| 摘要 |
<p>PROBLEM TO BE SOLVED: To erase the screen clearly when the power source is turned off by holding the potential of the auxiliary capacitor of a thin film transistor liquid crystal display device at the ground level when an external power source is disconnected. SOLUTION: The circuit consists of a capacitor C1 which has one end connected to the external power source VDD, a diode D1 which has its anode connected to the other terminal of the capacitor C1 and its cathode grounded, and a PMOS transistor M1 which has its gate terminal connected to the anode of the diode D1 and one terminal of the capacitor C1, its source terminal grounded, and its drain terminal connected to one terminal of the auxiliary capacitor Cst of the thin film transistor liquid crystal display device. Here, the diode D1 sets the reference potential of the gate potential of the PMOS transistor M1. Then whether or not the external power source VDD is disconnected is sensed and once the external power source VDD is disconnected, the PMOS transistor M1 discharges the voltage of the auxiliary capacitor Cst to hold its potential at the ground level.</p> |
