Gallium nitride's growing role in 400 V electric vehicles

The global automotive industry is undergoing a structural transition toward electrification, moving from internal combustion engines to electric drivetrains.

To accelerate mass-market adoption, plug-in electric vehicles (EVs) must achieve longer driving ranges, faster charging times, and lower total manufacturing costs. These requirements place strict performance demands on efficient power electronics, specifically the On-Board Charger (OBC) and the traction inverter.

For 400 V battery architectures, traditional silicon (Si) metal-oxide-semiconductor field-effect transistors (MOSFETs) and Insulated Gate Bipolar Transistors (IGBTs) have approached their theoretical semiconductor material limits.

While Silicon Carbide (SiC) has established itself as the baseline for early generations of powertrain systems, SiC devices are increasingly being challenged by the maturation of wide bandgap GaN technology across the automotive market.

Learn more about how GaN-on-Silicon and GaN-on-Silicon Carbide compare for power electronics.

This overview analyzes the technical and economic value of integrating GaN High-Electron-Mobility Transistors (HEMTs) into 400 V EV powertrains. The first section details a single-stage, bidirectional OBC topology utilizing GaN Bidirectional Switches (BDS).

This architecture eliminates the traditional, lossy DC-DC conversion stage found in conventional power supplies, minimizing component count and maximizing power density. The second section evaluates unidirectional GaN-based traction inverters, detailing how high-frequency switching reduces motor harmonic losses and allows for smaller, lighter, and more cost-effective system filters.

The power electronics bottleneck in 400 V EV architectures

The performance of an electric vehicle is fundamentally constrained by its power conversion efficiency.

In a standard 400 V EV powertrain, power electronics handle two primary tasks:

  • AC-to-DC Conversion: The On-Board Charger (OBC) converts grid AC power to DC power to charge the high-voltage battery pack.
  • DC-to-AC Conversion: The traction inverter converts the battery's DC energy into a multi-phase AC signal to drive the electric motor.
Block diagram of an electric vehicle powertrain inside a car silhouette, showing the On-Board Charger (AC/DC PFC rectifier stage followed by an isolated DC/DC converter), connected to the Battery, which feeds a DC/AC Inverter driving the Motor.

Block diagram of an electric vehicle powertrain inside a car silhouette, showing the On-Board Charger (AC/DC PFC rectifier stage followed by an isolated DC/DC converter), connected to the Battery, which feeds a DC/AC Inverter driving the Motor.

GaN in 400 V on-board chargers (OBC): the single-stage topology

Conventional bidirectional OBCs utilize a two-stage architecture:

  1. Active Front End (AFE): A power factor correction (PFC) stage (typically a totem-pole configuration) that rectifies grid AC to an intermediate DC link bus (usually 400 V to 450 V).
  2. Isolated DC-DC Converter: A resonant stage (typically a Dual Active Bridge (DAB) or LLC converter) providing galvanic isolation and precise voltage matching to the battery pack.

Over 70% of legacy and current-generation automotive OBCs utilize a two-stage topology. The first stage consists of an AC/DC Power Factor Correction (PFC) circuit — typically a bridgeless totem-pole configuration — which shapes the input current to match the grid voltage sine wave. The second stage is an isolated DC/DC converter, such as a Dual Active Bridge (DAB) or an LLC resonant converter, which provides galvanic isolation and regulates the output voltage to match the battery's state of charge.

This dual-stage approach requires a bulky electrolytic or film "DC-link" capacitor situated between the PFC stage and the DC/DC stage. The DC-link capacitor acts as an energy buffer, absorbing the twice-line-frequency (100 Hz / 120 Hz) pulsating power from the single-phase AC grid while providing a steady DC input to the downstream DC/DC stage. These capacitors take up significant physical volume, add weight, limit power density, and represent a primary point of failure due to electrolyte dry-out over elevated thermal lifetimes.

This dual-stage approach requires a high component count, multiple gate drivers, dual control loops, and a bulky intermediate DC-link bulk capacitor which is often an electrolytic or large film component prone to thermal aging and mechanical wear.

Learn more about how GaN enables high-frequency LLC resonant conversion. 

The main challenge of a single-stage matrix converter is managing the bidirectional AC voltage at the input. Standard discrete power semiconductors block voltage in only one direction. To handle AC waveforms, a Bidirectional Switch (BDS) is required to block voltage and conduct current in both directions.

Using traditional discrete components requires connecting two transistors back-to-back (either common-source or common-drain configuration).

Ndiscrete = 2 x Nswitches

This arrangement doubles the total RDS(on) because the current must pass through two independent transistor channels, increasing conduction losses:

Pcond =IRMS2 x (2 x RDS(on))

Furthermore, this setup doubles the component count, gate drive circuits, and printed circuit board (PCB) footprint.

GaN technology enables a unique alternative: the Monolithic Bidirectional Switch (BDS).

Because GaN is a lateral device structure based on a AlGaN/GaN heterostructure on a silicon substrate, Infineon has developed a single device with two independent gates sharing a single drift region.

This monolithic configuration yields several performance advantages:

  1. Shared Drift Region Conduction: The current flows through a single continuous 2DEG channel. The total on-resistance of a monolithic BDS is comparable to a single standard discrete GaN HEMT, rather than the doubled resistance of a back-to-back pair. Conduction losses drop by approximately 50%.
  2. True Four-Quadrant Operation: The monolithic device can block positive or negative voltages based on the bias states of Gate 1 and Gate 2 relative to their adjacent channels. It also conducts current forward or backward with equal efficiency.
  3. Drastic Reduction in Gate Drive Complexity: Instead of routing independent, isolated driver signals to four discrete FETs per full-bridge leg, the monolithic device simplifies layout optimization. It minimizes parasitic loop inductances (Lg and Ls), which reduces voltage ringing during high-speed dv/dt switching events.

Learn more about the HEMT structure and 2DEG channel behind this monolithic design.

Comparison diagram of a standard transistor versus a monolithic BDS. Top: two standard transistors with drain (D) and gate (G) terminals stacked back-to-back, listing four properties: voltage blocking only in one direction, current conduction in both directions, one gate with two modes of operation, and two devices back-to-back required for a single-stage converter. An arrow points down to the bottom section. Bottom: a single monolithic GaN bidirectional switch (BDS) symbol with two gates (G1, G2), two terminals (S1, S2), and a substrate (Sub), listing four properties: GaN as a lateral device with symmetrical structure is the optimal way to build a monolithic BDS on a single die, voltage blocking in both directions, controlled current conduction in both directions, and two gates with four modes of operation.
Schematic symbol of a monolithic GaN bidirectional switch (BDS), showing a single device with two source/drain terminals (S1, S2), two independent gates (G1, G2), and a substrate terminal (Sub).

Schematic symbol of a monolithic GaN bidirectional switch (BDS), showing a single device with two source/drain terminals (S1, S2), two independent gates (G1, G2), and a substrate terminal (Sub).

 

Comparison diagram of a standard transistor versus a monolithic BDS.

Top: two standard transistors with drain (D) and gate (G) terminals stacked back-to-back, listing four properties: voltage blocking only in one direction, current conduction in both directions, one gate with two modes of operation, and two devices back-to-back required for a single-stage converter. An arrow points down to the bottom section.

Bottom: a single monolithic GaN bidirectional switch (BDS) symbol with two gates (G1, G2), two terminals (S1, S2), and a substrate (Sub), listing four properties: GaN as a lateral device with symmetrical structure is the optimal way to build a monolithic BDS on a single die, voltage blocking in both directions, controlled current conduction in both directions, and two gates with four modes of operation.

By deploying a monolithic GaN BDS in a single-stage AC/DC matrix topology, OBC designs achieve significant improvements in power density, efficiency, and cost:

  • Elimination of the DC-Link Buffer: In a single-stage topology, energy is processed directly from AC to DC without a fixed intermediate DC voltage bus. While a small high-frequency filtering capacitor is still required to handle ripple, the large electrolytic or film DC-link capacitors are eliminated. This slashes OBC volume and weight.
  • Reduction in Component Count: Replacing four to eight discrete unidirectional switches with nearly half the number of monolithic GaN BDS packages reduces the part count, simplifies the gate driver bias supplies, and shrinks the required printed circuit board (PCB) footprint.
  • Increased Power Density and Efficiency: Operating at higher frequencies shrinks the size of magnetic components (transformers and EMI filters). Combined with zero reverse recovery (Qrr) and low gate charge (Qg), single-stage GaN OBCs in a 400 V EV battery charging converter achieves a peak efficiency above 98% and maintains over 97% efficiency across the entire charging range, enabled by soft-switching operation and the low switching losses of GaN devices.

To quantify the advantages of this configuration, consider an 11 kW bidirectional OBC operating on a three-phase AC grid charging a nominal 400 V battery pack.

The main challenge of a single-stage matrix converter is managing the bidirectional AC voltage at the input. Standard discrete power semiconductors block voltage in only one direction. To handle AC waveforms, a Bidirectional Switch (BDS) is required to block voltage and conduct current in both directions.

Using traditional discrete components requires connecting two transistors back-to-back (either common-source or common-drain configuration).

Ndiscrete = 2 x Nswitches

This arrangement doubles the total RDS(on) because the current must pass through two independent transistor channels, increasing conduction losses:

Pcond =IRMS2 x (2 x RDS(on))

Furthermore, this setup doubles the component count, gate drive circuits, and printed circuit board (PCB) footprint.

GaN technology enables a unique alternative: the Monolithic Bidirectional Switch (BDS).

Because GaN is a lateral device structure based on a AlGaN/GaN heterostructure on a silicon substrate, Infineon has developed a single device with two independent gates sharing a single drift region.

This monolithic configuration yields several performance advantages:

  1. Shared Drift Region Conduction: The current flows through a single continuous 2DEG channel. The total on-resistance of a monolithic BDS is comparable to a single standard discrete GaN HEMT, rather than the doubled resistance of a back-to-back pair. Conduction losses drop by approximately 50%.
  2. True Four-Quadrant Operation: The monolithic device can block positive or negative voltages based on the bias states of Gate 1 and Gate 2 relative to their adjacent channels. It also conducts current forward or backward with equal efficiency.
  3. Drastic Reduction in Gate Drive Complexity: Instead of routing independent, isolated driver signals to four discrete FETs per full-bridge leg, the monolithic device simplifies layout optimization. It minimizes parasitic loop inductances (Lg and Ls), which reduces voltage ringing during high-speed dv/dt switching events.

Learn more about the HEMT structure and 2DEG channel behind this monolithic design.

Comparison diagram of a standard transistor versus a monolithic BDS. Top: two standard transistors with drain (D) and gate (G) terminals stacked back-to-back, listing four properties: voltage blocking only in one direction, current conduction in both directions, one gate with two modes of operation, and two devices back-to-back required for a single-stage converter. An arrow points down to the bottom section. Bottom: a single monolithic GaN bidirectional switch (BDS) symbol with two gates (G1, G2), two terminals (S1, S2), and a substrate (Sub), listing four properties: GaN as a lateral device with symmetrical structure is the optimal way to build a monolithic BDS on a single die, voltage blocking in both directions, controlled current conduction in both directions, and two gates with four modes of operation.
Schematic symbol of a monolithic GaN bidirectional switch (BDS), showing a single device with two source/drain terminals (S1, S2), two independent gates (G1, G2), and a substrate terminal (Sub).

Schematic symbol of a monolithic GaN bidirectional switch (BDS), showing a single device with two source/drain terminals (S1, S2), two independent gates (G1, G2), and a substrate terminal (Sub).

 

Comparison diagram of a standard transistor versus a monolithic BDS.

Top: two standard transistors with drain (D) and gate (G) terminals stacked back-to-back, listing four properties: voltage blocking only in one direction, current conduction in both directions, one gate with two modes of operation, and two devices back-to-back required for a single-stage converter. An arrow points down to the bottom section.

Bottom: a single monolithic GaN bidirectional switch (BDS) symbol with two gates (G1, G2), two terminals (S1, S2), and a substrate (Sub), listing four properties: GaN as a lateral device with symmetrical structure is the optimal way to build a monolithic BDS on a single die, voltage blocking in both directions, controlled current conduction in both directions, and two gates with four modes of operation.

By deploying a monolithic GaN BDS in a single-stage AC/DC matrix topology, OBC designs achieve significant improvements in power density, efficiency, and cost:

  • Elimination of the DC-Link Buffer: In a single-stage topology, energy is processed directly from AC to DC without a fixed intermediate DC voltage bus. While a small high-frequency filtering capacitor is still required to handle ripple, the large electrolytic or film DC-link capacitors are eliminated. This slashes OBC volume and weight.
  • Reduction in Component Count: Replacing four to eight discrete unidirectional switches with nearly half the number of monolithic GaN BDS packages reduces the part count, simplifies the gate driver bias supplies, and shrinks the required printed circuit board (PCB) footprint.
  • Increased Power Density and Efficiency: Operating at higher frequencies shrinks the size of magnetic components (transformers and EMI filters). Combined with zero reverse recovery (Qrr) and low gate charge (Qg), single-stage GaN OBCs in a 400 V EV battery charging converter achieves a peak efficiency above 98% and maintains over 97% efficiency across the entire charging range, enabled by soft-switching operation and the low switching losses of GaN devices.

To quantify the advantages of this configuration, consider an 11 kW bidirectional OBC operating on a three-phase AC grid charging a nominal 400 V battery pack.

Unidirectional GaN power devices for 400 V traction inverters

While the OBC requires bidirectional power delivery to support Vehicle-to-Grid (V2G) and Vehicle-to-Home (V2H) applications, the primary traction inverter remains predominantly unidirectional. It focuses on converting DC battery power into a three-phase AC signal to drive the propulsion motor. With GaN, EVs can achieve longer vehicle range or reduce battery size and cost.

During regenerative braking, power flows in reverse (AC to DC). However, this operation is handled directly via the standard three-phase bridge configuration using synchronous rectification routines. It does not require complex matrix switches or bidirectional blocking capabilities. Therefore, standard unidirectional discrete GaN FETs (HEMTs) or multi-chip GaN power modules are well-suited for this application.

Learn more about how a GaN FET switches and why it outperforms silicon.

The main design challenge for traction inverters is current handling. A typical 150 kW traction inverter operating on a 400 V DC bus requires continuous phase currents exceeding 350 ARMS, with peak acceleration currents reaching 500 A – 600 A.

Modern automotive GaN designs address these issues through:

  • RSP Innovations: Advanced design and manufacturing enables single-die devices with exceptionally low nominal on-resistance (RDS(on) ≤ 10 mΩ).
  • Substrate-Agnostic Processing: Utilizing GaN-on-Silicon IDM processes enables high manufacturing yields at lower costs.
  • Low-Inductance SMT Packaging: Surface Mount Technology (SMT) packages minimize stray source and drain inductances down to pico-henry levels (< 0.5 nH).
  • Direct Plated Copper (DPC) & Sintering: Replacing wire bonds with top-side copper clips and silver-sintered die attachments reduces thermal resistance (θJC ≤ 0.15°C/W). This enables stable continuous current ratings over 100 A per discrete package.

For demanding power applications such as high-power traction, power modules with paralleled multiple GaN dies within a single low-induction power module are another implementation. This approach distributes the current while maintaining GaN's fast switching advantages.

In the more traditional inverters, silicon IGBTs generally switch between 8 kHz and 15 kHz. This low frequency produces a stepped, distorted current waveform containing significant high-frequency harmonics relative to the fundamental sinusoidal excitation frequency (ffund).

These current harmonics (3rd, 5th, 7th, 11th, etc.) do not produce useful mechanical torque. Instead, they generate parasitic magnetic fields within the stator core and rotor structure, leading to additional losses:

  1. Core Losses (Hysteresis and Eddy Currents): Scaled exponentially with frequency and harmonic flux density.
  2. Rotor High-Frequency Copper Losses: Skin and proximity effects concentrate harmonic currents on the outer surfaces of rotor bars or permanent magnet retaining sleeves, causing localized heating.

Peddy ∝ f2 x B2

By replacing Si IGBTs with GaN HEMTs, the inverter switching frequency can increase to 40 kHz – 100 kHz without significantly impacting switching losses. This high-frequency operation yields several benefits:

  • The current ripple is reduced, creating a smoother approximation of a pure sine wave.
  • Total Harmonic Distortion (THD) decreases significantly.
  • High-frequency motor core and rotor losses drop by up to 40-60%, improving overall powertrain efficiency.

This efficiency improvement directly impacts real-world driving range. Even a modest 1.5% to 2.5% improvement in average inverter efficiency across standard city and highway driving cycles allows OEMs to reduce the physical battery capacity by 1.5 – 2.5 kWh while maintaining the same rated driving range. This yields substantial cost savings at production scale.

The main design challenge for traction inverters is current handling. A typical 150 kW traction inverter operating on a 400 V DC bus requires continuous phase currents exceeding 350 ARMS, with peak acceleration currents reaching 500 A – 600 A.

Modern automotive GaN designs address these issues through:

  • RSP Innovations: Advanced design and manufacturing enables single-die devices with exceptionally low nominal on-resistance (RDS(on) ≤ 10 mΩ).
  • Substrate-Agnostic Processing: Utilizing GaN-on-Silicon IDM processes enables high manufacturing yields at lower costs.
  • Low-Inductance SMT Packaging: Surface Mount Technology (SMT) packages minimize stray source and drain inductances down to pico-henry levels (< 0.5 nH).
  • Direct Plated Copper (DPC) & Sintering: Replacing wire bonds with top-side copper clips and silver-sintered die attachments reduces thermal resistance (θJC ≤ 0.15°C/W). This enables stable continuous current ratings over 100 A per discrete package.

For demanding power applications such as high-power traction, power modules with paralleled multiple GaN dies within a single low-induction power module are another implementation. This approach distributes the current while maintaining GaN's fast switching advantages.

In the more traditional inverters, silicon IGBTs generally switch between 8 kHz and 15 kHz. This low frequency produces a stepped, distorted current waveform containing significant high-frequency harmonics relative to the fundamental sinusoidal excitation frequency (ffund).

These current harmonics (3rd, 5th, 7th, 11th, etc.) do not produce useful mechanical torque. Instead, they generate parasitic magnetic fields within the stator core and rotor structure, leading to additional losses:

  1. Core Losses (Hysteresis and Eddy Currents): Scaled exponentially with frequency and harmonic flux density.
  2. Rotor High-Frequency Copper Losses: Skin and proximity effects concentrate harmonic currents on the outer surfaces of rotor bars or permanent magnet retaining sleeves, causing localized heating.

Peddy ∝ f2 x B2

By replacing Si IGBTs with GaN HEMTs, the inverter switching frequency can increase to 40 kHz – 100 kHz without significantly impacting switching losses. This high-frequency operation yields several benefits:

  • The current ripple is reduced, creating a smoother approximation of a pure sine wave.
  • Total Harmonic Distortion (THD) decreases significantly.
  • High-frequency motor core and rotor losses drop by up to 40-60%, improving overall powertrain efficiency.

This efficiency improvement directly impacts real-world driving range. Even a modest 1.5% to 2.5% improvement in average inverter efficiency across standard city and highway driving cycles allows OEMs to reduce the physical battery capacity by 1.5 – 2.5 kWh while maintaining the same rated driving range. This yields substantial cost savings at production scale.

Key takeaways on GaN topology and device selection

Gallium Nitride is no longer an emerging technology; it is a vital catalyst for the future of sustainable e-mobility. As the automotive industry pushes towards greater efficiency, lighter vehicles, and a more decentralized energy grid, Infineon's GaN power semiconductors equip automotive designers and engineers with the reliable, automotive-qualified solutions required to design cutting-edge, market-leading EV power systems.

In On-Board Chargers, single-stage matrix topologies utilizing monolithic Bidirectional Switches (BDS) eliminate the traditional dual-stage configuration. This removes the intermediate DC link, lowers component counts, reduces conduction losses, and achieves high power densities.

In traction inverters, GaN power transistors and their architectures enable high switching frequencies that reduce motor harmonic losses and improve overall thermal performance. This capability allows for smaller, integrated sine-wave output filters that mitigate dv/dt degradation while protecting motor insulation and bearings.

System-level benefits — including reduced weight, smaller physical footprints, and lower overall vehicle manufacturing costs — position GaN components as a key technology for the next generation of electric mobility.

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Frequently asked questions about GaN topology and device selection

What is a GaN BDS?

A GaN BDS (Gallium Nitride Bidirectional Switch) is an advanced GaN power switch capable of both blocking voltage and conducting current in both directions.

It integrates two switching channels on a single monolithic chip.

Bidirectionality allows power to flow both from the grid to the vehicle (G2V) and from the vehicle back to the grid, home, or load (V2G, V2H, V2L).

An OBC (On-Board Charger) converts AC power from the electrical grid into high-voltage DC power to safely charge the EV's traction batteries.

Traditional OBC topologies typically use a complex "two-stage" topology: an AC/DC Power Factor Correction (PFC) stage followed by a DC/DC resonant converter, separated by large, bulky DC-link capacitors.

GaN BDS allows for an innovative "single-stage" bidirectional topology. Instead of separate PFC and DC/DC stages, it directly converts AC to corrected AC or DC, removing several intermediate bulky components.

In many single-stage topologies utilizing GaN BDS, the bulky and expensive electrolytic DC-link capacitors can be completely eliminated or drastically reduced.

An EV traction inverter — often called a gallium nitride traction inverter when built with GaN transistors — is a critical powertrain component.

It converts the direct current (DC) from the high-voltage battery into alternating current (AC) to drive the electric propulsion motor.

GaN transistors deliver significantly lower switching losses, higher energy efficiency, and faster switching speeds compared to traditional silicon counterparts.

This directly addresses automakers' demands for extended vehicle range.

GaN traction inverters can achieve peak efficiencies up to 98%. This translates to roughly a 40% reduction in power losses compared to legacy silicon IGBT solutions under typical driving cycles.

The high efficiency of GaN reduces energy waste during acceleration and deceleration. This optimization can extend an EV's driving range by up to 5% using the exact same battery capacity.

GaN enables a 33% to 50% increase in power density. Because the transistors switch faster, the sizes of the internal capacitors, busbars, and housing are drastically reduced, enabling a lighter, more compact system.

Higher switching frequencies generate a smoother, more sinusoidal current waveform.

This significantly reduces total harmonic distortion (THD) in the motor windings, decreasing motor core losses and lowering rotor operating temperatures.

Yes. To achieve the hundreds of kWs required by EV motors, multiple GaN dies are driven in parallel.