On-board electrical system for a vehicle
An on-board electrical system for a motor vehicle contains a first energy storage unit with a first voltage level and a second energy storage unit with a second voltage level. A control unit controls a flow of current between the first energy storage unit and the second energy storage unit in both directions. A polarity-reversal protection diode connects the first energy storage unit for supplying operating voltage to the control unit. A switching element bridges the polarity-reversal protection diode when the polarity of the first energy storage unit is correct. The first voltage level is compared with the second voltage level by a comparator and the switching element is moved to its open state when the first voltage level drops to a threshold voltage value which is below the second voltage level.
1. An on-board electrical system for a vehicle, comprising:
a first energy storage unit outputting a first voltage level;
a second energy storage unit outputting a second voltage level;
a control unit controlling a flow of current between said first energy storage unit and said second energy storage unit in both directions;
a polarity-reversal protection diode connecting said first energy storage unit to said control unit for supplying an operating voltage;
a switching element connected in parallel with said polarity-reversal protection diode; and
a comparison unit configured for comparing the first voltage level with the second voltage level, said comparison unit configured to close said switching element to short said polarity-reversal protection diode when the comparing determines that the first voltage level is above the second voltage level, and said comparison unit configured to open said switching element so that said polarity-reversal protection diode is not shorted by said switching element when the comparing determines that the first voltage level has fallen to a voltage threshold value lying below the second voltage level.
2. The on-board electrical system according to claim 1 , wherein the voltage threshold value is adjustable.
3. The on-board electrical system according to claim 1 , wherein said comparison unit is a comparator having a time-delayed response characteristic.
4. The on-board electrical system according to claim 1 , wherein said switching element is a semiconductor switch.
5. The on-board electrical system according to claim 1 , wherein the on-board electrical system is configured without potential isolation with respect to said first and second energy storage units.
6. The on-board electrical system according to claim 1 , wherein the on-board electrical system is configured with potential isolation with respect to said first and second energy storage units.
7. The on-board electrical system according to claim 1 , wherein said first energy storage unit is used as an operating voltage source for a load circuit having electrical loads.
8. The on-board electrical system according to claim 1 , wherein the first and second voltage levels are in each case a nominal voltage of said first and second energy storage units respectively.
9. The on-board electrical system according to claim 1 , wherein said control unit manages a battery.
10. The on-board electrical system according to claim 1 , wherein:
said comparison unit is a comparator; and
the vehicle is a motor vehicle.
11. The on-board electrical system according to claim 4 , wherein said semiconductor switch is selected from the group consisting of a transistor and an electromechanical switch.