Save on BOM Costs with New C3M 650V MOSFET

The U.S. electricity consumption is expected to grow from just over 4,000 billion kWh in 2020 to about 5,500 billion kWh by 2050.^[i] The increasing consumption, not just in the United States but worldwide, will come partly from the electrification of transport, including electric vehicles (EVs), and an increase in computing resources around the world -- billions of personal computing as well as connected devices in an Internet of Things (IoT) that depends on an increasing number of server farms.

All application markets, particularly EVs and computing, benefit from lowering the cost of power consumed and the amount of space taken up to deliver the same or greater functionality at a lower cost — competitively and sustainably serving market demand.

To succeed in the EV market, companies need to extend range and lower bill of materials (BOM) costs to effectively compete with the entrenched internal combustion engine (ICE). To achieve additional range, manufacturers need higher-capacity battery systems, which can be accomplished by either increasing battery size or through higher power efficiency. Unfortunately, increasing battery size also adds weight to the vehicle, which drives up power consumption. Conversely achieving better power efficiency through more power from the same sized-battery results in lower weight, better-conserved power, and most importantly, reduces consumers’ “range anxiety.”

In the IT segment, on the other hand, a data center’s power, cooling, and real-estate costs easily and quickly surpass initial hardware costs. New energy-efficiency standards, like 80+ Titanium, aim to reduce those costs by increasing system efficiency, but can be difficult to achieve without driving up the BOM costs due to additional components used in more complex topologies.

Lower costs, increased efficiency with Silicon Carbide

These considerations have a solution in Silicon Carbide (SiC) — a semiconductor technology that has already been widely adopted in chargers for EVs and power supplies for servers and telecom equipment. Its advantages over Silicon (Si) make it ideal for designs that require more power density in size-limited applications.

Silicon Carbide enables high power efficiency and high thermal conductivity that are well-suited to high-power-density applications. SiC-based designs are lighter because they can better handle heat and operate at higher ambient temperatures, requiring less bulky thermal management solutions. They also enable higher switching frequencies that call for smaller, lighter magnetics and other passive components.

Introducing Wolfspeed’s Third-Gen 650V SiC MOSFETs

Wolfspeed established its technology leadership in 650V SiC with the introduction of the 6^th generation Schottky diodes that enabled the highest levels of system efficiency. Wolfspeed continues that leadership with the introduction of the 3^rd-generation 15-mΩ and 60-mΩ (R_DS(on) at 25°C) 650V MOSFETs, which further capitalizes on silicon carbide’s advantages to push switching losses lower and power efficiency and power density higher.

The new devices — C3M0015065D, C3M0015065K, C3M0060065D, C3M0060065J, and C3M0060065K — are qualified for operation over a wide temperature range of –40°C to 175°C and are available in through-hole (TO-247-3, TO-247-4) and surface-mount (TO-263-7) packages.

A key parameter to look for in lowering losses is a low on-state resistance. Wolfspeed’s new MOSFETs offer the industry’s lowest on-state resistances in a discrete package over the entire operating temperature range, with the 60-mΩ MOSFETs specified for an R_DS(on) of just 80 mΩ at 175°C.

The ultra-low reverse-recovery charge (Qrr) of the devices, with the 60-mΩ MOSFET offering Qrr of 62 nC, which reduces switching losses and enables higher switching frequencies that will reduce the size and weight of the transformers, inductors, capacitors, and other passive components in the system.

To combat the concern of device capacitance as another component that increases switching losses as switching frequency increases, Wolfspeed has achieved much lower device capacitances for the devices with, for example, the small-signal output capacitance C_oss of just 80 pF for the 60-mΩ models and 289 pF for the 15-mΩ models.

The device models differ in the specified values of R_DS(on), continuous drain current I_D, and the packages they are available in Table 1.

Push BOM costs down

The new 650V SiC devices help drive down costs in several ways. With up to 50% lower conduction losses and up to 75% lower switching losses but three-times higher power density compared with Silicon-based 650V MOSFETs, Wolfspeed’s devices not only save costs by helping achieve higher efficiencies but also by driving down BOM costs toward magnetics and cooling apparatus.

For instance, a typical AC/DC section of a 6.6-kW bidirectional on-board charger (OBC) of an electric vehicle (EV) comprises four 650V IGBTs, several diodes and a 700-µH L1 inductor that contributes to over 70-percent of the BOM cost. Implemented using four 650V SiC MOSFETs, the design requires an L1 of just 230 µH. This drives down BOM costs by nearly 18 percent over the IGBT-based design.

Similar savings are seen in the DC/DC section of the OBC due to the significantly lower cost of magnetics.

In this application, the overall typical BOM costs are about 15% lower with Wolfspeed’s devices, while peak system efficiency is 97%, compared with 94% for a Si-based system (Chart 1).

Accelerate time-to-market with reference designs

Wolfspeed provides extensive support for its devices with reference designs, and the new MOSFETs are no different in that respect. For the OBC application discussed above, the company’s global applications engineering team created a 6.6-kW bidirectional design that has a DC link of 380 V to 425 V and a battery side output of 250 V to 450 V.

The AC/DC side uses the highly efficient and cost-effective totem pole topology, one that Si-based implementations could not achieve without compromising on complexity and component count. The DC/DC side, meanwhile, takes switching frequencies to a high 150-kHz to 300-kHz range—up to 3x faster than typical silicon implementations.

Click here to learn more about the new C3M 650V SiC MOSFETs and reference designs.

^[i] U.S. Energy Information Administration, Annual Energy Outlook 2020.

Product and Reference Design Solutions

Reference Designs

Explore Wolfspeed’s 650V SiC MOSFETs, companion parts, and reference designs to learn more about how SiC MOSFET technology from Wolfspeed can help you build better products that are up for the demands of today’s modern devices.