| 摘要 |
PURPOSE:To achieve a higher economy with a smaller size, by comparatively collating a primary side current of an insulation type power source circuit with a command value. CONSTITUTION:Input current (i) of a power source circuit 6 is proportional to a resistance load current I, which permits detection of a current I flowing through a resistance load RL by checking the current (i). As a resistance (r) is connected in series to the input side of the circuit 6, voltage V6 is proportional to the current I. The voltage V6 is amplified with an amplifier AMP7 to reach a voltage V7. Amplification factor K of the AMP7 is so set that an output voltage V2 of a digital/analog converter DAC42 equals the voltage V7 when an analog output device 2 operates normally. The AMP7, a collation circuit 8 and the converter DAC42 composes a fault detection circuit 31. Since the primary side of the circuit 6 is insulated from the secondary side, the amplifier AMP7 connected to the primary side need not to be of an insulation type. This enables economical and compact construction of the apparatus.
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