Liquid crystal display driving circuit with low power consumption and precise voltage output

• US 6,232,948 B1
• Filed: 04/27/1998
• Issued: 05/15/2001
• Est. Priority Date: 04/28/1997
• Status: Expired due to Term

• Current Assignee: Gold Charm Limited (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Tsuchi, Hiroshi
• Primary Examiner(s): CHANG, KENT WU
• Application Number:
  US09/066,550
• Time in Patent Office: 1,114 Days
• Field of Search: 345/87, 345/89, 345/94, 345/95, 345/98, 345/99, 345/204, 345/211
• US Class Current: 345/99
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A driving circuit for a liquid crystal display in an active matrix scheme is provided. The driving circuit comprises a multi-value voltage generating circuit, a selection circuit and an output circuit. The output circuit includes an output circuit input terminal for inputting a voltage selected by the selection circuit, a first switch connected between the output circuit input terminal and the driving circuit output terminal, a transistor having a drain connected to the first voltage source, a gate connected to the output circuit input terminal and a source connected to the driving circuit output terminal, and a second switch connected between the driving circuit output terminal and the second voltage source. During a first driving period, the driving circuit output terminal is precharged to a predetermined voltage by controlling the first switch and the second switch. During a second driving period, the transistor is operated as a source follower to output a voltage to the driving circuit output terminal. During a third driving period, the voltage of the output circuit input terminal is directly outputted to the driving circuit output terminal through the first switch.

Claims

1. A driving circuit for a liquid crystal display comprising:

multi-value voltage generating means for generating a plurality of voltages;

selection circuit means for selecting a voltage required for driving from the voltages generated by said multi-value voltage generating means; and

output circuit means for inputting the voltage selected by said selection circuit means, and outputting a desired voltage to a driving circuit output terminal,

wherein said output circuit means includes an output circuit input terminal for inputting the voltage selected by said selection circuit means, said driving circuit output terminal, a first voltage source, a second voltage source, a first switch connected between said output circuit input terminal and said driving circuit output terminal, a transistor having a drain connected to said first voltage source, a gate connected to said output circuit input terminal and a source connected to said driving circuit output terminal, and a second switch connected between said driving circuit output terminal and said second voltage source.

2. A driving circuit for a liquid crystal display according to claim 1, wherein said output circuit means has three stages of driving periods, that is, a first driving period in which said driving circuit output terminal is precharged to a predetermined voltage with said second voltage source by controlling said first switch and said second switch, a second driving period in which said transistor is operated as a source follower to output a voltage to said driving circuit output terminal and a third driving period in which the voltage at said output circuit input terminal is directly outputted to said driving circuit output terminal through said first switch.

3. A driving circuit for a liquid crystal display according to claim 1, wherein said multi-value voltage generating means is a voltage dividing circuit comprising a third voltage source, a fourth voltage source and a resistance element group connected between the third voltage source and the fourth voltage source.

4. A driving circuit for a liquid crystal display according to claim 1, wherein said multi-value voltage generating means includes means for generating n voltages Vk (k=1,2,. . . ,n) and n auxiliary voltages Vk+Vok (k=1,2,. . . ,n) which are shifted by the voltage Vok from the voltages Vk, multi-value voltage generating means output terminal from which said n voltages Vk or said n auxiliary voltages Vk+Vok are outputted, a first switch group for controlling an output of said n voltages Vk to said multi-value voltage generating means output terminal, and a second switch group for controlling an output of said n auxiliary voltage Vk+Vok to said multi-value voltage generating means output terminal.

5. A driving circuit for a liquid crystal display comprising:

multi-value voltage generating means for generating a plurality of voltages;

selection circuit means for selecting a voltage required for driving from the voltages generated by said multi-value voltage generating means; and

output circuit means for inputting the voltage selected by said selection circuit means, and outputting a desired voltage to a driving circuit output terminal,

wherein said output circuit means includes an output circuit input terminal for inputting the voltage selected by said selection circuit means, said driving circuit output terminal, a first voltage source, a second voltage source, a switch connected between said output circuit input terminal and said driving circuit output terminal, an n channel type MOS transistor having a drain connected to the first voltage source, a gate connected to said output circuit input terminal and a source connected to said driving circuit output terminal, and a p channel type MOS transistor having a drain connected to said second voltage source, a gate connected to said output circuit input terminal and a source connected to said driving circuit output terminal.

6. A driving circuit for a liquid crystal display according to claim 5, wherein said output circuit means has two stages of driving periods, that is, a first driving period in which said n channel type MOS transistor or said p channel type MOS transistor is operated as a source follower to output a voltage to said driving circuit output terminal by controlling said switch, a second driving period in which the voltage at said output circuit input terminal is directly outputted to said driving circuit output terminal through said switch.

7. A driving circuit for a liquid crystal display according to claim 5, wherein said multi-value voltage generating means is a voltage dividing circuit comprising a third voltage source, a fourth voltage source and a resistance element group connected between the third voltage source and the fourth voltage source.

8. A driving circuit for a liquid crystal display according to claim 5, wherein said multi-value voltage generating means includes means for generating n voltages Vk (k=1,2,. . . ,n) and n auxiliary voltages Vk+Vok (k=1,2,. . . ,n) which is shifted by the voltage Vok from the voltage Vk, multi-value voltage generating means output terminal from which said n voltages Vk or said n auxiliary voltages Vk+Vok are outputted, a first switch group for controlling an output of said n voltages Vk to said multi-value voltage generating means output terminal, and a second switch group for controlling an output of said n auxiliary voltages Vk+Vok to said multi-value voltage generating means output terminal.