24 BIDIRECTIONAL CHARGING https://my.avnet.com/silica/ Issue 3 2026 Power Electronics Europe www.power-mag.com well as domestic and commercial-scale energy storage systems. BDC Design Priorities When designing a BDC system, engineers must balance efficiency, cost, size, and safety against the specific requirements of the application. Those requirements vary with power level, voltage range, thermal constraints, isolation needs, and the intended bidirectional function, so the design process is shaped by trade-offs rather than a single preferred approach. One of the first and most important decisions is the choice of conversion topology. Different topologies offer different advantages and disadvantages, which in turn affect the size, cost, and efficiency of the overall power conversion system. The most suitable solution therefore depends on the application, the power tier, and the performance priorities of the design. The switching control strategy is another key consideration. Depending on the chosen topology, power level, and semiconductor technology, designers may use phase-shift or resonant control techniques and tune parameters such as dead-time to balance efficiency and safe bidirectional operation. Optimising those settings helps minimise switching and conduction losses while preventing unsafe current or voltage stresses. Safety must also be considered in relation to both power tier and topology. While topologies such as DAB and CLLC provide inherent galvanic isolation through their transformers, designers must still address insulation, fault protection, and regulatory requirements, especially at higher power levels. Choosing a BDC Topology Topology choice depends on whether the system is connected through an AC grid interface or coupled directly to a DC bus. Grid-connected bidirectional wallboxes and stationary converters typically combine a grid-facing PFC or inverter stage with an isolated bidirectional DC-DC stage, while DC-coupled systems may place the gridfacing stage elsewhere but still require isolation and protection for safe battery integration. For the grid-facing stage, totem-pole PFC can be attractive where high efficiency and lower component count are priorities, although EMC and control complexity must be managed. In higher-power three-phase systems, Vienna bridge rectifiers are often considered for the grid-facing PFC stage, particularly where efficiency, lower input current distortion, and three-phase operation are priorities. For the isolated DC-DC stage, CLLC and DAB are common, with DAB often favoured where bidirectional control, flexible voltage matching, and robust power regulation are priorities. In building energy systems, these choices directly affect how efficiently storage can be integrated with onsite generation, charging, and wider power management functions. DAB is particularly versatile because it combines high efficiency with the ability to handle a broad range of input and output voltages. It also operates at constant switching frequency and can deliver lower current ripple than resonant topologies, which simplifies control and supports predictable bidirectional operation, even if packaging density can be slightly lower than some resonant alternatives. That makes it attractive wherever minimising energy loss is important. A DAB comprises two full-bridge H-bridges connected across an isolated high-frequency transformer. Power flows bidirectionally by modulating the phase shift between the primary and secondary bridges, allowing precise regulation of energy transfer while maintaining galvanic isolation. In practical terms, designers implementing a DAB need to select highspeed MOSFETs or power modules, the high-frequency transformer, and passive elements that help manage leakage inductance, switching losses, and softswitching conditions. Avnet Silica’s portfolio supports these design requirements with solutions from leading manufacturers, including onsemi, ROHM Semiconductor, STMicroelectronics, and Nexperia. The combination of efficiency, isolation, and flexible voltage handling explains why DAB is such an important topology in modern BDC design. Semiconductor Choices for BDC Besides topology, semiconductor technology plays a major role in BDC design. Device selection affects switching speed, thermal output, efficiency, and cost. Thus, it has a direct impact on overall converter performance. IGBTs remain well established and can handle the current requirements of many bidirectional conversion topologies, particularly where lower switching frequencies and cost sensitivity are priorities. However, Silicon carbide (SiC) has better switching-loss and RDS(on) behaviour, making it better suited to higher-voltage designs where converter losses must be minimised. These advantages are especially valuable in three-phase applications, where efficiency, thermal performance, and power density are all important, but they can also support lower-output-power designs where efficiency remains a top priority. At power levels above 10 kW, SiC is prominent in applications such as EV charging and gridscale storage. Gallium nitride (GaN) fits a different part of the design space. It is currently better suited to compact, lower-voltage, singlephase home energy systems or BDCs, where high switching frequency and reduced size can be beneficial. This is partly due to breakdown-voltage limits. Single-phase systems often work with internal DC bus voltages around 400 V, which can align well with 650 V GaN devices. Three-phase systems, however, often operate with internal DC bus voltages closer to 800 V, beyond 650 V GaN devices’ capabilities. Some highervoltage and higher-power GaN solutions are emerging, but SiC remains the more established choice for higher-voltage, higher-power bidirectional systems. BDC by Power Tier Power conversion design is shaped by multiple interdependent factors, including efficiency targets, input voltage range, output power, thermal constraints, and the intended bidirectional functionality. The Figure 3: DAB topology is highly efficient and supports a wide range of input and output voltages Source: adapted from Huiqing Wen et al., ‘Bidirectional dual-active-bridge DC-DC converter with triple-phase-shift control’, ResearchGate.
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