ON-BOARD ELECTRICAL NETWORK OF A MOTOR VEHICLE

An on-board electrical network () of a motor vehicle () has a first voltage circuit (I) and a second voltage circuit (II), wherein the first voltage circuit has a first operating voltage higher than a second operating voltage in the second voltage circuit. The first voltage circuit is connected to the second voltage circuit via a DC voltage converter (). The first voltage circuit has a battery () and the second voltage circuit has a main battery () and an auxiliary voltage source (). By means of a first switching element () and a second switching element () at least one of transmission control unit () and/or integrated hybrid controller () are supplied with electrical energy from the main battery () and/or the auxiliary voltage source (). Control unit () and/or hybrid controller () can be selectably disconnected from either the main battery () and/or the auxiliary voltage source ().