TECHNICAL FIELD

The present disclosure relates to circuitry for an electrical vehicle. Aspects relate to a transformer circuit, to a system, and to a vehicle.

BACKGROUND

Electric vehicles and hybrid electric vehicles comprise traction motors, and traction batteries for supplying electrical energy to the traction motors. Some traction batteries can be recharged with electrical energy from outside the vehicle, such as electrical energy from an electrical grid. The traction battery may be recharged with electrical energy from an AC grid. OBC (on-board charger) circuitry converts the AC power from the grid to DC power for providing to the traction battery. The traction battery may also be recharged with electrical energy from a DC source outside the vehicle. To accommodate DC charging, a further DC-DC converter can be supplied to convert the electrical energy from the DC source to a suitable voltage for supplying to the traction battery, for example 400V or 800V depending on the battery configuration.

Furthermore, the traction battery may supply energy to power further auxiliary systems within the vehicle. Such auxiliary systems may require the traction battery to provide multiple different voltage outputs depending on the system. Examples include drive inverters which operate at 400V, or advanced driver assistance systems (ADAS) and vehicle lights which operate at 12 V.

As DC-DC and OBC circuitry in electric vehicles are generally of fixed voltage output and input, to accommodate the different voltage requirements for auxiliary systems within a vehicle, multiple DC-DC converters are utilised inside the vehicle to convert the power supplied by the traction battery to each voltage output for the auxiliary systems.

This use of multiple DC-DC converters inside the vehicle to provide the flexibility to supply power to the vehicle systems and accommodate different charging requirements undesirably contributes to an increasing complexity, and cost, of the electrical architecture of the vehicle.

It is an aim of examples disclosed herein to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a transformer circuit, a system and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a transformer circuit for an electric vehicle. The transformer circuit comprises an input for receiving electrical energy; a first output for providing electrical energy to a first electrical bus of the vehicle at a first voltage; a second output for providing electrical energy to a second electrical bus of the vehicle at a second voltage; and a multi-coil transformer disposed between the input, the first output and the second output, the multi-coil transformer comprising a primary winding connected to the input; a first secondary winding connected to the first output; and a second secondary winding connected to the second output, wherein the multi-coil transformer is arranged such that, in use, electrical energy can be provided to the first output and the second output simultaneously.

Advantageously, the transformer circuit reduces the amount of circuitry required in the electric vehicle to provide energy to each vehicle bus at a different voltage. A single multi-coil transformer can be used in contrast to a dedicated transformer and switching circuitry between a battery pack and each auxiliary vehicle bus and charging input. In particular, the battery pack does not need to be disposed between the charging input and each DCDC converter for providing energy to auxiliary loads. Thus, the total complexity and cost of transformer circuitry for the vehicle is reduced.

The first secondary winding and second secondary winding are electrically isolated. Thus, the first secondary winding and the second secondary winding can each be tailored to provide power at a different output voltage.

Advantageously, the multi-coil transformer is omnidirectional. In this way, each of the first output and second output may also act as an input to the transformer. Thus, the multi-coil transformer may be used both to charge a battery pack from a charging input, and to discharge the battery pack to power the second electrical bus of the vehicle.

The first voltage may be higher than the second voltage. The first voltage and second voltage may be non-overlapping ranges.

The first electrical bus may comprise a battery connection terminal for providing electrical power to a traction battery of the vehicle or receiving electrical power from the traction battery of the vehicle. Thus, the traction battery may be charged or discharged via the first output. The first voltage may comprise a nominal voltage in the range of 600V to 1000V or 450V to 850V. For example, the first voltage may be substantially 800V. In other embodiments, the first voltage may comprise a nominal voltage in the range 300V to 1000V, for example substantially 400V. The first voltage may be defined as an operating voltage of the traction battery.

The second electrical bus may be for providing electrical power to one or more auxiliary electrical units of the vehicle at the second voltage. In some embodiments, the auxiliary electrical units may comprise high voltage (HV) electrical units such as one or more of a heater; a chiller; an air conditioning compressor; a power-assisted steering system; an active roll control pump; a suspension compressor; and a heated windscreen. The second voltage may comprise a nominal voltage in the range 200V to 500V or 250V to 450V, for example 400V.

In some embodiments, the auxiliary electrical units may comprise high voltage (LV) electrical units such as an advanced driver assistance system (ADAS) of the vehicle, an infotainment system of the vehicle, a lighting system of the vehicle, a seat adjustment system of the vehicle or a seat heating system of the vehicle. The second voltage may comprise a nominal voltage in the range 9V to 60V or 9V to 16V, for example 12V.

The transformer circuit may comprise a third output for providing electrical energy to a third electrical bus of the vehicle at a third voltage, wherein the multi-coil transformer comprises a third secondary winding connected to the third output. The third voltage may be lower than the first voltage and the second voltage. In some embodiments, the third voltage comprises a nominal voltage in the range 9V to 60V. The third electrical bus may be for providing electrical power to one or more of: an advanced driver assistance system (ADAS) of the vehicle, an infotainment system of the vehicle, a lighting system of the vehicle, a seat adjustment system of the vehicle or a seat heating system of the vehicle.

The transformer circuit may comprise a primary side circuit connecting the input to the primary winding of the transformer, and a secondary side circuit connecting the secondary winding of the transformer to the output. The input may comprise an AC charging input and an ACDC converter configured to receive electrical energy from the AC charging input and provide electrical energy to the primary winding via the primary side circuit. The ACDC converter may have a totem pole topology.

The transformer circuit may comprise a DC link capacitor bank disposed between the input and the primary side circuit, wherein the ACDC converter is arranged to provide electrical energy to the primary side circuit via the DC link capacitor bank.

The transformer circuit may comprise DC charging input between the ACDC converter and the primary side circuit, such that the DC charging input is configured to receive electrical energy from a DC source and provide electrical energy to the primary winding via the primary side circuit.

The multi-coil transformer may be omnidirectional. That is, the multi-coil transformer may be configured to: in a first charging configuration, provide electrical energy from the input to each of the first electrical bus and the second electrical bus via the first output and the second output; and in a second discharging configuration, provide electrical energy from the first electrical bus to the second electrical bus via the first output and the second output.

According to another aspect there is provided a transformer circuit for an electric vehicle, comprising: an input for receiving electrical energy; an output for providing electrical energy to an electrical bus of the vehicle at an output voltage; and a DCDC converter disposed between the input and the output, the DCDC converter comprising: a transformer comprising a primary winding and a secondary winding, a primary side circuit connecting the input to the primary winding of the transformer, and a secondary side circuit connecting the secondary winding of the transformer to the output; the input comprising: an AC charging input, an ACDC converter configured to receive electrical energy from the AC charging input and provide electrical energy to the primary winding via the primary side circuit; and a DC charging input arranged between the ACDC converter and the primary winding, such that the DC charging input is configured to receive electrical energy from a DC source and provide electrical energy to the primary winding via the primary side circuit.

Advantageously, a dedicated transformer does not need to be provided for each of the AC charging input and the DC charging input. Thus, the total amount of transformer circuitry in the vehicle is reduced, thereby reducing complexity and cost.

The transformer circuit may comprise a DC link capacitor disposed between the input and the primary side circuit of the DCDC converter, wherein the ACDC converter and the DC charging input each provide electrical energy to the primary side circuit via the DC link capacitor. That is, a common DC link capacitor is used for both the AC charging input and DC charging input, thereby reducing transformer circuitry in vehicle.

The transformer circuit may further comprising a switch arranged to switch the transformer circuit between a first configuration for receiving electrical energy from the DC charging input, and a second configuration for receiving electrical energy from the AC charging input. The switch may be disposed at the DC charging input. Thus, in the first configuration, the DCDC converter is utilised as part of the on-board charger (OBC) of the vehicle. In the second configuration, the DCDC converter is utilised for direct DC charging of the vehicle.

The DCDC converter may be bidirectional. For example, the DCDC converter may be a CLLC DCDC converter. When the DCDC converter is operating in a positive or forward direction, the primary side circuit is arranged to operate as an inverter and the secondary side circuit is arranged to operate as a rectifier. When the DCDC converter is operating in a reverse or negative direction, the primary side circuit is arranged to operate as a rectifier and the secondary side circuit as an inverter.

In other embodiments, the DCDC converter may be operable in one direction only. For example, the primary side circuit may operate always as an inverter, and the secondary side circuit may operate always as a rectifier.

The ACDC converter may have a totem pole topology.

Optionally, the electrical bus comprises a battery connection terminal for providing electrical power to a traction battery of the vehicle or receiving electrical power from the traction battery of the vehicle. The output voltage may comprise a nominal voltage in the range 300V to 1000V, for example substantially 400V or substantially 800V.

The transformer circuit may comprise a further output for providing electrical energy to a further electrical bus of the vehicle at a further output voltage. The DCDC converter may therefore comprise a further secondary side circuit, and the transformer may be a multi-coil transformer comprising a further secondary winding connected to the further output via the further secondary side circuit.

Advantageously the DCDC converter can be omnidirectional, such that each of the output and further output may also act as an input to the DCDC converter. In this way, the electrical bus (for example the electrical bus connected to the traction battery) can provide energy to the further electrical bus when there is no charging input.

Beneficially this reduces number of transformers required as it negates the need for a dedicated transformer between the electrical bus and further electrical bus, thereby reducing complexity and cost.

Optionally, the output voltage is higher than the further output voltage. The output voltage and further output voltage may be non-overlapping ranges.

The further output voltage may comprise a nominal voltage in the range 9V to 60V or 9V to 16V, for example 12V. The further electrical bus may thus be for providing electrical power to one or more low voltage (LV) auxiliary electrical units of the vehicle at the further output voltage. The LV auxiliary units may include one or more of an advanced driver assistance system (ADAS) of the vehicle, an infotainment system of the vehicle, internal or external lighting associated with the vehicle, a seat heating system, a seat adjustment system.

The DCDC converter may be omnidirectional. That is, the DCDC converter may be configured to: in a first charging configuration, provide electrical energy from the input to each of the electrical bus and the further electrical bus via the output and the further output; and in a second discharging configuration, provide energy from the electrical bus to the further electrical bus via the output and the further output.

According to another aspect there is provided a battery system for an electric vehicle, comprising: a transformer circuit according to one of the aspects above; a charging input for receiving electrical energy and providing electrical energy to the input of the transformer circuit; and a vehicle traction battery configured to connect to an output of the transformer circuit.

According to another aspect there is provided a vehicle comprising the transformer circuit or the battery system according to the aspects above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1A shows a prior art voltage conversion system 100;

Figure 1 B shows on-board charger (OBC) circuitry;

Figures 1 C and 1 D each show a DCDC converter;

Figures 2A and 2B each show a transformer circuit according to an embodiment;

Figure 3 shows a transformer circuit according to another embodiment;

Figures 4A and 4B each show a transformer circuit according to an embodiment;

Figure 5 shows a transformer circuit according to another embodiment;

Figure 6A shows a transformer circuit according to another embodiment;

Figure 6B shows a transformer circuit according to another embodiment;

Figure 7 shows a flow chart of a method;

Figure 8 shows a battery system for a vehicle in accordance with an embodiment; and

Figure 9 shows a vehicle in accordance with an embodiment. DETAILED DESCRIPTION

Examples disclosed here may provide efficient voltage conversion circuitry for an electric vehicle.

With reference to Figure 1A, a prior art voltage conversion system 100 is illustrated. The system 100 comprises a traction battery 120 for supplying electrical energy to a traction motor. The traction battery 120 is arranged to operate at a predefined voltage, for example 400V or 800V. The traction battery 120 can be charged by providing electrical energy from a charging source external to the vehicle. As the charging source may not supply electrical energy at the predefined voltage, conversion circuitry is provided as part of the voltage conversion system 100 to convert the electrical energy to a suitable voltage for the traction battery. It can be desired to charge the traction battery 120 from an AC grid. The system 100 thus comprises OBC (on-board charger) circuitry 110 which converts the AC power 111 from the grid to DC power 112 for providing to the traction battery 120.

Example OBC circuitry is illustrated in Figure 1 B. An AC grid supplies electrical power 111 to an ACDC converter portion 110- A comprising the eight switches Q1-Q8 to a DC link capacitor bank C1. In the illustrated example, the AC grid supplies three phase electrical power 111. The link capacitor bank C1 stores the DC voltage output by the ACDC converter 110-A.

A DCDC converter portion 110-B then regulates the DC voltage stored in C1 to a suitable voltage for supplying to the traction battery 120. In the illustrated example, the DCDC converter portion 110-B comprises a primary side circuit (the switches Q9 to Q12), the transformer T1 , and a secondary side circuit (the switches Q13 to Q16). The primary side circuit acts as an inverter and supplies electrical energy to a primary winding of the transformer. A secondary winding of the transformer then connects to the traction battery 120 via the secondary side circuit, which acts as a rectifier. The primary side circuit may be a primary H-bridge arrangement. The secondary side circuit may be a secondary H-bridge arrangement.

The traction battery 120 may also be recharged with electrical energy from a DC source outside the vehicle. To accommodate DC charging, a further DC-DC converter 150 can be supplied to convert the electrical energy 151 from the DC source to electrical energy 152 at a suitable voltage for supplying to the traction battery 120, for example 400V or 800V depending on the battery configuration. For example, the traction battery 120 may operate at 800V and the electrical energy 151 may be supplied from the DC source at 400V. Thus, the DC-DC converter 150 can be arranged to convert 400V DC energy from the DC source to 800V DC energy to supply the traction battery 120.

The traction battery 120 is utilised to supply power to one or more auxiliary vehicle systems, having different voltage requirements. In particular, it may be desired to provide power to both LV (low voltage) and HV (high voltage) auxiliary vehicle systems simultaneously. LV systems (wherein LV may be defined as under 60V), may include vehicle lighting systems, seat warming systems, or an advanced driver assistance system (ADAS). HV systems (which may operate at substantially 400V, between 250V to 450V) may include vehicle systems such as a heater, a chiller, an air conditioning compressor, a power- assisted steering system; an active roll control pump, a suspension compressor, a HV coolant heater, a HV water pump and a heated windscreen. As will be appreciated, the power supplied by the traction battery 120 may not be directly compatible with the auxiliary vehicle systems. For example, the traction battery 120 may be configured at 800V, and the auxiliary systems may be configured at 12V and 400V respectively. The conversion system 100 may therefore be configured to provide power to both a LV vehicle bus (e.g. for 12V auxiliary systems) and a HV vehicle bus (e.g. for 400V auxiliary systems). Conventionally, a respective DCDC converter is provided to connect the traction battery to each vehicle bus. As shown in Figure 1 A, a first DCDC converter 130 is provided to convert electrical energy 131 supplied by the traction battery to electrical energy 132 supplied to a LV electrical bus (e.g. a 12V bus) of the vehicle and a second DCDC converter 140 is provided to convert electrical energy 141 supplied by the traction battery to electrical energy 142 supplied to a HV electrical bus (e.g. a 400V bus) of the vehicle. A circuit diagram illustrating an example first DCDC converter 130 is shown in Figure 1C and a circuit diagram illustrating an example second DCDC converter 140 is shown in Figure 1 D.

The voltage conversion system 100 illustrated in Figures 1A to 1 D comprises dedicated transformer circuitry to link the traction battery 120 to each power source and each vehicle bus to which the traction battery 120 provides power. Consequently, the vehicle conversion system 100 may be bulky and expensive to manufacture.

According to the present invention, there is provided an improved voltage conversion system having reduced complexity and cost to that shown in Figures 1A to 1 D. By adapting the on board charging (OBC) circuitry 110, elements of the circuitry can be adapted to provide a multi-directional transformer circuit for providing the requisite voltage adaption between the traction battery and each vehicle bus and power source, negating the need for additional dedicated DCDC converters.

With reference to Figure 2A, there is provided a transformer circuit 200 in accordance with an embodiment of the present invention. The transformer circuit 200 comprises an input 211 for receiving electrical energy, such as from an external power source. The transformer circuit 200 further comprises a first output 221 for providing electrical energy to a first electrical bus of the vehicle at a first voltage, and a second output 231 for providing electrical energy to a second electrical bus of the vehicle at a second voltage different to the first voltage.

The transformer circuit 200 comprises a DCDC converter including a multi-coil transformer 210 disposed between the input 211 , the first output 221 and the second output 231. The multi-coil transformer 210 comprises a primary winding 212 connected to the input via a primary side circuit, a first secondary winding 214 connected to the first output 221 via a first secondary side circuit and a second secondary winding 216 connected to the second output 231 via a second secondary side circuit. The arrangement of the multi-coil transformer 210 is such that in use, electrical energy can be provided to the first output 221 and the second output 231 simultaneously. Advantageously, a single transformer circuit 210 can be harnessed to supply two different DC voltage requirements at each of the first output 221 and second output 231 by tailoring each secondary winding 214, 216 to result in the required voltage.

The DCDC converter including the multi-coil transformer is configured to be omnidirectional, such as a DCDC converter of a CLLC type. That is, each of the first output and second output may also act as an input to the transformer 210. If electrical current is supplied to the primary coil 212, consequently a current will be generated in each of the first secondary coil 214 and the second secondary coil 216, thereby supplying electrical energy to each of the first output 221 and the second output 231. Conversely, if electrical current is supplied by the first electrical bus at the first output 221 to the first secondary coil 214, consequently a current will be generated in each of the primary coil 212 and the second secondary coil 216. Advantageously, examples disclosed herein thus reduce the total number of transformers required in the voltage conversion circuitry of a vehicle, as the multi-coil transformer 210 may facilitate bridging multiple vehicle buses having multiple voltage requirements.

The multi-coil transformer 210 may be arranged such that the first voltage is higher than the second voltage. It will be appreciated that the first and second voltage may each be tailored by the turn ratio of the primary coil 212 to each secondary coil 214, 216. The turn ratio a for each secondary coil may be defined as a = = wherein m is the number of turns on the primary coil 212, n? is the number of turns on the respective secondary coil 214, 216, Vi is the voltage at the input 211 and V? is the resultant voltage at the respective output 221 , 231. Thus, adjusting the number of turns in each secondary coil 214, 216 can effectively adjust the first voltage and the second voltage provided.

The first voltage and the second voltage may be non-overlapping ranges. In this way, two different voltage requirements may be simultaneously supplied using one transformer 210.

The first electrical bus connected to the first output 221 may provide a connection to a traction battery of the vehicle. That is, the first electrical bus may comprise a battery connection terminal for connecting to the traction battery. Electrical power may be provided to the traction battery via the first electrical bus during a charging phase, and electrical power may be supplied from the traction battery through the first electrical bus during a discharging phase, for supplying power to a traction battery or one or more auxiliary systems. As such, the first output 221 although denoted an “output” may also function as an input when the traction battery is being discharged and thus supplying electrical energy through the first electrical bus.

The first voltage may thus be arranged to correspond to the configuration of the traction battery. In some examples, the first voltage comprises a nominal voltage in the range 450V to 850V, e.g. substantially 800V. In other examples, the first voltage comprises a nominal voltage in the range 250V to 450V, e.g. substantially 400V.

The second electrical bus connected to the second output 231 may be arranged to provide electrical power to one or more auxiliary electrical units of the vehicle at the second voltage. The second voltage may thus correspond to the operating voltage of the relevant auxiliary electrical units. In some examples, the second voltage comprises a nominal voltage in the range 250V to 450V, e.g. substantially 400V. In this way, the second electrical bus may provide power to HV auxiliary units of the vehicle, such as a heater unit, a chiller unit, an air conditioning compressor, a power-assisted steering system, an active roll control pump, a suspension compressor, or a heated windscreen. In other examples, the second voltage comprises a nominal voltage in the range 9V to 16V, e.g., substantially 12V. Thus, the second electrical bus may provide power to LV auxiliary units of the vehicle, such as an advanced driver assistance system (ADAS), an infotainment system, a lighting system, a seat adjustment system or a seat heating system.

With reference to Figure 2B, according to an illustrated example the transformer circuit 200 may comprise a third output 241 for providing electrical energy to a third electrical bus of the vehicle at a third voltage. The multi-coil transformer 210 thus comprises a third secondary winding 218 connected to the third output 241 via a third secondary side circuit. The third voltage is different to the first voltage and the second voltage. In this way, the second electrical bus and the third electrical bus may respectively supply power to auxiliary vehicle units having different voltage requirements. In some examples, the second electrical bus may provide power to HV auxiliary units of the vehicle and the third electrical bus may provide power to LV auxiliary units of the vehicle.

The transformer circuit 200 may thus be used to replace the separate on-board charger (OBC) circuitry 110, first DCDC converter 130 and the second DCDC converter 140 in the voltage conversion system 100. Instead, the conversion capabilities may be integrated into a single transformer circuit 200 having reduced complexity and cost.

With reference to Figure 3, there is illustrated a transformer circuit 300 according to an embodiment of the invention. The transformer circuit 300 comprises analogous features to the transformer circuit 200 shown in Figure 2B. In particular, the transformer circuit 300 comprises an input 311 , a first output 321 for providing energy to a first electrical bus at a first voltage, a second output 331 for providing energy to a second electrical bus at a second voltage, and a third output 341 for providing energy to a third electrical bus at a third voltage. As discussed, in some embodiments the first electrical bus provides a connection to a traction battery of the vehicle at substantially 800V, the second electrical bus is arranged to provide electric power to HV auxiliary units of the vehicle at substantially 400V, and the third electrical bus is arranged to provide electrical power to one or more LV auxiliary units of the vehicle at substantially 12V. However, the purpose of the first to third electrical bus and the value of the first to third voltage may vary in other embodiments.

The transformer circuit 300 comprises a DCDC converter 305 disposed between the input 311 , the first output 321 , the second output 331 and the third output 341. The DCDC converter 305 comprises a multi-coil transformer 310 having a primary winding 312 connected to the input via a primary side circuit 350; a first secondary winding 314 connected to the first output via a first secondary side circuit 360-A; a second secondary winding 316 connected to the second output via a second secondary side circuit 360-B, and a third secondary winding 318 connected to the third output via a third secondary side circuit 360-C. Thus, the DCDC converter 305 can effectively replace three separate DCDC converters by utilising a multi-coil transformer 310 to provide three separate outputs.

For example, the combination of the primary side circuit 350, the transformer 310 and the first secondary side circuit 360-A can be considered as a first DCDC converter arranged to supply energy at the first voltage. The combination of the primary side circuit 350, the transformer 310 and the second secondary side circuit 360-B can be considered as a second DCDC converter arranged to supply energy at the second voltage. The combination of the primary side circuit 350, the transformer 310 and the third secondary side circuit 360-C can be considered as a third DCDC converter arranged to supply energy at the third voltage. Thus, the DCDC converter 305 is effectively able to replace three separate vehicle components utilising a common primary side circuit 350 and transformer 310.

The transformer circuit 300 comprises an input having an AC charging input 330 and an ACDC converter portion 340. The AC charging input is configured to receive electrical energy from an AC source such as an AC grid. The AC source may be a multi-phase AC source, such as a three phase AC source. As discussed, the multi-coil transformer 310 is omnidirectional. As such, the AC charging input 330 may also function as an output for three phase AC power. The ACDC converter portion 340 shown is analogous to that illustrated in Figure 1 B. The ACDC converter portion 340 has a totem pole topology and comprises the eight switches Q1 to Q8. The totem pole topology advantageously negates the need to have a separate circuit for each phase of AC power. The ACDC converter portion 340 is arranged to receive electrical energy from the AC charging input 330 and provide DC electrical energy indirectly to the primary winding 312 via the primary side circuit 350.

In the illustrated embodiment, the transformer circuit 300 comprises a DC link capacitor bank 345 comprising one or more DC link capacitors. The ACDC converter portion 340 may be tailored to boost the electrical power to the output from the ACDC converter portion 340 for storage in the DC link capacitor bank 345. The ACDC converter 340 may thus be tailored to boost the electrical power from an AC input voltage to a DC input voltage. For example, for a three phase AC source the ACDC converter portion 340 may convert the electrical power from between 200VAC-440VAC to between 600VDC-800VDC. For a single phase AC source, the ACDC converter portion 340 may convert the electrical power from between 85VAC-230VAC to between 450VDC-600VDC. The electrical energy stored in the DC link capacitor bank 345 is then provided as input to the DCDC converter 305 through the primary side circuit 350. When the DCDC converter 305 is operating in a positive, or forward mode, the primary side circuit 350 is arranged as an inverter to supply current from the DC link capacitor C1 to the primary winding 312 of the multi-coil transformer 310. Each secondary side circuit 360 is then arranged as a rectifier to supply current from each secondary winding 314, 316, 318 to each output 321, 331, 341 at a respective DC output voltage.

The DCDC converter 305 illustrated is arranged as a bidirectional CLLC converter. Thus, each of the primary side circuit 350 and first to third secondary side circuits 360-A, 360- B, 360-C can function either as a rectifier or an inverter depending on the direction of power transfer.

With reference to Figure 4A, there is shown a transformer circuit 400 for an electric vehicle according to another example. The transformer circuit 400 is adapted to receive both an AC charging input (such as from an AC grid) and a DC charging input (such as from a DC fast charger). As discussed with reference to Figure 1, if both AC charging and DC charging are accommodated typically a separate DCDC converter is provided for the DC charging input in additional to the ACDC conversion circuitry provided for the AC charging input. According to the present invention, a single transformer circuit 400 is provided to accommodate both AC and DC charging, thereby reducing the total number of components used.

The transformer circuit 400 comprises an input 411 for receiving electrical energy, and an output 421 for providing electrical energy to an electrical bus of the vehicle at an output voltage. The output 421 may be equivalent to the first output 221, 321 of the transformer circuits 200 and 300. That is, the electrical bus may provide a connection to a traction battery of the vehicle. For example, the output voltage may be substantially 400V or 800V. The transformer circuit 400 comprises a DCDC converter 405 disposed between the input 411 and the output 421, the DCDC converter 405 comprising a transformer 410 having a primary winding 412 and a secondary winding 414. The DCDC converter 405 further comprises a primary side circuit 450 connecting the input 411 to the primary winding 412 of the transformer 410. The primary side circuit 450 can function as an inverter. The DCDC converter 405 further comprises a secondary side circuit 470 connecting the secondary winding 414 of the transformer 410 to the output 421. The secondary side circuit 470 can function as a rectifier. The input 411 comprises both an AC charging input 430 and a DC charging input 460. The input 411 further includes an ACDC converter portion 440 to receive electrical energy from the AC charging input 430 and provide electrical energy in the form of DC current to the primary winding 412 via the primary side circuit 450. The DC charging input 460 is arranged between the ACDC converter 440 and the primary side circuit 450 such that the DC charging input 460 is configured to receive electrical energy from a DC source, such as a DC fast charger, and provide electrical energy to the primary winding 412 via the primary side circuit 450.

In this way, the primary winding 412 is arranged to receive electrical energy from the DC charging input 460 and also from the AC charging input 430 via the ACDC converter portion 440. Thus, the same circuitry can be used to facilitate both AC and DC charging. It will be appreciated that AC charging and DC charging may be mutually exclusive, that is the transformer circuit 400 may either be used to perform AC charging from the AC charging input 430 or DC charging from the DC charging input 460. The ACDC converter portion 440 may have a totem pole topology analogous to that illustrated in Figure 1 B or Figure 3. Each of the primary side circuit 450 and secondary side circuit 470 may be arranged as in Figure 3, so that the DCDC converter 405 can be bidirectional.

The turn ratio of the transformer 410 can then be tailored to convert the DC electrical energy from each of the ACDC converter portion 440 and the DC charging input 460 to an output voltage suitable for the electrical bus connected to the output 421, e.g.., an output voltage suitable for charging the traction battery of the vehicle. Depending on the configuration of the traction battery, the output voltage may be for example substantially 400V or substantially 800V. As can be seen, a single transformer 410 is provided for use with both the DC charging input and the AC charging input, in contrast to utilising separate transformer circuitry as shown in Figure 1 A. Thus, the present invention advantageously reduces the total amount of transformer circuitry provided to facilitate both AC and DC charging of a traction battery.

With reference to Figure 4B, the transformer circuit 400 may comprise at least one further output 431 for providing electrical energy to a further electrical bus of the vehicle at a further output voltage. For example, the further electrical bus may be for supplying energy to a HV or LV auxiliary unit of the vehicle, as described with reference to the second and third electrical bus of Figures 2A, 2B and 3. The transformer 400 shown in Figure 4B comprises a second secondary coil 416 connected to the second output 431 via a further secondary side circuit 470-B. Thus, the integrated DC charging input 460 can be provided in combination with the multi-coil transformer of Figures 2A, 2B and 3. The transformer circuit 400 of Figure 4B is adapted to receive a charging input from both a DC source and an AC source as in Figure 4A and also supply electrical energy at multiple voltages to multiple electrical buses having different voltage requirements as in Figure 2A, 2B and 3. For example, the further output voltage may be in the range 9V to 16V or the range 45V to 52V for providing electrical power to one or more LV auxiliary electrical units of the vehicle at the further output voltage such as an advanced driver assistance system (ADAS) of the vehicle or an infotainment system or the like.

With reference to Figure 5, there is shown a transformer circuit 500 according to another example.

The transformer circuit 500 comprises an AC input 530, an ACDC converter portion 540, a DC charging input 560 and a DCDC converter 505. The DC charging input 560 is arranged between the ACDC converter portion 540 and a primary side circuit 550 such that the DC charging input 560 is configured to receive electrical energy from a DC source, such as a DC fast charger, and provide electrical energy to the primary winding 512. The DC charging input 560 is thus connected between the ACDC converter 540 and the primary side circuit 550 at a DC link capacitor bank 545. The DCDC converter 505 comprises a transformer 510 having a primary coil 512 as described with reference to Figures 4A and 4B. The transformer 510 is a multicoil transformer 510. Thus, the transformer circuit 500 comprises a first output 521, a second output 531 and a third output 541 each for providing electrical energy to a respective electrical bus of the vehicle at a respective output voltage, as described with reference to Figure 3. The DCDC converter 505 further comprises the primary side circuit 550, a first secondary side circuit 570-A, a second secondary side circuit 570-B and a third secondary side circuit 570-C.

Each of the ACDC converter portion and the DC charging input are arranged to supply electrical energy to the DC link capacitor bank 545 comprising one or more DC link capacitors. The DC link capacitor bank 545 is then connected to the primary coil 512 of the transformer via the primary side circuit 550. The multi-coil transformer 510 further comprises a first secondary coil 514 connected to the first output 521 via the first secondary side circuit 570-A, a second secondary coil 516 connected to the second output 531 via the second secondary side circuit 570-B and a third secondary coil 518 connected to the third output 541 via the third secondary side circuit 570-C.

The DCDC converter 505 is arranged to be omnidirectional. That is, each of the primary side circuit 550 and first to third secondary side circuits 570-A, 570-B, 570-C can operate either as an inverter or a rectifier depending on the direction of power transfer, as described with reference to Figure 3.

Although the example transformer circuit 500 shown in Figure 5 illustrates three secondary coils 514, 516, 518 each connected to a respective output 521 , 531 , 541 , it will be appreciated that the transformer circuit may comprise any number of secondary coils each connected to a respective output for providing electrical energy and a respective output voltage. For example, the multi-coil transformer 510 may comprise one, two, four or five secondary coils.

With reference to Figure 6A, there is shown a transformer circuit 610 according to another example. The transformer circuit 610 is analogous to the transformer circuit 500, except the transformer circuit 610 only comprises two secondary coils 514, 516, two respective secondary side circuits 570-A, 570-B and two respective outputs 521, 531.

With reference to Figure 6B, there is shown a transformer circuit 620 according to another example. The transformer circuit 620 is analogous to the transformer circuit 500 or 610, except the transformer circuit 620 only comprises one secondary coil 514, one secondary side circuit 570 and one output 521.

The transformer circuit 620 further comprises a switch 561 at the DC charging input 560. The switch 561 is arranged to switch the transformer circuit 620 between a first configuration for receiving electrical energy from the DC charging input 561 , and a second configuration for receiving electrical energy from the AC charging input 530. Thus, the switch 561 can ensure that AC charging and DC charging are mutually exclusive, i.e., that the DC charging input 560 and AC charging input 530 do not concurrently supply energy to the DC link capacitor bank 545. Although the switch 561 is only illustrated in Figure 6B, in some embodiments a switch 561 may be analogously implemented with the DC charging input in any of the embodiments of Figures 4A, 4B, 5 or 6A. With reference to Figure 7, there is shown a flow chart of a method 700 illustrating the omnidirectional function of the transformer circuits according to the present invention. The method 700 may be performed using any of the transformer circuits 200, 300, 400, 500, 610, 620. Each of the transformer circuits 200, 300, 400, 500, 610, 620 as described with reference to Figures 2 to 6 are omnidirectional. That is, each output may also act as an input to the transformer, and vice versa. For example, taking the transformer circuit 300, each of the input 311 and the first to third output 321, 331, 341 may function as either an input or an output to the transformer 310. In this way, the same transformer circuit 300 can be used either to charge or to discharge a traction battery connected to the first output 321 . The method 700 will be described with reference to the transformer circuit 300, however it will be appreciated that the method may be applied to any of the transformer circuits 200, 400, 500, 610, 620.

The method 700 comprises a block 710 of determining whether a traction battery is charging, that is determining whether the input 311 is receiving electrical energy from a power source, such as an AC grid. Depending on whether the input 311 is receiving electrical energy from a power source, the flow of power within the transformer circuit 300 will differ, as will be explained.

If the input 311 is receiving electrical energy, the transformer circuit 300 may be considered to be in a first charging configuration. In block 720 the multi-coil transformer 310 is configured to provide electrical energy from the input 311 to each of the first electrical bus, the second electrical bus and the third electrical bus via the first output 321, second output 331 and third output 341. That is, the transformer circuit 300 is arranged such that the electrical energy from the input 311 (e.g., from the AC charging input 330) is provided via the multi-coil transformer 310 to both charge the traction battery in the first electrical bus and power both HV and LV auxiliary loads of the vehicle. Thus, the primary side circuit 340 is controlled to function as an inverter, and the secondary side circuits 360-A, 360-B and 360-C are all controlled to function as rectifiers.

If the input 311 is not receiving electrical energy, i.e., the traction battery is not charging, the transformer circuit may be considered to be in a second discharging configuration. In block 730 the multi-coil transformer is configured to provide electrical energy from the first electrical bus to the second output, third output and the input. Thus, the first secondary side circuit 360- A is controlled to function as an inverter, and each of the primary side circuit 350, the second secondary side circuit 360-B and the third secondary side circuit 360-C are controlled to function as rectifiers. In this way, the energy from the traction battery can be readily converted and supplied to power the HV and LV auxiliary loads of the vehicle using the multi-coil transformer, as well as supplying electrical energy at the input. For example, the battery can be used to supply three-phase AC power at the AC charging input 330 as the ACDC converter portion 340 is bidirectional. In the embodiments of Figures 4A, 4B, 5, 6A and 6B, the energy from the traction battery can be converted and supplied to either the AC charging input 430, 530 or the DC charging input 560.

With reference to Figure 8, there is illustrated a battery system 800 for an electric vehicle according to an embodiment of the invention. The battery system 800 comprises a traction battery 820 for powering one or more traction motors of an electric vehicle. The battery system 800 further comprises a charging input 811 for receiving electrical energy from an external source, such as one or more of an AC grid or a DC charger. The battery system 800 further comprises a transformer circuit 810 connected to each of the charging input 811 and a vehicle bus connected to the traction battery 820. The transformer circuit 810 may be one of the transformer circuits 200, 300, 400, 500, 600 as described herein. With reference to Figure 9, there is illustrated a vehicle 900 according to an embodiment of the invention. The vehicle 900 may be an electric vehicle (EV) or a plug-in hybrid vehicle (PH EV). The battery system 800 may be implemented on the vehicle 900.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Further aspects of the disclosure are set out in the following numbered paragraphs:

1. A transformer circuit for an electric vehicle, comprising: an input for receiving electrical energy; a first output for providing electrical energy to a first electrical bus of the vehicle at a first voltage; a second output for providing electrical energy to a second electrical bus of the vehicle at a second voltage; and a multi-coil transformer disposed between the input, the first output and the second output, the multi-coil transformer comprising a primary winding connected to the input; a first secondary winding connected to the first output; and a second secondary winding connected to the second output, wherein the multi-coil transformer is arranged such that, in use, electrical energy can be provided to the first output and the second output simultaneously.

2. The transformer circuit of paragraph 1 , wherein the first voltage is higher than the second voltage.

3. The transformer circuit of any preceding paragraph, wherein the first voltage and second voltage are non-overlapping ranges.

4. The transformer circuit of any preceding paragraph, wherein the first electrical bus comprises a battery connection terminal for providing electrical power to a traction battery of the vehicle or receiving electrical power from the traction battery of the vehicle.

5. The transformer circuit of any preceding paragraph, wherein one or more of: the first voltage comprises a nominal voltage in the range 600V to 1000V; and the second voltage comprises a nominal voltage in the range 200V to 500V.

6. The transformer circuit of any of paragraphs 1 to 4, wherein one or more of: the first voltage comprises a nominal voltage in the range 300V to 1000V; and the second voltage comprises a nominal voltage in the range 9V to 60V. 7. The transformer circuit of any preceding paragraph, wherein the second electrical bus is for providing electrical power to one or more auxiliary electrical units of the vehicle at the second voltage.

8. The transformer circuit of any preceding paragraph, comprising a third output for providing electrical energy to a third electrical bus of the vehicle at a third voltage, wherein the multi-coil transformer comprises a third secondary winding connected to the third output.

9. The transformer circuit of paragraph 8, wherein the third voltage is lower than the first voltage and the second voltage.

10. The transformer circuit of paragraph 8 or 9, wherein the third voltage comprises a nominal voltage in the range 9V to 60V.

11. The transformer circuit of any of paragraph 8 to 10, wherein the third electrical bus is for providing electrical power to one or more of: an advanced driver assistance system (ADAS) of the vehicle, an infotainment system of the vehicle, a lighting system of the vehicle, a seat adjustment system of the vehicle or a seat heating system of the vehicle.

12. The transformer circuit of any preceding paragraph, the transformer circuit comprising: a primary side circuit connecting the input to the primary winding of the transformer; a secondary side circuit connecting the secondary winding of the transformer to the output; the input comprising an AC charging input and an ACDC converter configured to receive electrical energy from the AC charging input and provide electrical energy to the primary winding via the primary side circuit.

13. The transformer circuit of paragraph 12, wherein the ACDC converter has a totem pole topology.

14. The transformer circuit of paragraph 12 or 13, further comprising a DC link capacitor bank disposed between the input and the primary side circuit, wherein the ACDC converter is arranged to provide electrical energy to the primary side circuit via the DC link capacitor bank.

15. The transformer circuit of any of paragraph 12 to 14, comprising a DC charging input between the ACDC converter and the primary side circuit, such that the DC charging input is configured to receive electrical energy from a DC source and provide electrical energy to the primary winding via the primary side circuit.

16. The transformer circuit of any preceding paragraph, wherein the multi-coil transformer (210) is omnidirectional.

17. The transformer circuit of paragraph 16, wherein the multi-coil transformer is configured to: in a first charging configuration, provide electrical energy from the input to each of the first electrical bus and the second electrical bus via the first output and the second output; and in a second discharging configuration, provide electrical energy from the first electrical bus to the second electrical bus via the first output and the second output.

18. A battery system for an electric vehicle, comprising: a transformer circuit according to any preceding paragraph; a charging input for receiving electrical energy and providing electrical energy to the input of the transformer circuit; and a vehicle traction battery configured to connect to the first output of the transformer circuit. 19. A vehicle comprising the transformer circuit of any of paragraphs 1 to 17 or the battery system of paragraph

18.