Power Electronics Europe Feb/March 2023

12 POWER DENSITY https://www.allegromicro.com/en Issue 1 2023 Power Electronics Europe www.power-mag.com Solving the Challenges of Increasing Power Density By Reducing Number of Power Rails By Andy Wang, Business Line Director, High-Voltage Power Business Unit Allegro MicroSystems The world continues to become increasingly electrified, and both the demand for energy and the requirements placed on that energy continue to expand. Between automobile electrification, internet traffic, and renewable energy, a global need has developed for high-power-density technologies that can deliver more power output from the same or less amount of space as legacy solutions. In electrical vehicles, particularly in on-board charger applications, higher power density equates to a smaller, lighter-weight form factor that allows faster charging and frees more space for the battery. This ultimately leads to more driving distance per charge. In data centers, government regulations are driving the need to improve power density. For example, beginning in 2023, the power supply of a European data center must achieve a Titanium Plus efficiency rating (greater than 96 percent efficiency), which effectively doubles power density requirements compared to legacy systems. In microinverters for solar panels, the market continues to push for smaller system size with an increase in power level. This article overviews some of the challenges associated with high- power-density solutions and some of the technologies that can best enable the desired outcome. An innovative technology is then presented that simplifies power-system design for all these markets, with cascading benefits. Overview of power transistor choices Common applications today demand high-density power conversion in high- current, high-temperature, high-voltage environments. Achieving the market demand necessitates use of technologies that can support higher switching frequency with reduced conduction losses at much higher temperatures than conventional silicon insulated-gate bipolar transistors (IGBTs) and silicon MOSFETs. The latest trend that allows engineers to achieve the goal of increasing power output while reducing solution size is the adoption of wide-bandgap semiconductors. Wide-bandgap devices— such as silicon carbide (SiC) and gallium nitride (GaN)—have better on-state resistance per specific area than conventional silicon IGBTs and silicon MOSFETs. This performance improvement allows a wide-bandgap power device to enable high-frequency operation and leads to system size reduction. As described in “Why gate drivers are key to successful electric vehicle designs,” Power Electronics Europe, 2022, Issue 4, for applications that require voltages up to 1700 V, the required high-voltage, high- current, high-temperature performance is better achieved by SiC transistors than silicon IGBTs. Many common applications also demand a small system design with switching speed as fast as 2 MHz. This reduced-size, high-speed switching performance is better served by GaN devices. Regardless of semiconductor selection—GaN or SiC—achieving the desired performance often requires use of many power devices that must adhere to the strict safety standards established for electric vehicles and various industrial and data-center applications. Meeting these standards requires careful selection of system components. One of the most critical components among these devices is the isolated gate driver, which is used to turn on and turn off the selected transistor. Understanding the importance of gate drivers and switch-matching The success of a power conversion system is heavily influenced by the isolated gate driver. Isolated gate drivers enable the transfer of data and power