Electrical system for a motor vehicle

An electric system for a motor vehicle, the vehicle comprising at least one power supply battery, the electric system comprising an electric charger intended to be connected both to said battery and also to an electric network outside the vehicle supplying an AC voltage or to electric equipment, and a microcontroller, the charger being able to charge the battery from an external electric network or to allow the battery to power said equipment, the charger comprising:

• a) a power factor corrector circuit able to convert an AC voltage into a DC voltage and vice versa,
• b) a DC-DC voltage converter connected between the power factor corrector circuit and the battery and able to convert a DC voltage into another DC voltage, said DC-DC voltage converter comprising a first H-bridge, and a second H-bridge, each H-bridge comprising four switches, a first switch being connected between a high point and a midpoint, a second switch being connected between the midpoint and a low point, a third switch being connected between the high point and a second midpoint and a fourth switch being connected between the second midpoint and the low point, the voltage converter also comprising a transformer electrically connecting the first H-bridge and the second H-bridge, each H-bridge being able to operate in:
• i) a first operating mode, in which the first switch and the fourth switch are open and closed simultaneously, the second switch and the third switch are open and closed simultaneously in contrast to the first switch and the fourth switch,
• ii) a second operating mode, in which the fourth switch is always closed, the third switch is always open, and the first switch and the second switch are alternately open and closed,
• the microcontroller being configured to:
• a) command the opening and closing of each switch of the first bridge and of the second bridge of the DC-DC voltage converter by transmitting to each switch a command signal that is characterized by a frequency, the high state of the command signal making it possible to command the closure of a switch and the low state of the command signal making it possible to command the opening of a switch, a first frequency range defining the set of frequencies of the command signal for which the first bridge or the second bridge operates in the first operating mode and a second frequency range defining the set of frequencies of the command signal for which the first bridge or the second bridge operates in the second operating mode,
• b) activate the second operating mode of the first bridge or of the second bridge by transmitting:
• i) an opening command signal to the third switch,
• ii) a closing command signal to the fourth switch,
• iii) a command signal to the first switch and to the second switch for a predetermined time, the frequency of each command signal being equal to the maximum value of the second frequency range over a predetermined time,
• c) activate the second operating mode of the first bridge or of the second bridge by transmitting a command signal to each switch of the first bridge, respectively of the second bridge, the frequency of each transmitted command signal being equal to the maximum value of the first frequency range over a predetermined time.