JP2005134682A - Liquid crystal driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal driving device where power consumption and a chip size are reduced. <P>SOLUTION: The liquid crystal driving device is provided with an upper side prevention circuit 16 for preventing a voltage exceeding the withstand voltage of an upper side common potential output circuit 11 from being applied thereto, and a bottom side prevention circuit 17 for preventing a voltage exceeding the withstand voltage of a bottom side common potential output circuit 12 from being applied thereto. When an output potential of the upper side common potential output circuit 11 is outputted to an output terminal 15, a switch circuit 13 is brought into the ON state and a switch circuit 14 is brought into the OFF state. When an output potential of the bottom side common potential output circuit 12 is outputted to the output terminal 15, the switch circuit 13 is brought into the OFF state and the switch circuit 14 is brought into the ON state. In this switching, the upper side prevention circuit 16 and the bottom side prevention circuit 17 prevent the circuits from voltage over the withstand voltage by temporarily bringing the circuits into the OFF state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal driving device used for a television receiver, a personal computer, a workstation and the like.

A conventional liquid crystal driving device that supplies an upper common potential and a lower common potential to a liquid crystal display panel by switching is configured as shown in FIG.
11 is an upper common potential output circuit, 12 is a lower common potential output circuit, 13 is an upper switch circuit, 14 is a lower switch circuit, 15 is an output terminal, and the output terminal 15 is connected to the common electrode of the liquid crystal display panel. ing.

  First, when the upper common potential is required for the liquid crystal display panel, the upper common potential is supplied from the output terminal 15 to the liquid crystal display panel by turning the upper switch circuit 13 on and the lower switch circuit 14 off. Supply.

When the lower common potential is required for the liquid crystal display panel, the upper switch circuit 73 is turned off and the lower switch circuit 74 is turned on, so that the lower side from the output terminal 15 to the liquid crystal display panel is set. Supply a common potential.
JP-A-9-138669

  However, in this configuration, when the common potential supplied to the liquid crystal display panel is switched from the upper common potential to the lower common potential, the upper common potential output circuit 11 slightly supplies the lower common potential output circuit 12. The applied potential is applied.

  For this reason, the circuit withstand voltage and power supply range of the upper common potential output circuit 11 and the lower common potential output circuit 12 are both the potential ranges that the upper common potential output circuit 71 and the lower common potential output circuit 72 need to output. There is a problem that power consumption, withstand voltage of circuit elements, and chip size are increased.

  The liquid crystal driving device of the present invention is a liquid crystal driving device that switches between an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel. The output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via an upper switch circuit that is turned on when the common potential is supplied, and the lower switch that is turned on when the lower common potential is supplied. The output of the lower common potential output circuit and the common potential output terminal are connected via a side switch circuit, and temporarily when the lower switch circuit is turned off and the upper switch circuit is turned on. An upper prevention circuit that is turned off is interposed between the output of the upper common potential output circuit and the upper switch circuit, so that the upper switch A lower prevention circuit that is temporarily turned off at the timing when the lower circuit is turned on and the lower switch circuit is turned on, between the output of the lower common potential output circuit and the lower switch circuit. It is characterized by being interposed in.

  Further, an upper delay circuit that delays propagation of voltage from the upper prevention circuit to the upper common potential output circuit is interposed between the upper common potential output circuit and the upper prevention circuit, and the lower common potential output circuit And a lower delay circuit for delaying the propagation of a voltage from the lower prevention circuit to the lower common potential output circuit.

  In addition, an upper second switch circuit is provided between the upper common potential output circuit and the upper prevention circuit so that the output of the upper prevention circuit switches to the on state after the output returns to the on state, and the lower common potential output A lower second switch circuit that switches to an on state after the output of the lower prevention circuit returns to an on state is interposed between the circuit and the lower prevention circuit.

  The liquid crystal driving device of the present invention is a liquid crystal driving device that switches between an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel. The output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via an upper switch circuit that is turned on when the common potential is supplied, and the lower switch that is turned on when the lower common potential is supplied. The output of the lower common potential output circuit and the common potential output terminal are connected via a side switch circuit, the connection point between the output of the upper switch circuit and the output of the lower switch circuit, and the common potential output terminal When the upper switch circuit is switched to the OFF state and the lower common potential is output, the lower switch circuit is switched to the ON state before the lower switch circuit is switched to the ON state. When changing the potential of the output terminal to be an appropriate potential for the common potential output circuit and switching the lower switch circuit to the off state and outputting the upper common potential, before switching the upper switch circuit to the on state, An appropriate potential setting circuit for changing the potential of the output terminal so as to be an appropriate potential for the upper common potential output circuit is provided.

  The liquid crystal driving device of the present invention is a liquid crystal driving device that switches between an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel. The output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via an upper switch circuit that is turned on when the common potential is supplied, and the lower switch that is turned on when the lower common potential is supplied. An output of the lower common potential output circuit and the common potential output terminal are connected via a side switch circuit, and the lower switch circuit is turned off between the output of the upper common potential output circuit and the upper switch circuit. When the upper switch circuit is switched to the ON state, the upper switch circuit is turned on using the threshold voltage characteristics of the MOS transistor. An upper MOS transistor that prevents application of an overvoltage to the mon potential output circuit is interposed, and the upper switch circuit is switched off between the output of the lower common potential output circuit and the lower switch circuit, and A lower MOS transistor is provided that prevents the application of an overvoltage to the lower common potential output circuit using the threshold voltage characteristics of the MOS transistor at the timing when the lower switch circuit is turned on. And

  The liquid crystal driving device of the present invention is a liquid crystal driving device that switches between an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel, The output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via an upper MOS transistor, and the output of the lower common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected to the lower side. It is connected via a side MOS transistor, and the upper MOS transistor and the lower MOS transistor are switched to switch the upper common potential and the lower common potential to be supplied to the common potential output terminal.

  The liquid crystal driving device of the present invention can prevent an unnecessary potential from being applied to the common potential output circuit by providing an upper prevention circuit and a lower prevention circuit and temporarily turning off the circuit at the time of switching. A common potential output circuit can be made in a wide voltage range, reducing power consumption and chip size.

Further, the reliability is improved by adding the upper delay circuit, the lower delay circuit, or the upper second switch circuit and the lower second switch circuit.
Further, by providing an appropriate potential setting circuit after the upper switch and the lower switch, it is possible to prevent an unnecessary potential from being applied to the common potential output circuit.

  Further, by providing an upper MOS transistor between the upper switch and the upper common potential output circuit and providing a lower MOS transistor between the lower switch and the lower common potential output circuit, the threshold voltage characteristics of the MOS transistor By using this, it is possible to more reliably prevent unnecessary potential from being applied to the common potential output circuit.

  In addition, an upper MOS transistor is provided between the output terminal and the upper common potential output circuit, and a lower MOS transistor is provided between the output terminal and the lower common potential output circuit, so that unnecessary potential is applied to the common potential output circuit. This can be prevented, the power consumption of the upper common potential output circuit and the lower common potential output circuit can be reduced, and the chip size of the component can be reduced.

Hereinafter, each embodiment of the present invention will be described with reference to FIGS.
In addition, the same code | symbol is attached | subjected and demonstrated to what comprises the same effect | action as FIG. 7 which shows a prior art example.
(Embodiment 1)
As shown in FIG. 1, 11 is an upper common potential output circuit, 12 is a lower common potential output circuit, 13 is an upper switch circuit, 14 is a lower switch circuit, and 17 is an output terminal. An upper prevention circuit 16 is interposed between the upper common potential output circuit 11 and the upper switch circuit 13. A lower prevention circuit 17 is interposed between the lower common potential output circuit 12 and the lower switch circuit 14.

  The upper prevention circuit 16 includes a diode 16a having one end connected to a connection line between the output of the upper common potential output circuit 11 and the input of the upper switch circuit 13, and the other end 16b of the diode 16a is the upper common circuit. The potential output circuit 11 is connected to the same potential as the lower potential.

  The lower prevention circuit 17 includes a diode 17a having one end connected to a connection line between the output of the lower common potential output circuit 12 and the input of the lower switch circuit 14, and the other end 17b of the diode 17a is The lower common potential output circuit 12 is connected to the same potential as the upper potential.

When the common potential supplied to the liquid crystal display panel is the upper potential, the upper switch circuit 13 is connected and the lower switch circuit 14 is turned off.
In this state, the upper common potential output circuit 11 and the output terminal 15 are connected, and the upper common potential is output to the output terminal 15.

  Next, when outputting the lower common potential to the output terminal 15 from this state, first, the upper switch circuit 13 in the on state is turned off. Next, the lower switch circuit 14 is turned on.

  At this time, in the conventional case, the upper common potential may be temporarily applied to the lower common potential output circuit 12, but in this (Embodiment 1), since the lower prevention circuit 17 is interposed, The lower side prevention circuit 17 can temporarily prevent the upper side common potential from being applied to the lower side common potential output circuit 12, so that the lower side common potential output circuit 12 can be formed within a necessary power supply range. Become.

  Further, when the upper common potential is output from this state, first, the lower switch circuit 14 is turned off. Next, the upper switch circuit 13 is turned on. At this time, the upper common potential output circuit 11 can be formed in a necessary power supply range by temporarily preventing the lower common potential from being applied to the upper common potential output circuit 11 by the upper prevention circuit 16.

  Thus, it is possible to prevent an unnecessary potential from being applied to the upper common potential output circuit 11 and the lower common potential output circuit 12 by the upper prevention circuit 16 and the lower prevention circuit 17, and the upper common potential output circuit 11. The power consumption of the lower common potential output circuit 12, the breakdown voltage of the circuit element, and the chip area can be reduced.

  More specifically, when the power supply ranges of the upper common potential output circuit 11 and the lower common potential output circuit 12 can each be halved, the power consumption can be reduced by half. Moreover, since the power supply range is halved, the withstand voltage of the circuit elements can be halved. When the withstand voltage of the circuit element is halved, for example, it is possible to change from a high withstand voltage element to a low withstand voltage element. In this case, the circuit area of the upper common potential output circuit and the lower common potential output circuit can also be reduced by half.

(Embodiment 2)
FIG. 2 shows the liquid crystal drive device of (Embodiment 2), and an upper delay circuit 18 is interposed between the upper common potential output circuit 11 and the upper prevention circuit 16 of (Embodiment 1) shown in FIG. The only difference is that a lower delay circuit 19 is interposed between the lower common potential output circuit 12 and the lower prevention circuit 17.

  The upper delay circuit 18 is configured to delay the propagation of the voltage applied from the upper prevention circuit 16 to the upper common potential output circuit 11, and the lower delay circuit 19 is configured to output the lower common potential from the lower prevention circuit 17. The circuit 12 is configured to delay the propagation of the voltage applied to the circuit 12.

  The upper delay circuit 18 includes a resistor 18a interposed in series with a connection line between the output of the upper common potential output circuit 11 and the input of the upper prevention circuit 16, and a capacitor 18b interposed between the reference potential 18c. It consists of and.

  The lower delay circuit 19 is interposed between a resistor 19a and a reference potential 19c that are connected in series to a connection line between the output of the lower common potential output circuit 12 and the input of the lower prevention circuit 17. And a capacitor 19b.

  With this configuration, when the common potential supplied from the output terminal 15 to the liquid crystal display panel is the upper potential, the upper switch circuit 13 is turned on and the lower switch circuit 14 is turned off. In this state, the upper common potential output circuit 11 and the output terminal 15 are connected, and the upper common potential is output to the output terminal 17.

Next, when outputting the lower common potential from this state, first, the upper switch circuit 13 in the on state is turned off. Next, the lower switch circuit 14 is turned on.
At this time, the upper common potential may be temporarily applied to the lower common potential output circuit 12 conventionally, but the upper common potential is temporarily applied to the lower common potential output circuit 12 by the lower prevention circuit 17. prevent.

  However, since the lower common potential output circuit 12 may be applied while the lower prevention circuit 17 is at an appropriate potential, the lower delay circuit 19 delays the propagation of the voltage, thereby lowering the lower common potential. An unnecessary potential can be prevented from being applied to the output circuit 22, and the lower common potential output circuit 22 can be formed in a necessary power supply range.

  Further, when the upper common potential is output from this state, first, the lower switch circuit 14 is turned off. Next, the upper switch circuit 13 is turned on. At this time, there is a case where the lower common potential is temporarily applied to the upper common potential output circuit 21, but the upper prevention circuit 16 temporarily prevents the lower common potential from being applied to the upper common potential output circuit 11. I can do it. However, the upper common potential output circuit 11 may be applied to the upper common potential output circuit 11 while the upper prevention circuit 16 is at an appropriate potential. It is possible to prevent an unnecessary potential from being applied, and the upper common potential output circuit 21 can be formed in a necessary power supply range.

(Embodiment 3)
FIG. 3 shows the liquid crystal drive device of (Embodiment 3), and an upper second switch circuit 20 is interposed between the upper common potential output circuit 11 and the upper prevention circuit 16 of (Embodiment 1) shown in FIG. The only difference is that a lower second switch circuit 21 is interposed between the lower common potential output circuit 12 and the lower prevention circuit 17.

  When the common potential supplied to the liquid crystal display panel is the upper potential, the upper switch circuit 13 and the upper second switch circuit 20 are turned on, and the lower switch circuit 14 and the lower second switch circuit 21 are turned off. . In this state, the upper common potential output circuit 11 and the output terminal 15 are connected, and the upper common potential is output to the output terminal 15.

  When the lower common potential is output next from this state, first, the upper switch circuit 13 and the upper second switch circuit 20 in the connected state are turned off. Next, the lower switch circuit 14 is turned on. At this time, after the potential is lowered by the lower prevention circuit 17, the second lower switch circuit 21 is turned on to prevent unnecessary electric potential from being applied to the lower common potential output circuit 12. Thus, the lower common potential output circuit 12 can be formed within a necessary power supply range.

  In order to output the upper common potential from this state, first, the lower switch circuit 14 and the lower second switch circuit 21 are turned off. Next, the upper switch circuit 13 is brought into a connected state. At this time, by setting the second upper switch circuit 20 in a connected state after the upper potential prevention circuit 16 has reached an appropriate potential, it is possible to prevent an unnecessary potential from being applied to the upper common potential output circuit 11. Thus, the upper common potential output circuit 11 can be formed in a necessary power supply range.

(Embodiment 4)
FIG. 4 shows the liquid crystal drive device of (Embodiment 4), and is between the output terminal 15 and the connection point between the output of the upper switch circuit 13 and the output of the lower switch circuit 14 of the conventional example shown in FIG. The only difference is that an appropriate potential setting circuit 22 is interposed.

  The appropriate potential setting circuit 22 switches the lower common potential output circuit 12 before switching the lower switch circuit 14 to the on state when the upper switch circuit 13 is switched to the off state and the lower common potential is output. In the case where the potential of the output terminal 15 is changed so as to be an appropriate potential for the switch, the lower switch circuit 14 is switched to the OFF state and the upper common potential is output, the upper switch circuit 13 is switched to the ON state before the switch The potential of the output terminal 15 is changed so as to be an appropriate potential for the common potential output circuit 11.

  The appropriate potential setting circuit 22 is the same as the upper power supply of the lower common potential output circuit 12 and the switch circuit 22a interposed between the lower potential power supply of the upper common potential output circuit 11 and the same potential 22b and the output terminal 15. The switch circuit 22d is interposed between the potential 22c and the output terminal 15.

  When the common potential supplied to the liquid crystal display panel is the upper potential, the upper switch circuit 13 is turned on and the lower switch circuit 14 is turned off. In this state, the upper common potential output circuit 11 and the output terminal 15 are connected, and the upper common potential is output to the output terminal 15.

  When the lower common potential is output next from this state, first, the upper switch circuit 13 in the on state is turned off. Next, the appropriate potential setting circuit 22 changes the potential of the output terminal 15 so as to be an appropriate potential for the lower common potential output circuit 12. Thereafter, by turning on the lower switch circuit 14, it is possible to prevent an unnecessary potential from being applied to the lower common potential output circuit 12, and the lower common potential output circuit 12 is formed in a necessary power supply range. It will be possible. Further, when the upper common potential is output from this state, first, the lower switch circuit 14 is turned off. Next, the potential of the output terminal 15 is changed by the appropriate potential setting circuit 22 so that the potential becomes appropriate for the upper common potential output circuit 11. Thereafter, by turning on the upper switch circuit 13, it is possible to prevent an unnecessary potential from being applied to the upper common potential output circuit 11, and the upper common potential output circuit 11 can be formed in a necessary power supply range. It becomes like this.

(Embodiment 5)
FIG. 5 shows the liquid crystal driving device of (Embodiment 5), and an upper MOS transistor 23 is interposed between the upper common potential output circuit 11 and the upper switch circuit 13 of the conventional example shown in FIG. Yes. The only difference is that a lower MOS transistor 24 is interposed between the lower common potential output circuit 12 and the lower switch circuit 14.

  When an unnecessary potential is applied to the upper common potential output circuit 11 and the lower common potential output circuit 12, an unnecessary potential is applied by turning off the upper MOS transistor 23 and the lower MOS transistor 24. Can be prevented.

  When the common potential supplied to the liquid crystal display panel is the upper potential, the upper switch circuit 13 is turned on and the lower switch circuit 14 is turned off. In this state, the upper common potential output circuit 11 and the output terminal 15 are turned on, and the upper common potential is output to the output terminal 15.

When the lower common potential is output next from this state, first, the upper switch circuit 13 in the on state is turned off. Next, the lower switch circuit 14 is turned on.
At this time, conventionally, there is a case where the upper common potential is temporarily applied to the lower common potential output circuit 12, but by utilizing the threshold voltage characteristics of the lower MOS transistor 24, the lower common potential is applied. It is possible to prevent the upper common potential from being applied to the output circuit 12, and the lower common potential output circuit 12 can be formed in a necessary power supply range.

  In order to output the upper common potential from this state, first, the lower switch circuit 14 is turned off. Next, the upper switch circuit 13 is turned on. At this time, the lower common potential may be temporarily applied to the upper common potential output circuit 11 in the prior art, but by utilizing the threshold voltage characteristics of the upper MOS transistor 23, the upper common potential output circuit 11 is used. 11 can be prevented from being applied with the lower common potential, and the upper common potential output circuit 11 can be formed in a necessary power supply range. Note that the gate voltages of the upper MOS transistor 23 and the lower MOS transistor 24 need to be appropriate potentials when the upper switch circuit 13 and the lower switch circuit 14 are in the ON state, respectively.

(Embodiment 6)
FIG. 6 shows the liquid crystal drive device of (Embodiment 6), and the source-drain of the upper MOS transistor 23 is interposed in place of the upper switch circuit 13 of the conventional example shown in FIG. The only difference is that the source / drain of the lower MOS transistor 24 is interposed in place of the lower switch circuit 14. In the liquid crystal driving device of (Embodiment 6), the gate potential of the MOS transistor of FIG. 5 is set to the off potential when it is necessary to turn off the upper switch circuit or the lower switch circuit. Thus, the upper switch circuit and the lower switch circuit can be deleted.

  When the common potential supplied to the liquid crystal display panel is the upper potential, the gate potential using the threshold voltage characteristic of the upper MOS transistor 23 is set so that an unnecessary potential is not applied to the upper common potential output circuit 11. A gate potential at which the lower MOS transistor 24 is turned off is applied. In this state, the upper common potential output circuit 11 and the output terminal 15 are turned on, and the upper common potential is output to the output terminal 15.

  When the lower common potential is output next from this state, first, a gate potential at which the upper MOS transistor 23 in the on state is turned off is applied. Next, by applying a gate potential using the threshold voltage characteristics of the lower MOS transistor 24 so that an unnecessary potential is not applied to the lower common potential output circuit 12, the lower common potential output circuit 12 is It becomes possible to make it in the necessary power supply range.

  When the upper common potential is output from this state, first, a gate potential at which the lower MOS transistor 24 is turned off is applied. Next, a gate potential utilizing the threshold voltage characteristics of the upper MOS transistor 23 is applied, and a gate potential at which the lower MOS transistor 24 is turned off is applied, whereby a lower common potential is applied to the upper common potential output circuit 11. By preventing this, the upper common potential output circuit 11 can be formed in a necessary power supply range. Note that the gate voltages of the upper MOS transistor 23 and the lower MOS transistor 24 are changed from the gate potential for using the threshold voltage to the respective MOS transistors when the output terminal 15 reaches an appropriate potential. It may be changed to the gate potential at which is turned on.

FIG. 2 is a main part configuration diagram of the liquid crystal driving device according to the first embodiment of the present invention. Configuration diagram of main part of liquid crystal driving device of (Embodiment 2) of the present invention Configuration diagram of main part of liquid crystal driving device of (Embodiment 3) of the present invention Main part configuration diagram of liquid crystal driving device of (Embodiment 4) of the present invention Configuration diagram of main part of liquid crystal driving device of (Embodiment 5) of the present invention Structure diagram of main part of liquid crystal drive device according to (Embodiment 6) of the present invention Configuration diagram of conventional liquid crystal drive device

Explanation of symbols

11 upper common potential output circuit 12 lower common potential output circuit 13 upper switch circuit 14 lower switch circuit 15 output terminal 16 upper prevention circuit 17 lower prevention circuit 18 upper common potential output circuit 19 lower common potential output circuit 20 upper second 2 switch circuit 21 lower second switch circuit 22 appropriate potential setting circuit 23 upper MOS transistor 24 lower MOS transistor

Claims (6)

A liquid crystal driving device that switches an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel,
Connect the output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel via the upper switch circuit that is turned on when the upper common potential is supplied,
Connect the output of the lower common potential output circuit and the common potential output terminal via the lower switch circuit that is turned on when the lower common potential is supplied,
An upper prevention circuit that is temporarily turned off when the lower switch circuit is turned off and the upper switch circuit is turned on is provided between the output of the upper common potential output circuit and the upper switch circuit. Intervening,
A lower prevention circuit that is temporarily turned off when the upper switch circuit is turned off and the lower switch circuit is turned on. The output of the lower common potential output circuit and the lower switch circuit Liquid crystal driving device interposed between the two. Between the upper common potential output circuit and the upper prevention circuit, an upper delay circuit that delays the propagation of voltage from the upper prevention circuit to the upper common potential output circuit is interposed,
The lower delay circuit which delays the propagation of the voltage concerning the said lower common potential output circuit from the said lower side prevention circuit between the said lower side common potential output circuit and the said lower side prevention circuit is interposed. Liquid crystal drive device. Between the upper common potential output circuit and the upper prevention circuit, an upper second switch circuit that switches to the on state after the output of the upper prevention circuit returns to the on state is interposed,
2. The lower second switch circuit that is switched between the lower common potential output circuit and the lower prevention circuit is switched on after the output of the lower prevention circuit returns to the on state. Liquid crystal drive device. A liquid crystal driving device that switches an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel,
Connect the output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel via the upper switch circuit that is turned on when the upper common potential is supplied,
Connect the output of the lower common potential output circuit and the common potential output terminal via the lower switch circuit that is turned on when the lower common potential is supplied,
When outputting the lower common potential by switching the upper switch circuit to the OFF state between the connection point between the output of the upper switch circuit and the output of the lower switch circuit and the common potential output terminal, When switching the output terminal potential so that it is appropriate for the lower common potential output circuit before switching the side switch circuit to the ON state, and switching the lower switch circuit to the OFF state and outputting the upper common potential In addition, a liquid crystal driving device provided with an appropriate potential setting circuit for changing the potential of the output terminal so that the potential becomes an appropriate potential for the upper common potential output circuit before the upper switch circuit is turned on. A liquid crystal driving device that switches an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel,
Connect the output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel via the upper switch circuit that is turned on when the upper common potential is supplied,
Connect the output of the lower common potential output circuit and the common potential output terminal via the lower switch circuit that is turned on when the lower common potential is supplied,
Between the output of the upper common potential output circuit and the upper switch circuit, the threshold voltage characteristic of the MOS transistor is used when the lower switch circuit is turned off and the upper switch circuit is turned on. And an upper MOS transistor for preventing application of overvoltage to the upper common potential output circuit,
Between the output of the lower common potential output circuit and the lower switch circuit, the threshold voltage characteristics of the MOS transistor at the timing when the upper switch circuit is turned off and the lower switch circuit is turned on. A liquid crystal driving device including a lower MOS transistor that prevents overvoltage from being applied to the lower common potential output circuit by using the above-described circuit. A liquid crystal driving device that switches an upper common potential generated from an upper common potential output circuit and a lower common potential generated from a lower common potential output circuit and supplies the same to a liquid crystal display panel,
The output of the upper common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via an upper MOS transistor,
The output of the lower common potential output circuit and the common potential output terminal to the liquid crystal display panel are connected via a lower MOS transistor,
A liquid crystal driving device configured to switch between the upper MOS transistor and the lower MOS transistor to switch between an upper common potential and a lower common potential and to supply the same to the common potential output terminal.

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