Study Of The Noise Effect Of The Liquid Crystal Display On The Capacitive Touch Panel

With the rapid development of touch screen control technology,especially the technology of capacitive touch screen control,the LCD module with touch screen panel is used more and more widely.In order to achieve the goal of lighter and thinner,the better optical effect,lower cost and the higher mass production efficiency,the distance between the touch screen sensing layer and the LCD module is becoming closer and closer,which resulting in more interference of liquid crystal display to the touch panel.In order to reduce the noise effect from liquid crystal display to capacitive touch panel,this paper first summarizes the existing theories about the causes of liquid crystal display's surface noise.The existing theories show that the liquid crystal display's noise to capacitive touch screen roots in the fluctuation of VCOM,which is the voltage reference of common electrodes,but they did not do further research.Besides,the existing methods of reducing the LCD's noise do not have much obvious and positive effects.Therefore,this paper analyzes the regularity of LCD's surface noise,and compares it with the principle of LCD's driving circuits,eventually finds the root cause of the TFT LCD's noise effect to capacitive touch panel.After that,this paper puts forward the method of reducing the surface noise of the liquid crystal display panel based on improving the driving circuits of the LCD.Furthermore,we designed an actual circuit to produce a special waveform in order to verify the solution.The test results indicate that this solution can reduce the LCD's noise to about 200 mV,which meets the requirement of noise effect from LCD to capacitive touch panel.