Shift register and display device

• US 20050017942A1
• Filed: 07/22/2004
• Published: 01/27/2005
• Est. Priority Date: 07/23/2003
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Takahashi, Shinya, Tsujino, Sachio
• Granted Patent: US 7,365,728 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters

Abstract

A display device is provided with a shift register having a plurality of bistable circuits, each of the bistable circuits being connected to a corresponding scanning line. An RS flip-flop circuit provided in each of the bistable circuits functions as a memory portion for discriminating a start position of a display region for partial display. When partial display is carried out, first, only the RS flip-flop circuit corresponding to the start position of the display region is put into the set state, that is, only the bistable circuit corresponding to the start position of the display region is put into the set state. Moreover, the scanning lines that are connected to the bistable circuits from the start position to the end position are driven sequentially. During this, only the bistable circuit corresponding to the start position is kept in the set state, and the other bistable circuits are kept in the reset state.

Claims

1. A shift register comprising:

a plurality of bistable circuits connected in series, each of the bistable circuits having a first state and a second state and outputting a stage output signal of a logic level in accordance with the state of that bistable circuit, and all or some of the plurality of bistable circuits sequentially taking on the first state for a predetermined time each in accordance with a clock signal that is inputted from outside;

a start position setting circuit for keeping the bistable circuit at a start position, which is the bistable circuit specified by a start position instruction signal that is inputted from outside, in the first state; and

a reset circuit for setting the bistable circuits other than the bistable circuit at the start position to the second state, after the bistable circuit at an end position, which is the bistable circuit specified by an end position instruction signal that is inputted from outside, has been set to the first state;

wherein, when the bistable circuit at the start position is kept at the first state, the bistable circuits from the start position to the end position are sequentially set to the first state for the predetermined time each in accordance with the clock signal.

2. The shift register according to claim 1, wherein the start position setting circuit keeps the bistable circuit at the start position in the first state by preventing the bistable circuit at the start position from taking on the second state.

3. The shift register according to claim 1,

wherein a start signal that is set at a first logic level at a process start at every frame period, which is a cycle of partial driving in which the bistable circuits from the start position to the end position sequentially take on the first state for a predetermined time each in accordance with the clock signal, a start position setting signal for specifying the bistable circuit corresponding to the start position based on the start position instruction signal, and a final-stage reset signal for setting all bistable circuits except for the bistable circuit at the start position to the second state, are inputted from outside;

wherein the start position setting circuit comprises a first logic gate that is provided in each bistable circuit, the first logic gate outputting a signal of the first logic level when both the start position setting signal and a second-subsequent output signal that is outputted by the bistable circuit two stages after that bistable circuit are at the first logic level, and outputting a signal of a second logic level when at least one of the second-subsequent output signal and the start position setting signal is at the second logic level;

wherein the reset circuit comprises a second logic gate that is provided in each bistable circuit, the second logic gate outputting a signal of the first logic level when the final-stage reset signal and a prior-stage state signal that is set at the first or the second logic level depending on whether or not any of the bistable circuits arranged at the stages prior to that bistable circuit is in the first state are both at the first logic level, and outputting a signal of the second logic level when at least one of the prior-stage state signal and the final-stage reset signal is at the second logic level;

wherein each of the bistable circuits;

is set to the first state when the stage output signal that is outputted from the bistable circuit one stage prior to that bistable circuit is at the first logic level;

outputs a signal of the first logic level as the stage output signal of that bistable circuit when the start signal is at the first logic level or the bistable circuit one stage prior to that bistable circuit is in the first state, and that bistable circuit is in the first state, and the clock signal is at the first logic level;

outputs a signal of the first logic level as the prior-stage state signal to be received by the bistable circuit of the stage subsequent to that bistable circuit when the prior-stage state signal that is outputted from the bistable circuit one stage prior to that bistable circuit is at the first logic level, or that bistable circuit is in the first state; and

is set to the second state when the first logic gate or the second logic gate within that bistable circuit outputs a signal of the first logic level.

4. The shift register according to claim 3, wherein the number of the phases of the clock signal is at least three.

5. A display device comprising a scanning line driving circuit for driving a plurality of scanning lines and a signal line driving circuit for driving a plurality of signal lines, the display device having a partial display function in which a portion of a display screen serves as a display region;

at least one of the scanning line driving circuit and the signal line driving circuit comprising a shift register; and

the shift register comprising;

a plurality of bistable circuits connected in series, each of the bistable circuits having a first state and a second state and outputting a stage output signal of a logic level in accordance with the state of that bistable circuit, and all or some of the plurality of bistable circuits sequentially taking on the first state for a predetermined time each in accordance with a clock signal that is inputted into the shift register from outside the shift register;

a start position setting circuit for keeping the bistable circuit at a start position, which is the bistable circuit specified by a start position instruction signal that is inputted from outside, in the first state; and

a reset circuit for setting the bistable circuits other than the bistable circuit at the start position to the second state, after the bistable circuit at an end position, which is the bistable circuit specified by an end position instruction signal that is inputted into the shift register from outside the shift register, has been set to the first state;

wherein, when the bistable circuit at the start position is kept at the first state, the bistable circuits from the start position to the end position are sequentially set to the first state for the predetermined time each in accordance with the clock signal.

6. The display device according to claim 5, wherein the start position setting circuit keeps the bistable circuit at the start position in the first state by preventing the bistable circuit at the start position from taking on the second state.

7. The display device according to claim 5,

wherein a start signal that is set at a first logic level at a process start at every frame period, which is a cycle of partial driving in which the bistable circuits from the start position to the end position sequentially take on the first state for a predetermined time each in accordance with the clock signal, a start position setting signal for specifying the bistable circuit corresponding to the start position based on the start position instruction signal, and a final-stage reset signal for setting all bistable circuits except for the bistable circuit at the start position to the second state, are inputted into the shift register from outside the shift register;

wherein the start position setting circuit comprises a first logic gate that is provided in each bistable circuit, the first logic gate outputting a signal of the first logic level when both the start position setting signal and a second-subsequent output signal that is outputted by the bistable circuit two stages after that bistable circuit are at the first logic level, and outputting a signal of a second logic level when at least one of the second-subsequent output signal and the start position setting signal is at the second logic level;

wherein the reset circuit comprises a second logic gate that is provided in each bistable circuit, the second logic gate outputting a signal of the first logic level when the final-stage reset signal and a prior-stage state signal that is set at the first or the second logic level depending on whether or not any of the bistable circuits arranged at the stages prior to that bistable circuit is in the first state are both at the first logic level, and outputting a signal of the second logic level when at least one of the prior-stage state signal and the final-stage reset signal is at the second logic level;

wherein each of the bistable circuits;

is set to the first state when the stage output signal that is outputted from the bistable-circuit one stage prior to that bistable circuit is at the first logic level;

outputs a signal of the first logic level as the stage output signal of that bistable circuit when the start signal is at the first logic level or the bistable circuit one stage prior to that bistable circuit is in the first state, and that bistable circuit is in the first state, and the clock signal is at the first logic level;

outputs a signal of the first logic level as the prior-stage state signal to be received by the bistable circuit of the stage subsequent to that bistable circuit when the prior-stage state signal that is outputted from the bistable circuit one stage prior to that bistable circuit is at the first logic level, or that bistable circuit is in the first state; and

is set to the second state when the first logic gate or the second logic gate within that bistable circuit outputs a signal of the first logic level.

8. The display device according to claim 7, wherein the number of the phases of the clock signal is at least three.

9. The display device according to claim 7, further comprising:

a start position setting signal generating circuit for outputting a signal of the second logic level as the start position setting signal when the stage output signal that is outputted from the bistable circuit two stages after bistable circuit at the start position is at the first level; and

a final-stage reset signal generating circuit for outputting a signal of the first logic level as the final-stage reset signal when the stage output signal that is outputted from bistable circuit at the end position changes from the first logic level to the second logic level.