Source driver controlling slew rate

• US 7,760,199 B2
• Filed: 05/31/2006
• Issued: 07/20/2010
• Est. Priority Date: 05/31/2005
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: An, Chang-Ho
• Primary Examiner(s): Lefkowitz; Sumati
• Assistant Examiner(s): Amadiz; Rodney
• Application Number:
  US11/443,308
• Publication Number:
  US 20060279356A1
• Time in Patent Office: 1,511 Days
• Field of Search: 345 98-100, 345/204, 345/87, 345/94, 345211-213, 326/87, 327/111, 327/170, 330252-261, 330/278, 330/291, 330/294
• US Class Current: 345/204
• CPC Class Codes: H03F 2203/45471 the CSC comprising one or more extra current sources
• CPC Class Codes: H03F 2203/45506 the CSC comprising only one switch
• CPC Class Codes: H03F 3/45219 Folded cascode stages

Abstract

A source driver employed in a liquid crystal display device uses a slew-rate control signal to regulate a slew rate of its output buffers, which makes an output voltage selectively operable at a low slew rate. Such a source driver can reduce (if not prevent) distortion of a common voltage.

Claims

1. A source driver, of a liquid crystal display device, comprising:

a plurality of output buffers to drive source lines;

a voltage sharing unit to share voltage levels on the source lines during a charge-sharing interval; and

a controller configured to generate a slew-rate control signal in response to the charge-sharing interval, the slew-rate control signal being input to the plurality of output buffers, wherein

slew rates of the plurality of output buffers vary according to the input slew-rate control signal,

the controller generates the slew-rate control signal that is activated after an end of the charge-sharing interval, and

the slew-rate control signal is not active during the charge-sharing interval.

2. The source driver as set forth in claim 1, wherein an interval of the slew-rate control signal is equal to the charge-sharing interval.

3. The source driver as set forth in claim 1, wherein the voltage sharing unit includes a plurality of sharing switches.

4. The source driver as set forth in claim 3, wherein:

the controller is further configured to generate a sharing-switch control signal; and

the plurality of sharing switches operate according to the sharing-switch control signal.

5. The source driver as set forth in claim 1, wherein:

the output buffers operate to selectively exhibit reduced slew rates according to the slew-rate control signal.

6. A source driver, of a liquid crystal display device, comprising:

output buffers to drive source lines;

output switches to regulate output voltages on the source lines;

charge-sharing switches to share voltage levels on the source lines during a charge-sharing interval; and

a control signal generator configured to provide a slew-rate control signal in response to the charge-sharing interval, the slew-rate control signal being input to the plurality of output buffers, and to provide switching signals for operating the output switches and the charge-sharing switches, in response to an end of the charge-sharing interval, wherein

the slew rate control signal regulates slew rates of the output buffers and is not active during the charge-sharing interval,

the control signal generator includes at least one of;

a switch controller that generates the switching signals, the switching signals including an output-switch control signal and a sharing-switch control signal to regulate the output switches and the charge-sharing switches, respectively; and

a slew-rate controller that generates the slew-rate control signal,

the output-switch control signal and the sharing-switch control signal are generated with reference to an output enable signal received from an entity external to the source driver; and

the slew-rate control signal is generated in response to the sharing-switch control signal.

7. The source driver as set forth in claim 6, wherein an active time of the slew-rate control signal is at least substantially the same as an active interval of the sharing-switch control signal.

8. The source driver as set forth in claim 6, wherein the output buffers further operate to selectively exhibit reduced slew rates according to the slew-rate control signal.

9. The source driver as set forth in claim 8, wherein each output buffer comprises:

an input circuit to receive an analog image signal and an output voltage of a corresponding output buffer;

an amplifier circuit to amplify the analog image signal;

a capacitive circuit to stabilize a frequency characteristic of the output voltage; and

an output circuit to drive the source line in response to signals from the amplifier circuit.

10. The source driver as set forth in claim 9, wherein the input circuit further operates to control current of a current-source transistor in response to the slew-rate control signal.

11. The source driver as set forth in claim 9, wherein each output buffer is a rail-to-rail operation amplifier.