (56) and the transistors 58 and 60, as well as the transistor 62 which is the third and fourth switching element,
64 are connected in series. Then, the transistors 62 and 64 are turned on / off by the control signal 31 formed according to the signal states of the first and second input signals. Here, the transistor 62, which is the third switching element, may be connected in series to at least the first switching element 50, (52), and the transistor 64, which is the fourth switching element, may be at least the fourth switching element. 2 is a switching element 54, (5
It may be connected in series to 6). Therefore, for example, the transistors 62 and 64 which are the third and fourth switching elements are connected to the lower side of the transistors 58 and 60 (power source E
2)) may be provided.

In the first embodiment, when the first and second input signals having mutually opposite phases are input by the above configuration, the voltage amplitude is changed from the first power supply voltage (E1) to the second power supply voltage (E1). It becomes possible to convert into the power supply voltage (E2).

Further, in this level shift circuit, even when both the first and second input signals are at the same level, the control signal 31 turns off the transistors 62 and 64 to ensure normal operation. Is possible.

That is, in the conventional level shift circuit, as shown in FIG.
As described in 1 (A) to (C), for example, the first and second
If both input signals are at the L level (E1 level), the current path of the level shift circuit becomes conductive, and the state becomes inoperable. On the other hand, in the level shift circuit according to the first embodiment, when the first and second level shift circuits are both at the L level, the control signal 31
Is set to the E2 level, the current path of the level shift circuit is cut off, and thus the inoperable state can be avoided.

Since the first embodiment has such characteristics, signals of all modes (HL, LH, HH, LL) should be input as the first and second input signals. Is possible. Thus, for example, when the present first embodiment is applied to a high voltage drive circuit, it is possible to arrange a predetermined logic circuit, which is conventionally arranged in the subsequent stage of the level shift circuit, in the preceding stage of the level shift circuit. Becomes By arranging the logic circuit in the preceding stage of the level shift circuit in this way, it becomes unnecessary to drive the logic circuit with a high voltage. As a result, it is possible to prevent the occurrence of glitches in the high voltage power supply, improve the display characteristics and the like, reduce the area occupied by these logic circuits, and reduce the area of the semiconductor chip. It should be noted that the embodiments in which the logic circuit can be arranged in the preceding stage of the level shift circuit in this manner will be described later in detail as the second and third embodiments.

Further, according to this level shift circuit, the voltage level inversion period of the first and second input signals, that is, the first and second input signals are changed from the H and L levels to the L and H levels, or , L, H level to H, L level, it is possible to prevent the current path of the level shift circuit from becoming conductive and generating a through current. That is, in this level shift circuit, in addition to the first and second switching elements, the transistors 62 and 64 that are the third and fourth switching elements are provided in series. Therefore, in such a state that the current path is conductive, the transistors 62 and 64 are turned off by a predetermined control signal, thereby preventing the generation of a through current and the conductive state of the current path. As a result, it is possible to prevent deterioration of display characteristics and increase in size of the transistors 50 to 56 and the element driving transistor. The embodiment in this case will be described later in detail as a fourth embodiment.

(2) Second Embodiment Next, a second embodiment of the present invention will be described. The second embodiment is an embodiment in which the level shift circuit according to the present invention is applied to a drive circuit for STN liquid crystal.

FIG. 2 shows a circuit diagram of a liquid crystal drive circuit according to the second embodiment. This liquid crystal drive circuit includes a logic circuit 70,
The level shift circuits 5, 6, 7 and the output drive circuit 80 are included, and like the conventional liquid crystal drive circuit shown in FIG. 12, four values (V0, V2, V) are obtained from the data signal and the alternating signal.
3, V5) is an output signal forming circuit. Here, the level shift circuit according to the present invention is applied to the level shift circuit 6, and the conventional level shift circuit is applied to the level shift circuits 5 and 7. Further, unlike the conventional liquid crystal drive circuit shown in FIG. 12, the logic circuit 70 is arranged in the preceding stage of the level shift circuit.

The logic circuit 70 includes inverters 9, 10 and NO.
It is composed of R circuits 11 and 12 and NAND circuits 13 and 14, and performs a predetermined logical operation on the input data signal and alternating signal to input signals 23, 24, 25 and 26 to the level shift circuits 6 and 7. Is formed. Here, since the logic circuit 70 is arranged in the preceding stage of the level shift circuit, the transistors forming the logic circuit 70 can be operated by the logic circuit driving voltage VSS instead of the liquid crystal driving voltage V5. Has become.

Output signals 23, 24, 2 of the logic circuit 70
Reference numerals 5 and 26 serve as inputs to the level shift circuit 6 and the level shift circuit 7 according to the present invention, and the voltage amplitude is converted into the liquid crystal drive voltage V5. Then, the level shift circuit 6,
Output signals 27, 28, 2 level-shifted by 7
Reference numerals 9 and 30 designate the output drive circuit 8 composed of Nch transistors 19 and 20 and Pch transistors 21 and 22.
It has been input to 0.

The alternating signal is supplied to the level shift circuit 5
Thus, the voltage amplitude is level-shifted to the liquid crystal driving voltage V5. The control signal 31 formed by this level shift is the transistor 62 which is the third and fourth switching elements of the level shift circuit 6 according to the present invention.
64 is input. Further, the control signal 31 is input to the gate electrodes of the Nch transistors 17 and 18 whose drain regions are connected to the output signals 29 and 30 of the level shift circuit 7.

Power sources V0, V2, V3 and V are provided in the source regions of the transistors 19 to 22 constituting the output drive circuit 80.
5 is connected. The drain regions of the transistors 19 to 22 are commonly connected, and the commonly connected drain outputs are output to the respective liquid crystal elements as liquid crystal drive signals. With the above configuration, in the liquid crystal drive circuit according to the present embodiment, binary output is changed to quaternary output (V
0, V2, V3, V5).

Next, the operation of the present liquid crystal drive circuit will be described with reference to FIGS. FIG. 3 shows a truth table showing the relationship between the data signal and the AC signal and the output signal, and FIG. 4 shows the data signal, the AC signal, and the signals 27 to 3.
0, the actual waveform diagram of the output signal is shown.

First, the case where the AC signal is at the L level (VSS level) will be described. In this case, the control signal 31 input to the transistors 62 and 64 that are the third and fourth switching elements of the level shift circuit 6 becomes the V5 level. Therefore, the Nch transistors 62 and 64 of the level shift circuit 6 are turned off, and the level shift circuit 6
The current path between the power supplies is cut off. Furthermore, at this time,
Since the alternating signal is at the L level, N in the logic circuit 70
The output signals 23 and 24 of the OR circuits 11 and 12 become L level. As a result, the Pch transistors 50 and 54 of the level shift circuit 6 are turned on, and the output signals 27 and 28 of the level shift circuit 6 are both at the GND level. As a result, the Pch transistor 2 in the output drive circuit 80
1, 22 will be set to the off state. From this, when the AC signal is at the L level, the output signal of the level shift circuit 6 is always at the GND level, and it can be considered that the level shift circuit 6 is in the non-selected state.
As described above, the level shift circuit according to the present invention includes the first,
Since the normal operation is achieved even when the second inputs are both at the L level, the logic circuit 70 can be arranged in the preceding stage of the level shift circuit.

In this case, the first and second input signals are applied to the input of the level shift circuit 7 through the logic circuit 70 according to the state of the data signal. Then, the output signals 29 and 30 of the level shift circuit 7 are input to the gate electrodes of the Nch transistors 19 and 20 in the output drive circuit 80, and as described above, at this time, the Pch transistor 21. , 22 are off. Therefore, the output signal of the output drive circuit 80 becomes V5 level when the data signal is at L level (VSS level), and becomes V3 level when it is at H level (GND level).

As described above, when the alternating signal is at the L level, data corresponding to the data signal is output to the output signals 29 and 30 of the level shift circuit 7, and the output drive circuit 80.
As the output signal of, the data of V3 and V5 levels is output according to the data signal. Therefore, when the AC signal is at the L level, it can be said that the level shift circuit 7 is in the selected state.

In this case, the Nch transistor 1
Since the L-level AC signal is input to the gate electrodes of the Nch transistors 17 and 18,
Is off.

Next, the case where the alternating signal is at the H level (GND level) will be described. In this case, the control signal 31 input to the transistors 62 and 64 that are the third and fourth switching elements of the level shift circuit 6 becomes the GND level. Therefore, the transistors 62 and 64 are turned on, and the level shift circuit 6 level-shifts and converts the voltage amplitudes of the first and second input signals 23 and 24, similarly to a normal level shift circuit. Then, the output signals 27 and 28 of the level shift circuit 6 are input to the gate electrodes of the Pch transistors 21 and 22 of the output drive circuit 80. As a result, the output signal of the output drive circuit 80 becomes V0 level when the data signal is at L level (VSS level), and becomes V2 level when it is at H level (GND level). Thus, it can be said that the level shift circuit 6 is in the selected state when the alternating signal is at the H level.

In this case, since the AC signal is at the H level, the NAND circuits 13 and 14 of the logic circuit 70 always output the H level. Therefore, the output signals 29 and 30 of the level shift circuit 6 should be in a high impedance state. However, in the output signals 29 and 30,
The drain regions of the Nch transistors 17 and 18 to which the control signal 31 is connected to the gate electrodes are connected. Since the alternating signal is at the H level, this control signal 3
1 is at the GND level, and therefore the Nch transistors 17 and 18 are in the ON state. For this reason,
The output signals 29 and 30 of the level shift circuit 7 are fixed to the V5 level, and the Nch transistor 1 of the output drive circuit 80 is fixed.
9 and 20 will be set to an off state.

As described above, the second book shown in FIG.
In the embodiment, the level shift circuit 6 is controlled by the control signal 31.
Is switched between the selected state and the non-selected state.
In the second embodiment, this operation makes it possible to realize the same function as the conventional example.

Now, in the second embodiment, the logic circuit 70 is used.
Can be arranged in the preceding stage of the level shift circuit.
Therefore, in the conventional example, the liquid crystal driving voltage V5 (for example, -20
It is possible to operate the logic circuit operating at -40V) at the logic circuit driving voltage VSS (for example, -5V). Therefore, even if a through current is generated in the NOR circuits 11 and 12 and the NAND circuits 13 and 14 when the data signal or the AC signal is changed, this through current is applied to the liquid crystal driving voltage V.
5 will not be adversely affected by the occurrence of glitches. Therefore, the stable liquid crystal driving voltage V5 can be supplied to the liquid crystal display device, and the display quality of the liquid crystal display device can be significantly improved.

Further, in the second embodiment, since the logic circuit 70 can be operated at an operating voltage extremely lower than that of the conventional example, the current consumption can be extremely reduced.
That is, generally, the consumed current is i = c (load capacity) · v
It is represented by (operating voltage) and f (operating frequency). Therefore, the operating voltage of the logic circuit is, for example, -20 to 20 in the conventional example.
The voltage of −40V is changed to −5V in the second embodiment.
Since it can be set to V, the current consumption can be extremely reduced. In particular, since liquid crystal display devices are often used in portable equipment, long-time operation with a battery and low current consumption are required for size reduction and weight reduction. From this, it is understood that the liquid crystal drive circuit according to the second embodiment has a very superior configuration as compared with the conventional example.

The second embodiment shown in FIG. 2 has a structure in which one level shift circuit is added to the conventional example shown in FIG. However, in the second embodiment of FIG. 2, the level shift circuit 6 and the level shift circuit 7 are exclusively operated by the control signal 31 as described above. Therefore, the current consumption of the level shift circuit is as shown in FIG.
It can be regarded as equivalent to the conventional example shown in FIG. As a result, it is understood that the liquid crystal drive circuit according to the second embodiment can save the current consumption reduced in the logic circuit as compared with the conventional example.

Further, the liquid crystal drive circuit according to the second embodiment has a constitution which is superior to the conventional example also in terms of the occupied area as shown in FIG.

That is, a high breakdown voltage transistor operating at a high voltage of −20 to −40 V has an area about 5 times larger than that of a normal transistor operating at −5 V in order to realize the same driving capability. I need.

Further, when laying out a semiconductor chip, it is necessary to arrange a so-called guard band around the source region of the transistor. These guard bands are necessary to prevent latch-up, which is particularly likely to occur when the drive voltage supplied to the source region is high. Therefore, in a high breakdown voltage transistor that needs to be driven at a higher voltage than an ordinary transistor, the area occupied by this guard band must be very large.

From the above two points, in the second embodiment, the area occupied by the logic circuit 70 can be made extremely small as shown in FIG.

Now, the level shift circuit 6 according to the present invention
Has a configuration in which Nch transistors 62 and 64 are added as compared with the conventional level shift circuit. But,
These Nch transistors 62 and 64 are transistors which do not take out from the intermediate drain as shown in FIG. Therefore, the Nch transistors 62 and 64 have Nc
They can be arranged at the minimum pitch (pitch between gate electrodes) with the h transistors 58 and 60, and the addition of these transistors 62 and 64 hardly increases the semiconductor chip area. Further, the transistors 17 and 18 added in the output drive circuit 80 also pull down the output signal of the level shift circuit 7 which is set to the high impedance state, and thus are transistors of a very small size. Therefore, there is almost no increase in the semiconductor chip area due to the addition of these transistors.

Further, the second embodiment shown in FIG. 2 has a structure in which one level shift circuit 7 is added as compared with the conventional example. However, when the level shift circuit 6 and the level shift circuit 7 are laid out side by side, the Nch and Pch transistors of each level shift circuit can be formed in the same well.

As described above, in the second embodiment, the area occupied by the logic circuit is reduced, the level shift circuit, and Nc are reduced.
If the increase in occupied area due to the addition of the h transistors 17, 18, 62, 64 is totaled, the area of the liquid crystal drive circuit can be reduced as a whole as compared with the conventional example. This point will be clear from FIG.

Moreover, as shown in FIG. 5, the semiconductor chip formed by the liquid crystal drive circuit of the conventional example has a vertically long shape, whereas the semiconductor chip formed by the liquid crystal drive circuit of the second embodiment is made. The chip has a horizontally long shape. Therefore, the second embodiment is the best for realizing a slim chip. If the liquid crystal drive circuit is made into a slim chip, the ratio of the effective display area of the liquid crystal panel (the ratio of the size of the liquid crystal panel to the size of the device) can be increased as shown in FIG. This ratio of effective display area is one of the very important performances in this type of liquid crystal panel.
Therefore, in this sense as well, the second embodiment has a significantly superior structure to the conventional example.

(3) Third Embodiment Next, a third embodiment of the present invention will be described. The third embodiment is an embodiment in which the level shift circuit according to the present invention is applied to a drive circuit for MIM liquid crystal.

FIG. 7 shows a circuit diagram of a liquid crystal drive circuit according to the third embodiment. This liquid crystal drive circuit includes a logic circuit 70,
It is configured to include level shift circuits 6, 7, and 8 and an output drive circuit 80. Then, the logic circuit 70 outputs the output signal of the shift register arranged in the preceding stage of the liquid crystal drive circuit, and F
The R signal is input. The FR signal is also input to the level shift circuit 5. In the source regions of the Nch transistors 19 and 20 and the Pch transistors 21 and 22 in the output drive circuit 80, the power supplies V0, V2, V4,
V5 is connected. Then, the common drain of these transistors 19 to 22 becomes an output signal of the present liquid crystal drive circuit and is used as a common signal for driving the liquid crystal element. Since the third embodiment has substantially the same main part of the configuration as the liquid crystal drive circuit according to the second embodiment shown in FIG. 2, a detailed description of the configuration will be omitted.

FIG. 8 is a waveform diagram showing the operation of the third embodiment. As shown in the figure, the common signal which is the output signal of the liquid crystal drive circuit is synchronized with the FR signal by V1,
The output is inverted between V5 or between V0 and V4.

As is clear from the configuration of the third embodiment shown in FIG. 7, the third embodiment has the same advantages as the second embodiment with respect to the conventional example. That is, the logic circuit 70
Can be arranged in the preceding stage of the level shift circuit, so that the logic circuit 70 can be operated at, for example, -5V. As a result, it is possible to improve the display characteristics, reduce the area of the semiconductor chip, and slim the chip.

(4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, during the voltage level inversion period of the first and second input terminals of the level shift circuit, the third and fourth switching elements are turned off by a predetermined control signal, and the current of the level shift circuit is changed. This is an example of blocking a route.

FIG. 9A shows a circuit diagram of the fourth embodiment.
FIG. 9B shows a waveform diagram of each signal such as the control signal 31.

As shown in FIG. 9A, the control signal 31 for turning on / off the Nch transistors 62 and 64 which are the third and fourth switching elements is formed by the one-shot multivibrator 92. The one-shot multivibrator 92 includes a D-flip-flop 47.
A clock signal is input via. The clock signal is a signal synchronized with the inversion of the voltage levels of the first and second input signals. Therefore, as shown in FIG. 9B, from the one-shot multi-vibrator 92,
During the voltage level inversion period of the first and second input signals, the transistors 62 and 64 are set to the off state, and the control signal 31 for cutting off the current path of the level shift circuit 90 is output.

Since the fourth embodiment operates as described above, it is possible to prevent the shoot-through current generated during the voltage level inversion period of the first and second input signals. Therefore, for example, when the fourth embodiment is applied to a high voltage drive circuit such as a liquid crystal drive circuit (STN, MIM, TFT, etc.) or a multi-bit high voltage output driver, the occurrence of glitches in a high voltage power supply is generated. Can be prevented, and display characteristics and the like can be improved.

Further, according to the fourth embodiment, the response speed of the level shift circuit 90 can be made extremely fast,
Further, the occupied area can be reduced. That is, according to the fourth embodiment, since the transistors 62 and 64 are turned off during the voltage level inversion period of the first and second input signals, the level shift circuit is not short-circuited. Therefore, the response speed of the level shift circuit 90 can be made extremely fast. As a result, the size of the transistors 50 to 60 of the level shift circuit 90 or the element driving transistor to which the level shift circuit is connected can be significantly reduced. As described above, according to the fourth embodiment, by newly providing the third and fourth switching elements which are turned on / off by the predetermined control signal, the characteristic improvement and the function addition of the level shift circuit are realized. It becomes possible.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the gist of the present invention.

For example, in the above-described first to fourth embodiments, the level shift circuit for level shifting the power supply voltage on the negative side and the high voltage drive circuit using the level shift circuit have been described. It is naturally applicable to a level shift circuit for level shifting the power supply voltage on the side and a high voltage drive circuit using the level shift circuit.

In the second and third embodiments, the case where the present invention is applied to the liquid crystal drive circuit used for the STN liquid crystal and the MIM liquid crystal has been described, but the present invention is not limited to this and, for example, the TFT liquid crystal is used. It can be applied to all kinds of liquid crystal drive circuits. Further, the present invention can be widely applied not only to the liquid crystal drive circuit but also to a semiconductor circuit having a multi-bit high withstand voltage output.

[0070]

According to the present invention, even if both the first and second input signals are at the same level, for example, normal circuit operation can be guaranteed, and the conventional level shift circuit is arranged at the subsequent stage. It is possible to arrange another logic circuit before the level shift circuit. Therefore, this logic circuit can be driven by the logic circuit driving voltage. As a result, it is possible to prevent the occurrence of glitches and the like in the high voltage power supply, and it is possible to greatly improve the performance such as the display characteristics of the high voltage drive circuit. Furthermore, the current consumption of the semiconductor circuit and the chip area can be reduced, and the slim chip of the semiconductor device can be achieved.

Further, according to the present invention, it is possible to prevent a shoot-through current from being generated during the voltage level inversion period of the first and second input signals. Therefore, it is possible to prevent the occurrence of glitches and the like in the high voltage power supply, and it is possible to improve the performance such as the display characteristics of the high voltage drive circuit. Further according to the invention, the first,
It is possible to prevent the current path of the level shift circuit from being short-circuited during the voltage level inversion period of the second input signal. Therefore, the response operation of the level shift circuit can be made extremely fast. As a result, the size of the switching element forming the level shift circuit or the size of the element driving transistor to which the level shift circuit is connected can be significantly reduced.

[Brief description of drawings]

1A and 1B are circuit diagrams showing a level shift circuit according to a first embodiment of the present invention, and FIG.
Is a truth table for explaining the operation.

FIG. 2 is a circuit diagram showing a liquid crystal drive circuit according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a truth table of a liquid crystal drive circuit according to a second embodiment.

FIG. 4 is a waveform diagram showing an operation of the liquid crystal drive circuit according to the second embodiment.

FIG. 5 is a schematic explanatory diagram for explaining reduction in area of a semiconductor chip according to a second embodiment.

FIG. 6 is a schematic explanatory diagram for explaining slimming of a semiconductor chip according to a second embodiment.

FIG. 7 is a circuit diagram showing a liquid crystal drive circuit according to a third embodiment of the present invention.

FIG. 8 is a waveform diagram showing an operation of the liquid crystal drive circuit according to the third embodiment.

FIG. 9 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a level shift circuit in the case of level shifting the power source on the plus side.

11A and 11B are circuit diagrams showing a conventional level shift circuit, and FIG. 11C is a truth table for explaining the operation thereof.

FIG. 12 is a circuit diagram showing a liquid crystal drive circuit to which a conventional level shift circuit is applied.

[Explanation of symbols]

6, 7, 8, 33, 90, 94, level shift circuit 8, 9, 10, 34, 35 inverter 11, 12, 36, 38 NOR circuit 13, 14, 37, 39 NAND circuit 17, 18, 19, 20 , 52, 56, 58, 60, 6
2, 64, 152, 156, 158, 160 Nch transistors 21, 22, 50, 54, 150, 154 Pch transistors 23, 24, 25, 26, 27, 28, 29, 30, 4
4, 45, 46 Signal line 31 Control signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 5/66 102 B 9068-5C

Claims (4)

[Claims] 1. The voltage amplitudes of the first and second input signals are set to the first voltage amplitude.
In the level shift circuit for converting the power supply voltage of 1 to the second power supply voltage, a third switching element is provided in addition to the first and second switching elements that are turned on / off by the first and second input signals. A fourth switching element is provided in series with the first switching element, a fourth switching element is provided in series with the second switching element, and the third and fourth switching elements are provided in the first and second switching elements. ON / OFF by the control signal formed according to the signal state of the input signal of
A level shift circuit characterized by switching between conduction and interruption of a current path. 2. The method according to claim 1, wherein the third and fourth switching elements are the first and second switching elements.
When the input signals of are both at the upper level or both are at the lower level, the control signal turns off,
A level shift circuit characterized in that the current path is cut off. 3. The first and second switching elements according to claim 1, wherein the third and fourth switching elements are the first and second switching elements.
The level shift circuit is turned off by the control signal during the voltage level inversion period of the input signal, and the current path is cut off. 4. A high-voltage drive circuit for generating a high-voltage drive signal for driving a predetermined element with a second power supply voltage, a logic circuit for forming first and second input signals by a predetermined logical operation. A level shift circuit for converting the voltage amplitudes of the first and second input signals from the first power supply voltage to the second power supply voltage; and the high voltage drive signal formed by the output signal of the level shift circuit. And a third switching element in addition to the first and second switching elements which are turned on / off by the first and second input signals, in the level shift circuit. A fourth switching element is provided in series with the switching element and a fourth switching element is provided in series with the second switching element. These third and fourth switching elements are the first and second switching elements. It is turned off by a predetermined control signal when the force signal in both the cases or together lower level in the upper level, the high voltage drive circuit the current path of the level shift circuit is characterized in that it is cut off.