Low power intelligent current source for monitoring a high voltage

A voltage monitor circuit comprising:

• an input terminal for receiving a voltage to be monitored and through which an input current flows,
• an output terminal at which a voltage is derived indicative of the voltage to be monitored,
• a current source,
• a current mirror comparison means coupled to the current source for comparing a current derived from the current source with said input current that flows through the input terminal thereby to derive at its output a voltage indicative of the monitored voltage,
• wherein said current mirror comparison means further comprises,
• a first current mirror circuit having a first terminal coupled to said current source, a second terminal coupled to said output terminal, a second current mirror circuit having a first terminal coupled to said input terminal and a second terminal coupled to a third terminal of the first current mirror circuit, and a third current mirror circuit having a first terminal coupled to the second terminal of the first current mirror circuit and a second terminal coupled to a common terminal of the second current mirror circuit such that a current flowing through the common terminal also flows through the second terminal of the third current mirror circuit, and
• means coupling said output terminal to said output of the current mirror comparison means.

A voltage monitor circuit comprising:

• an input terminal for receiving a voltage to be monitored, said input terminal being coupled to the voltage monitor circuit via a current path that does not include a control electrode of a transistor,
• an output terminal at which a voltage is derived indicative of the voltage to be monitored,
• a current source,
• a current mirror comparison means coupled to the current source and to said input terminal for limiting an input current that flows through said input terminal to a value determined by said current source and for comparing a current derived from the current source with said input current thereby to derive at its output a voltage indicative of the monitored voltage,
• a DC supply voltage terminal coupled to the current mirror comparison means to supply a DC operating voltage thereto independent of said current source, and
• means coupling said output terminal to said output of the current mirror comparison means.

A voltage monitor circuit comprising:

• an input voltage terminal for receiving a voltage to be monitored and through which an input current flows,
• an output terminal at which a voltage is derived indicative of the voltage to be monitored,
• a current source,
• a current mirror comparison means comprising;
• a first transistor current mirror means having an output coupled to the current source for comparing a current derived from the current source with a current derived from said input current that flows through the input terminal thereby to derive at its output a voltage indicative of the monitored voltage,
• a second transistor current mirror means comprising transistors of the same transistor conductivity type as those of said first transistor current mirror means, and having an output coupled to the input terminal and having an input which receives a current derived from said current source whereby said input current is limited to a value determined by said current source, and
• means coupling said output terminal to said output of the first transistor current mirror means.