A brief analysis of the chip evolution under the integration and modularization of electric vehicle power systems

From 2007 to 2021, China's automobile industry has been booming, with automobile sales peaking in 2018. In this process, we have seen the rapid development of joint ventures, the rise of independent brands, and the growth of emerging companies in the field of electric vehicles. At present, in the period of great changes in the automobile industry, different design and development requirements have been put forward for multiple tracks such as electrification, intelligence, networking, and sharing. This has led to the fact that in the most competitive Chinese market, vehicle companies have begun to break the original development pace of "five-year replacement and three-year model change". At present, car companies are implementing large-scale investment in electrification transformation on the basis of fuel vehicle sales, including transformation at the software level.

As shown in the figure below, we can see a very important feature, that is, the powertrain and thermal management system, including the drive system, battery system, charging and power electronics and thermal management system, have begun to further integrate and develop to a certain extent, entering a highly integrated stage. The gray parts in the figure below will serve as the basic components of future smart electric vehicles and will develop on the road of scale and integration.

Figure 1 The development foundation and expansion of electric vehicles

Combination of powertrain

The integration we experienced in the past few years was mainly about electrified power architecture, which basically includes power system terminal devices such as on-board charger (OBC), high voltage DC/DC (HV DC/DC), inverter (ACDC) and power distribution unit (PDU). Since there are many of these components, integration can be applied at the mechanical, control or power system level in platform development considerations.

At present, there are very clear practices. One is modular integration - 3+3+3: drive system (three-in-one drive of motor, inverter and reducer) + battery system (battery + OBC + DC/DC integration), thermal management integration (PTC, compressor and pipelines, valves). We are already familiar with this, and it has become a routine practice.

As for more integration, as shown in the figure below, GM's "8-in-1" highly integrated electric drive unit on the Ultium platform includes a motor, inverter and reducer, a vehicle controller, an integrated PDU, an OBC and two DC/DCs.

Figure 2 General Motors' "8-in-1" highly integrated electric drive unit

We can see that as competition becomes increasingly fierce, if car companies want to reach a certain level in scale, they need to make in-depth simplifications based on the original modularization and integrate these components into an integral component, which can bring many benefits:

1) Optimizing the characteristics and efficiency of the three-electric system and electric vehicle architecture can improve the manufacturability of the final assembly by reducing the number of parts in the final assembly;

2) Through the structural system, the wiring harnesses for high-voltage connections can be reduced, the structure can be merged and the brackets can be reduced to achieve the goal of overall weight reduction. Most importantly, the complexity of management at the vehicle level can be reduced;

3) Considering the future, standardize and modularize each component so that it can be reused as much as possible during the integration process;

4) Optimize costs during the integration process, leaving a lot of room for cost reduction.

Here we see two directions. One is the different stages of integration in terms of chips and circuits. As mentioned before, there are different stages of integration from different electrical, structural and control levels. Let's take the integration of on-board charger and DC/DC as an example. These two components are completely independent. Our ultimate goal is to merge functions and make the two highly integrated components reused to a certain extent at the component level as much as possible, and to change the circuit structure through detailed design to achieve the goal of simplifying costs.

Note: This block diagram is from TI's official website TI.COM.CN, which contains a selection list of these components. Among them, TI's ultra-low latency C2000™ MCU helps achieve higher switching frequencies (up to 1 to 2 MHz), and wide bandgap switches made of materials such as GaN and optimized high-speed gate drivers can significantly reduce component size and improve system efficiency.

Phase 1: OBC and DC/DC are only physically put together. Both are independent, as shown in the figure below, and are two parts of the whole.

Phase 2: Both components use one structural shell and share cooling channels.

The third stage: control level integration, integrating the control logic circuits of the two components.

Phase 4: At the power topology level, some circuit devices (switching devices and magnetic devices) are reused.

Figure 3 Integration of OBC and high voltage DC/DC converter at different levels

It is also from this perspective that, from the perspective of power device integration, considering that the full-bridge rated voltage of the on-board charger and the high-voltage DC/DC are the same, it is possible to consider using them together, making it possible for the two components to reuse the full-bridge shared power switch. Integrating the two transformers together can achieve magnetic integration, with the same rated voltage on the high-voltage side, so it may eventually become a three-terminal transformer. Under this design, the performance of the DC/DC low-voltage output will be limited, and it is possible to consider adding a built-in buck converter.

Figure 4 Power-level reuse of OBC and DC/DC

The second direction is centralized processing at the control and algorithm levels.

Taking the design direction of a certain brand's integrated thermal management as an example, not only component integration is adopted here, but also the physical parts of all components are centralized. The 12 components in the traditional thermal management system are integrated into one, and the substrate is used to replace the original interconnected pipelines, so as to reduce the number of pipelines in the thermal management system by 40% and the number of components by 10%. The most important thing is control integration. The control parts of all components are centralized, and the control systems of key components such as compressors and water pumps are all integrated into the EDU (Electric Drive Unit). The benefits of this are software expansion, upgrading and function optimization, reducing the probability of component electronic control failure, and enhancing the diagnosis and maintenance of each component's life cycle. Most importantly, this is in line with the technical direction of centralized management and release of future automotive software.

Figure 5 Integrated thermal management system

summary:

Smart electric vehicles will subvert the entire industry in the future. In the whole process, the integration and sharing of electrified components are the basis. The advantages in the number of parts and system simplicity are very obvious, and from the initial structural integration to the integration of electronic and electrical aspects. With the gradual development of software control, the overall pace of development of smart cars will be faster, and more core support for chips and software in the three-electric system will be needed.

reference document:

1）Achieving High Efficiency and Enabling Integration in EV Powertrain Subsystems Using C2000™ Real-Time MCUs

2）A High-Performance, Integrated Powertrain Solution: The Key to EV Adoption

3）Reduce EV cost and improve drive range by integrating powertrain systems