Electric and hybrid vehicles can charge their high-voltage battery subsystems through DC charging piles or ordinary AC power sockets. On-board chargers (OBC) are the core system for AC charging. As one of the leaders in automotive functional electronics, ON Semiconductor provides a wide range of products including silicon carbide (SiC) MOSFETs, super junction MOSFETs, IGBTs, and automotive power modules (APM) for electric vehicle OBCs and DC charging piles, as well as complete systems. solutions to support designers in optimizing performance and speeding up development cycles with expertise and experience. This article will mainly introduce high-efficiency OBC solutions for mainstream power levels.
Typical OBC System Architecture and Power Levels

A typical OBC consists of multiple cascaded stages, including power factor correction (PFC), DC-DC converter, secondary rectification, auxiliary power, control and drive circuits.

Figure 1: Typical OBC System Architecture

OBCs come in a variety of power levels, the higher the power level, the shorter the charging time. The OEM must define the appropriate OBC power level based on the vehicle requirements. These OBCs require high-power AC power, powered by either single-phase or three-phase power, depending on the design of the OBC. The most popular OBC power classes are 3.3kW, 6.6kW, 11kW, and 22kW; each corresponds to a different common AC power class, as shown in Table 1. ON Semiconductor can provide single-phase 3.3 kW, 6.6 kW and three-phase 11 kW OBC scheme power class AC power configuration
3.3 kW single phase 120 V / 30 A 1 x 3.3 kW converter
6.6 kW single phase 240 V / 30 A 1 x 6.6 kW converter
11 kW 3-phase 440 V / 15 A 3 x 3.3 kW converters
22 kW 3-phase 440 V / 30 A 3x 3.3 kW converters 3-phase 11 kW on-board charger platform SEC-3PH-11-OBC-EVB

SEC-3PH-11-OBC-EVB is ON Semiconductor's new three-phase 11 kW PFC-LLC OBC platform featuring AEC-Q101 qualified SiC power devices and drivers, including 1200 V, 80mΩ NVHL080N120SC1 high performance SiC MOSFETs, 6 A SiC MOSFET gate driver NCV51705 and 650 V, 30 A SiC diode FFSB3065B-F085, system efficiency over 95%. The kit takes a modular approach with a user-friendly Graphical User Interface (GUI) to simplify and speed up evaluation. LLC systems are driven by embedded software in voltage or current control mode. The platform demonstrates the high energy efficiency, high power density, and small footprint that SiC devices can provide for OBC, and can also serve as a learning environment for developing 3-phase PFC-LLC topological systems. The key parameters of the kit are: input voltage 195 to 265 Vac, DC bus voltage max 735 Vdc, output voltage 200 to 450 Vdc, output current 0 to 40 A, maximum frequency fs 400 kHz.
Figure 2: ON Semiconductor's three-phase 11 kW OBC kit

6.6 kW OBC Reference Design

This 6.6 kW OBC reference design uses a three-channel interleaved PFC-LLC for high energy efficiency and high power density with reduced current ripple, and the bus voltage can be adjusted according to the output voltage to optimize energy efficiency. Input voltage 90 to 264 Vac, output current 0 to 16 A, typical energy efficiency 94%. Key devices include super junction MOSFET NVHL040N65S3F, NTPF082N65S3F, 650 V, 30 A SiC diode FFSP3065A, PFC controller FAN9673, LLC controller FAN7688, etc.
Energy-efficient IGBTs address an important trend in EV on-board charging: Bidirectional charging Bi-directional charging (V2X) between EV batteries and buildings or grids will become an important trend in EV on-board charging. Bidirectional charging should consider charge-discharge energy efficiency to ensure that no energy is wasted during conversion, requiring a totem-pole bridgeless PFC, where reverse recovery performance is critical. IGBTs with integrated external SiC diodes offer higher energy efficiency than MOSFET solutions because there are no associated forward or reverse recovery losses. Figure 3 is a circuit diagram of bidirectional charging. For K3 and K4, devices with fast switching, low saturation voltage drop Vcesat, and low forward voltage Vf are required. ON Semiconductor offers a wide range of AEC automotive compliant IGBTs, including 650 V/750 V/ 950 V 4th generation trench field stop IGBTs and 1200 V ultra-high speed trench field stop IGBTs with lower losses and higher Power density, and the hybrid IGBT solution AFGHL50T65SQDC with integrated SiC diode.
Figure 3: Bidirectional charging circuit diagram

SiC solution reduces losses

SiC reduces switching and conduction losses compared to silicon solutions, offering a new level of performance. ON Semiconductor has been engaged in the development of wide bandgap for nearly 10 years, and is one of the few suppliers with both silicon, SiC and gallium nitride (GaN) technologies, providing automotive-grade 650 V SiC diodes (covering 6 A to 50 A), 1200 V SiC diodes (covering 10 A to 40 A), 1200 V SiC MOSFETs (covering 20 to 80 mΩ). These SiC diodes have a maximum junction temperature of 175°C, high inrush current capability, positive temperature coefficient, easy paralleling, no reverse recovery losses, and are AEC-Q101 and Production Part Approval Program (PPAP) compliant. These SiC MOSFETs have a maximum junction temperature of 175°C, offer high-speed switching and low capacitance, are 100% tested with Unclamped Inductive Load (UIL), and are AEC-Q101 and Production Part Approval Program (PPAP) compliant.
Super junction MOSFET: better performance than planar silicon solution, more cost advantage than SiC solution Superjunction MOSFET discretes are available with KGD die and APM modules in 2018.
Superjunction MOSFETs are available in fast version (FAST Version), easy drive version (Easy Drive Version) and fast recovery version (FRFET Version). The express version is mainly aimed at industrial grade applications. The easy-to-drive version reduces voltage spikes and electromagnetic interference (EMI) due to built-in gate resistor Rg and optimized capacitors. The fast recovery version has a best-in-class body diode.
APM module

APM modules can be used in various power stages such as PFC, LLC conversion, and rectification of OBC, reducing the number of components, reducing size and weight, increasing power density, and reducing total system cost. Such as the APM16 launched by ON Semiconductor in 2018, a highly integrated compact design with flexibility to integrate all silicon and SiC technologies, full-bridge or half-bridge topologies, low thermal impedance, and compliance with AQG324, IEC60664-1, IEC60950-1 and other standards .
gate drive

ON Semiconductor provides high-drive current drivers to improve system energy efficiency. The isolation technology is safe, reliable, and certified. It does not generate EMI and is not affected by system-generated EMI. Strong common-mode transient suppression can resist high voltage and high power switching applications. system voltage transients that occur. Such as 16-pin isolated gate driver NCV57000 high-current single-channel IGBT driver, built-in galvanic safety isolation design, providing high-efficiency operation in power supply applications requiring high reliability, with high current at Miller plateau voltage, galvanic Isolation rating greater than 5 kVrms, meeting UL 1577 requirements, operating voltages greater than 1200 V, other features include soft shutdown to suppress spikes, programmable delay desaturation (DESAT) protection, propagation delay typical 66 ns, short circuit IGBT gate clamp, etc.
Summarize

The on-board charging market is growing along with the growing demand for electric powertrains for electric vehicles. In addition to providing a wide range of super junction MOSFETs, IGBTs, and gate drivers, ON Semiconductor also launches hybrid IGBTs, SiC MOSFETs, and APM modules with integrated SiC in response to trends such as V2X and challenges such as power levels and footprints, and PFC for on-board charging. , DC-DC, rectifier, auxiliary power supply, drive and other power stages, improve energy efficiency, performance, power density, reduce loss and space, and actively expand the existing product lineup, launched for 3.3kW, 6.6kW, 11kW OBC development kits with other mainstream power levels help speed up design and evaluation. Its latest three-phase 11 kW on-board charger platform SEC-3PH-11-OBC-EVB adopts SiC technology, with an energy efficiency level of over 95% and high power density. Executable digital controls and available GUI ensure a hassle-free start-up and user-friendly experience, and also serve as a learning environment for developing 3-phase PFC-LLC topology systems.