Shift register unit, shift register, gate driving circuit and display panel

A shift register unit, comprising a trigger signal input terminal, an input circuit, a pull-up circuit, a pull-down control circuit, a plurality of pull-down circuits, and a signal output terminal,

• wherein the trigger signal input terminal is electrically connected to a control terminal of the input circuit, and configured to provide an active signal to the control terminal of the input circuit in an input stage of the shift register unit,
• an output terminal of the input circuit is electrically connected to a control terminal of the pull-up circuit, and the input circuit is configured to provide an active signal to the control terminal of the pull-up circuit when the control terminal of the input circuit receives an active signal,
• an input terminal of the pull-up circuit is electrically connected to an initial signal terminal, an output terminal of the pull-up circuit is electrically connected to the signal output terminal, and the pull-up circuit is configured to electrically connect the input terminal of the pull-up circuit to the output terminal of the pull-up circuit when the control terminal of the pull-up circuit receives an active signal,
• an input terminal of each of the pull-down circuits is electrically connected to a second level signal terminal, a first output terminal of each of the pull-down circuits is electrically connected to the signal output terminal, a second output terminal of each of the pull-down circuits is electrically connected to the control terminal of the pull-up circuit, and each pull-down circuit is configured to electrically connect an input terminal of the pull-down circuit to the first and second output terminals of the pull-down circuit when a control terminal of the pull-down circuit receives an active signal, and
• the pull-down control circuit comprises a plurality of pull-down control signal output terminals electrically connected to the control terminals of the pull-down circuits, respectively, and is configured to sequentially provide active signals to the control terminals of respective pull-down circuits in a pull-down stage, such that the pull-down circuits are turned on in different frame periods, respectively, each of the frame periods being a time period for displaying one frame of image.