| 摘要 |
A three-phase switch checking circuit is provided to check three phases according to signals outputted from a switch by inputting the same signal to one switch. In a three-phase switch checking circuit, a switch(SW) connected with a non-inverting terminal of a comparer(C) and a second output end(D) to switch an input signal side terminal and a contact terminal has: a first switching phase connected with the input signal side terminal; a second switching phase connected with neither the input signal side terminal nor the contact terminal; and a third switching phase connected with the contact terminal to output different signals to a first output end(D') and the second output end according to the switching phases. A first resistance unit(10) is formed with a first resistance(R1) and a second resistance(R2) at 3 kilo-ohms and 2 kilo-ohms respectively, and is connected to each other in parallel. One end of the first resistance is connected with an inverting terminal of the comparer, and the other end is connected with the earth. The second resistance is serially connected with the input end on one end. The first and second resistances are connected in parallel to drop voltage of 5 volts input signal at the first, second, and third switch phases to output to the inverting terminal of the comparer. A second resistance unit(20) is formed with a third resistance(R3) and a fourth resistance(R4) at 2 and 3 kilo-ohms respectively, and is connected in parallel to each other. The third resistance is connected with the non-inverting terminal output end of the comparer on one end and with the earth on the other end. The fourth resistance is connected with the input end. 5 volts input signal drops voltage by the third and fourth resistances to be inputted to the second output end and the inverting terminal of the comparer.
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