POWERlab / Research / Power Converters

High-density power converters

Ultra-compact liquid-cooled power converters leveraging wide-band-gap GaN devices and monolithic microfluidic integration for maximum efficiency and power density at the system level.

The challenge

Pushing the limits of power density

Modern power electronics demands ever-higher power densities — more watts per liter, less volume per kilowatt. Thermal management is the primary bottleneck: conventional heat sinks and fan-based cooling cannot keep pace with the heat fluxes generated by high-frequency GaN switching stages.

Our group addresses this by co-designing power converters with integrated microfluidic cooling from the ground up, combining high-performance GaN transistors, advanced circuit topologies, and embedded liquid cooling to achieve power densities an order of magnitude beyond conventional designs.

GaN-on-Si converter with integrated microfluidic cooling
Key innovations

Converter architectures

4 converter concepts
Monolithic integration

In-chip microfluidic cooling on GaN power IC: 78 kW/l

We demonstrated the integration of in-chip microfluidic cooling directly on GaN power integrated circuits, combining power switches, gate drivers, logic, and cooling into a single liquid-cooled chip. A 0.44 kW 48 V–24 V dc–dc converter was realized in a compact 1/32nd brick form factor, achieving an outstanding power density of 78 kW/l with 95% efficiency. The in-chip cooling delivered a 14× reduction in thermal resistance and a 4× increase in output power compared to conventional heat-sink and fan cooling — removing thermal limitations from power IC design and enabling a new generation of ultra-compact converters.

In-chip microfluidic cooling integrated on GaN power IC — concept, module, and 78 kW/l prototype
Monolithic integration

Integrated GaN IC with embedded microfluidic cooling

To demonstrate the potential of embedded cooling at the device level, we monolithically integrated a full-bridge rectifier onto a single GaN-on-Si die. Rectification was provided by four high-performance tri-anode Schottky barrier diodes with a breakdown voltage of 1.2 kV and high-frequency capability up to 5 MHz. A three-layer PCB with embedded coolant delivery channels was developed to guide the coolant directly to the device, fully leveraging the compactness of high-performance microchannel cooling.

Integrated GaN IC with embedded microfluidic cooling
System integration

Liquid-cooled multi-level converter with 10× power density

We developed microfluidic cold plates attached to 20 GaN power transistors to cool a 2.5 kW multi-level converter. A thermal resistance of just 0.2 K/W was measured at a flow rate of 1.2 ml/s and a pressure drop of 600 mbar. Experimental results demonstrated a 10-fold increase in power density compared to conventional cooling, offering a transformative thermal-management approach to achieve far more compact and efficient power converters.

Liquid-cooled multi-level GaN converter with microfluidic cold plates
Circuit topology

Impulse rectification boost converter: 98.6% efficiency, 52 kW/l

We demonstrated a full-scale optimization of a kilowatt-range megahertz-class boost converter based on the impulse rectification topology proposed by our group. High-performance GaN transistors are employed alongside various high-frequency magnetic materials (MnZn, NiZn, and air) with different geometries to realize a wide-bandwidth inductor. The optimized converter achieved a peak efficiency of 98.6% along with an ultra-high power density of 52 kW/l (850 W/in³) — setting a new benchmark for compact, efficient power conversion.

Impulse rectification boost converter — circuit, inductor, and efficiency plot
Selected references

Key publications

2024

R. van Erp, N. Perera, L. Nela, I. O. Elhagali, H. Zhu and E. Matioli, “In-Chip Microfluidic Cooling Integrated on GaN Power IC Reaching High Power Density of 78 kW/l,” IEEE Transactions on Power Electronics, vol. 39, no. 8, 2024.

2021

A. Jafari, M. Samizadeh Nikoo, R. van Erp and E. Matioli, “Optimized Kilowatt-Range Boost Converter Based on Impulse Rectification With 52 kW/l and 98.6% Efficiency,” IEEE Transactions on Power Electronics, 2021.

2020

R. Van Erp, R. Soleimanzadeh, L. Nela, G. Kampitsis, E. Matioli, “Co-designing electronics with microfluidics for more sustainable cooling,” Nature, 2020.

2020

R. Van Erp, G. Kampitsis, E. Matioli, “Efficient microchannel cooling of multiple power devices with compact flow distribution for high power-density converters,” IEEE Transactions on Power Electronics, 2020.

2019

R. van Erp, G. Kampitsis and E. Matioli, “A manifold microchannel heat sink for ultra-high power density liquid cooled converters,” IEEE APEC, Anaheim, CA, USA, 2019.

2019

G. Kampitsis, R. van Erp and E. Matioli, “Ultra-High Power Density Magnetic-less DC/DC Converter Utilizing GaN Transistors,” IEEE APEC, Anaheim, CA, USA, 2019.

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