Power converter

Abstract

A power converter 700, particularly for a vehicle, receives an input voltage and provides an output voltage. The power converter comprises a first bridge 210 having a first plurality of Gallium Nitride, GaN, transistors 706-712, a second bridge 230 comprising a second plurality of GaN transistors 724, 726, and a planar magnetic system 220 coupling the first bridge to the second bridge. The planar magnetic system may comprise a planar transformer 716 that may have a first winding 718 and a second winding 720, 722. The planar magnetic system may comprise an inductor 714. The power convener may comprise a printed circuit board, PCB. The first bridge, the planar magnetic system and the second bridge may be provided on the PCB. The power converter may be included in a battery pack and / or battery management system. A vehicle may comprising the power converter, the battery pack, or the battery management system. The vehicle may comprise a high voltage battery coupled to the input of the first bridge and a low voltage battery coupled to the output of the second bridge.

Description

TECHNICAL FIELD The present disclosure relates to a power converter for a vehicle. Aspects of the invention relate to a power converter for a vehicle, a battery pack, comprising a power converter, a battery management system comprising the power converter, and a vehicle comprising a power converter, a battery pack or a battery management system. BACKGROUND Battery electric vehicles (BEVs) and hybrid electric vehicles include a number of power converters. In a vehicle, power converters receive an input voltage and provide an output voltage with a different voltage level. The auxiliary power module (APM) is a power converter which provides an interface between a high voltage and a low voltage, such as between a high voltage battery and a low voltage battery or low voltage auxiliary load. There is a need to ensure that the auxiliary power module offers high efficiency as well as high-power density. SUMMARY OF THE INVENTION Aspects and embodiments of the invention relate to a power converter for a vehicle, to a battery pack comprising a power converter, to a battery management system comprising the power converter, and to a vehicle comprising a power converter, a battery pack or a battery management system. According to an aspect of the invention there is provided a power converter for a vehicle, the power converter comprising: a first bridge; a second bridge; and a planar magnetic system. According to an aspect of the present invention, there is provided a power converter for a vehicle, the power converter configured to receive an input voltage and provide an output voltage, the power converter comprising: a first bridge comprising a first plurality of gallium nitride, GaN, transistors; a second bridge comprising a second plurality of GaN transistors; and a planar magnetic system coupling the first bridge to the second bridge. Any type of Gallium Nitride transistor may be used, such as GaN High Electron Mobility Transistors (HEMTs) or GaN Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). GaN transistors have unique characteristics, including low on-state resistance, ultra-low output capacitance, zero reverse recovery loss, and higher thermal stability. These characteristics allow the power converter of the battery management system to operate at a higher frequency compared to silicon or silicon carbide transistors. By switching the power converter at a higher switching frequency, the size of any magnetics, such as inductors or transformers, may be reduced, as the ripple current is reduced at higher frequencies. The lower on state resistance of the GaN transistors reduces or minimises the conduction loss in the system, allowing reduced heatsink sizes. Overall, this provides a power converter with an increased power density and smaller package size. As the size of the magnetics may be reduced, planar magnetics, which are typically smaller or lower profile, may also be used in the power converter system. Planar magnetics may comprise inductors or transformers. Compared to helically wound magnetics, planar magnetics have a lower profile (height or distance from the mounting connections of the magnetics). Planar magnetic devices are typically more than 25% to 50% shorter than wire wound magnetic devices. Using planar magnetics therefore removes components that project substantially above a base, substrate or PCB of the power converter, improving the packaging of the converter and improving the power density. The power converter is a DC-DC converter, receiving a DC input voltage and providing a DC output voltage. The converter may be a step-down converter acting to reduce the input voltage to a lower output voltage. The first bridge acts as an inverter, changing the DC input to an AC signal. The second bridge acts as a rectifier, rectifying the AC signal and providing the DC output. The power converter allows a high-voltage battery pack to be coupled to the input of the first bridge. A low-voltage battery may be coupled to an output of the second bridge. The power converter may further comprise one or more heatsinks coupled to the first bridge and the second bridge of the power converter, arranged to dissipate heat generated by the first bridge and the second bridge. The planar magnetic system may comprise a planar transformer. The transformer acts to change the voltage level in dependence on the number of winding turns on the primary and secondary sides of the transformer. This provides voltage conversion, for example voltage reduction between the primary and secondary windings. The planar transformer may comprise a first winding and a second winding. The first winding may be coupled to an output of the first bridge and the second winding may be coupled to an input of the second bridge. The planar magnetic system may comprise a planar inductor. The first plurality of GaN transistors may four GaN transistors. The second plurality of GaN transistors may comprise two GaN transistors. The power converter may comprise a printed circuit board, PCB. The first bridge, the planar magnetic system and the second bridge may be provided on the PCB. Providing the first bridge, second bridge and planar magnetic system on the printed circuit board comprises coupling or connecting the first bridge, second bridge and planar magnetic system to the printed circuit board. Each of these components may then be coupled or connected to one another using conductive traces, such as copper traces, on the circuit board. A single PCB comprising planar components and GaN transistors provides a compact power converter. The power converter may further comprise a heat sink coupled to at least one of the first bridge and the second bridge. The first bridge may comprise an input for receiving the input voltage. The first bridge is an input bridge and may be referred to as a high-voltage bridge where the converter is a step-down converter acting to reduce the voltage. A high voltage may be a voltage greater than 220v, for example 400v, 800v or 1200v. The first bridge receives the input voltage supplied by an external system, such as a high-voltage battery. The second bridge may comprise an output for providing the output voltage. The second bridge is an output bridge and may be referred to as a low-voltage bridge where the converter is a step-down converter acting to reduce the voltage. A low voltage may be a voltage less than 50v, for example 48v, 24v or 12v. The second bridge provides the output voltage to an external system, such as a low-voltage battery and low-voltage loads within a vehicle. According to an aspect of the present invention, there is provided a battery pack comprising the power converter. The battery pack may be a high-voltage battery, for example a battery with a voltage greater than 220v, for example 400v, 800vor 1200v. The increased power density and reduced size of the power converter allows the power converter to be packaged within the high-voltage battery pack, leading to better thermal management and space management within the vehicle. According to an aspect of the invention, there is provided a battery management system comprising the power converter. Including the power converter within the battery management system or battery management control module allows the battery management system to regulate the charge level of a low-voltage battery using a high-voltage battery. According to an aspect of the invention, there is provided a vehicle comprising the power converter, the battery pack or the battery management system. The vehicle may comprise a high voltage battery coupled to the input of the first bridge; and a low voltage battery coupled to the output of the second bridge. 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 1 is a diagram of a vehicle comprising a power converter; Figure 2 is a block diagram of the power converter; Figure 3a is a graph comparing the conduction losses of power converters comprising different transistor types; Figure 3b is a graph comparing the switching losses of power converters comprising different transistor types; Figure 4 is a graph of the thermal resistance compared to the area of a heat sink; Figure 5 is a graph comparing the area product of a transformer against the switching frequency; Figure 6 is a schematic diagram of a power convertor comprising input and output systems; Figure 7 is a detailed circuit level schematic diagram of the power convertor; Figure 8 is a PCB implementation of the power convertor. DETAILED DESCRIPTION The present disclosure relates to a power converter for a battery management system of a vehicle. Power converters may be used in battery electric vehicles (BEVs) or hybrid electric vehicles to modify the voltage of an input power supply. BEVs typically include a high voltage battery, a low voltage battery and one or more low voltage auxiliary loads. Figure 1 illustrates a vehicle 100 according to an embodiment of the present invention. Vehicle 100 comprises a high voltage battery or battery pack 110. The high voltage battery 110 may be the primary battery of the vehicle 100, used to supply power to drive the electric motors (not shown) of the vehicle 100. In a vehicle 100, the high voltage battery 110 may have a voltage of 200v, 400v, 800v, 1200v, 1600v, or any other suitable voltage. The high voltage battery 110 may comprise a number of batteries connected in series or parallel. For example, the high voltage battery 110 may comprise a first battery with a voltage of approximately 400v and a second battery with a voltage of 400v, with the first battery and second battery connected in series to provide a total output voltage of 800v. Each battery may comprise a plurality of battery cells. A number of auxiliary loads 140 within the vehicle 100 operate on a lower voltage than that supplied by the high voltage battery 110. For example, the auxiliary loads 140 may be 12v, 24v or 48v loads. Auxiliary loads 140 may comprise head lamps, wiper blade motors, electronic power steering systems, internal lighting, various electronic control modules among other loads. Due to the voltage differences, the auxiliary loads 140 cannot be directly supplied by the high voltage battery 110. So as to power the auxiliary loads 140, the vehicle 100 comprises a low voltage battery 130 coupled to the auxiliary loads 140. The vehicle 100 further comprises a power converter 120, which may be referred to as an auxiliary power module, coupled to the high voltage battery 110 and to the low voltage battery 130 and the auxiliary loads 140. The power converter 120 is configured to receive a high voltage input from the high voltage battery 110, reduce the voltage level, and supply a low voltage output to the low voltage battery 130 and the auxiliary loads 140. In this way, the high voltage battery 110 can be used to charge the low voltage battery 130 and to power the auxiliary loads 140. In some cases, the power converter 120 may directly supply the auxiliary loads 140, removing the need for the low voltage battery 130. The vehicle 100 may further comprise a battery management system 150. The battery management system 150 may operate to control the high voltage battery 110 and the power converter 120. Figure 2 illustrates a power converter 200 or auxiliary power module for the vehicle 100 according to an embodiment of the present invention, which may be the power converter 120 shown in Figure 1. The power converter 200 is configured to receive an input voltage and provide an output voltage. The power converter 200 comprises a first bridge 210. The first bridge 210 may be referred to as a high-voltage (HV) bridge. The first bridge 210 comprises a plurality of transistors or switches and is configured to act as an inverter. Inverters receive a DC input signal and provide an AC output signal. The output of the first bridge 210 is coupled to the input of a magnetic system 220. The magnetic system 220 may comprise a transformer and additionally or alternatively an inductor. The magnetic system 220 may be configured to reduce a received input voltage to a lower output voltage (or to increase the voltage in some situations). This may be achieved through the use of varying numbers of turns across a number of different windings of the magnetic system 220. The output of the magnetic system 220 is coupled to a second bridge 230. The second bridge 230 may be referred to as a low-voltage (LV) bridge. The second bridge 230 comprises a plurality of transistors or switches and is configured to act as a rectifier. Rectifiers receive an AC input signal and provide a DC output signal. As such, the power converter 200 receives a DC input signal, inverts the signal to generate an AC signal, modifies the voltage of the AC signal using the magnetic system, and rectifies the reduced voltage AC signal to provide a DC output signal. Typically, the auxiliary power modules or power converters 200 used in BEVs 100 require a number of switches or transistors in each bridge. These switches or transistors are turned on and off to invert or rectify the received input signal. Ideally, switches used in power converters would have zero on-state resistance. However, as switches are not ideal when turned on or closed, each switch has an on-state resistance which causes conduction losses. This reduces the efficiency of the power converter. These losses reduce the power density of the power converter 200. Further, the magnetics that form part of the magnetic system 220 are large, projecting a large distance from any substrate that the power converter 200 is formed on. This further reduces the power density of the power converter 200. There is a clear need to provide a power converter 200 with high efficiency and high-power density for use in a battery electric vehicle. The bridges of a power converter 200 may use silicon (Si) or silicon carbide (SiC) transistors. For example, the first bridge 210 may use SiC transistors and the second bridge 230 may use Si transistors. However, Si transistors present a number of disadvantages. In particular the frequency at which a Si transistor is switched may be between 10kHz and 70kHz. So as to improve the efficiency of the power converter 200, the first bridge 210 comprises a first plurality of gallium nitride, GaN, transistors and the second bridge 230 comprises a second plurality of GaN transistors. Gallium nitride transistors have unique characteristics compared to othertransistor types, including low on-state resistance. Conduction losses are caused by the on-state resistance of the transistor and occur when the transistor is switched on. The lower on-state resistance of the transistors reduces the conduction losses in the power converter 200, increasing the efficiency of the power converter 200. Figure 3a shows a comparison of the conduction losses in the transistors of the first bridge 210 and second bridge 230 when different combinations of transistor types (Si, SiC and GaN) are used in the first bridge 210 and second bridge 230. The Y—axis 326 shows the conduction loss of the transistors in watts. Bars 302 and 304 relate to the conduction losses in the first bridge 210 transistors and second bridge 230 transistors of the power converter respectively where the first bridge transistors 210 are silicon carbide and the second bridge 230 transistors are silicon. Bars 306 and 308 relate to the conduction losses in the first bridge 210 transistors and second bridge 230 transistors of the power converter respectively where the first bridge transistors 210 are gallium nitride and the second bridge 230 transistors are silicon. Bars 310 and 312 relate to the conduction losses in the first bridge 210 transistors and second bridge 230 transistors of the power converter respectively where the first bridge transistors 210 are gallium nitride and the second bridge 230 transistors are gallium nitride. As can be seen in Figure 3a, the conduction losses in the first bridge 210 transistors are similar for all three power converters. However, the conduction losses are significantly lower in the transistors of the second bridge 230 where GaN devices are used in both the first bridge 210 and the second bridge 230. Switching losses are energy losses that occur in a power converter whilst the transistors of the bridges switch or transition from off-to-on and from on-to-off. Switching losses occur due the charging and discharging of any capacitances within the transistor as the current changes during the transitions. Figure 3b shows a comparison of the switching losses in the transistors of the first bridge 210 and second bridge 230 when different combinations of transistor types (Si, SiC and GaN) are used in the first bridge 210 and second bridge 230. The Y—axis 326 shows the switching loss of the transistors in watts. Bars 314 and 316 relate to the switching losses in the first bridge 210 transistors and second bridge 230 transistors of the power converter 200 respectively where the first bridge 210 transistors are silicon carbide and the second bridge 230 transistors are silicon. Bars 318 and 320 relate to the switching losses in the first bridge 210 transistors and second bridge transistors of the power converter respectively where the first bridge transistors 210 are gallium nitride and the second bridge 230 transistors are silicon. Bars 322 and 324 relate to the switching losses in the first bridge 210 transistors and second bridge transistors of the power converter respectively where the first bridge transistors 210 are gallium nitride and the second bridge 230 transistors are gallium nitride. As can be seen in Figure 3b, the switching losses in the first bridge 210 transistors are significantly higher in a power converter 200 where the transistors of the first bridge 210 are silicon carbide. Whilst the switching losses 324 in the second bridge 230 of the GaN-GaN converter (a converter with GaN transistors in the first 210 and second 230 bridge) are higher than switching losses in the second bridge 230 of the other power converter arrangements, it is clear from Figure 3a that the conduction losses for the GaN-GaN converter in the second bridge 230 are significantly lower than those of the other power converter arrangements. As such, the combined conduction and switching losses are significantly lower for a GaN-GaN converter compared to a SiC-Si converter or a GaN-Si converter. The GaN-GaN power converter therefore offers significantly improve power efficiency when compared to other power converter types. Conduction losses and switching losses result in the temperature of the switches increasing. To improve circuit performance, heatsinks may be coupled to the first bridge 210 and second bridge 230 of the power converter 200. As the conduction and switching losses are reduced in a GaN-GaN power converter 200, the components require smaller heat sinks to dissipate the energy. Heat sinks are rated using thermal resistance depending on the heat flow between the device the heat sink is coupled to and ambient air (which is a sum of the thermal resistances of the device to the heat sink and the heat sink to the ambient air). The lowerthe thermal resistance in °C / W, the better the heat sink is at dissipating heat, as a larger change in power loss causes a smaller increase in the temperature of the device. As such, where the power loss of the transistors is smaller, a heat sink with a greater thermal resistance can be used to maintain the transistors at the same temperature. The power converter 200 comprising GaN devices in the first bridge 210 and second bridge 230 has significantly reduced switching and conduction losses, allowing a heat sink with a higher thermal resistance to be used. Figure 4 shows a graph of the thermal resistance of a heat sink compared to the area of the heat sink. The X axis 402 shows the area of the heat sink in square inches. The Y axis 404 is the thermal resistance of the heat sink in °C / W. There is a clear exponential relationship between the thermal resistance in °C / W and the area of the heat sink. The lower the thermal resistance, the larger the heatsink area. The power converter 200 comprising GaN devices in the first bridge 210 and second bridge 230 has significantly reduced switching and conduction losses, allowing a heat sink with a higher thermal resistance to be used. As there is an exponential relationship between heat sink size and thermal resistance, this allows a heat sink with an exponentially smaller area to be used. This significantly reduces the size of the power converter 200, resulting in greater power density for a GaN-GaN converter compared to a converter using different transistor types. The first bridge 210 and second bridge 230 of the power converter 200 are switched at a switching frequency. This allows the bridges to act as inverters and rectifiers, respectively. Silicon transistorbased power converters are typically switched at between 10kHz and 70kHz. The use of Gallium nitride transistors allows the bridges to be switched at a greater switching frequency, for example at 300- 500kHz. With a greater switching frequency, the size of the magnetic system 220 can be significantly reduced. The magnetic system 220 comprises one or more transformers and additionally or alternatively one or more inductors. The transformer couples or connects the first bridge 210 to the second bridge 230 and acts to reduce the voltage at the output of the first bridge. Figure 5 shows a graph of the area product of a transformer of the magnetic system 220 with respect to the switching frequency. The X axis of 502 of the graphs shows the switching frequency of the bridges of the power converter in kHz. The Y axis 504 shows the area product (in cm4) of the transformer. The area product of a transformer is the product of the core window area of the transformer and the core cross-sectional area. As can be seen, there is an exponential reduction in the area product of the transformer as the switching frequency is increased. As well as lower conduction losses, gallium nitride device transistors can be switched at higher frequencies compared to silicon transistors. As such, the power converter comprising GaN transistors can include a smaller transformer and thus magnetic system 220 compared to a power converter that does not include GaN devices. Traditional magnetic components are wire wound devices, such as helically wound devices. The ability to operate at higher switching frequencies and therefore to use smaller magnetic systems 220 allows the use of planar devices or planar magnetics. Planar magnetics are magnetic components that have a smaller size and lower parasitic components (e.g. parasitic inductance) compared to traditional magnetic components. Compared to helically wound magnetics, planar magnetics have a lower profile (height or distance from the mounting connections of the magnetics). Planar magnetic devices are typically more than 25% to 50% shorter than wire wound magnetic devices. Using planar magnetics 220 therefore removes components that project substantially above a base, substrate or PCB of the power converter 200, improving the packaging of the converter and improving the power density. The use of a GaN-GaN transistor arrangement provides significantly improved efficiency, whilst also enabling the use of smaller heatsinks and smaller magnetic systems (and in particular planar magnetics). As such, the power density of the power converter is significantly improved. Figure 6 is a schematic diagram of a power converter 600. The power converter 600 includes a first bridge 210, a magnetic system 220 and a second bridge 230 as described with respect to Figure 2. The power converter further comprises an input system 640 coupled to the input of the first bridge 210 and an output system 650 coupled to the output of the second bridge 230. The input system 640 may comprise input terminals for receiving an input signal, such as a high-voltage input signal. The output system 650 may comprise output terminals for providing an output signal, such as a low-voltage output signal. A low voltage output signal is a signal with a lower voltage when compared to the high-voltage input signal. The input system 640 may comprise a first, high voltage or primary battery or battery pack. A high voltage may be a voltage greater than 220v, for example 400v, 800v or 1200v or a voltage therebetween. The high voltage battery may be used to supply power to the electric motors of the vehicle 100. The first bridge 210, coupled to the input system 640, receives the input signal supplied by the battery. The output system 650 may comprise a second, low voltage or auxiliary battery or battery pack. Additionally or alternatively, the output system 650 may comprise one or more auxiliary loads. A low voltage may be a voltage less than 50v, for example 48v, 24v or 12v or a voltage therebetween. The second bridge 230 provides an output voltage to the output system 650 comprising the low voltage battery and low-voltage loads within the vehicle 100. Figure 7 is a detailed schematic diagram of a power converter 700 comprising the input system 640, the first bridge 210, the magnetic system 220, the second bridge 230 and the output system 650. The input system 640 includes a first input terminal 702 and a second input terminal 704 for receiving an input signal. The first input terminal 702 and second input terminal 704 may be coupled or couplable to a high voltage battery. The first bridge 210 comprises four GaN transistors 706-712. It should be understood that where a single GaN transistor is shown, multiple GaN transistors connected in parallel may instead be used to allow the system to operate at a higher current level. The first bridge 210 is coupled to the magnetic system 220. The magnetic system 220 comprises an inductor 14 and a transformer 716. The inductor 714 acts to improve power transfer from the high-voltage side (including the first bridge 210) to the low voltage side (including the second bridge 230). Transformer 716 comprises a first or primary winding 718. The first winding 718 is coupled to the first bridge 210. The transformer further comprises a second or secondary winding 720, 722. The secondary winding may comprise one or more windings. Figure 4 shows the secondary winding having two windings 720, 722. The secondary winding 720, 722 is coupled to the second bridge 230. The transformer 716 acts to provide electrical or galvanic isolation between the first bridge 210 and the second bridge 230, separating the different voltage levels at the input and output of the power converter 700. The number of turns on each of the first winding 718 and second winding 720, 722 is selected in dependence on the desired voltage change between the input and the output of the power converter 700. For example, to reduce the voltage, the secondary winding 720, 722 has fewer turns when compared to the primary winding 718. The second winding 720, 722 of the transformer 716 is coupled to the second bridge 230. The second bridge 230 comprises two GaN transistors 724, 726. The second bridge is coupled to the output system 650, which includes a first output terminal 728 and a second output terminal 730 for receiving an input signal. The first output terminal 728 and second output terminal 730 may be coupled or couplable to a low voltage battery and one or more auxiliary or low voltage loads. The power converter 200, 600, 700 may be implemented on a printed circuit board within the vehicle 100. Figure 8 is a side profile view of a power converter 800 comprising a printed circuit board (PCB) 810. The first bridge 210, second bridge 230 and planar magnetic system 220 are provided on the circuit board, such that the components are physically coupled to the printed circuit board 810. The first bridge 210, second bridge 230 and planar magnetic system 220 are coupled or connected to one another using conductive traces or tracks on the printed circuit board 810. The input system 640 comprises an input terminal block and the output system 650 comprises an output terminal block on the printed circuit board 810. The power converter 800 further comprises a first heat sink 820 and a second heat sink 830. The first heat sink 820 is coupled to the first bridge 210 and acts to dissipate heat generated by the GaN transistors of the first bridge 210. The second heat sink 830 is coupled to the second bridge 230 and acts to dissipate heat generated by the GaN transistors of the second bridge 230. It should be understood that a single heatsink may be provided that is coupled to the first bridge 210, the second bridge 230 and to one or more further components of the power converter 800 or other systems provided in proximity to the power converter 800. The heat sink may comprise a cooling channel within which a coolant material is circulated to extract heat from the transistors. The cooling channel may be attached or coupled to the top side of the transistors of the first bridge 210 and second bridge 230 where the transistors are specified as top-cooled devices. Alternatively, the cooling channel may be attached or coupled to the PCB 810 on which the transistors are mounted if the transistors are specified as bottom cooled devices. If a conventional metallic heat sink is used, it may be attached to the top of the transistors of at least one of the first bridge 210 and the second 230 bridge or to the PCB 810. Battery electric vehicles 100 may comprise a battery management system 150 or battery management control module used to control the charging and discharging of the high-voltage and low-voltage or auxiliary batteries within the vehicle 100. The battery management system 150 or battery management control module may comprise any of the power converters 200, 600, 700, 800 described previously, enabling the battery management system 150 to control the charging of the low-voltage battery 130 using the high-voltage battery 110. 5 The high-voltage battery 110 is one of the largest components within a vehicle 100. So as to improve vehicle packaging, the high-voltage battery 110 may comprise any of the previously described power converters 200, 600, 700, 800, such that the power converter is within or part of the high voltage battery pack. 10 As shown in Figure 1, the vehicle 100 comprises power converter 120, which may be any previously described power converter 200,600, 700, 800. The vehicle 100 further comprises a high-voltage battery 110, low voltage battery 130 and one or more auxiliary loads 140. The high-voltage battery 110 may comprise the power converter 120, or alternatively, the vehicle may comprise a battery management 15 system 150 which comprises the power converter 120. 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.

Claims

1. A power converter for a vehicle, the power converter configured to receive an input voltage and provide an output voltage, the power converter comprising:a first bridge comprising a first plurality of gallium nitride, GaN, transistors;a second bridge comprising a second plurality of GaN transistors; and a planar magnetic system coupling the first bridge to the second bridge.

2. The power converter according to claim 1, wherein the planar magnetic system comprises a planar transformer.

3. The power converter according to claim 2, wherein the planar transformer comprises a first winding and a second winding.

4. The power converter according to claim 3, wherein the first winding is coupled to an output of the first bridge and the second winding is coupled to an input of the second bridge.

5. The power converter according to any preceding claim, wherein the planar magnetic system comprises a planar inductor.

6. The power converter according to any preceding claim, wherein the first plurality of GaN transistors comprise four GaN transistors.

7. The power converter according to any preceding claim, wherein the second plurality of GaN transistors comprise two GaN transistors.

8. The power converter according to any preceding claim, wherein the power converter comprises a printed circuit board, PCB.

9. The power converter according to claim 8, wherein the first bridge, the planar magnetic system and the second bridge are provided on the PCB.

10. The power converter according to any preceding claim, wherein the first bridge comprises an input for receiving the input voltage.

11. The power converter according to any preceding claim, wherein the second bridge comprises an output for providing the output voltage.

12. A battery pack comprising the power converter according to any preceding claim.

13. A battery management system comprising the power converter according to any of claims 1 -11.

14. A vehicle comprising the power converter according to any of claims 1-11, the battery pack according to claim 12 or the battery management system according to claim 13.

15. The vehicle according to claim 14, the vehicle further comprising: a high voltage battery coupled to the input of the first bridge; and a low voltage battery coupled to the output of the second bridge.

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