JPH02210492A - Liquid crystal display driving device - Google Patents

Abstract

PURPOSE:To easily reduce electric power consumption without deteriorating the characteristics of the liquid crystal display element by providing the power source of the driving circuit of the liquid crystal display element with plural pieces of bidirectional transfer gates and adding a function to stop the clock signal of the liquid crystal display element. CONSTITUTION:Both bidirectional transfer gate circuits 20, 21 conduct and a clock phiLCD for a liquid crystal operates when the standby signal generated in the internal circuit of an integrated circuit device or inputted from an external terminal is a VSS level. The liquid crystal display element makes an ordinary operation of non-lighting when segment data is the VSS level and of lighting at a VDD level. The liquid crystal driving clock phiLCD stops and both the bidirectional transfer gate circuits 20, 21 become non-conducting when the standby signal attains the VDD level and, therefore, the power source for driving the liquid crystal is not supplied and the output attains a high impedance state. The standby function is easily realized in this way without deteriorating the characteristics of the liquid crystal display element and the electric power consumption is reduced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a driving device for a liquid crystal display element.

(Prior Art) In recent years, the number of electronic devices using liquid crystal display elements, including desk-top computers, has increased, and since dry batteries are often used as a power source for these devices, it is desired to reduce the power consumption of the devices.

FIG. 3 shows a conventional integrated circuit device that directly drives a liquid crystal display element. However, the driving method for the liquid crystal display element is a general static method.

In FIG. 3, 1 and 2 are P-channel MOS transistors, 4 and 5 are N-channel M, OS transistors, 10 is an EX, -NOR circuit, 30 is a liquid crystal common electrode drive circuit, and 31 is a liquid crystal segment electrode drive circuit. It is.

FIG. 4 shows a timing chart of drive signals for a liquid crystal display element during lighting and non-lighting in a conventional example.

Next, the operation of the above conventional example will be explained. In FIG. 3, the clock input terminal φL'CD is used as a gate input, and the power supply terminal V. I, and ground V S , between P channel M
OS transistor] and an N-channel MOS transistor 4 are connected in series to form a so-called liquid crystal common electrode drive circuit 30.
Then, the output signal terminals CO, , I are taken out from the connection point where the drains of the MO5I transistors are shared. In addition, the clock input terminal φ1. A separate circuit configured similarly to the liquid crystal common electrode drive circuit 30 is provided, and the output of the EX-NOR circuit 10 whose input terminals are C11 and display data input is connected to the common gate of the liquid crystal segment. An electrode drive circuit 31 is configured, and its output terminal is designated as S Out.

φ1. . 0 is a drive clock signal for a liquid crystal display element obtained by frequency-dividing the clock input terminal of an integrated circuit device or a signal from a clock oscillation circuit, and the display data signal is at the power supply voltage V p 11 level when lighting a segment electrode, and is non-active. When lit, it is at V 3 B level. As shown in FIG. 4, when the display data D is at the VSS level, the signal output from the output terminal C01 of the liquid crystal common electrode drive circuit 30 and the output terminal S of the liquid crystal segment drive circuit 31. The signal output of ut becomes the same, and the potential difference between the common electrode and the segment electrode of the liquid crystal display element becomes ◯, so that the liquid crystal display element is not lit.

Next, when the display data D is at the vDD level, the output terminal C8U and the output terminal S are output. ut becomes the signal output of the opposite phase,
The potential difference between the common electrode and the segment electrode of the liquid crystal display element becomes the power supply voltage ■Dllll, and the device is turned on.

(Problems to be Solved by the Invention) However, in the conventional liquid crystal display driving device described above, the clock signal for driving the liquid crystal display element is constantly in operation, so the device consumes a lot of power. In order to achieve this, if the clock signal is stopped when the segment lights up,
There was a problem that the characteristics of the liquid crystal display element deteriorated. For this reason, a clock signal is required even in a standby state or when a liquid crystal display is not required, making it unsuitable for electronic devices where low power consumption is desired.

The present invention solves the above-mentioned conventional problems, and aims to provide a liquid crystal display driving device that easily realizes lower power consumption without deteriorating the characteristics of the liquid crystal display element. .

(Means for solving the problem) In order to achieve the above object, the present invention has a plurality of bidirectional transfer gates in the power supply of the drive circuit of the liquid crystal display element, and stops the clock signal of the liquid crystal display element. It has the added function of

(Function) Therefore, according to the present invention, the bidirectional transfer circuit 1 to the power supply for driving the liquid crystal display element is made non-conductive by the standby control signal in the device, so that the power supply for driving the liquid crystal display element is made non-conductive. Since the outputs of all output terminals are in a high impedance state, it is possible to stop the drive clock signal for the liquid crystal display element without degrading the characteristics of the liquid crystal display element, which makes it easy to reduce power consumption. has.

(Example) FIG. 1 shows a circuit showing one embodiment of the present invention.

@I M, 1, 2 and 3 are P channel M
O8+- transistor, 4, 5 and 6 are N channel M
OS transistor, 10 is EX, -NOR circuit,
11 is an OR circuit, 12 is an inverter circuit, and 20 is a bidirectional transfer gate circuit consisting of a P-channel MOS transistor whose source and substrate are connected to a power supply terminal VD. Reference numeral 21 denotes a bidirectional transfer gate circuit, which is composed of an N-channel MOS transistor whose source and substrate are connected and which are connected to ground terminals (2) and (8).

Reference numeral 30 denotes a liquid crystal common electrode drive circuit, in which the drain of a P-channel MOS transistor 1 whose respective gates are commonly connected, and the N-channel MOS transistor 08 whose source and substrate are commonly connected.
It is connected to the drain of the L-transistor 4, and the connection point is used as an output terminal CoU, which is used to output a common electrode drive signal for the liquid crystal display element.

31 is a liquid crystal segment electrode drive circuit, which is used by connecting the output of the EX, -NOR circuit 10 to a common gate of a circuit having the same configuration as the liquid crystal common electrode drive circuit 30. 32 is a frequency dividing circuit.

The liquid crystal common electrode drive circuit 30.21 is connected to the bidirectional transfer gate circuit 20.21, respectively. It is connected to the sources of the P-channel MOS transistors 1 and 2 of the liquid crystal segment 1 to the electrode drive circuit 31 and the sources of the N-channel MOS transistors 4 and 5, and a standby signal is transmitted directly or via the inverter 12 to the bidirectional transfer gate circuit 20. .21 P
Channel MO8I-Rangemetal 3. N channel MO
It is connected to each gate of the 3+- range terminal, and also inputs the standby signal and the input signal φ to the OR circuit 11, and performs the OR circuit.
The output of the circuit 11 is connected as an input to a frequency dividing circuit 32, and the output of the frequency dividing circuit 32 is connected to the common gate of the liquid crystal common electrode driving circuit 30 and one input of the EX-NOR circuit 10. ing.

FIG. 2 is a diagram showing the timing of this embodiment.

Next, the operation of the above embodiment will be explained. In FIG. 1, when the standby signal generated in the internal circuit of the integrated circuit device or inputted from the external terminal is at the vss level, the bidirectional transfer circuits 1 and 20 and 21 are both conductive, and the liquid crystal clock φ1. cn works. As shown in FIG. 2, when the segment data D is at the V55 level, the liquid crystal display element does not light up, and when the segment data D is at the V n n level, it performs the normal operation of lighting. Next, when the standby signal reaches VDD level,
The liquid crystal drive clock φLCD is stopped by the OR circuit 11 in the liquid crystal clock generation source, and both the bidirectional transfer gate circuits 20 and 21 become non-conductive, so the liquid crystal drive power supply Vr+n+tcn+ + V5sLtcn+ is not supplied and output. becomes a high impedance state.

In this embodiment, a static driving method is used for the liquid crystal display element, but it goes without saying that the present invention can also be applied to a dynamic driving method, which is often used as a power source for liquid crystals.

The configuration of the bidirectional transfer gate circuit may be a circuit configuration in which P-channel MO8+- transistors and one N-channel MOS transistor are connected in parallel in consideration of the substrate bias effect. It goes without saying that stopping the liquid crystal driving clock source can also be applied to self-excited oscillation circuits such as crystal oscillation circuits.

(Effects of the Invention) As is clear from the above embodiments, the present invention can easily realize a standby function without deteriorating the characteristics of the liquid crystal display element even if the driving clock oscillation of the liquid crystal display element is stopped.
This has the effect of reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a liquid crystal display driving device according to an embodiment of the present invention, FIG. 2 is a timing diagram of the embodiment of FIG. 1, FIG. 3 is a circuit diagram of a conventional liquid crystal display driving device, and FIG. 4 is a timing diagram of the conventional example shown in FIG. 1.2.3 ・P channel Mos+ ~ transistor,
4,5.6...N-channel MOS transistor,
10...EX, -N OR circuit, 11 ・O
R circuit, 12... Inverter circuit, 20.21...
Bidirectional transfer gate circuit, 30...Liquid crystal common electrode drive circuit, 31...Liquid crystal segment electrode drive circuit, 32...
・Frequency divider circuit. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] The output of the OR circuit that inputs and connects the input signal and standby signal is connected to a frequency dividing circuit, and the output of the frequency dividing circuit is connected to the drain of the P channel MOS transistor and the N channel M
A common electrode drive signal is connected to the drain of the OS transistor and has a common gate, and is connected to the common gate of the first output drive circuit of a so-called common electrode drive signal, and has the same configuration as the first output drive circuit. An exclusive OR inverting circuit (EX-NOR) whose output side is connected to a common gate of a second output drive circuit having a data input terminal and a separate input terminal, and a power supply terminal and The sources and ground terminals of the P-channel MOS transistors of the first and second output drive circuits are connected via transfer gates between the N-channel MOS transistors of the first and second output drive circuits, and A liquid crystal display drive device characterized by having a configuration in which a gate is turned on and off by a standby signal.