Daniel Murphy, Senior Director, Product Management, CGD
Gallium nitride (GaN) is moving into higher-power electric vehicle (EV) applications as engineers look for ways to improve power-conversion efficiency and reduce the size of vehicle power electronics.
While GaN is already established in lower-power applications, advances in device design are expanding its potential role in EV power architectures. Higher switching frequencies can improve power density, but engineers still have to weigh those gains against broader system requirements.
To explore where GaN can make the greatest difference, we spoke with Daniel Murphy, senior director, Product Management at Cambridge GaN Devices (CGD). In this interview, Murphy discusses how GaN can influence vehicle efficiency and what engineers should consider when evaluating the technology.
Here’s what he has to say…
Where in the EV power architecture can GaN deliver the greatest vehicle-level efficiency gains?
GaN can improve efficiency across several stages of an EV’s power architecture, but some of the greatest vehicle-level gains are likely to come from the traction inverter, onboard charger (OBC), and high-voltage-to-low-voltage dc-dc converter.
The traction inverter is particularly important because it continuously processes propulsion power between the battery and motor. By enabling higher switching frequencies and lower switching losses, GaN can improve conversion efficiency while reducing the quantity, size, and weight of associated components.
In the OBC and dc-dc converter, GaN’s higher-frequency operation allows designers to shrink magnetics and improve power density while reducing conversion losses. At the vehicle level, GaN can also contribute to lower mass, reduced packaging volume, and less demanding cooling requirements.
A traction inverter converts dc battery power to ac for the EV traction motor, making conversion efficiency an important factor in overall vehicle energy use.
How do GaN’s lower switching and conduction losses translate into energy savings over real-world drive cycles?
The efficiency gains of GaN become particularly relevant under real-world driving conditions, where power electronics rarely operate at a single steady-state point. Instead, EVs experience frequent load changes during acceleration, cruising, regenerative braking, and auxiliary power operation. GaN devices reduce switching losses through their low gate charge and fast switching characteristics, while low RDS(on) values help minimize conduction losses.
Additionally, GaN high-electron-mobility transistors (HEMTs) avoid many of the reverse-recovery losses associated with conventional silicon devices. Across an entire drive cycle, these reductions mean that less battery energy is dissipated as heat within the power electronics, allowing a greater proportion of stored energy to be used for propulsion and potentially extending driving range for a given battery capacity.
How does GaN’s higher switching frequency affect passive component size and weight?
One advantage of GaN is its ability to operate at much higher switching frequencies than conventional silicon technologies. While silicon insulated-gate bipolar transistors (IGBTs) typically switch at around 8 to 12 kHz and silicon carbide devices often operate up to approximately 250 kHz, GaN devices can switch at frequencies approaching 1 MHz. This higher frequency allows engineers to achieve the same filtering and energy-storage performance with substantially smaller inductors, transformers, and other magnetic components.
The resulting reductions in size and weight can have a meaningful impact on vehicle efficiency, as lighter power electronics contribute directly to lower overall vehicle mass and improved packaging flexibility.
When does increasing switching frequency begin to reduce the overall efficiency benefit?
Higher switching frequency is not automatically beneficial in every application. Although increasing frequency enables smaller passive components, it also increases switching-related losses, gate-drive power requirements, and electromagnetic interference challenges.
At some point, the additional losses associated with switching more frequently begin to offset the benefits gained from smaller magnetics and improved power density. The optimum operating frequency, therefore, depends on the specific application and must be evaluated at the system level. Engineers typically seek a balance between efficiency, thermal performance, electromagnetic compatibility, and packaging requirements rather than simply maximizing switching frequency.
How can GaN reduce thermal management demands at the vehicle level?
GaN devices generate less heat during power conversion, which can significantly reduce thermal management requirements throughout the vehicle. Lower semiconductor losses mean less waste heat must be removed from inverters, chargers, and dc-dc converters, allowing designers to reduce the size of heat sinks and other cooling hardware. Lower operating temperatures can also improve reliability and extend component lifetime by reducing thermal stress and keeping components within their designed operating ranges.
At the vehicle level, every watt of heat that does not need to be removed translates into reduced cooling-system workload and lower parasitic energy consumption, creating benefits that extend well beyond the power semiconductor.
How can GaN influence battery use or driving range under real-world operating conditions?
GaN does not increase battery capacity, but it can improve the proportion of stored energy that ultimately reaches the driven wheels. More efficient power conversion in the traction inverter reduces propulsion losses, while improvements in onboard charging and auxiliary power conversion minimize energy losses elsewhere in the vehicle. The reduced cooling requirements associated with lower heat generation can further decrease auxiliary energy consumption.
In addition, the smaller and lighter power electronics enabled by higher-frequency operation can contribute to overall vehicle mass reduction. Taken together, these effects improve battery utilization and can translate into measurable range gains without increasing battery size, which can be valuable for vehicle OEMs.
More efficient power conversion in the onboard charger can reduce energy losses during EV charging.
What system-level metrics should engineers use to evaluate GaN benefits beyond peak component efficiency under typical operating conditions?
Evaluating GaN solely based on peak device efficiency risks overlooking some of its vehicle-level advantages. Engineers should instead focus on metrics that capture performance across representative operating conditions. These include:
- Total energy losses over standardized drive cycles
- Battery-to-wheel efficiency
- Vehicle energy consumption expressed in Wh/km
- Charging efficiency across the full operating range of the OBC
Thermal metrics such as total heat generation and cooling-system power consumption are also important, as are power-density measures including kW per liter and kW per kilogram. These broader metrics provide a more accurate picture of how GaN affects overall vehicle efficiency, packaging, and system performance.
As GaN matures, what vehicle-level efficiency gains could become possible in future EV architectures?
As GaN technology matures, one of its larger impacts may come from enabling new approaches to power-electronics architecture rather than simply improving existing designs. Higher-frequency operation could support much smaller and lighter traction inverters, onboard chargers, and dc-dc converters, while also facilitating more distributed and efficient zonal power architectures.
Continued advances in thermal performance may allow further reductions in cooling-system complexity and weight. The ability to operate large numbers of devices in parallel could also enable higher-power inverter designs without sacrificing efficiency. Ultimately, future vehicle-level gains are likely to result from combining higher efficiency with lower mass, higher power density, and more integrated electrical architectures, which are difficult to realize using today’s conventional silicon-based approaches.
Filed Under: Electric Motor, Featured Contributions, Onboard Charging, Q&As