Battery charger for a motor vehicle, associated vehicle and method of implementation

Abstract

A battery charger (2) for a motor vehicle (1) comprises a primary circuit (5) intended to be connected to an electricity supply network (R1), and two secondary circuits (6, 7) connected to the primary circuit by means of a transformer (8). The transformer comprises three high-voltage cores (40, 41, 42) and one low-voltage core (43), the primary circuit and the first secondary circuit being connected to the high-voltage cores, the second secondary circuit being connected to the low-voltage core, the high-voltage cores and the low-voltage core being arranged in the transformer so that the mutual inductance between the windings (15, 16, 17) of the primary circuit is equal, and so that the mutual inductance between each of the windings of the primary circuit and the winding of the second secondary circuit is equal, the condition being satisfied by the high-voltage cores being equidistant from one another and each of the high-voltage cores being equidistant from the low-voltage core.

Description

Technical Field

[0001] This invention relates to a battery charger for motor vehicles.

[0002] More specifically, the present invention relates to a battery charger for charging batteries with different voltages, a vehicle including such a charger, and a method of using such a charger. Background Technology

[0003] Motor vehicles may be equipped with an electric drive system including an electric motor or a hybrid drive system combining, for example, an internal combustion engine and an electric motor, a traction battery for storing energy to supply power to the electric motor, and a charger for recharging the traction battery.

[0004] Battery chargers are typically designed to charge batteries from single-phase or three-phase power grids, so it is not possible to use the same charger to charge traction batteries from both types of power grids.

[0005] Depending on the type of powertrain, the voltage across the traction battery varies considerably, typically ranging from 150 volts to 450 volts, and in some cases even reaching 800 volts.

[0006] Auxiliary components with high power consumption (typically above 1 kW) and connected to the traction battery must be configured to operate optimally at the voltage present at both ends of the traction battery.

[0007] Such auxiliary components include, for example, an air conditioning compressor, a heating element, and a DC-DC power converter responsible for supplying power to the vehicle's low-voltage (12V) network.

[0008] However, adapting auxiliary components to various voltage ranges of traction batteries presents technical challenges and requires significant additional costs, particularly development costs, unit costs of auxiliary components produced in small batches, and storage and management costs of the resulting various types of auxiliary components.

[0009] See reference WO 2019 / 199964, which discloses three-phase or single-phase charging devices connected to the power grid. These charging devices include a first output terminal connected to a high-voltage battery and a second output terminal connected to a low-voltage battery, and these devices include multiple rectifier stages.

[0010] Charging devices transfer electrical energy from the grid to the battery and from one battery to another.

[0011] However, the charging equipment is designed to work with single-phase or three-phase power grids.

[0012] In addition, the topology of charging devices includes a large number of inputs and outputs as well as complex magnetic circuits, making the devices bulky and complex to manufacture, and resulting in generally low energy conversion efficiency.

[0013] Document CN 110149053 discloses a charging device that allows the exchange of electrical energy flow between three DC power sources.

[0014] However, the device does not allow one of the DC voltage sources to be charged by the household power grid that supplies AC voltage.

[0015] The paper entitled “Analysis and design of multiport DC / DC converter for nextgeneration hybrid vehicle subsystems” (Toyota R&D Review, Vol. 48, No. 2 (2017)) proposes a DC power converter that allows a single battery to power two circuits with different voltages across them, and the voltage across the circuits being lower than that across the battery.

[0016] However, the power converter does not allow the battery to be charged via the power grid.

[0017] Also refer to the paper entitled “Consideration of PDM and power decoupling method in an isolated single-phase matrix converter for battery charger” (Toyota R&D Review, Vol. 48, No. 2 (2017)), which discloses a charging device including a primary circuit and a secondary circuit, the primary circuit including a single-phase input stage employing direct matrix conversion.

[0018] This charging device enables the reduction of second harmonics in the secondary circuit during charging via a single-phase power grid.

[0019] However, this charger does not allow charging batteries with different voltages.

[0020] In addition, the charger works with a single-phase power grid.

[0021] Therefore, it is proposed to overcome all or some of the shortcomings of existing charging devices, in particular by providing a compact charger that can charge batteries with different voltages, to work with both single-phase and three-phase power grids, and with improved efficiency. Summary of the Invention

[0022] In view of the foregoing, the present invention provides a battery charger for motor vehicles, the battery charger comprising a primary circuit intended to be connected to a power grid and two secondary circuits connected to the primary circuit via a transformer, the primary circuit comprising three converters, each converter being capable of being connected to one phase of a three-phase power grid on its input side.

[0023] The transformer comprises three high-voltage cores and a low-voltage core. The primary circuit and the first stage circuit are connected to these high-voltage cores, and the second stage circuit is connected to the low-voltage cores. These high-voltage and low-voltage cores are arranged in the transformer such that the mutual inductance between the windings of the primary circuit is equal, and the mutual inductance between each winding of the primary circuit and the winding of the second stage circuit is equal. This condition is satisfied by placing the high-voltage cores equidistant from each other and by placing each winding of the high-voltage core and the low-voltage core equidistantly.

[0024] According to one characteristic, each converter in a three-phase primary circuit is connected on the output side to a primary coil wound with different high-voltage iron cores, and each converter is designed to connect to a different phase of a three-phase power grid.

[0025] Preferably, each converter in the three-phase primary circuit is connected on the output side to a primary coil wound with different high-voltage iron cores, and the two converters in the two-phase primary circuit are intended to be connected in parallel to the phase of the single-phase power grid, and the two converters are configured to be driven in opposite phases.

[0026] Advantageously, the primary circuit includes three secondary power converters, each connected to a secondary coil wound with a different high-voltage iron core, and these secondary power converters are designed to be connected to the primary battery.

[0027] According to another feature, the primary circuit includes three secondary coils and a secondary power converter. These secondary coils are connected in series with each other, and each secondary coil is wound with a different high-voltage iron core. The secondary power converter is connected to these secondary coils and is intended to be connected to the primary battery.

[0028] Advantageously, the second-stage circuit includes a low-voltage coil and a low-voltage power converter, the low-voltage coil being wound with a low-voltage iron core, the low-voltage power converter being connected to the low-voltage coil, and the converter being designed to be connected to a second battery.

[0029] The present invention also relates to a motor vehicle comprising two batteries and a charger as described above, wherein the first battery is connected to a first primary circuit and the second battery is connected to a second secondary circuit, and the voltage across the first battery is higher than the voltage across the second battery.

[0030] The present invention also relates to a method for charging the battery of a motor vehicle.

[0031] The method includes regulating the electrical energy transmitted from a primary circuit to two secondary circuits. The primary circuit is connected to the power grid and three high-voltage cores of a transformer. A first secondary circuit is connected to these three high-voltage cores and a first battery. A second secondary circuit is connected to the low-voltage cores of the transformer and a second battery. These high-voltage and low-voltage cores are arranged in the transformer such that the mutual inductance between each winding in the primary circuit is equal, and the mutual inductance between each winding in the primary circuit and the winding in the second secondary circuit is equal. This condition is satisfied by placing the high-voltage cores equidistant from each other and by placing each high-voltage core and the low-voltage core equidistant from each other. The regulation of the power transmitted to the first and second batteries is determined based on the phase difference between the control signals of the primary circuit.

[0032] According to one feature, the method includes charging the second battery when the phase difference between the control signals of the power converter driving the primary circuit is less than Pi / 3.

[0033] Advantageously, the method further includes transferring electrical energy between the first and second batteries via a transformer, the transfer including correcting flux drift generated by converting electrical energy from a source battery selected from the first and second batteries by modifying the duration of a voltage pulse generated from a source battery supplied to the transformer. Attached Figure Description

[0034] Other objects, features, and advantages of the invention will become clear from the following description, given only by way of non-limiting example and with reference to the accompanying drawings, in which:

[0035] [ Figure 1 A vehicle including a charger according to a first embodiment of the invention is illustrated schematically;

[0036] [ Figure 2 This schematically illustrates one embodiment of the charger's power converter;

[0037] [ Figure 3 An embodiment of the transformer of the charger according to the present invention is illustrated schematically;

[0038] [ Figure 4 An embodiment of a magnetic half-element of a transformer according to the present invention is illustrated schematically;

[0039] [ Figure 5 An example of the control signals of a charger according to the present invention is shown;

[0040] [ Figure 6This illustrates an example of flux change through a high-pressure core and through a low-pressure core when the phase difference is π / 3.

[0041] [ Figure 7 This illustrates an example of flux changes through a high-voltage core and through a low-voltage core when the phase difference is less than π / 3.

[0042] [ Figure 8 A portion of the charger according to the invention is shown schematically;

[0043] [ Figure 9 The flux control circuit according to the present invention is illustrated schematically.

[0044] [ Figure 10 ]as well as

[0045] [ Figure 11 This schematically illustrates a voltage pulse generated by a power converter; and

[0046] [ Figure 12 The second embodiment of the charger according to the invention is illustrated schematically. Detailed Implementation

[0047] Figure 1 A hybrid or electric motor vehicle 1, for example, is shown with a three-phase power grid R1 that delivers 16 amps per phase, and a first embodiment of a reversible charger 2 including a battery powered by the grid R1 to recharge or discharge a first battery 3 and a second battery 4 connected to the charger 2.

[0048] The voltage across the first battery 3 is higher than the voltage across the second battery 4. The first battery 3 is, for example, a traction battery with a voltage of 400 volts across its terminals, and the voltage across the second battery 4 is, for example, 48 volts across its terminals. The second battery is intended to power, for example, the electrical auxiliary equipment or computer of the vehicle 1.

[0049] The charger 2 includes a primary circuit 5 connected to the power grid R1, two secondary circuits 6 and 7 connected to the primary circuit 5 via a transformer 8, and a processing unit UT.

[0050] The primary circuit 5 includes three primary power converters 12, 13 and 14. Each primary power converter is connected on one side to different phases L1, L2 and L3 of the power grid R1, and on the other side to the neutral point N of the power grid R1.

[0051] Each primary converter 12, 13, 14 is connected on the output side to a corresponding primary coil 15, 16, 17, which is powered by the corresponding primary power converter 12, 13, 14 and forms the primary winding of transformer 8.

[0052] The primary circuit 5 may further include a switch 18 connecting the two phases L1 and L2 of the primary circuit 5.

[0053] When charger 5 is connected to the power grid R1, switch 18 is in the open state.

[0054] The primary circuit 6 includes three secondary power converters 25, 26, and 27, each connected to secondary coils 22, 23, and 24, and each secondary power converter 25, 26, and 27 is further connected to the first battery 3. The secondary coils 22, 23, and 24 form the first portion of the secondary winding of the transformer 8.

[0055] The second-stage circuit 7 includes a low-voltage coil 28 forming a second portion of the secondary winding of the transformer 8, and a low-voltage power converter 29 connected to the low-voltage coil 28, which is further connected to the second battery 4.

[0056] Charger 2 charges the first battery 3 and the second battery 4 from the power grid R1.

[0057] Primary power converters 12, 13, and 14 are generated by four-quadrant components that specifically include diodes and transistors.

[0058] Figure 2 An example of an embodiment of the power converter of charger 2 is shown.

[0059] Since the primary power converters 12, 13 and 14, the secondary power converters 25, 26 and 27 and the low-voltage power converter 29 have the same architecture, only the architecture of the primary power converter 12 will be described in detail.

[0060] The converter 12 includes four switching units CEL1 to CEL4 and a capacitor C1. Each switching unit includes a transistor T and a freewheeling diode D1.

[0061] The input terminal of the first unit CEL1 is connected to phase L1, the first terminal of capacitor C1, and the input terminal of the second unit CEL2.

[0062] The output terminal of unit CEL1 is connected to the input terminal of the third unit CEL3 and the first terminal of winding 15.

[0063] The output terminal of the third unit CEL3 is connected to the neutral point N, the second terminal of capacitor C1, and the output terminal of the fourth unit CEL4.

[0064] The output of the second unit CEL2 is connected to the input of the fourth unit CEL4 and the second end of winding 15.

[0065] Secondary power converters 25, 26, and 27, as well as low-voltage power converter 29, are, for example, reversible power converters and are generated using diodes and transistors.

[0066] The first battery 3 and the second battery 4 can supply power to the power grid R1 via the charger 2.

[0067] Figure 3 An embodiment of transformer 8 is shown, including primary coils 15, 16 and 17, secondary coils 25, 26 and 27, and low-voltage coil 28.

[0068] The transformer 8 includes a first magnetic half-element 30 and a second magnetic half-element 31, which are identical, stacked, and made of, for example, ferrite.

[0069] Half-element 30 and 31 are, for example, circular.

[0070] Figure 4 An embodiment of the magnetic half-element 30 is shown.

[0071] The first magnetic half-element 30 includes three high-voltage half-cores 32, 33 and 34, and one low-voltage half-core 35.

[0072] Similarly, the second half-element 31 includes three high-voltage half-cores 36, 37 and 38, and one low-voltage half-core 39.

[0073] The first half-element 30 and the second half-element 31 are stacked on top of each other, such that the high-voltage half-cores 32, 33, and 34 and the low-voltage half-core 35 of the first half-element 30 are in contact with the high-voltage half-cores 36, 37, and 38 and the low-voltage half-core 39 of the second half-element 31. This causes the half-cores 32 and 36, 33 and 37, and 34 and 38 to contact each other to form high-voltage cores 40, 41, and 42, and consequently, the low-voltage half-cores 35 and 39 contact each other to form a low-voltage core 43. Figure 2 ).

[0074] Primary coils 15, 16 and 17 are wound, for example, around the high-voltage half-cores 32, 33 and 34 of the first half-element 30, and secondary coils 22, 23 and 24 are wound, for example, around the high-voltage half-cores 36, 37 and 38 of the second half-element 31.

[0075] Low-voltage coil 28, for example, is wound around low-voltage iron core 43.

[0076] High-voltage cores 40, 41, and 42, and low-voltage core 43 are arranged in the transformer such that the mutual inductances M1, M2, and M3 between coils 15 and 16, 16 and 17, and between 15 and 17 are equal, and the mutual inductances M4, M5, and M6 between each pair of coils 15 and 22, 16 and 23, and 17 and 24 between the primary circuit and the first secondary circuit 6 are equal. Similarly, the mutual inductance between each primary coil 15, 16, and 17 on one side and the secondary coil 28 on the other side is equal, and the mutual inductance between each secondary coil 22, 23, and 24 on one side and the secondary coil 28 on the other side is equal.

[0077] For example, such as Figure 4 As shown, when the half-element 30 and 31 are circular, the low-voltage iron core 43 is placed at the center of the disk, and the high-voltage iron cores 40, 41 and 42 are placed equidistantly from each other so as to obtain the same mutual inductance between the windings. The two adjacent high-voltage iron cores form a 120° angle with respect to the low-voltage iron core.

[0078] Transformer 8 allows the connection of primary circuit 5, first-stage circuit 6, and second-stage circuit 7, while reducing the complexity of the magnetic circuit (especially by reducing the number of coils) and the volume of the magnetic circuit (especially by reducing the volume of ferrite).

[0079] The reduction in ferrite volume lowers iron loss and effectively reduces the copper length of the coil, thereby reducing copper loss, which helps improve the efficiency of charger 2.

[0080] Furthermore, the geometry of the magnetic circuit of the transformer 8, including the first half-element 30 and the second half-element 31, balances the magnetic coupling within the magnetic circuit to allow for the use of similar control strategies to control each phase of the charger 2.

[0081] Control strategies may include, for example, setting a phase difference between each winding 15, 16 and 17 of the primary circuit 5 and the neutral point N of the power grid R1, or implementing a freewheeling phase.

[0082] In the first implementation mode of charger 2, charger 2 charges batteries 3 and 4.

[0083] The power transferred from charger 2 to batteries 3 and 4 depends on the phase difference between control signals S12, S13 and S14 of primary power converters 12, 13 and 14. These control signals drive the transistors of the power converter.

[0084] By causing an imbalance in the phase differences between the magnetic fluxes Ф1, Ф2, and Ф3 generated by the primary coils 15, 16, and 17 at the switching frequencies of power converters 12, 13, and 14, the phase difference between the control signals is controlled. Zero-sequence components are generated between each phase of the primary circuit 5.

[0085] The magnetic flux transferred from the high-voltage cores 40, 41 and 42 to the low-voltage core 43 is denoted as Ф4, and the magnetic flux Ф4 is transferred to the low-voltage coil 28.

[0086] The zero-sequence component associated with the control of secondary converters 25, 26, 27, and 29 allows for the differentiation of the power flow transmitted from the grid R1 to the first battery 3 and the second battery 4.

[0087] Control signals S12, S13 and S14 are generated by the processing unit UT.

[0088] In addition, the processing unit UT controls power converters 25, 26, 27 and 29.

[0089] Figure 5 This demonstrates that the phase difference as a function of time t is the phase difference. An example of control signals S12, S13, and S14.

[0090] Readers can also refer to Figure 6 The figure shows when the phase difference When the magnetic flux Ф1, Ф2, Ф3 and Ф4 are equal to π / 3, the changes of magnetic flux Ф1, Ф2 and Ф3 with time.

[0091] Compared to the amplitudes of magnetic fluxes Ф1, Ф2, and Ф3, the amplitude of magnetic flux Ф4 is smaller, therefore the voltage amplitude induced in coil 28 is smaller.

[0092] When the voltage induced in coil 28 is low, the transistors of converter 29 can be turned off, so that no current is transferred to battery 4 through their freewheeling diodes.

[0093] The power delivered by charger 2 is specifically used to charge the first battery 3.

[0094] Figure 7 It shows when the phase difference When the flux is less than π / 3, the magnetic flux Ф1, Ф2, Ф3 and Ф4 change with time.

[0095] The flux Ф4 generated by fluxes Ф1, Ф2, and Ф3 is large enough to induce a voltage in coil 28, which is large enough to charge the second battery 4 via converter 29. Fluxes Ф1, Ф2, and Ф3 further generate induced voltages in coils 22, 23, and 24, which are large enough to charge the first battery 3 via the first primary circuit 6.

[0096] According to the second implementation mode, the charger 2 transmits electrical energy between the first battery 3 and the second battery 4 via the transformer 8, and the primary circuit 5 is not powered by the power grid R1.

[0097] Since the primary circuit 5 and the secondary circuit 6 are in phase, an example of transferring energy from one battery to another via converters 12 and 25 will be described in detail. This method is applied to other converters in the same way.

[0098] For the sake of simplicity, Figure 8 The diagram shows a converter 12 of a primary circuit 5 connected to the neutral point of phase L1 and circuit R1, a converter 25 of a first-stage circuit 6 connected to a first battery 3, and a transformer 8 connecting circuit 5 and circuit 6.

[0099] Due to the energy exchange between the two batteries, a voltage V1 is generated across the coil 15 of converter 12, and a voltage V2 is generated across the coil 22 of converter 25.

[0100] Assume that the energy of the first battery 3 is transferred to the second battery 4 via the secondary circuit 7 (not shown).

[0101] As a variant, energy is transferred from the second battery 4 to the first battery 3.

[0102] During energy transfer, flux drift, which is generated by the conversion of electrical energy, usually occurs.

[0103] To correct flux drift, the processing unit UT employs a flux control circuit 44, such as... Figure 9 As shown.

[0104] The processing unit UT corrects flux drift generated by converting electrical energy from the source batteries selected from batteries 3 and 4 by modifying the duration of the positive or negative portion of the voltage pulse 50 generated using the source battery, which powers the transformer 8.

[0105] The flux control circuit 44 includes an amplifier 45 that receives voltage V1 as input, and an integrator 46 that includes an input terminal connected to the output terminal of the amplifier 45 and an output terminal connected to the input terminal of the low-pass filter 47.

[0106] The control circuit 44 further includes a timing determination module 48 for generating the correction time Tc, and a signal determination module 49 for generating a signal representing the symbol SELEC. The input terminals of the timing determination module 48 and the symbol determination module 49 are connected to the output terminal of the filter 47.

[0107] The control circuit 44 processes the voltage V1 so that the duration of the positive or negative portion of the voltage pulse 50 generated by the coil 22, which is applied to the transformer 8, can be extended or shortened according to the value of the symbol SELEC by adding or subtracting the correction time Tc.

[0108] The symbol SELEC is a graph of the average flux of transformer 8, indicating the direction of the correction to be applied, which is ideally zero.

[0109] Figure 10 and Figure 11 The diagram shows the reduction (dashed line) of the positive portion of pulse 50 achieved by subtracting time Tc from the time of arrival at the falling edge, and the increase (dashed line) of the negative portion of pulse 50 achieved by adding time Tc to the time of arrival at the rising edge.

[0110] Energy transfer from one battery to another enables redundancy in energy storage, which is especially important when powering safety-critical equipment such as sensors and computers used when the vehicle is driving autonomously.

[0111] The energy transfer from one battery to another also makes it possible to precharge the “high-voltage” primary circuit 6 using the second battery 4 without the need for additional precharging equipment inside the first battery 3.

[0112] Hereinafter, elements identical to those described above are indicated by the same reference numerals.

[0113] Figure 12 A second embodiment is shown, which includes a single-phase power grid R2 with phase L, for example, delivering 32 amps, and a hybrid or electric motor vehicle 1 is powered by the power grid R2, the vehicle 1 including a charger 2.

[0114] Charger 2 and Figure 1 The difference in the first embodiment of the charger 2 shown is that when switch 18 is closed, phase L of the power grid R2 supplies power to converters 12 and 13 of the primary circuit 5, but not to converter 14.

[0115] Converters 12 and 13 are inverted to minimize the current spectrum conducted by the two phases L1 and L2.

[0116] Depending on the state of switch 18, charger 2 can be powered by single-phase grid R2 (switch closed) or three-phase grid R1 (switch open) without modifying the structure of charger 2 or making the power or magnetism of charger 2 too great.

[0117] Furthermore, since the two converters 12 and 13 are placed in parallel, the current supplied by phase L of the grid R2 can be twice the current supplied by one of the phases of the three-phase grid R1.

[0118] In addition, the first stage circuit 6 and Figure 1 The difference in the secondary circuit of the first embodiment of the charger 2 shown is that it includes a single reversible power converter 51 connected to three secondary coils 52, 53 and 54, which are connected in series with each other.

[0119] The converter 51 is further connected to the first battery 3.

[0120] Each secondary coil 52, 53 and 54 is wound around a different primary half-core 36, 37 and 38 of the second half-element 31.

Claims

1. A battery charger (2) for a motor vehicle (1), the battery charger comprising a primary circuit (5) intended for connection to a power grid (R1, R2) and two secondary circuits (6, 7) connected to the primary circuit via a transformer (8), the primary circuit comprising three converters, each converter capable of being connected to one phase of a three-phase power grid on its input side, characterized in that, The transformer includes three high-voltage cores (40, 41, 42) and one low-voltage core (43). The primary circuit and the first-stage circuit are connected to the high-voltage cores, and the second-stage circuit is connected to the low-voltage core. The high-voltage and low-voltage cores are arranged in the transformer such that the mutual inductance between the windings (15, 16, 17) of the primary circuit is equal, and the mutual inductance between each of these windings of the primary circuit and the winding of the second-stage circuit is equal. This condition is satisfied by placing the high-voltage cores equidistant from each other and by placing each of these high-voltage cores equidistant from the low-voltage core.

2. The charger as claimed in claim 1, wherein, Each converter (12, 13, 14) of the primary circuit is connected on the output side to a primary coil (15, 16, 17) wound with different high-voltage iron cores (40, 41, 42), and each converter is designed to be connected to a different phase of the three-phase power grid (R1).

3. The charger as described in claim 1, wherein, Each converter (12, 13, 14) of the primary circuit is connected on the output side to a primary coil (15, 16, 17) wound with different high-voltage iron cores (40, 41, 42). The two converters (12, 13) of the primary circuit are intended to be connected in parallel to the phase of the single-phase power grid (R2), and the two converters are configured to be driven in opposite phases.

4. The charger as described in any one of claims 1 to 3, wherein, The primary circuit (6) includes three secondary power converters (25, 26, 27), each of which is connected to a secondary coil (22, 23, 24) wound with different high-voltage iron cores (40, 41, 42). These secondary power converters are intended to be connected to the primary battery (3).

5. The charger as described in any one of claims 1 to 3, wherein, The first primary circuit (6) includes three secondary coils (52, 53, 54) and a secondary power converter (51). The secondary coils are connected in series with each other and each secondary coil is wound with a different high-voltage iron core (40, 41, 42). The secondary power converter is connected to these secondary coils and is intended to be connected to the first battery (3).

6. The charger as claimed in any one of claims 1 to 3, wherein, The second stage circuit (7) includes a low-voltage coil (28) and a low-voltage power converter (29), the low-voltage coil being wound around the low-voltage core (43), the low-voltage power converter being connected to the low-voltage coil, and the low-voltage power converter being intended to be connected to the second battery (4).

7. A motor vehicle (1) comprising two batteries (3, 4) and a charger (2) as claimed in any one of claims 1 to 6, wherein a first battery (3) is connected to the first primary circuit (6) and a second battery (4) is connected to the second secondary circuit (7), wherein the voltage across the first battery is higher than the voltage across the second battery.

8. A method for charging batteries (3, 4) of a motor vehicle (1), characterized in that, The method includes regulating the electrical energy transmitted from a primary circuit (5) to two secondary circuits (6, 7), the primary circuit being connected to the power grid and three high-voltage cores (40, 41, 42) of a transformer (8), the first secondary circuit being connected to the three high-voltage cores and a first battery (3), and the second secondary circuit being connected to the low-voltage core (43) of the transformer and a second battery (4), the high-voltage cores and the low-voltage cores being arranged in the transformer such that the mutual inductance between each of the windings of the primary circuit is equal, and the mutual inductance between each of the windings of the primary circuit and the winding of the second secondary circuit is equal, the condition being satisfied by placing the high-voltage cores equidistant from each other and by placing each of the high-voltage cores and the low-voltage core equidistant, the regulation of the power transmitted to the first battery and the second battery being determined according to the phase difference between the control signals (S12, S13, S14) of the primary circuit.

9. The method of claim 8, comprising charging the second battery (4) when the phase difference between the control signals (S12, S13, S14) of the power converter driving the primary circuit (5) is less than π / 3.

10. The method of any one of claims 8 and 9, further comprising transferring electrical energy between the first battery and the second battery via the transformer (8), the transfer comprising correcting flux drift generated by converting electrical energy from a source battery selected from the first battery and the second battery by modifying the duration of a voltage pulse (50) generated from a source battery supplied to the transformer (8).

Images