Fraunhofer Embeds GaN Power ICs on Single Chip
Researchers at the Fraunhofer-Institute for Applied Solid State Physics IAF have incorporated their patented Gallium-Nitride (GaN) power ICs, DC-DC converter for energy-efficient power electronics.
In the early stages of power electronics research at the Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg, Germany, a team of scientists developed a user-friendly, highly integrated GaN voltage converter rated for 600V applications. Their mission was to integrate several power components, control circuits, and sensors to be combined on a single semiconductor chip.
A Closer look at the PCB-embedded, GaN-on-Si, half-bridge circuit including gate and DC link capacitors. Image used courtesy of Fraunhofer IAF.
In 2017, Fraunhofer IAF announced the integration of their GaN Power ICs in power charging stations for electric vehicles. The small footprint minimizes negative influences such as line impedances, improving the electrical switching characteristics.
What makes GaN Power ICs better than silicon-based ICs? The wide-bandgap. GaN can enable higher power densities and is suited to high heat levels with solid thermal conductivity. Systems made with wide-bandgap materials can be thinner, lighter, and stronger to handle more power than systems with lower bandgaps.
Progression Through Power Electronics
Researchers at Fraunhofer IAF have been developing transistors, monolithic integrated circuits (ICs), and modules for a wide range of applications. Aiming for high-frequency applications and instances that require fast power switching. Their GaN Power ICs offer low-noise, linear, energy-efficient, small-footprint specifications.
They have embedded their innovative gallium nitride-based integrated power circuits (GaN Power ICs) as a half-bridge in a printed circuit board (PCB), which features all critical wiring, including gate and DC link capacitors, within the package. The result is an extremely compact and efficient voltage converter suited for all 600 volts applications.
An X-ray image of the half-bridge circuit and circuit diagram of the integrated GaN Power ICs. Image used courtesy of Fraunhofer IAF.
GaN Power ICs utilize a half-bridge circuit, this DC-DC converter uses two input switches to control the output voltage of the transformer. It can supply an output voltage of a higher or lower value of the input voltage and provide electrical isolation.
Fraunhofer IAF’s half-bridge circuit consists of two GaN high electron mobility transistors and two integrated diodes. The transistors have a breakdown voltage of more than 600 volts and an on-state resistance of 120 mΩ. A folded chip layout enables the DC link capacitance to be tightly connected between the supply voltage and the ground. This design creates an optimized power path and allows for clean, stable switching at high frequencies. The operation of this circuit was demonstrated by Fraunhofer IAF in 2016 with a down converter from 400 to 200 volts at a switching frequency of 3 MHz.
Several Components Side-by-Side on a Single Chip
Stefan Mönch, a researcher at Fraunhofer IAF discussed the capabilities of Fraunhofer’s GaN-based developments saying, “GaN-on-Si technology allows monolithically integrated circuits for half-bridge converters but does not solve the wiring problem to external capacitors. However, these critical connections to gate drivers and DC link capacitors are essential for clean and efficient switching behavior.”
The physical characteristics of GaN materials are what make it unique; the current is able to flow parallel to the surface of the chip, giving designers all connections (conductor paths) located on the top of the circuit. Making it easier for having several discrete components to be laid out on a single chip.
We can expect to see more developments with GaN-based power electronics since GaN substrates enable higher power densities to be achieved while being energy-efficient. And a big take away from Fraunhofer’s research is its method of depositing low-cost silicon substrate (GaN-on-Si) on GaN materials. Silicon is a standard design methodology and by following Fraunhofer’s research, developers can make chip technology suitable for cost-efficient mass production.
