Open-circuit failure detection circuit

#The present invention relates to a broken-wire failure detection circuit with a failure detection function for outputting a voltage out of a normal output-voltage range as a dialog voltage when a broken-wire failure occurs in a power line, signal line, or ground line of an electric or electronic circuit connected to a higher circuit.

#FIG. 16 is a circuit diagram showing a configuration of a conventional broken-wire failure detection circuit. As shown in FIG. 16, the conventional broken-wire failure detection circuit includes a functional circuit 1 composed of an electric or electronic circuit in which the first resistance means 21 is connected between a power line 11 and a signal line 12, and the second resistance means 22 is connected between the signal line 12 and a ground line 13.

#The power line 11 of the functional circuit 1 is connected to a power line 41 of a higher circuit 4 that supplies power to the functional circuit 1. The signal line 12 of the functional circuit 1 is connected to a signal output terminal 45 via a signal line 42 of the higher circuit 4. A signal output-circuit section 3 is provided in the functional circuit 1. A signal from a signal output-circuit output stage amplifier 31 in the signal output-circuit section 3 is output from a signal output terminal 45 via the signal lines 12 and 42. The ground line 13 of the functional circuit 1 is connected to a ground line 43 of the higher circuit 4.

#FIG. 1 is a circuit diagram showing a configuration of a broken-wire failure detection circuit according to the first embodiment of the present invention;

#FIG. 2 is a circuit diagram showing a broken power line in the broken-wire failure detection circuit according to the first embodiment of the present invention;

#FIG. 3 is a circuit diagram showing a broken ground line in the broken-wire failure detection circuit according to the first embodiment of the present invention;

#Hereunder, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

#FIG. 1 is a circuit diagram showing a configuration of a broken-wire failure detection circuit according to the first embodiment of the present invention. As shown in FIG. 1, the broken-wire failure detection circuit according to the first embodiment comprises the third resistance means 23 connected between a functional-circuit-side power line 11 and a functional-circuit-side ground line 13 of a conventional broken-wire failure detection circuit shown in FIG. 16. That is, in a functional circuit 101, the first resistance means 21 is connected between the power line 11 and a signal line 12. The second resistance means 22 is connected between the signal line 12 and the ground line 13. Furthertmore, the third resistance means 23 is connected between the power line 11 and the ground line 13. Other arrangements of the functional circuit 101 and a configuration of the higher circuit 4 are the same as those shown in FIG. 16. Thus, they are denoted by the same reference numerals used in FIG. 16, and their descriptions are omitted.

#In the configuration shown in FIG. 1, if a connection between the power line 11 of the functional circuit 101 and the power line 41 of the higher circuit 4 is broken as shown in FIG. 2, the second resistance means 22, the fifth resistance means 25 of the higher circuit 4, and the first and third resistance means 21 and 23, all of which constitute a series-connected unit, are connected in parallel. At this time, an apparent pull-down-resistance value, which is indicated by a composite resistance value (R2//R02//R5//(R1//R01+R3//R03)) obtained by adding an internal resistance values R01, R02, and R03, becomes below a pull-down-resistance value obtained when a connection between the power lines 11 and 41 is broken in the conventional configuration shown in FIG. 16. In this case, R3 denotes a resistance value of the third resistance means 23.