JPH05341731A - Liquid crystal driver circuit - Google Patents

Abstract

PURPOSE:To provide a liquid crystal driver circuit which can obtain more kinds of output reference voltage with fewer kinds of input reference voltage and output control circuits. CONSTITUTION:Reference voltage V1-V3 are binary signals, and signals of which shapes of waveform such as pulse width, timing, and the like are different. These reference voltage V1-V3 are controlled for passing through AND circuits 11-13 by a H/L signal voltage level of control data D1-D3. The single or plural reference voltage passing through the AND circuits 11-13 are made a signal A in a OR circuit 14. The signal A is made a direct current signal B in a rectifier circuit 15, and outputted as a signal O via a buffer amplifier 16. A voltage level of the outputted signal O is proportional to area per unit hour of the signal A, and its value is varied depending on selection and combination of the reference voltage V1-V3. By using this liquid crystal driver circuit, a variation value of output reference voltage increases theoretically and exponentially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driver circuit used in a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, for example, in the case of an 8-gradation digital type liquid crystal driver output circuit, eight analog switches are provided and eight different reference voltages are input to the inputs of the analog switches to turn on / off each analog switch. By controlling the OFF state and selecting one of the reference voltages, a total of eight types of voltages were output to the output stage.

[0003]

According to the circuit structure of the prior art, an analog switch corresponding to the number of gradations is required,
When the number of gradations is increased, the reference voltage and the number of analog switches are increased, and there is a problem that the current consumption and the integrated chip size are increased due to the increase in the number of circuits.

An object of the present invention is to solve the above problems and to provide a highly efficient liquid crystal driver circuit which realizes more gradations with a small number of circuits without increasing the number of analog switches.

[0005]

A liquid crystal driver circuit for displaying and driving a liquid crystal panel of the present invention in multiple gradations includes a gate circuit for individually controlling passage of a plurality of pulse signals, and at least one gate circuit passing through the gate circuit. And a rectifier circuit that smoothes the pulse signal.

Further, a liquid crystal driver circuit for driving a liquid crystal panel to display in multiple gradations includes a switch circuit for individually controlling passage of a plurality of input reference voltages having different voltage values, and at least one input reference voltage passing through the switch circuit. And means for outputting the average value of.

[0007]

As described above, according to the liquid crystal driver circuit of the first aspect of the invention, the passage of a plurality of different types of pulse signals is individually controlled using the gate circuit, and the passed pulse signals are ORed. Are integrated into one signal by. The aggregated signal is smoothed by the rectifier circuit to be an output signal.

Further, according to the liquid crystal driver output circuit of the second invention, conduction of a plurality of types of reference voltages is controlled, and an average of a single signal or a plurality of signals passing through the gate circuit is output as an output signal.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a first embodiment of the liquid crystal driver circuit of the present invention, FIG. 2 shows the signal waveform of each part on the circuit of FIG. 1, and FIG. 3 shows the relationship between control data and output signals.

The liquid crystal driver circuit of FIG. 1 has three ANDs.
Circuits 11, 12 and 13, OR circuit 14, rectifier circuit 1
5 and a buffer amplifier circuit 16. The input terminals a, b and c of the circuit are reference voltages V1 and V2.
, V3 are input terminals, terminals i, j and k are input terminals for control data D1, D2 and D3, and terminal O is an output terminal of this circuit.

An example of signal generation of the liquid crystal driver circuit having the above circuit configuration is shown in FIG. The reference voltages V1, V2 and V3 applied to the input terminals a, b and c are pulse signals as shown in FIG. The control signals represented in FIG. 2 are D1 = 1, D2 = 0, D3, respectively.
= 1 and the two reference voltages V1 and V3 pass through the AND circuits 11 and 13 and are combined by the OR circuit 14 and output. The output signal A of the OR circuit 14 is smoothed by the rectifier circuit 15 into a DC signal B, which is input to the buffer amplifier circuit 16. Input signal B that has passed through the buffer amplifier circuit 16
Becomes an output signal O having the same voltage level as the input signal.

FIG. 2 shows an example of the input / output relationship of FIG. 1 together with the intermediate points A and B in detail. FIG. 3 shows a list of all combinations of input / output relationships. As shown in the table of FIG. 3, according to this circuit, eight kinds of output signals Va 'to Vh are provided by three control signals D1, D2 and D3.
´ can be obtained.

FIG. 4 shows a second embodiment of the liquid crystal driver circuit according to the present invention, which is a liquid crystal driver circuit of 15 gradation digital system. FIG. 5 is a logic table showing the input / output relationship of the circuit of FIG. The liquid crystal driver circuit shown in FIG.
0, analog switches 41 to 48, and a buffer amplifier circuit 49. 8 types of terminals a to
h is an input terminal for reference voltages V1 to V8
Reference numeral 1 represents an input terminal for the control data D1 to D4, and terminal O represents an output terminal of this circuit.

The control circuit 40 is a unit for generating a control signal based on the data structure of the control data D1 to D4, and the signal causes the input / output of the analog switches A1 to A8 to be turned on.
/ OFF is controlled. In this embodiment, the resistance between the input and output of the analog switches A1 to A8 is a value that can be ignored with respect to the input impedance of the buffer circuit 49.

Reference voltages V1 to V8 having different voltage values are input to the input terminals a to h of FIG. The reference voltage V1 which is turned on by the control of the analog switches A1 to A8
V8 is input to the buffer circuit, current amplified, and output to the output terminal O. The relationship between the input and output signals is determined by the configuration of the control circuit 40 as described above, and is configured as shown in FIG. 5 in the embodiment.

According to the circuit configuration of the present invention, the same number of analog switches as in the prior art is used, and the conventional 8 gradations are changed to 1
A liquid crystal driver circuit with 5 gradations can be obtained. In the above two embodiments, the ON control between the input and output of the reference voltage is set to 1 or 2, but it is also effective to add 3 or more simultaneous ON controls. Although the OR circuit is used for the circuit that uses a plurality of types of input signals as one output signal, other circuits such as an AND circuit and an adder circuit can be used, and a plurality of types of circuits can be used together with the selection circuit. Is also effective. According to the various types of gate control, the types of reference voltages obtained can be increased, and the efficiency of the circuit configuration can be further improved.

[0017]

The liquid crystal driver circuit of the present invention has more input reference voltages, a gate circuit or a switch circuit for controlling the passage to the output circuit, and the like, as compared with the same type of circuit based on the prior art. It is possible to obtain the following types of output reference voltages. Therefore, it is possible to improve the efficiency such as the chip size of the drive circuit, the device cost, and the current consumption with respect to the number of gradations for driving the liquid crystal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a liquid crystal driver circuit of the present invention.

FIG. 2 is a timing chart of signals in the circuit of FIG.

FIG. 3 is a diagram showing a list of output signals with respect to control input signals in the circuit of FIG. 1 together with signals at intermediate points.

FIG. 4 is a circuit diagram showing a second embodiment of the liquid crystal driver circuit of the present invention.

5 is a diagram showing a list of output signals with respect to control input signals in the circuit of FIG.

[Explanation of symbols]

 11, 12, 13 AND circuit 14 OR circuit 15 Rectifier circuit 16 Buffer amplifier circuit

Claims (2)

[Claims] 1. A liquid crystal driver circuit for displaying and driving a liquid crystal panel in multiple gradations, comprising: a gate circuit which individually controls passage of a plurality of pulse signals; and at least one pulse signal which has passed through the gate circuit is smoothed. A liquid crystal driver circuit having a rectifying circuit for converting into a liquid crystal. 2. A liquid crystal driver circuit for driving a liquid crystal panel to display in multiple gradations, comprising a switch circuit for individually controlling passage of a plurality of input reference voltages having different voltage values, and at least one switch circuit passing through the switch circuit. And a means for outputting an average value of two input reference voltages.