WAVE SENDING CIRCUIT FOR ULTRASONIC SENSOR

摘要

PROBLEM TO BE SOLVED: To increase energy for sending ultrasonic wave without increasing the number of parts greatly and improve an S/N ratio of an ultrasonic sensor more than a conventional one. SOLUTION: A wave sending circuit 2 sends ultrasonic waves by driving an ultrasonic vibrator 1 by high frequency signals. A switching circuit 4 switches direct current power supplied from a power supply circuit 10 which is a direct current power supply in a switching element Q1 consisting of a transistor to generate the high frequency signal and give it to a parallel circuit of the ultrasonic vibrator 1 and a coil L1. As a result, the voltage applied to the ultrasonic vibrator 1 due to electromotive force generated in the coil L1 by switching of the switching element Q1 has such wave shape that vibrates between an output voltage V in the power supply circuit 10 and a negative voltage-Va, and a voltage larger than the output voltage V as an absolute value is applied.