Nec Corporation

Sei Saitoh

Hiroshi Shiba

Kohei Matsuda

A driver circuit to drive a display by inverting the voltage polarity operates with a reduced power consumption. The driver circuit includes a driving voltage selector circuit including positive and negative driving voltage selector circuits alternately arranged therein and a circuit which conducts a change-over operation between a state in which signals respectively from the positive and negative driving voltage selector circuits are respectively outputted to first and second terminals in a first horizontal period and a state in which signals respectively from the positive and negative driving voltage selector circuits are respectively sent to second and first terminals in a second horizontal period.

Driver circuit for driving liquid-crystal display

In a driving circuit for a multiple gray scale liquid crystal device, the least significant half of a given image data is decoded by a sub decoder, and one interpolating voltage is selected from a plurality of interpolating voltages by a sub switch circuit in accordance with the decoded result, so that the selected interpolating voltage Vc is applied across a capacitor. Next, the most significant half of the given image data is decoded by a main decoder, and one main voltage is selected from a plurality of main voltages by a main switch circuit in accordance with the decoded result, so that the selected main voltage Vk is supplied to one terminal of the capacitor. With this, a voltage V.sub.CH at the other terminal of the capacitor becomes {Vc+Vk}. Accordingly, by selecting Vc and Vk, it is possible to generate a number of output driving voltages corresponding to a number of gray scale levels, with a reduced number of external voltage supplies and with a reduced cost.

Circuit for driving liquid crystal device

A liquid crystal display driving circuit comprises a plurality of transfer gates having their one end connected in common to a source line of a liquid crystal display panel and their other end connected to a plurality of driving voltages, respectively, for supplying a different voltage to the source line. A control circuit receives an image input data for selectively turning on the transfer gates, for the purpose of realizing a multiple gray scale display. The control circuit is configured to turn on one transfer gate selected from the plurality of transfer gates during a first period of one display period, and then, to maintain the turned-on condition of the selected transfer gate during the remaining period of one display period, or to simultaneously turn on two transfer gates which are selected from the plurality of transfer gates and which include the selected transfer gate during the remaining period of one display period.

An improvement of the LCD driving semiconductor IC which supplies a plurality of source driving voltages (corresponding to the horizontal scanning voltage of a CRT) to a plurality of source driving lines of an active matrix type LCD of TFT base is proposed. Each of sample/hold circuit that is provided in one-to-one correspondence to the source driving lines which carry out polarity inversion and extraction of voltage sample values of an image signal for every one line of horizontal scanning of applied voltages to liquid crystal cells for the purpose of preventing the deterioration of liquid crystal cells consisting of pixel display electrodes and counter electrodes of LCD and a liquid crystal material inserted between the electrodes, is composed of complementarily operating first circuit part and second circuit part, and the correspondence relation between polarity display pulse that controls the complementary operation of these circuit parts and the polarity of the voltage sample value, and these first/second circuit parts is fixed. By so doing, the variation range of the input voltage to each buffer amplifier of the first/second circuit parts was limited, the source-drain region formation process of the input transistor of its amplifier was simplified, and facilitated the improvement of the accuracy of the source driving voltage with respect to the input image signal.

Semiconductor device for driving liquid crystal display panel

A driving circuit for a liquid crystal display comprises: a selector driving circuit having a plurality of shift registers and latch circuits for outputting hold signals latched in the latch circuits; a plurality of selector circuits each for selecting one reference coltage corresponding to the hold signal; a plurality of hold capacitors each being charged by the selected reference voltage; and a plurality of source follower circuits each receiving the hold voltage from the hold capacitor and outputting a driving voltage for the liquid crystal display. The driving circuit further comprise a plurality of comparator circuits each receiving the output driving voltage and the reference voltage selected and switching the connection of a ramp voltage to the hold capacitor. Each source follower circuit provided for each stage requires a constant current source and only one output driver transistor instead of as many transistors as the number of gradations, which transistor commonly operates over all the gradations. The driving circuit may comprise a plurality of level shifting or biasing circuits supplying to the respective selector circuits level-shifted reference voltages whose potentials are higher than the normal reference voltages by the amount of a biasing voltage applied to the constant current sources of the source follower circuits.

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Tokyo, Japan

Sei Saitoh