Capacitance variation detection circuit, touch screen and touch detection method

A touch screen, comprising:

• a detection capacitor, wherein a first terminal of the detection capacitor is connected to a first power source via a seventh switch, a second terminal of the detection capacitor is connected to the reference ground;
• and
• a capacitance variation detection circuit, configured to detect a capacitance variation of the detection capacitor, wherein the capacitance variation detection circuit comprises:
• a denoising capacitor, wherein one terminal of the denoising capacitor is connected to the first terminal of the detection capacitor via a second switch and to a reference ground via a third switch, and the other terminal of the denoising capacitor is connected to the first power source via a fourth switch and to the reference ground via a fifth switch;
• an operational amplifier, wherein a positive input terminal of the operational amplifier is connected to a second power source, and a negative input terminal of the operational amplifier is connected to the first terminal of the detection capacitor via a first switch;
• and
• an integrating capacitor, wherein two terminals of the integrating capacitor are connected via a sixth switch, and are connected between the negative input terminal of the operational amplifier and an output terminal of the operational amplifier.

A touch detection method, applied to a touch screen, wherein the method comprises:

• at a first stage, connecting one terminal of a detection capacitor and one terminal of a denoising capacitor to a first power simultaneously, and connecting the other terminal of the detection capacitor and the other terminal of a denoising capacitor to a reference ground simultaneously;
• at a second stage, disconnecting the detection capacitor from the first power source, connecting the detection capacitor to the negative input terminal of the operation amplifier, switching the one terminal of the denosing capacitor from being connected to the first power source at the first stage to being connected to the reference ground, and connecting the other terminal of the denoising capacitor to the negative input terminal of the operational amplifier;
• and
• acquiring an output result of the operational amplifier, and judging whether there is a touch operation according to the output result.