Patent attributes
A voltage detecting apparatus with a capacitor having a switch for detecting a voltage of a direct-current power source, which can detect a malfunction of the switch without additional parts and effects to a measurement time in a normal condition, is provided. When a microcomputer measures a voltage between both terminals of a capacitor plural times, the sampled voltages are at most a prescribed threshold value, and a voltage decreases at least a prescribed difference of voltages in sampling order (each of all measured voltages between both terminals decreases at least a potential deference from a voltage measured previously in sampling order). Furthermore, when the voltage between both terminals of the capacitor becomes 0 volt in condition that a fifth switch SW5 is opened, it is judged that the fifth switch is in an abnormal condition.
