Auxiliary power units are ubiquitous in battery electric vehicle (BEV) and hybrid electric vehicle (HEV) power supply applications and are crucial for powering various low-voltage subsystems typically below 20 V for control, communication, safety, drive, etc. Important, moreover, the power supply itself may come from a +400 V DC high-voltage bus, such as an on-board charging (OBC) system or a 48 V or 12 V battery voltage rail. With such a wide range of applications, the requirements for auxiliary power supply are very diverse, resulting in countless alternatives and applications in the market.
Although these power supplies are auxiliary systems, high reliability and stability need to be ensured as they are powering critical blocks such as logic level circuits which may include core controllers, or turning on and off power mosfet Gate drivers for transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs). At the same time, a compact design and an excellent price/performance ratio are required, since these systems are not a core part of the application and should therefore spend as few resources as possible to get the job done. Safety is also paramount, and in most cases the system must comply with automotive standards, which also stipulate electromagnetic interference limits. Also, the flexibility to accommodate a wide input voltage range and adapt to different use cases makes it stand out. Last but not least, the auxiliary power supply needs to provide high voltage isolation, especially if required by regulation, or functional isolation, for reliable operation.
Depending on the above requirements corresponding to the application, the auxiliary power supply is used in different topologies - flyback, boost, buck-boost, etc. They can employ alternative switching mechanisms, such as quasi-resonant or fixed frequency, and utilize integrated or discrete techniques to deliver the required power.
Figure 1. Schematic of an isolated auxiliary power supply based on a flyback topology, operating under quasi-resonant peak current mode control
ON Semiconductor has recently launched four new solutions: high-voltage auxiliary power supplies for BEVs and PHEVs based on 800 V and 400 V batteries and delivering 15 W or 40 W of power, and a power supply for IGBT and silicon carbide (SiC) MOSFET drivers. Isolated power supply. These solutions address the above challenges and meet the required requirements.
The SECO-HVDCDC1362-15W15V-GEVB and SECO-HVDCDC1362-40W15V-GEVB are extremely efficient and flexible primary-side regulated (PSR) auxiliary power supplies optimized for BEV and PHEV vehicle powertrains. These designs provide a stable 15 V over a wide input DC voltage range of 250 V to 900 V, making them suitable for 400 V and 800 V battery systems.
The solution leverages the multiple advantages of the NCV1362 quasi-resonant peak current PSR flyback controller, the cost-optimized NVHL160N120SC1 160mΩ 1200 V silicon carbide (SiC) MOSFET, and the FFSD0665B-F085 SiC diode. Thanks to the high blocking voltage capability and ultra-low gate charge (34 nC) value of the SiC FET, switching losses are significantly reduced, and the design exhibits excellent energy efficiency, up to 86% at low AC conditions. The excellent drive capability of the NCV1362 controller enables direct operation of SiC FETs at 12 V without the need for a pre-driver, simplifying layout and reducing bill of materials. The flyback transformer provides 4 kV of isolation, fully implemented with automotive-grade semiconductors and passives.
Figure 2. Energy efficiency of SECO−HVDCDC1362−15W15V−GEVB
Figure 3. SECO−HVDCDC1362−15W15V−GEVB block diagram
Figure 4. Advantages of a 15 W high voltage auxiliary supply
The SECO-LVDCDC3064-IGBT-GEVB is an isolated power supply for IGBT drivers, providing the required stable voltage rails (-7.5 V and 15 V, 50 mA per shunt) for high efficiency over a wide input voltage range (6 Vdc to 18 Vdc) switch. An additional +7.5 V rail is also provided to support any other lower voltage logic. The system utilizes the NCV3064 DC-DC converter, enabling a compact and robust design with minimal bill of materials. The board is fully implemented with automotive qualified components and is pin compatible with commercial IGBT DC-DC power supplies, providing an isolated driver power solution out of the box. Another SiC variant SECO-LVDCDC3064-SIC-GEVB using the same NCV3064 would be suitable for SiC MOSFET switches providing +20 V/-5V rails for gate drivers.
Figure 5. Advantages of 1.5 W IGBT Isolated Driver Power Supply (SECO-LVDCDC3064-IGBT−GEVB)
Figure 6. SECO-LVDCDC3064-IGBT−GEVB Block Diagram
New power supplies designed for 400 V and 800 V battery systems, and isolated power supplies for IGBT and SiC gate drivers are designed for direct integration into application systems.
ON Semiconductor's broad lineup of products and tools for automotive auxiliary power solutions helps meet the requirements of each application and provide an optimal solution. In addition to a comprehensive lineup of AC-DC controllers and regulators, DC-DC controllers and regulators, power MOSFETs, diodes and protection devices to fully realize a wide range of designs, we also provide extensive hardware and software evaluation and Development tools help engineers by speeding up the development phase and reducing time-to-market for new products.