ST's Capacitive Touch Button Solution 4

Zero-crossing detection

Hardware zero-crossing detection

Zero-crossing detection can be implemented in hardware. In hardware design, additional zero-crossing detection circuits, such as those shown in Figure 4 or Figure 5, can be added. By determining the key state when the output at terminal B is high, the touch key can be detected during periods of minimal electromagnetic radiation.  diode

2) Software Zero-Crossing Detection 

Hardware zero-crossing detection increases the complexity of circuit design and raises solution costs. In our solution, we employ software-based zero-crossing detection tailored to the working environment of induction cookers, thereby reducing costs and effectively mitigating interference from the main power circuit on touch buttons  diode

2. Power grid interference

Due to the varying quality of domestic power grids, in areas with poor grid conditions, the normal operation of touch buttons on induction cookers may be affected. If a power supply cannot be used, the power supply is a device that provides power to electronic equipment, also known as a power supply unit, which delivers the necessary electrical energy to all components in a computer.

Isolation will reveal the differences shown in Figure 6 (blue indicates no button press, red indicates a button press). These figures are only under conditions where the induction cooker is not powered on. When the cooker operates, the generated electromagnetic radiation will make the observed signals even more chaotic. Experiments have shown that isolating from the external power grid or using software filtering can significantly improve the button press effect.