JP3237231B2 - LCD drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC for electronic equipment.
The present invention relates to an LCD drive circuit used for driving a D display device.

[0002]

2. Description of the Related Art Conventionally, an LCD display device has been widely used in electronic equipment. To drive the LCD display device, a microcomputer having a built-in LCD drive circuit or
An LCD drive IC was used.

Hereinafter, a conventional LCD drive circuit will be described with reference to the drawings. FIG. 4 shows a conventional LC.
3 shows a configuration of an LCD drive circuit when a D drive IC is used. In FIG. 4, 1 is "HIG
A microcomputer that performs “H” logic, “LOW” logic, and “high resistance” output, 2 is an LCD drive IC, and 3 is an LCD display device.

The operation of the LCD drive circuit configured as described above will be described below. The microcomputer 1 inputs data for LCD display to the LCD drive IC 2. The LCD drive IC 2 reads data from the microcomputer 1 and creates a waveform to be input to the LCD display device 3. At this time, for SEG1 to SEGn, “H
IGH ”logic or“ LOW ”logic, and CO
M1 and COM2 have waveforms as shown in FIG. By outputting the signal waveform generated by the LCD drive IC 2 to the LCD display device 1 as described above, the required display content is displayed on the LCD display device 1.

FIG. 5 is a diagram showing a configuration of a conventional LCD drive circuit when a microcomputer having a built-in LCD drive circuit is used. In FIG. 5, reference numeral 1 denotes a microcomputer having a built-in LCD drive circuit, and reference numeral 2 denotes an LCD display device.
The operation of the LCD drive circuit configured as described above will be described below.

[0006] As shown in FIG. 6, waveforms of SEG, COM1, and COM2 are generated by an LCD drive IC in which the microcomputer 1 is built. By outputting this waveform to the LCD display device 2, a required LCD display can be obtained.

[0007]

However, in the above configuration, when an LCD display device is used, some kind of LCD drive dedicated circuit is required, and an LCD drive IC or a microcomputer of a type having a built-in LCD drive circuit is required. Use becomes essential. As a result, the selection range of the microcomputer is limited, and the use of a microcomputer with an LCD drive circuit or an LCD drive IC increases costs.

The present invention has been made in view of the above-mentioned conventional technology, and provides a circuit capable of driving an LCD display device without using an LCD drive circuit built-in microcomputer and an LCD drive IC.

[0009]

In order to achieve this object, an LCD drive circuit according to the present invention comprises a circuit for generating a common input waveform for LCD drive by dividing a microcomputer output and a voltage resistance.

[0010]

According to the above configuration, an intermediate potential required for the LCD drive can be generated, and a common waveform for the LCD drive can be obtained by resistance division.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an LCD drive circuit in a case where "HIGH" logic, "LOW" logic and "high resistance" output are output as microcomputer outputs.

In FIG. 1, 1 is a microcomputer having "HIGH" logic output, "LOW" logic output and "high resistance" output, 2 is an LCD display device, and 3, 4, 5, and 6 are resistance division. Is a resistor for generating a midpoint potential.

The operation of the LCD drive circuit configured as described above will be described below. SEG1-SE
For Gn, the microcomputer output terminal is “HIGH”
Alternatively, when “LOW” is output, the LCD display device reads “HIGH” or “LOW” as it is. Next, the operation of COM which is a feature of the LCD drive circuit will be described. First, when COM1 is a “HIGH” logic output, the COM1 input of the LCD display device 2 is “HI”.
GH ". When COM1 has a “LOW” logic output, the COM1 input of the LCD display device 2 is “LOW”. Next, when COM1 has a “high resistance” output, the COM1 input of the LCD display device 2 has a voltage value obtained by dividing Vcc by the resistances of Ra and Rb. Here, when Ra = Rb,
The COM1 input of the LCD display device 2 has a voltage of 1/2 Vcc. Similarly, the COM2 input of the LCD display device 2 is set to “HIG”
H ", 1/2 Vcc and" LOW "can be obtained.

By controlling COM1 and COM2 as described above, an LCD display device control waveform as shown in FIG. 3 can be created, and a required display can be displayed on the LCD display device.

FIG. 2 is a diagram showing a second embodiment of the LCD drive circuit when the microcomputer has only "HIGH" logic output and "LOW" logic output. In FIG. 2, 1 is a microcomputer having "HIGH" logic output and "LOW" logic output, 2 is an LCD display device, 3 and 4 are inverter circuits, 5 and 6 are analog switches, 7, 8
And 9 are resistors for voltage division.

The operation of the LCD drive circuit configured as described above will be described below. SEG1-SE
As for Gn, the “HIGH” logic output “L
The "OW" logic output allows the LCD display device to be SEG1-SEG.
EGn reads “HIGH” and “LOW”.

Next, the operation of the common will be described with reference to FIG. When the COMA output of the microcomputer is "HIG
H ", when the COMB output is" HIGH ", the analog SW1 is ON, and since the output of the COMB is inverted and input to the SW2 control, the analog SW2 is OFF,
The output of MA is inverted by the inverter 2, and the connection point of the resistor Rc to the inverter 2 becomes “LOW”. Therefore L
COM1 input of CD display device is “HIGH” of COMA
, And the voltage divided by the resistor Rb and the resistor Rc is input to the COM2 input. At this time, if the resistance values of the resistor Rb and the resistor Rc are made equal, the COM2 input becomes 1/2 V
cc.

Next, the COMA output becomes "HIGH" output,
When the COMB output is a “LOW” output, the “LOW” output inverted by the inverter 2 appears at the connection point between the resistor Rc and the inverter 2. When the COMB output is "L"
OW ”, the analog SW1 is OFF, and the output of the inverter 1 is“ HIGH ”.
N. Therefore, the COM1 input of the LCD display device is
The voltage value is divided by the resistance Ra and the resistance Rb.
If the resistance values of the resistor Ra and the resistor Rb are equal, C
The OM1 input becomes 1/2 Vcc. The COM2 input reads the output "LOW" of the inverter 2. Similarly, when COMA is “LOW” logic and COMB is “HIGH” logic, the case where both COMA and COMB have “LOW” logic output can be considered.

FIG. 6 is a diagram showing input voltages of COM1 and COM2 with respect to outputs of COMA and COMB. By making the COM waveform as described above,
It can be displayed on a CD.

[0020]

As described above, according to the present invention, the "HIG
A microcomputer having a “H” logic output, a “LOW” logic output, and a “high resistance” output and a resistor for voltage division, or “HIG”
A microcomputer with a built-in LCD drive circuit or a dedicated LCD drive IC by a microcomputer having a logic output of "H" and a logic output of "LOW" and an LCD driver circuit composed of a logic circuit, an analog switch and a resistor for voltage division
The LCD can be driven without using the.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an LCD drive circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the LCD drive circuit.

FIG. 3 is a diagram showing an input signal waveform and an output logic of the LCD drive circuit.

FIG. 4 is a configuration diagram of an LCD drive circuit according to a conventional example.

FIG. 5 is a configuration diagram of the LCD drive circuit.

FIG. 6 is a diagram showing an example of a signal waveform input to the LCD drive circuit.

[Explanation of symbols]

 1 microcomputer 2 LCD display device 3 resistor 4 resistor 5 resistor 6 resistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 520 G09G 3/36

Claims (2)

(57) [Claims] A microcomputer having "HIGH" logic output, "LOW" logic output and "high resistance" output, and an LCD display
In LCD drive circuit constituted by, double for making neutral potential of the voltage source Vcc by resistance division
A first series resistor group consisting of a number of resistors and a second series resistor.
Have anti-group, the common first microcomputer output terminal of the first series resistor group 1
The common 2 of the microcomputer output terminal is connected to the second series resistor
The common 1 of the LCD display is connected to the second node of the resistor group , respectively, and is connected to the first node of the first series resistor group.
In point, another common input, common 2, is connected to the second series resistor.
Connected to the second node of the anti-arm, and the microcomputer output terminal outputs “HIGH” or “LOW”.
Input, the common input on the LCD display is
Reads "GH" or "LOW" and when the microcomputer output terminal outputs "high resistance", LCD display
Are connected to the first and second series resistors.
LC wherein a voltage divided by a group is input
D drive circuit. 2. A microcomputer having a "HIGH" logic output and a "LOW" logic output, and an LCD display.
Control by the signal input to the control terminal in the LCD drive circuit
And a plurality of resistors for voltage division connected in series, and one end of a series resistor group consisting of the plurality of resistors is connected to a microcomputer.
To the common A of the power terminal, and the other end via the second inverter
The control terminal of the first analog switch is connected to the common A of the microcomputer output terminal.
The output terminal is connected to the common B, and the control terminal of the second analog switch is connected to the second input terminal.
Connected to the common B of the microcomputer output terminal via the inverter.
The common 1 among the plurality of common inputs of the LCD display is
At the first node of the series resistor group, another common input,
Mon 2 is connected to each of the second nodes of the series resistance group.
And the first analog switch is the input of its control terminal
The first node of the series resistor group and the series resistor group
To an end on the side connected to the common A so that it can be short-circuited.
It is continued, the second analog switch inputs of the control terminal
A second node of the series resistance group and the series resistance group
Of the other end, that is, the side connected to the second inverter
LCD characterized in that it is short-circuited to the end.
Drive circuit.