| 摘要 |
PURPOSE:To always set switch sensitivity to a proper value, and to prevent a malfunction due to noise, etc., by detecting a touch capacity component in case when a human body has touched a touch electrode, comparing it with a prescribed reference capacity component, and processing it. CONSTITUTION:When no finger touches a touch electrode T1, a switch SW-off signal (x) is outputted from a gate 19 to an input waveform A, being delayed by time Dx corresponding to a floating capacity of the electrode and the case. When a finger touches the electrode T1, a touch capacity component Cy is added, and a delayed portion of time Dx+Dy is outputted as an SW on signal (x) from the gate 19. This switching circuit is used for a sense circuit, on-time of the signal (x) is latched, and a value E which has divided this value by a constant K is compared with a reference value DMIN of the minimum sensitivity generating no malfunction, which has been stored in a memory. In case of E>DMIN, a selector selects the signal E, decides that the SW is on, an on-signal of its signal (x) is stored in a latch, and from a touch capacity component of that time, a reference capacity component of the next touch time is derived. |
