GaN Talk Blog

Power electronics engineers are constantly working towards designs with higher efficiency and higher power density while maintaining high reliability and minimizing cost. Advances in design techniques and improved component technologies enable engineers to consistently achieve these goals. Power semiconductors are at the heart of these designs and their improvements are vital to better performance. In this EPC space blog, we will demonstrate how GaN power semiconductors allow for innovation in the harsh radiation environments of space applications.

GaN power semiconductors offer designers in the high reliability market a sudden and significant improvement in electrical performance over their silicon power MOSFET predecessors. Table 1 compares radiation hardened GaN and Si power semiconductor device characteristics important for circuit designers to increase efficiency and power density in their converter.

Rethinking the Ordinary and Overcoming Mental Biases

Motor drive applications span several markets: industrial, appliance, and automotive. A commonality that occurs regardless of market is that when a new technology is proposed, it faces resistance to its adoption; after all, it is human nature to stick with what is known and resist change.

Brushless DC (BLDC) motors are popular and finding increasing application in robotics, e-mobility, and drones. Such applications have special requirements such as lightweight, small size, low torque ripple, low audible noise, and extreme precision control.  To address these needs, the inverters powering the motors need to operate at higher frequency but require advanced techniques to reduce the resultant higher power loss. Enhancement-mode gallium nitride (eGaN ^®) transistors and integrated circuits offer the ability to operate at much higher frequencies without incurring significant losses. 

Brick DC-DC converters are widely used in data center, telecommunication and automotive applications, converting a nominal 48 V bus to (or from) a nominal 12 V bus. Advances in GaN integrated circuit (IC) technology have enabled the integration of the half bridge and gate drivers, resulting in a single chip solution that simplifies layout, minimizes area, and reduces cost.

This application note discusses the design of a digitally controlled bi-directional 1/16th brick converter using the integrated GaN power stage for 48 V-to-12 V application, with up to 300 W output power, and peak efficiency of 95%.

The standard dimension of the 1/16th brick converter is 33 x 22.9 mm (1.3 x 0.9 inch). The height limit for this design is set to 10 mm (0.4 inch).

Acknowledgement - This application note and associated hardware was developed in collaboration with Semiconductor Power Electronics Center (SPEC) at University of Texas at Austin.

Motivation

The expansion of applications such as cloud computing, wearables, machine learning, autonomous driving, and IoT drive us towards an even more data-intensive world, increasing demands on data centers and power consumption [1, 2]. The importance of efficiency, power density, and cost of the AC to DC switching power supply is driving innovative solutions that eGaN FETs can solve to yield ultra-high efficiency power factor correction (PFC) front-end rectifier solutions that are the focus of this how-to-application note.

Efficient Power Conversion (EPC) is increasing the performance distance between the aging silicon power MOSFET and eGaN transistors with 100 V ratings.  The new fifth-generation “plus” devices have about 20% lower R_DS(on) and increased DC ratings compared with the prior fifth-generation products.  This performance boost comes from the addition of a thick metal layer and a conversion from solder balls to solder bars.

Efficient Power Conversion (EPC) is doubling the performance distance between the aging silicon power MOSFET and eGaN® transistors with 200 V ratings.  The new fifth-generation devices are about half the size of the prior generation.  This performance boost comes from two main design differences, as shown in figure 1.  On the left is a cross-section of the fourth generation 200 V enhancement-mode GaN-on-Si process.  The cross-section on the right is the fifth-generation structure with reduced distance between gate and source electrodes and an added thick metal layer. These improvements, plus many others not shown, have doubled the performance of the new-generation FETs.

Packaged SEE Immune and Radiation Hardened enhancement mode gallium nitride (eGaN) devices offer dramatically improved performance over the aging Rad Hard silicon MOSFET, enabling a new generation of power converters in space operating at higher frequencies, higher efficiencies, and greater power densities than ever achievable before.

GaN FETs can switch significantly faster than Si MOSFETs causing many system designers to ask − how does higher switching speeds impact EMI?

This blog discusses simple mitigation techniques for consideration when designing switching converter systems using eGaN^® FETs and will show why GaN FETs generate less EMI than MOSFETs, despite their fast-switching speeds.

Beyond just performance and cost improvement, the most significant opportunity for GaN technology to impact the power conversion market comes from its intrinsic ability to integrate multiple devices on the same substrate. GaN technology, as opposed to standard silicon IC technology, allows designers to implement monolithic power systems on a single chip in a more straightforward and cost-effective way.

Today, the most common building block used in power conversion is the half bridge. In 2014, EPC introduced a family of integrated half-bridge devices which became the starting point for the journey towards a power system-on-a-chip. This trend was expanded with the introduction of the EPC2107 and EPC2108, which integrated half bridges with integrated synchronous bootstrap. In 2018 we further continued the integration path with the introduction of eGaN ICs combining gate drivers with high-frequency GaN FETs in a single chip for improved efficiency, reduced size, and lower cost. Now, the ePower™ Stage IC family redefines power conversion by integrating all functions in a single GaN-on-Si integrated circuit at higher voltages and higher frequency levels beyond the reach of silicon.