On-board electrical network of a motor vehicle

An on-board electrical network of a motor vehicle comprising:

• a first voltage circuit;
• a second voltage circuit;
• and
• a DC-to-DC converter coupled between the first voltage circuit and the second voltage circuit;
• wherein the first voltage circuit has a first operating voltage which is higher than a second operating voltage in the second voltage circuit;
• wherein the first voltage circuit comprises a first battery at the first operating voltage;
• wherein the second voltage circuit comprises a main battery and an auxiliary voltage source both at the second operating voltage;
• wherein the second voltage circuit further comprises at least one of a transmission control unit and an integrated hybrid controller;
• wherein the second voltage circuit further comprises a first switching element connected between the main battery and the least one of a transmission control unit and an integrated hybrid controller and a second switching element connected between the auxiliary voltage source and the least one of a transmission control unit and an integrated hybrid controller;
• wherein each of the first and second switching elements is normally in a closed state to supply electrical energy from the main battery and the auxiliary voltage source to the at least one of a transmission control unit and an integrated hybrid controller, wherein the first switching element is switched to an open state in response to detection of a fault associated with the main battery, and wherein the second switching element is switched to an open state in response to detection of a fault associated with the auxiliary voltage source.