| 摘要 |
PURPOSE:To detect the disconnection of a load circuit with a simple constitution, by detecting the change of the primary side impedance caused by the conduction of anogher voltage control element when the control voltage applied to a voltage control element exceeds the prescribed limit by the disconnection of the load circuit. CONSTITUTION:The output device 6 receives the digital output from the CPU which is not shown in the diagram and then converts the output into the analog current quantity to supply it to the process 8 to be controlled. At the same time, the device 6 amplifies the input signal by the FET63 and the transistor TR64 and then applies the amplified input to the process 8. In case when a disconnection occurs in a load circuit, no current flows to the process 8 to extinguish the both- end voltage V3 of the resistance RS. As a result, the operational amplifier circuit 62 saturates the output voltage VO in order to increase the voltage VS and then turns on the voltage control element FET71. The on and off of the FET71 is detected by the monitor circuit 73 via the pulse transformer 72. In such way, the disconnection of a load circuit can be detected with a simple constitution. |
