Pulse output circuit, and display device, drive circuit, display device, and pulse output method using same circuit
In one embodiment of the present invention, a source driver includes a shift register including latch stages each including a level shifter that level-shifts clock signals so that the signals are fed into a set-reset flip-flop as inverted set input signals. Outputs from the set-reset flip-flop are delayed by a hazard preventing circuit and then fed into a level shifter in the next latch stage as enable signals. A delay trimming circuit causes a NAND circuit to perform a NAND operation with respect to outputs obtained by a delay of the outputs by a delay circuit and outputs from the level shifter in the next latch stage, so that a sampling pulse is derived. This allows for provision of a pulse output circuit capable of further trimming delay in output pulses and of securing a sufficient interval between the output pulses.
1. A pulse output circuit for sequentially outputting pulses from different output terminals, the pulse output circuit comprising:
a shift register including
a plurality of latch stages, connected in series, which have flip-flops for generating first pulses serving as source pulses of the pulses outputted from the output terminals, respectively; and
a delay trimming circuit for (i) generating second pulses from the first pulses, respectively, each of the second pulses having: start timing obtained by a delay of start timing of a first pulse; and end timing generated using start timing of an input pulse to a flip-flop in a first latch stage existing immediately after a second latch stage in which the first pulse is generated, the input pulse not having passed through the flip-flop of the first latch stage existing immediately after the second latch stage and (ii) outputting the second pulse as a pulse to be outputted from a corresponding one of the output terminals, wherein:
the first latch stage existing immediately after the second latch stage includes
a hazard preventing circuit for outputting an output signal as an enable signal by a delay of the output signal of the flip-flop of the second latch stage, and
a level shifter for (i) carrying out a level-shifting operation with use of the enable signal inputted from the hazard preventing circuit and (ii) generating the input pulse to the flip-flop of the first latch stage existing immediately after the second latch stage;
the hazard preventing circuit of the first latch stage existing immediately after the second latch stage delays the output signal of the flip-flop of the second latch stage so that end timing of the input pulse to the flip-flop, which input pulse is generated by the level shifter, is later than timing obtained by a delay of end timing of the first pulse of the second latch stage.
2. The pulse output circuit according to claim 1 , wherein:
each of the flip-flops is a set-reset flip-flop; and
the shift register generates an input pulse to a flip-flop by level-shifting an input clock signal inputted in the shift register.
3. The pulse output circuit according to claim 2 , wherein the input pulse to the flip-flop in the first latch stage is used as a reset signal for a flip-flop in the second latch stage in which the first pulse is generated.
4. A drive circuit for a display device, comprising a pulse output circuit recited in claim 1 , wherein the second pulse is outputted as a sampling pulse for a video signal of the display device.
5. A display device comprising a drive circuit recited in claim 4 .
6. A pulse output method for sequentially outputting pulses from different output terminals, the pulse output circuit comprising the steps of:
generating, with use of flip-flops in latch stages of a shift register, first pulses as source pulses for the pulses outputted from the output terminals, respectively; and
generating second pulses each of the second pulses having: start timing obtained by a delay of start timing of a first pulse; and end timing generated using start timing of an input pulse to a flip-flop in a first latch stage existing immediately after a second latch stage in which the first pulse is generated, the input pulse not having passed through the flip-flop of the first latch stage existing immediately after the second latch stage, and outputting the second pulse as a pulse to be outputted from a corresponding one of the output terminals, wherein:
the first latch stage existing immediately after the second latch stage generates, as an enable signal, a signal obtained by a delay of the output signal of the flip-flop of the second latch stage so that end timing of the input pulse to the flip-flop generated by the level shifter is later than timing obtained by a delay of end timing of the first pulse of the second latch stage; and
the input pulse to the flip-flop is generated by level-shifting a input clock signal with use of the enable signal.
7. The pulse output method according to claim 6 , wherein:
each of the flip-flops is a set-reset flip-flop.
8. The pulse output method according to claim 7 , wherein the input pulse to the flip-flop in the first latch stage is used as a reset signal for a flip-flop in the second latch stage in which the first pulse is generated.