| 摘要 |
PROBLEM TO BE SOLVED: To ensure that abnormal voltages can be detected even if the (+) and (-) side divided voltages of a positive-negative dc power source fluctuate likewise by providing an abnormality output when detecting that each of the (+) and (-) side divided voltages of a positive-negative dc power source has dropped to a predetermined level or less. SOLUTION: Voltage dividing circuits 11A, 11B comprise resistances R1 to R4 that divide the (+) and (-) side voltages of a positive-negative dc power source such as a±15-voltage power source, each of the divided voltages VA, VB becoming 1.25V when±15V becomes 13V. When it is 1.25V or less, voltage- detecting ICs 13A, 13B output H, and the secondary side output of each photocoupler 15A, 15B becomes H. This output is inverted by inverters 17A, 17B and input to an abnormal output OR circuit 19. Thus when the±15-V source voltage is±13V or more, the outputs of the ICs 13A, 13B becomes L while the output of the circuit 19 becomes H, so that no abnormality is detected. When either or both of the (+) and (-) sides of the source voltage become 13V or less, one or both of the outputs of the ICs 13A, 13B become H while the output of the circuit 19 becomes L, and an abnormal state is announced to the outside by means of light-emitting diodes, etc.
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