Shift register and display device having the same
A shift register 10 is configured such that m unit circuits 11 each including a shift unit 12 and three buffer units 13 r, 13 g , and 13 b are in a multi-stage cascade connection and that 3 m signals in total including three signals from each stage are outputted. The m shift units 12 perform a shift operation, and a first signal Y is outputted from each stage. When a clock signal CK is at a high level, the first signal Y rises higher than a normal high level due to bootstrapping. The buffer unit 13 r controls an output signal YR to be at a high level based on the buffer control signal CR and the first signal Y. A buffer control circuit 7 controls buffer control signals CR, CG, and CB to be at a high level for a time period shorter than a half cycle of the clock signal. With this, a shift register with a reduced circuit amount and low power consumption is provided.
1. A shift register, comprising:
a buffer control circuit configured to output at least three buffer control signals; and
a plurality of unit circuits in a multi-stage cascade connection and capable of outputting at least four signals from each stage according to the buffer control signals and a clock signal which is different from the buffer control signals, wherein
each of the unit circuits includes a shift unit which operates in accordance with the clock signal and at least three buffer units, each corresponding to one of the buffer control signals, the shift unit includes:
a first transistor configured to apply an ON potential to a first node according to a set signal;
a second transistor configured to apply an OFF potential to the first node according to a reset signal;
a third transistor provided between an input node for the clock signal and a second node, and having a control terminal connected to the first node; and
a fourth transistor configured to apply an OFF potential to the second node according to the reset signal,
each of the at least three buffer units includes:
an output node;
a fifth transistor configured to apply an ON potential to the output node based on a potential at the first node and a corresponding buffer control signal; and
a sixth transistor configured to apply an OFF potential to the output node according to the reset signal,
each of the at least three buffer units is configured to output an output signal from the output node,
the shift unit is configured to output a signal on the second node as the set signal of a next-stage unit circuit and the reset signal of a previous-stage unit circuit,
the buffer control circuit is configured to control the buffer control signals to be at an ON level for a time period shorter than a half cycle of the dock signal, and
the buffer control circuit controls the buffer control signals to be at an ON level respectively for periods not overlapping with each other, the period being included in an ON-level period of the clock signal in a horizontal period and to be at an OFF level before the clock change to an OFF level.
2. The shift register according to claim 1 , wherein
the fifth transistor is provided between an input node for the buffer control signal and the output node, and has a control terminal connected to the first node.
3. The shift register according to claim 2 , wherein
the shift unit further includes a capacitance between the first node and the second node.
4. The shift register according to claim 3 , wherein
the buffer unit further includes a capacitance between the first node and the output node.
5. The shift register according to claim 1 , wherein
the buffer control circuit has a function for fixing the buffer control signals to an OFF level during a specified period.
6. The shift register according to claim 1 , wherein
the buffer control circuit has a function for controlling the buffer control signals to be at an ON level respectively during periods different from each other, and a function for controlling the buffer control signals to be at an ON level during a same period.
7. The shift register according to claim 1 , wherein
the shift unit further includes a circuit for applying an OFF potential to the first node according to a signal other than the reset signal.
8. The shift register according to claim 1 , wherein
the shift unit further includes a transistor for applying an OFF potential to the second node according to a signal other than the reset signal.
9. The shift register according to claim 1 , wherein
the buffer unit further includes a transistor for applying an OFF potential to the output node according to a signal other than the reset signal.
10. The shift register according to claim 1 , wherein
the shift unit further includes a transistor for applying an OFF potential to the first node according to a clear signal.
11. A display device, comprising:
a display panel including a pixel region in which a plurality of scanning signal lines are provided; and
a scanning signal line drive circuit including a shift register according to claim 1 , and monolithically formed on the display panel.