Power Electronics Europe Feb/March 2023

https://www.allegromicro.com/en POWER DENSITY 15 www.power-mag.com Issue 1 2023 Power Electronics Europe isolated DC-DC source to create the floating voltage required for controlling the high-side switches. The benefits cascade from there. By eliminating the need to provide an external bias power supply, all the tradeoffs and complexity in choosing the optimal combination of components vanish. The reduced component count/complexity amounts to fewer potential points of failure, which delivers greater reliability, leading to fewer potential warranty claims and enhanced product reputation. The reduced component count also results in smaller gate driver assemblies with shorter signal paths. The shorter signal path inherently results in reduced parasitic capacitance and inductance. As a result, the risk of damage caused by ringing and voltage spikes is significantly reduced and more space is available for the power stages, enabling the use of more-efficient designs. This solution also allows the gate driver to track the power consumption of the gate control with the switching frequency, enabling automatic optimization of efficiency. By enabling the elimination of auxiliary power supplies, Power-Thru gate drivers ultimately make design and qualification easier while lessening strain on engineering resources and accelerating research and development cycles. Simplifying power-conversion design by applying Power-Thru solutions Cost, design time, and unexpected problems: These are three of the most significant issues on the minds of project managers who are involved with the design of power conversion systems, and the innovative Power-Thru technology from Allegro can help to minimize all of them. The following example of an on- board charger illustrates the significant impact of the Power-Thru technology. This example uses a multilevel topology, which is known to enable high- efficiency power conversion. However, the design of a multilevel topology is very complex—particularly the gate driver. Each wide-bandgap power transistor of the on- board charger used in this example requires one gate driver to switch the power device. While the primary and secondary low-side switches share the respective power rail, each of the seven high-side switches requires its own isolated bias supply. This can result in nine separate bias rails for the system, which is extremely complex, as shown in Figure 2. When designing the same on- board charger with isolated gate drivers enabled by the Allegro Power-Thru technology, the nine power rails per phase can be merged into a single rail, as illustrated in Figure 3. This break-through system design and build simplification allows significantly reduced component count. All power stages can be implemented in a single board, only requiring a single capacitor and two resistors on the output, which speeds design time and improves the likelihood of early design success. Furthermore, the reduced component count reduces bill of material (BOM) costs and system size, and also unlocks new levels of build simplification. By reducing complexity, early success in testing and validation is more likely, and application of the technology can be more reliable because use of fewer parts equates to less opportunity for a failure. More importantly, the reduction of system size enables an increase in power density as the same amount of power can be delivered with smaller form factor. Unlocking new levels of conversion performance and simplification with Power-Thru In summary, power conversion systems need to be ever more efficient, compact, reliable and, ideally, less expensive. Wide-bandgap power switches allow for significant advances in achieving higher efficiency and higher power density, but they add system complexity and cost. Reducing system complexity can be achieved by focusing on another critical part of the power conversion system—the driving of the power FETs. The approach used to drive a power switch can have great impact on the solution as a whole, and drivers that enable the elimination of multiple power rails and bootstrap circuits have cascading benefits to the system. The new paradigm in power conversion—created by the Power- Thru technology inside Allegro high- voltage isolated gate drivers—uses a novel SiP gate drive that includes a magnetic coupling device placed in between the primary and secondary gate driver integrated circuits, which eliminates the need for bias supplies. The power needed to drive the gate of the switch is transferred with the gate on/off logic signals, thus completely eliminating the external auxiliary power required by conventional solutions. The Power- Thru technology enables shorter signal paths that reduce parasitics and voltage spikes, increase reliability, free up space, and lead to more- efficient designs. The embedded bias eliminates bootstrap circuitry, separate power supplies, and other complicated design tradeoffs. Considered as whole, the Power-thru technology provides advantages in all relevant system dimensions, unlocking significant system and design simplification, higher efficiency, and reduced component count leading to higher power density and reliability. https://www.allegromicro.com/en To receive your own copy of Power Electronics Europe subscribe today at: www.power-mag.com