Driven by intelligence and electrification, automotive MOSFET has great potential

Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is a field-effect transistor that can be widely used in analog and digital circuits.

MOSFET first appeared in the 1960s and was first used in analog circuits. Power MOSFET began to rise in the 1980s and has undoubtedly become the most important device in today's power electronics.

MOSFET has the characteristics of low control power and fast switching speed. It is widely used in low, medium and high voltage circuits and is the basic device of power semiconductors. Silicon-based MOSFET is the cornerstone of automotive power semiconductors, and the use per vehicle is expected to increase by 4 times. Before entering the era of new energy vehicles, MOSFET has been used in areas involving electric functions in fuel vehicles, with a use of about 100 per vehicle. With the start of automobile electrification, medium and high voltage MOSFETs are used in the automotive power domain as an important component of power sources such as DC-DC and OBC to complete the conversion and transmission of electric energy through electric braking, and the use per vehicle has increased to more than 200; in addition, with the development of automobile intelligence, ADAS, safety, infotainment and other functions require MOSFET as the basic device for power conversion to support digital, analog and other chips to complete the function realization, so that the use of medium and high-end models per vehicle can increase to more than 400. Automobile intelligence is the incremental space for medium and low voltage MOSFET devices, and automobile electrification is the direction of development of medium and high voltage devices such as super junction MOSFET. From 20 to 26, the global MOSFET market will increase from US$7.4 billion to US$8.9 billion, and the proportion of automotive applications will increase from 25% to 30%. Driven by new energy vehicles, the global automotive power device market will increase from US$4.8 billion to US$10.8 billion, and automotive MOSFET will increase from US$1.83 billion to US$2.67 billion. Among them, ADAS and non-fuel vehicle powertrain applications will grow fastest.

In August, sales of new energy vehicles remained strong, with a month-on-month growth of more than 12%. According to the China Association of Automobile Manufacturers, my country's new energy vehicles remained strong in August, with monthly sales of 666,000 units. Among them, BYD's sales of 174,000 units remained in the lead. In terms of new car-making forces, Aion sold 27,000 units, Xiaopeng 16,000 units, Nezha 16,000 units, Ideal 5,000 units, Weilai 11,000 units, Leapmotor 13,000 units, AITO 10,000 units, and Zeekr 7,000 units.

In August, the new energy passenger car market hit a record high, with B-class car sales strengthening. According to the China Passenger Car Association, the wholesale sales of pure electric vehicles in August reached 490,000 units, of which the sales of B-class electric vehicles grew fastest at 137,000 units, accounting for 28% of the pure electric market. The wholesale sales of pure electric A00 vehicles reached 124,000 units, down 5% from the previous month, accounting for 25% of the pure electric market; the wholesale sales of A0-class vehicles reached 93,000 units, accounting for 19% of the pure electric market. BYD's pure electric and plug-in hybrid dual-drive vehicles consolidate its leading position in new energy vehicles; traditional car companies represented by Chery Group and GAC Group performed outstandingly. In July, the number of motors and electronic controls installed in new energy passenger cars was 479,000 units, and the total number of OBC installed was 436,000 sets. In terms of electronic control systems, the number of three-in-one electric drive systems installed was 288,000 units, accounting for 60.1%, of which CRRC Times Electric installed 17,400 sets of electronic controls and 17,100 sets of systems, becoming one of the fastest growing manufacturers. The OBC market as a whole maintained a growth trend, and the top five positions remained basically unchanged.

In July, domestic suppliers of power modules for new energy passenger cars in my country, including Star Semiconductor, BYD Semiconductor, and CRRC Times Electric, accounted for more than 50% in total. According to NE Times statistics, in July 22, the number of power modules installed in my country's new energy passenger cars insured was about 424,000 sets, of which BYD Semiconductor installed about 99,000 sets (accounting for 23%), Star Semiconductor installed about 70,000 sets (accounting for 17%), and Times Electric installed about 55,000 sets (accounting for 13%). It is expected that the localization rate will increase month-on-month as the production capacity of each company is released.

Intelligent and electrified dual-wheel drive

Automotive MOSFET has great potential

Silicon-based MOSFET: the cornerstone of automotive power semiconductors In traditional fuel vehicles, medium and low voltage MOSFETs (metal-oxide semiconductor field-effect transistors) have been widely used in the area of ​​electric functions in the car. They are the main part of traditional automotive power devices, with a single car usage of about 100. With the start of automobile electrification, electric energy replaces fuel as the energy source for automobile driving, and the energy flow of the car changes. New energy vehicles no longer use gasoline engines, fuel tanks or transmissions, and the "three-electric system" is replaced by batteries, motors, and electronic control systems; accordingly, the core device for energy conversion, power semiconductor content, has greatly increased. Among them, medium and high voltage MOSFETs have begun to be widely used in medium voltage electric parts such as DC-DC and OBC of automobiles to assist in the conversion and transmission of electric energy, and the average usage per vehicle has increased to more than 200; in addition, with the development of automobile intelligence, ADAS, safety, infotainment and other functions all require the use of MOSFETs. According to data, the usage of MOSFETs per vehicle in mid-to-high-end models in the future is expected to increase to 400.

MOSFET can realize the "on" or "off" of the circuit by controlling the voltage, and finally realize the regulation of current and voltage. It is a fast "electronic switch". Taking the planar MOSFET as an example, by controlling the voltage between the drain and the source, and between the gate and the source, electrons can form a "channel" in the device to realize the conduction of the device; by adjusting the voltage, the conduction current can be controlled. Finally, by switching between "on" and "off", in conjunction with other components, the switching between direct current and alternating current, current frequency, voltage level and other states can be realized. Therefore, reducing the loss (such as on-resistance) in the device current transmission process to improve the conversion efficiency of electric energy is the main driving force for the evolution of MOSFET device technology.

Due to the different requirements of downstream applications for device performance such as withstand voltage, switching frequency, and on-resistance, MOSFET devices have developed different structures such as planar, trench, and super junction. Planar MOSFET structure can be used in small and medium current scenarios due to its large chip area (high withstand voltage) and simple process; trench MOSFET shortens the current conduction path (eliminating J-FET resistance) compared to planar MOSFET, and is widely used in low voltage and high current scenarios; on this basis, in order to further improve the withstand voltage and conduction performance of the trench gate structure, the super junction MOSFET (SJ-MOS) with uniform electric field strength and low resistance N layer design has emerged and is widely used in medium, high voltage and high current power supply scenarios.

MOSFET is the main device for automotive power transmission. MOSFET is widely used in automobiles involving (brushed and brushless) DC motors, power supplies and other components. As the application scenarios of automobile intelligence and electrification continue to enrich: Intelligent applications: ADAS: safety management, domain control system, parking system; Body electronics: body power supply, central control system, temperature control, gateway system, smart door locks, lighting system; Chassis and safety: suspension system, electronic assisted steering system, airbags, parking and anti-lock braking system; Infotainment system: display control, audio, instrument panel, entertainment function, telematics. Electrification applications (traditional cars and new energy vehicles are different) Traditional fuel vehicles: engine and transmission management, internal combustion engine auxiliary system, start-stop system; New energy vehicles: DC-DC power supply, on-board charger.

MOSFETs are widely used in traditional cars, with nearly 100 per car. In traditional cars, MOSFETs are used in key electronic power steering systems (EPS), electric brakes and injection systems, as well as heating, ventilation systems, and seat adjustments. Taking EPS as an example, the system requires 8 40V MOSFETs, 6 of which are used with the motor to complete the steering function, and 2 are used with the power management chip (PMIC) to achieve the circuit safety disconnection function.

The intelligentization of automobiles is the future development direction of medium and low voltage MOSFET devices. With the development of intelligent automobiles, ADAS, safety, infotainment and other functions require MOSFET as the basic device for power conversion to support digital, analog and other chips to complete the function. Taking the EPS system as an example, with the improvement of safety requirements, the system requires the addition of a fail-operational function, that is, adding a redundant system as a backup, so that the EPS can still work in the event of a rare failure; accordingly, the number of MOSFETs increased from 8 to 22.