| 摘要 |
PURPOSE: A digital input circuit for a train is provided to protect a circuit from external surge or noise by being insulated with a photo coupler. CONSTITUTION: An input signal of 72V is voltage-divided by a watt resistor(R1) and a division resistor(R2,R3). The divided voltage is applied to the inversion input terminal of a comparator(OP1) via a resistor(R4) and a 5V constant diode(ZD1). The voltage of 5V is applied to the non-inversion input terminal of the comparator as the reference voltage divided by a division resistor(R5,R6). The turn-on/turn-off input voltage of H or L outputted from the comparator is applied to a light emitting diode(D1) of a photocoupler(PC1).
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