A tangent angle circuit is connected to a plurality of scan line driving circuits and comprises: a charging module integrated on a control board to receive input of a direct current (DC) driving voltage and output a cut-in voltage to charge the scan line driving circuits; and a plurality of discharging modules integrated on the scan line driving circuits respectively to control the corresponding scan line driving circuits to discharge. In the present invention, by distributing the discharging modules on each of the scan line driving circuits respectively, the burden of load discharged charges on the discharging modules is reduced to avoid occurrence of an overhigh temperature; and the discharging modules are spatially separated, which is further favorable for reducing the temperature, releasing the space of the control board and reducing the area of the control board.