JPS60212734A - Driving circuit for liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device having high quality, which does not generate an uneven display at all by constituting an operational amplifier so that its saturation in scarcely generated, and obtaining a voltage value determined by a division ratio of a resistance. CONSTITUTION:Two diodes D1, D2 are connected in series, respectively, to both end sides of a group of resistances R1-R5 connected in series between input terminals I1, I2 to which two kinds of power supply voltages VDD, VD are applied. In this state, a voltage V1 and a voltage V6 are obtained from a connecting point of a diode D1 and the resistance R1, and a connecting point of a diode D2 and the resistance R5, respectively. According to such constitution, a voltage which has added a forward voltage of the diode D1 is applied between a power source of an operational amplifier A1 and a voltage V2, and in the same way, a voltage which has added a forward voltage of the diode D2 is applied between a power source of an operational amplifier A4 and a voltage V5, therefore the saturation of the operational amplifiers A1, A4 is scarcely generated.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a driving circuit for a liquid crystal display device, and particularly relates to a driving circuit for a liquid crystal display device.
I suitable for preventing display unevenness due to voltage fluctuations
It's related to power supply circuits.

[Background of the invention]

When a liquid crystal display device is time-divisionally driven using, for example, six different levels of voltage, a circuit shown in FIG. 1 is used as a power supply circuit for generating the six levels of voltage. That is, in the same figure, five voltage dividing resistors RJ and Rx are connected between the inputs 11+b to which two types of power supply voltages VDD and VD having different voltage values are applied.
, R3, R4, and R5, and four operational amplifiers A+, A2. A2, A4 y(
Connect each to its output terminal σI + 02 rαI
+ 04 + Os + 06 are six types of voltage Vl whose output voltage values are sequentially different from each other.

A power supply circuit that generates VB, Va + V4 r v51 v was used.

However, the power supply circuit configured in this way connects the ll sources of the operational amplifiers A+ to A4 to the voltage VDD (Vl).
and Vn (Vs), so when voltages V2 and v6 are close to voltages 1 and v6, respectively, operational amplifiers A1 and A that generate voltages V2 and Vae
4 becomes saturated and the voltage value deviates from the voltage value determined by the division ratio of the resistors R1 to R-, causing display unevenness.

To improve this problem, some methods have been proposed, such as omitting the operational amplifier or adding two dedicated power supplies for the operational amplifier. However, the former method This increases impedance and causes a different type of display unevenness from that described above. In addition, the latter requires two types of external power supplies separately, and a 4'M1 type power supply is required externally as a whole, resulting in an increase in system cost.

[Purpose of the invention]

Therefore, the present invention was made in view of the above-mentioned problems, and its purpose is to prevent the occurrence of display unevenness by making it difficult for the operational amplifier to saturate and obtaining a voltage value determined by the division ratio of the resistors. The present invention is to provide a driving circuit for a liquid crystal display device.

[Summary of the Invention] In order to achieve such an object, the present invention uses two types of power supplies with different voltage values, and the voltage value applied to the voltage dividing resistor and the voltage value applied to the operational amplifier are made different. It comes out.

[Examples of invention]

FIG. 2 is a diagram 69 of a power supply circuit showing an example of a driving circuit for a liquid crystal display device according to the present invention, and the same parts as those in the previous figure are given the same reference numerals. In the figure, two types of power supply voltages VDD *
Two diodes D1. DI are connected in series, and a voltage V1 is applied from the connection point between diode D and resistor R1:, diode D! A voltage v6 is obtained from the connection point between the resistor R1 and the resistor R1.

According to such a configuration, a voltage obtained by adding the forward voltage of the diode D1 is added between the power supply of the operational amplifier AI and the voltage v6, and the voltage V6 is similarly applied between the power supply of the operational amplifier AI and the voltage v6.
Diode D between! Since a voltage that is the sum of the forward voltages of is applied, saturation of the operational amplifier AI+A4 is less likely to occur. Since such a circuit configuration can be constructed by simply adding two diodes Dr and Ihk to a conventional circuit, there is no significant increase in cost. Moreover, when this power supply circuit is viewed from the outside as a black box, it is equivalent to the conventional example, and the system compatibility is good.

In addition, in the above embodiment, the case where two diodes were added was explained, but the present invention is not limited to this, and a resistor or a transistor may be used, and a combination of these may also be used as described above. Of course, similar effects can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, saturation of the operational amplifier is made difficult to occur and a voltage value determined by the division ratio of the resistors is obtained, so that a high-quality liquid crystal display without any display unevenness can be obtained. It has extremely good effects.

[Brief explanation of drawings]

Figure 1 is a power supply circuit diagram of a conventional drive circuit for a liquid crystal display device.
FIG. 2 is a power supply circuit diagram showing an example of a drive circuit for a liquid crystal display device according to the present invention. I r, I @ @ 6 M-6 input terminal, IRI
, Rg. fl s, fl4. fl, sa * m e resistance,
AI, AI. As, As...working operational amplifier, 0凰, 02. Os 104 101 , o, ...output terminal.

Claims (1)

[Claims] It is constructed so that n resistors are connected in series between two types of power supplies with different voltage values, and n-1 operational amplifiers are connected to each connection point of the resistors to obtain voltages with n+1 different voltage levels. A driving circuit for a liquid crystal display device, characterized in that an element that generates a potential difference is connected between the two types of power supplies and resistors at both ends of the resistors connected in series.