As electric vehicle (EV) performance continues to improve and driving ranges extend, onboard chargers (OBCs) face unprecedented challenges as critical components. Higher battery voltages demand faster charging rates, while designs must simultaneously achieve smaller footprints, lighter weights, and higher thermal efficiency. Addressing these challenges requires rethinking power conversion implementation at the component level. ROHM Semiconductor's newly developed HSDIP20-packaged 4-in-1 and 6-in-1 SiC plastic-encapsulated modules offer a novel solution to this challenge. Designed specifically for power factor correction (PFC) and LLC converter circuits within OBCs, as well as other high-power applications, this series promises significant improvements in power density and thermal management—parameters critical to modern EV systems.

Challenges of Traditional OBC Architecture
In conventional OBC architectures, top-mounted discrete SiC MOSFETs have been the standard solution. However, as power levels continue to increase, thermal management and maintaining a compact form factor become increasingly challenging. For surface-mount devices (SMDs), heat dissipation relies on the printed circuit board (PCB) or requires precise mounting of each individual package onto a heat sink using suitable thermal interface materials. This approach is nearing its limits in pursuing higher power density and system compactness. Furthermore, OBCs primarily employ two architectures: a modular design based on three identical single-phase modules, or a centralized architecture centered on a three-phase AC/DC converter (which also supports single-phase operation). The modular architecture requires more components, increasing demands on the DC link's energy storage capacity and consequently adding volume and cost. It also necessitates additional gate drivers and voltage/current sensing functions. In contrast, the centralized architecture requires fewer components, enabling a more cost-effective OBC and becoming the preferred architecture for high-power-density OBCs.

Technological Breakthroughs in SiC Modules
ROHM's HSDIP20 module offers a solution to the aforementioned challenges. SiC material, with its exceptional properties, is an ideal choice for OBC power semiconductors. ROHM's 4th generation SiC MOSFETs utilize a trench structure to achieve ultra-low on-resistance. Their extremely low Miller capacitance enables ultra-fast switching speeds, effectively reducing switching losses. These characteristics result in lower total losses, thereby alleviating the burden on thermal design.
The HSDIP20 module integrates 4 or 6 SiC MOSFETs within a full-bridge circuit, offering significant advantages over discrete components using the same chip technology. This module series employs aluminum nitride (AlN) ceramic to electrically isolate the heat sink pad from the MOSFET drain, achieving exceptionally low junction-to-case thermal resistance (Rth). This eliminates the need for thermal interface material (TIM) to electrically isolate the heat sink pad from the heat sink. Additionally, the molded material enables electrical isolation between chips within the power module. This allows for tighter chip placement than discrete solutions (which require consideration of creepage distances on the PCB), reducing PCB footprint and enhancing the power density of the OBC solution.
Data shows that in the PFC circuit commonly used in OBCs (employing six SiC MOSFETs), comparing six top-cooled discrete components with a single HSDIP20 module in a 6-in-1 configuration under identical conditions reveals that the HSDIP20 operates approximately 38°C cooler than the discrete structure (at 25W operation). Furthermore, the HSDIP20 achieves over 3 times the current density compared to top-mounted discrete components and over 1.4 times that of similar DIP modules, reaching industry-leading levels. In the aforementioned PFC circuit, the HSDIP20 reduces the installation area by approximately 52% compared to top-mounted discrete components.

Simplified Development Process, Reduced Risk
Beyond technical advantages, the HSDIP20 modules streamline the development process for engineers. Since electrical isolation is built into the module itself—unlike discrete solutions requiring external isolation handling—this series not only shortens development cycles and lowers costs but also minimizes the risk of insulation issues.
The HSDIP20 modules also offer excellent scalability. ROHM offers a wide range of RDS(on) specifications and topology options, making this series suitable for OBC applications across different power ranges. For example, ROHM has introduced a “hybrid” module utilizing a Six-pack topology. By combining MOSFETs with different RDS(on) values, this module provides a low-cost solution for totem-pole PFC circuits and enables easy implementation of both single-phase and three-phase operation using the same device. Furthermore, modules across all topologies share the same package form factor, facilitating easy application expansion. All power modules comply with the AQG324 standard.
In thermal performance demonstrations, the Six-pack module equipped with 36mΩ, 1200V SiC MOSFETs achieves exceptionally low single-chip thermal resistance through optimized internal structure. Its thermal performance delivers significant advantages, with maximum junction temperatures well below the 175°C limit permitted for SiC MOSFETs. This creates greater headroom for increasing power density, meeting the stringent demands of high-power OBCs. Switching loss results obtained from dual-pulse testing of this module are equally applicable to bidirectional DC/AC conversion stages. Simulation results indicate that an 11kW AC/DC conversion stage built using a 6-in-1 module based on 4th-generation SiC MOSFETs (36mΩ, 1200V) achieves approximately 99% efficiency at a switching frequency of 48kHz with forced air cooling (this efficiency value considers only semiconductor losses).

Broad Application Prospects
In the electric vehicle sector, batteries are rapidly advancing toward higher voltage levels to extend vehicle range and accelerate charging speeds. Simultaneously, the demand for increased output power in OBCs and DC-DC converters is growing significantly. Concurrently, the market demands miniaturization and weight reduction in these applications, with the core focus on enhancing power density. The HSDIP20 module aligns perfectly with this market trend.
Beyond EV OBC applications, the HSDIP20 module can be deployed in onboard DC-DC converters, electric compressors, and similar devices. In industrial settings, it serves EV charging stations, V2X systems, AC servo drives, server power supplies, PV inverters, and power conditioners.
As the electrification of vehicles and infrastructure accelerates, breakthroughs in component-level design like ROHM's HSDIP20 module are crucial. By overcoming thermal and power density constraints while simplifying system-level design, these innovations pave the way for smaller, faster, and more efficient EV charging and power conversion systems. Looking ahead, as technology continues to advance and mature, compact SiC modules will undoubtedly play an increasingly vital role in high-power-density applications, propelling the entire industry toward a new phase of development.