Device for maintaining voltage during startup for a motor vehicle

1. Device for maintaining voltage (DMT), designed to be associated with a rotary electrical machine (AD) which fulfils a function of starting of the thermal engine of a motor vehicle, this device (DMT) being designed, when the thermal engine is started, to supply an additional voltage for an electrical supply of the rotary electrical machine (AD), this additional voltage being added to a nominal voltage of the on-board electrical network (RB) of the vehicle which is supplied by a battery (BAT) contained in the vehicle as the main source of voltage, with the device comprising a second source of voltage (Ucap) and first and second electronic switches (K 1 , K 2 ), each comprising at least one transistor of the MOSFET type, wherein at least one MOSFET transistor (K 2 , K 2 n ′) of the switches, is mounted in series with the second source of voltage (Ucap), the device further comprising an ECU configured to control the at least one MOSFET transistor of the switches wherein the ECU controls the at least one MOSFET transistor of the switches in linear mode at the end of starting of the thermal engine.

2. Device according to claim 1 , wherein said ECU is further configured to control said MOSFET transistor functioning in linear mode at the end of starting of the thermal engine functions in either an open state, or in a closed state during the remainder of the starting operation.

3. Device according to claim 1 , characterized in that it comprises a current control loop ( 2 , 3 , 4 , 5 , 6 ) for the control in linear mode of the transistor (K 2 , K 2 n ′) of the second electronic switch.

4. Device according to claim 3 , characterized in that the ECU is further configured to control and limit electric current (I, I/n) which circulates in the transistor (K 2 , K 2 n ′) in linear mode by a set value (CK 2 ′) supplied as input to the current control loop ( 2 , 3 , 4 , 5 , 6 ).

5. Device according to claim 1 , characterized in that the second electronic switch comprises a plurality (n) of MOSFET transistors (IC 1 , IC 2 , . . . ICn) mounted in parallel, the plurality of MOSFET transistors being mounted in series with the second source of voltage (Ucap).

6. Device according to claim 5 , characterized in that said ECU is further configured to control each of the transistors (IC 1 , IC 2 , . . . ICn) in linear mode at the end of starting of the thermal engine, and the device comprises for each transistor a current control loop ( 2 , 3 , 4 , 5 , 6 ) for the control in linear mode of the transistor.

7. Device according to claim 1 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said ECU so as to be in either an open state or in a closed state.

8. Device according to claim 1 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

9. Device according to claim 8 , characterized in that it comprises a direct-direct converter (CDC) connected to the second source of voltage, in order to charge the supercapacitor (Ucap).

10. System for starting a thermal engine, characterized in that it comprises a device for maintaining voltage (DMT) according to claim 1 .

11. Device according claim 2 , characterized in that it comprises a current control loop ( 2 , 3 , 4 , 5 , 6 ) for the control in linear mode of the transistor (K 2 , K 2 n ′) of the second electronic switch.

12. Device according to claim 2 , characterized in that the second electronic switch comprises a plurality (n) of MOSFET transistors (IC 1 , IC 2 , . . . ICn) mounted in parallel, the plurality of MOSFET transistors being mounted in series with the second source of voltage (Ucap).

13. Device according to claim 3 , characterized in that the second electronic switch comprises a plurality (n) of MOSFET transistors (IC 1 , IC 2 , . . . ICn) mounted in parallel, the plurality of MOSFET transistors being mounted in series with the second source of voltage (Ucap).

14. Device according to claim 4 , characterized in that the second electronic switch comprises a plurality (n) of MOSFET transistors (IC 1 , IC 2 , . . . ICn) mounted in parallel, the plurality of MOSFET transistors being mounted in series with the second source of voltage (Ucap).

15. Device according to claim 2 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said configured ECU to be in either an open or in a closed state.

16. Device according to claim 3 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said configured ECU to be in either an open or in a closed state.

17. Device according to claim 4 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said configured ECU to be in either an open or in a closed state.

18. Device according to claim 5 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said configured ECU to be in either an open or in a closed state.

19. Device according to claim 6 , characterized in that the first switch (K 1 ) comprises at least one MOSFET transistor controlled by said configured ECU to be in either an open or in a closed state.

20. Device according to claim 2 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

21. Device according to claim 3 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

22. Device according to claim 4 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

23. Device according to claim 5 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

24. Device according to claim 6 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).

25. Device according to claim 7 , characterized in that the second source of voltage comprises a supercapacitor (Ucap).