Patent ID: 8368683

Claim:
A power-off control circuit adapted in a liquid crystal display panel, wherein the liquid crystal display panel comprises a gate pulse modulator and a level shifter having a level-shift output connected to the gate pulse modulator, the power-off control circuit comprises: a logic gate comprising: a first input to receive an internal power supply; a second input to receive a power state signal; a logic output to generate a control signal according to the first input and the second input; and a power state NMOS comprising: a drain connected to the second input and the internal power supply; a gate to receive the power state signal; and a source connected to a ground; and a control switch to receive the control signal and to be connected to the level-shift output; wherein when a power supply is on, the internal power supply is on and the power state signal is in a first state to turn on the power state NMOS such that the second input maintains at a low level and to make the control signal turn off the control switch; when the power supply is off, the internal power supply is on during a certain time period and the power state signal is in a second state opposite to the first state to turn off the power state NMOS such that the second input receives the internal power supply and maintains at a high level to make the control signal turn on the control switch in the certain time period such that the voltage of the level-shift output maintains at a certain level to make the gate pulse modulator turn on the gates of a plurality of pixels of a pixel array of the liquid crystal display panel to perform a discharge activity.