In recent years, in order to cope with climate change and reduce the synergistic effect of greenhouse gas emissions, governments of various countries have successively introduced certain indicators on automobile exhaust emissions. According to statistics from the National Highway Traffic Safety Administration, the average fuel economy will reach 40.4 miles per gallon by 2026; it was proposed at the United Nations Climate Change Conference in Paris that greenhouse gas emissions by 2030 will be reduced by 40% compared to 1990. On the one hand, the increasingly stringent emission regulations have prompted a fire in the new energy market, on the other hand, traditional fuel vehicles have gradually developed in the direction of hybrids.
The electrification of automobiles has become an irreversible trend. “Under such a background, automakers have two paths to follow: one is pure electric vehicles, using a high-voltage battery for electric vehicle manufacturing; the other is using mild hybrid electric vehicles (MHEV, Mild Hybrid Electronic Vehicle), MHEV uses a 48V system, and only needs to add a 48V battery and a 48V motor to the existing architecture to reduce greenhouse gas emissions from internal combustion engines by 13% to 22%.” Texas Instruments (TI) Motor Drive Business Unit Manager Kannan Soundarapandian pointed out.
Under the trend of vehicle electrification, light hybrid electric vehicles are involved and are a relatively important part. TI believes that light-hybrid electric vehicles will occupy a large share, not only have a large market space, but also have great market advantages, which can meet the requirements of reducing greenhouse gas emissions that countries need to meet.
In this regard, TI has recently introduced a highly integrated zero-level brushless DC (BLDC) motor driver DRV3255-Q1, suitable for 48V high-power motor control systems, such as MHEV traction inverters and starter generators.
MHEV motor drive system design requirements
According to Kannan, in order to realize the electrification of automobiles, the following requirements are required for the motor drive system:
1. Small size. Because the space of the circuit board is limited, a small size can gather more devices on the circuit board, which provides the system with a good realization of motor drive requirements.
2. In terms of functional safety, it can help customers easily achieve the ASIL-D level of functional safety of the system, which is the highest level in the industry. It is also designed in accordance with the requirements of ISO26262.
3. Support high-power applications. It can help customers drive a power motor of about 30kW, and a small circuit board space can drive high-power devices, helping to achieve better electrification.
Fourth, it must have a strong tolerance to harsh conditions, and a good tolerance in high temperature or high pressure environments. This device is a quality inspection that requires level 0.
TI believes that these four points can help customers in designing 48V motor drive applications. The 48V motor products that TI designs in accordance with these requirements perform well in terms of integration, functional safety, power and stability.
Usually the motor can be placed in the five places P0-P5. Most of the existing products are put together with the internal combustion engine, which is called the P0 architecture. As the power of the motor becomes larger and larger, it can be placed in other transmission system positions to better provide power requirements. The solution TI released this time is suitable for 48V P0 and P2 motors.
Smaller motor drive system
The 48V motor architecture seen on the market today is not highly integrated, and there are many different device requirements on the circuit board, including resistors, diodes, etc., as well as protection logic (ASC active short-circuit protection mechanism and logic). Because it is a three-phase motor, to repeat three sets of such devices, the number of devices will be large.
Common architecture of 48V motor drive system
TI’s highly integrated DRV3255-Q1 can remove those three different sets of devices and simplify it to only two resistors.
Simplified DRV3255-Q1 motor driver design
DRV3255-Q1 is an advanced three-phase 48V BLDC motor driver that integrates high-side and low-side active short-circuit logic, eliminating the need for external transistors and control logic. Compared with the existing three-phase 48V BLDC brushless motor drive, DRV3255-Q1 can help customers reduce board space by up to 30%.
This new motor driver integrates active short-circuit logic and dynamic fault response, not only helps designers simplify the design, but can also provide up to 30kW of motor power, while reducing the layout space of the 48V motor drive system and reducing the bill of materials cost. Such a design can help coexist with this electric motor system in a limited internal combustion engine space.
Regarding the advantages of the DRV3255-Q1 chip, Kannan summarized six major points:
1. It integrates high-side and low-side active circuit logic, and is the industry’s leading three-phase brushless driver.
2. Provide high-power drive, the drive power can be as high as 30kW, and can even meet the needs of driving some heavy vehicles.
3. A good protection mechanism is integrated in the chip, which can protect the 48V powertrain system from the impact of the harsh switching transient voltage as high as 95V.
Fourth, there is a high degree of internal integration, providing a small size solution, which can reduce 12-24 passive components.
5. Design according to the ISO26262 standard, which can help customers easily realize the system design of ASIL-D level.
6. It complies with the AECQ-100 level 0 standard, has a wide operating temperature range, and can be used in an environment of -40°C to 150°C.
Common applications
The most common application scenario for DRV3255-Q1 is a 48V motor drive system. In the overall system, the space of the circuit board is very small. If you want to put it in the motor, you need a relatively small circuit board for design.
In addition to the most common applications, TI expects 48V systems to be used in electric power steering applications such as motor-driven in the future. “Unmanned driving systems need to ensure intelligence and safety, so they need a high degree of redundancy. To ensure system redundancy, at least two systems running at the same time must coexist. At this time, if the power is purely powered by 12V single-phase power, the load There are certain restrictions and high reusability cannot be achieved. If one system uses 48V and the other uses 12V on this system, the redundancy is very high, and the chance of ensuring the normal operation of the system is better than that of a single system. The power supply will be higher.” Kannan analyzed.
Taking functional safety into consideration, the design of DRV3255-Q1 uses Texas Instruments’ certified functional safety hardware development process, and includes built-in safety mechanisms and documentation (such as failure modes, impact and diagnostic analysis, and functional safety manuals). In addition to the safety mechanism for the internal failure mode of the device, the digital input/output pins can also withstand the absolute maximum rating of 75V, protecting the DRV3255-Q1 from the overvoltage of the external 12V power supply.
Under the trend of automobile electrification, 48V mild hybrid has certain advantages in mileage and environmental issues, and it is a good choice in the transitional stage. TI provides a great advantage in integration, and at the same time provides a good environment detection function, can easily transfer some detected information from the drive to the processor, and better help customers build miniaturization 48V motor drive system. In addition, product innovation, system-level expertise, and continuous supply are also TI's advantages. Kannan concluded: "TI has a very good supply chain, with 14 production bases around the world, and also has its own process and packaging process. , Can guarantee the quality and quantity, and can be delivered on time. The customer cooperates with us, there is a good quality assurance and a guarantee on the delivery period. Our product and system-level expertise can help customers solve complex design problems and help Accelerate the design and mass production of electric, intelligent, and automated vehicles.”
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