| 摘要 |
<p>PURPOSE: To supply stable driving power to a vehicle detecting induction sensor and to accurately detect the presence of the vehicle by controlling an oscillation signal as the function of the current flowing to the route in series with a capacitive impedance. CONSTITUTION: A series resonance oscillator 16 is connected in series with an inductive load. A positive feedback circuit (resistors 120, 122, potentiometer 124, and diodes 126, 128) and a negative feedback circuit (resistor 130, potentiometer 132, and capacitor 134) are provided in the oscillator 16. After a feedback signal is removed from a current sensing resistor 118, the feedback signal is suppled to two amplifiers 104, 106 for generating an oscillator signal. In this case, a loop gain is changed at each half period by the diodes 126, 128, and the oscillator 16 is rapidly started and stabilized. The oscillator signal is controlled as the function of the current flowing to the series route capable of supplying stable driving power to the sensor irrespective of the loop inductance of the lead-in cable to the sensor.</p> |
