| 摘要 |
PURPOSE:To supply a stable current to a sensor circuit, by providing a voltage detecting means for conducting an SCR by detecting a fact that charge voltage of a capacitor connected between both terminals of the sensor circuit has exceeded a prescribed value. CONSTITUTION:When a sensor circuit 109 is off, a transistor TR108A becomes on, and a current is supplied to the sensor circuit by a series type constant-voltage circuit 108. The both ends of the circuit 109, constant voltage of differential voltage of Zener voltage VZ1 of a Zener diode ZD108B, and base-emitter voltage VBE of the TR108A is applied, and a capacitor C110 is charged. The sum of Zener voltage VZ2 of a ZD119 and gate voltage Vg of an SCR104 is selected higher than voltage across the circuit 109, therefore, no current flows to the ZD119, and the SCR104 is off. When the circuit 109 becomes off, the SCR104 becomes on and the TR109A becomes off, but as for the voltage of the C110 across the circuit 109, almost constant voltage of VZ2+Vg is applied. |
