JP3282703B2 - Drive circuit for liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a liquid crystal display device which supplies a plurality of gradation voltage levels to a liquid crystal display device capable of multi-gradation display and performs display according to the gradation voltage levels. is there.

[0002]

2. Description of the Related Art A driving circuit of a conventional liquid crystal display device is shown in FIG.
It is configured as shown in FIG. In the figure, reference numeral 101 denotes an AC signal, and the AC signal 101 is generated by a timing generation circuit (not shown) or the like. 10 is a brightness adjustment circuit, 102 and 104 are resistors, 103 is an operational amplifier, and 105 is a variable resistor. These resistors 102 and 104, the operational amplifier 103, and the variable resistor 105
This constitutes a brightness adjustment circuit. 11
1 to 115 are voltage-dividing resistors for generating gradation voltage levels;
Is a voltage follower circuit, 121 to 125 are high-throughput operational amplifiers, 131 to 135 are output buffers,
41 to 150 are resistors, 151 to 155 are capacitors,
V _{1 to} V ₅ are gradation voltage levels. These high throughput operational amplifiers 121 to 125 and output buffers 131 to 1
35, resistors 141 to 150 and capacitors 151 to 1
55 constitutes the voltage follower circuit 11.

An AC signal 101 generated by a timing generation circuit or the like is amplitude-converted by a brightness adjustment circuit 10 and converted into a voltage level based on the resistance ratio of the voltage dividing resistors 111 to 115. Thereafter, gradation voltage levels V _{1 to} V ₅ are generated by the voltage follower circuit 12 and supplied to the liquid crystal display device.

[0004]

Since the conventional driving circuit of a liquid crystal display device is constructed as described above, an alternating signal must be processed by an operational amplifier, and an expensive operational amplifier with a high slew rate is required. Was needed. Also,
Brightness can be adjusted by adjusting the amplitude of the AC signal, and the amplitude of each voltage value (V _{1 to} V ₅ ) of many gradations can be changed according to the voltage dividing resistance ratio. As for the adjustment, it is necessary to change the voltage dividing resistance ratio in accordance with the adjustment, and there is a problem that the adjustment cannot be realized unless the circuit configuration is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A circuit can be formed without using an expensive high-slew-rate operational amplifier, and a brightness and contrast adjustment mechanism can be easily incorporated. It is an object of the present invention to provide a driving circuit of a liquid crystal display device which can perform the above.

[0006]

A drive circuit for a liquid crystal display device according to the present invention uses an addition / subtraction circuit for brightness adjustment and contrast adjustment, and divides a DC voltage to generate a gradation voltage level. It was made. Further, the driving circuit of the liquid crystal display device according to the present invention,
The AC conversion after the voltage division was performed using an analog switch. Further, this is performed by using a variable resistor or a fixed resistor as a means for generating a gradation voltage level.

[0007]

The driving circuit of the liquid crystal display device according to the present invention is
Since the brightness adjustment and the contrast adjustment are configured using the addition / subtraction circuit, the contrast adjustment can be easily performed, and the configuration is such that the voltage is divided into alternating currents, so that an operational amplifier with a high slew rate is not required.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a reference voltage adjusting mechanism including a transistor and a resistor; similarly, 2 denotes a brightness adjusting mechanism, 3 denotes a contrast adjusting mechanism, and 101 denotes a contrast adjusting mechanism.
Is an AC signal generated by a timing generation circuit or the like;
11 to 124 are voltage dividing resistors for generating a gradation voltage level;
Reference numeral 4 denotes an addition / subtraction circuit for performing addition and subtraction. The addition / subtraction circuit 4 includes operational amplifiers 401 and 402,
403 and 404 are provided. 201-20
8 analog switch, v ₀₁ to v ₁₆ DC gray scale voltage level generated by dividing, 131-138 output buffer, V ₁ ~V ₈ is supplied to the liquid crystal display device for driving the liquid crystal display device This is the gradation voltage level.

The operational amplifier 401 adds a DC voltage value B set by the brightness adjustment mechanism 2 to a DC voltage value A set by the reference voltage adjustment mechanism 1.
The current and voltage values v ₀₁ and v ₁₆ are generated by subtraction by the operational amplifier 404. Further, the DC voltage value C set by the contrast adjustment mechanism 3 is subtracted from the DC voltage value v ₀₁ in the operational amplifier 402 to generate a DC voltage value v ₀₈ , and the DC voltage value C is converted in the operational amplifier 403 into the DC voltage value It is added to the voltage value v ₁₆ generates a DC voltage value V _09. The DC voltage values v ₀₁ , v ₀₈ , v ₀₉ , and v ₁₆ generated by the reference voltage adjustment mechanism 1, the brightness adjustment mechanism 2, the contrast adjustment mechanism 3, and the addition / subtraction circuit 4 are used as divided reference voltage values, DC voltage values v _{02 to} v ₀₇ and v according to the respective resistance ratios are set by the voltage dividing resistors 111 to 124.
_{10 ~v 15} is generated. From the DC voltage values v _{01 to} v ₁₆ generated according to the resistance ratios of the voltage dividing resistors 111 to 124, two DC voltage values are converted to the analog switches 201 to 20.
The switching is performed by 8 and the exchange is performed. An AC signal 101 generated by a timing generation circuit or the like is used for switching the analog switches 201 to 208.
The converted gray scale voltages V _{1 to} V ₈ are output to the output buffer 131.
138 to the liquid crystal display device.

[0010]

As described above, the drive circuit of the liquid crystal display device of the present invention uses the addition / subtraction circuits for brightness adjustment and contrast adjustment, respectively, and divides a DC voltage to generate a gradation voltage level. Therefore, a driving circuit having a simple configuration is provided.

Further, in the driving circuit of the liquid crystal display device according to the present invention, since the AC after the voltage division is performed by using the analog switch, a high slew rate operational amplifier is not required.
There is an effect that an inexpensive driving circuit for a liquid crystal display device can be obtained.

Further, the number of gradations can be easily increased with the same circuit configuration simply by increasing the number of voltage dividing resistors such as variable resistors or fixed resistors and the number of analog switches as means for generating the gradation voltage level.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a driving circuit of a liquid crystal display device according to the present invention.

FIG. 2 is a circuit diagram showing a driving circuit of a conventional liquid crystal display device.

[Explanation of symbols]

1 Reference voltage adjustment mechanism, 2 Brightness adjustment mechanism, 3
Contrast adjustment mechanism, 4 addition / subtraction circuit, 10
Brightness adjustment circuit, 11 voltage follower circuit, 101 AC signal, 102, 104 resistor, 1
03 Operational amplifier, 105 Variable resistor, 111 to 11
5 Voltage divider, 121-125 High-throughput operational amplifier, 131-135 Output buffer, 141-15
0 resistor, 151-155 capacitor.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-310919 (JP, A) JP-A-5-19232 (JP, A) JP-A-5-53534 (JP, A) 226422 (JP, A) JP-A-3-230116 (JP, A) JP-A-4-269708 (JP, A) JP-A-3-8319 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 520 G02F 1/133 575 G09G 3/36

Claims (3)

(57) [Claims] 1. A reference voltage adjusting mechanism for setting a first DC voltage value, a brightness adjusting mechanism for setting a second DC voltage value, a contrast adjusting mechanism for setting a third DC voltage value, and the reference voltage adjusting mechanism. By adding or subtracting the first DC voltage value set by the above, the second DC voltage value set by the brightness adjustment mechanism, and the third DC voltage value set by the contrast adjustment mechanism. An adding / subtracting circuit for generating a divided reference voltage value; and a gradation signal generating means for dividing the divided reference voltage value from the adding / subtracting circuit to generate a gradation voltage level. Drive circuit for liquid crystal display. 2. The drive circuit for a liquid crystal display device according to claim 1, further comprising an analog switch for switching and outputting a gray scale voltage level generated by the gray scale signal generation means as an output signal. 3. The liquid crystal according to claim 1, wherein the gray scale signal generating means for generating the gray scale voltage level by dividing the divided reference voltage value is a variable resistor or a fixed resistor. A driving circuit of a display device.