Touch key signal detection method and circuit based on mutual capacitance

Abstract

The invention discloses a mutual capacitance type touch key signal detection method. The method comprises the steps that initialization is carried out, wherein the electric charge quantity of an A point in the initialization phase is obtained; measurement is carried out, the voltage of the A point is obtained according to conservation of the electric charge of the A point; whether reference capacitance is larger than parasitic mutual capacitance or not is judged according to the judgment result of whether the voltage VA2 of a capacitive coupling point A is larger than the initial voltage of the capacitive coupling point A or not; whether a touch signal exists or not is judged according to the judgment result. Compared with the prior art, detection of the touch signal is completed within one period through a reference capacitance comparison method, the detection speed is much higher than that of a traditional relaxation oscillation method; Because of the single-period detection, a capacitor of a touch key does not need to be charged and discharged frequently, system power consumption is greatly saved; in addition, due to the method, a system has very low dynamic power consumption, working frequency can be flexibly changed, the touch key can be used under the low-power-consumption standby mode with the rigorous requirement for power consumption, and the hardware guarantee is provided for a full-touch human-computer interaction interface. The invention further discloses a detection circuit of the touch key signal detection method.

Description

technical field [0001] The present invention relates to the technical field of touch key signal detection, and more particularly relates to a mutual capacitance-based touch key signal detection method and a detection circuit thereof. Background technique [0002] The traditional touch button signal detection method is generally realized by the "relaxation oscillation" method based on self-capacitance. The basic principle of "relaxation oscillation" touch detection is a relaxation oscillator that is continuously charged and discharged. Without touching the switch, the relaxation oscillator has a fixed charge and discharge cycle, and the frequency is measurable. If you touch the switch with a finger or a stylus, the dielectric constant of the capacitor will increase, the charging and discharging cycle will become longer, and the frequency will decrease accordingly. Therefore, the change of the measuring cycle can detect the touch action. [0003] Please refer to Figure 1a ,...

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Problems solved by technology

[0005] (1) The detection speed is low; "relaxation oscillation" detects touch signals by detecting frequency changes. The detection circuit needs to pass several clock cycles to determine the change in frequency, and single-cycle touch signal detection cannot be realized.

[0006] (2) High power consumption; because it takes several clock cycles to detect the touch signal, the self-capacitance of the touch button is repeatedly charged and discharged, which increases the dynamic power consumption of the system

[0007] (3) It is difficult to realize the low-power standby mode; after "sleep", the general system will reduce the dynamic power consumption by reducing the operating frequency, and if the touch key of the "relaxation oscillation" method changes the frequency, it will cause signal misdetection, Therefore, in the standby mode and the working mode, the power consumption is almost the same, which cannot meet the long standby time requirement under the condition of battery power supply.

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