Electric vehicles have become the development trend of the automotive industry, but as automobile designs turn to electrification, current isolation is becoming more important to allow digital controllers to be securely connected to the high-voltage system of modern electric vehicles. This article will introduce you to the key changes in electric vehicle design and the solutions for isolation devices.
Types of Electric Vehicles: EV, HEV, & 48V MHEV
Global automakers are all announcing aggressive plans to produce new electric vehicles (EV), hybrid electric vehicles (HEV), and 48V mild hybrid electric vehicles (MHEV). Pure electric vehicles are achieving double-digit growth rates, and the emergence of 48V MHEV systems will electrify engine subsystems on standard internal combustion engines (ICE). The low cost of the 48V mild hybrid design and its ability to retrofit existing transmission systems will further accelerate the demand for power electronics in automotive applications.
Semiconductor Isolators in Electric Vehicles: Better Performance
As automobile designs turn to electrification, high-wattage power electronic devices will become the key components of the new electronic transmission systems and battery systems. These high-wattage electronic devices need to communicate with and be controlled by low voltage digital controllers, which requires electrical isolation between the controller and the power system. In these applications, current isolation (usually based on semiconductor isolation) is necessary to allow digital controllers to be securely connected to the high-voltage systems of modern electric vehicles.
EV Battery Management Systems
To compete with traditional ICE vehicles, the batteries used in the EV/HEV must have very high energy storage density, close to zero self-leakage current, and be able to charge in minutes rather than hours. In addition, battery management and the related power conversion systems must have minimal size and weight. EV/HEV battery management systems usually consist of four main circuit components, including on board charger (OBC), battery management system (BMS), DC/DC converter and main inverter. Besides, other systems besides electric vehicles themselves, such as charging piles, also have similar system requirements and isolation requirements.
Semiconductor Use in Electric Vehicles
Although different types of isolation techniques have been used in electric vehicles, manufacturers are increasingly turning to modern isolation technology based on semiconductors rather than older solutions based on optical couplers. Compared with optical couplers in demanding automotive applications, these modern isolators have many advantages, including longer service life, significantly improved temperature and aging stability, faster switching speed, and higher noise resistance.
Gallium Nitride (GaN) and Silicon Carbide (SiC) in Electric Vehicles
As automotive suppliers adopt broadband gap power transistors (such as GaN or SiC) to meet the ever-increasing power density, the advantage of semiconductor-based isolation becomes critical. These GaN or SiC systems usually use higher switching speed to reduce the size of the magnetic materials of the system.
Compared with Si IGBT, the SiC system provides higher blocking voltage, higher operating temperature and higher switching speed, and the GaN switch provides benefits from a wide range of power supply systems ranging from low kW to 10 kW. Since GaN provides lower switching loss, faster switching speed, higher power density, and a better thermal budget, the power output and energy efficiency of electric vehicles are improved, and the weight and cost are reduced, but this leads to significantly higher electrical noise.
Semiconductor Isolation in Electric Vehicles
In addition, electric vehicles seek to reduce the volume and weight of electric systems, but to reduce the size of these systems and increase the power density will increase the operating temperature, which will make the optical coupler overstress and reduce its performance. Semiconductor isolation in these higher temperature ranges has obviously better performance and reliability. It is an ideal choice for these higher speeds and higher noisy environments.
In order to meet the isolation requirements of the electric vehicle system, the Si8239x isolation gate driver introduced by Silicon Labs is a good solution. The Si8239x isolator provided by Silicon Labs is especially suitable for driving power MOSFETs and IGBTs in various switching power supply and motor control applications. Based on the proprietary chip isolation technology of Silicon Labs, the Si8239x isolator of Silicon Labs can achieve high noise immunity, low support delay and tilt, reduce changes with temperature and aging, and close matching between parts. The Si8239x device supports a withstand voltage up to 5 kVRMS.
The Si8239x combines two isolated drives with separate input controls or with separate inputs suitable for high power applications. The Si8239x offers a variety of unique features, including output UVLO fault detect, feedback and automatic shutdown for two drives, replace the EN (active high) of DIS (active low), 1 millisecond safety delayed-start time, automatic anti-fault driver with default low state (if VDDI fails) and the highly accurate dead time programmability. All drivers use 2.5 V - 5.5 V input VDD and a maximum driving supply voltage of 24V.
The Future of Electric Vehicle Innovation
The design of electric vehicles has achieved unprecedented innovation. As automobiles continue to become digitized, the devices with GaN or SiC broad-band gap power transistors will increase more and more and the demand for current isolators will increase. Therefore, the Si8239x isolator from Silicon Labs will be an excellent choice for related applications.