Patent attributes
A leak detecting circuit includes: a current path having one end connected to a conductor housing a device supplied with a direct-current voltage from a direct-current power source, and having another end connected to a negative electrode of the direct-current power source; the current path including a limiting resistance for limiting a current, a switch element having a first electrode, a second electrode, and a control electrode, conduction between the first electrode and the second electrode being controlled, a detecting resistance for detecting a current flowing through the current path, and a variable direct-current power source allowing a plurality of leak detecting reference voltages for detecting a leak to be selected, and having a negative electrode connected to the negative electrode of the direct-current power source; an amplifier for amplifying a voltage across the detecting resistance; and a constant-voltage circuit for making constant a potential difference between a voltage of the control electrode of the switch element and a voltage of a positive electrode of the variable direct-current power source; wherein a leak between the conductor and the direct-current power source is detected on a basis of the voltage across the detecting resistance, the voltage across the detecting resistance being amplified by the amplifier.
