Patent ID: 8854288

Claim:
A tangent angle circuit in a liquid crystal display (LCD) driving system, being connected to a plurality of scan line driving circuits, the tangent angle circuit comprising: a charging module, being integrated on a control board and configured to receive input of a direct current (DC) driving voltage and output a cut-in voltage to charge the scan line driving circuits, the charging module comprising: a switch sub-module, being configured to receive the input of the DC driving voltage and output the cut-in voltage to charge the scan line driving circuits; and a switch control sub-module, being configured to control the switch sub-module to turn on or turn off so as to control a charging time of the scan line driving circuits; and a plurality of discharging modules, being integrated on the scan line driving circuits respectively and configured to control the corresponding scan line driving circuits to discharge, each of the discharging modules comprising: a discharging control sub-module, being configured to control the discharging module to turn on or turn off so as to control a corresponding one of the scan line driving circuits to discharge; and a discharging sub-module, being configured to receive a discharge voltage of the corresponding scan line driving circuit and control a discharge in rate of the discharge voltage; wherein the discharging control sub-module comprises a first metal-oxide-semiconductor (MOS) transistor, the discharging sub-module comprises a discharge resistor, and the first MOS transistor has a gate for receiving a first control signal that controls the first MOS transistor to turn on or turn off, a source that is grounded, and a drain for receiving input of the discharge voltage via the discharge resistor; wherein the switch control sub-module comprises a second MOS transistor, the switch sub-module comprises a third MOS transistor, the second MOS transistor has a source that is grounded, a gate for receiving a second control signal that controls the second MOS transistor to turn on or turn off, and a drain connected to a gate of the third MOS transistor via a first resistor to control the third MOS transistor to turn on or turn off; a source of the third MOS transistor receives the input of the DC driving voltage, the DC driving voltage is inputted to the gate of the third MOS transistor via a second resistor and is also inputted to a drain of the third MOS transistor via a third resistor, and the drain of the third MOS transistor outputs the cut-in voltage to charge the scan line driving circuits.