How to achieve low power consumption and high performance in various ECUs in automobiles

High performance, low power consumption is the direction of current electronic technology development. How do you achieve low power consumption for various ECUs in automobiles?

First, the ECU also consumes fuel

According to incomplete statistics, China’s car ownership is more than 200 million, and the resulting energy consumption and environmental pollution problems are becoming more and more serious. At present, countries all over the world are starting to reduce fuel consumption by reducing engine displacement, improving engine technology, and developing new energy vehicles. The engine is the main fuel-consuming component in the car, but many ECUs are also hidden "fuel consumption".

Figure 1 Car congestion

Second, CAN bus introduction

The ECU communication interaction uses the CAN bus, which is a bus applied to the serial communication protocol and is one of the most extensive fieldbuses in the world. The current CAN bus has been widely used in automotive electronics, rail transit, new energy and other fields. Multi-node, big data capacity, and energy saving are the development directions of the current CAN bus.

Figure 2 CAN bus application industry

In the direction of CAN bus, the international standards established by ISO have the following six parts. Among them, ISO11898-1, ISO11898-2, and ISO11898-3 are well known to engineers. In this paper, we focus on low-power strategies related to ISO11898-6 selective wake-up.

ISO11898-1: Data link layer and physical layer signals

ISO11898-2: High speed access unit

ISO11898-3: Low speed fault tolerant access unit

ISO11898-4: Time Triggered Communication

ISO11898-5: Low-power, high-speed access unit

ISO11898-6: High-speed access unit with selective wake-up

Figure 3 energy saving mode

Third, why should low power consumption

Some readers may want to ask, how much power can an ECU unit consume? Is it worth the trouble for power consumption? First of all, gasoline is not free. For traditional cars, the power consumption of the in-vehicle electronic unit comes from fuel. Experimental data shows that 100 W ≈ 0.1 liter / 100 km. In addition, 1 liter of diesel / 100 km = 26,5 g CO2 / km, 1 liter of gasoline / 100 km = 23,2 g CO2 / km, it can be seen that the fuel loss caused by ECU work, air pollution problems can not be underestimated.

Figure 4 Energy Conservation

Fourth, how to achieve low power consumption

Reducing the power consumption of the ECU can be started from two aspects. On the one hand, the low-power electronic devices are carefully selected, and on the other hand, the functional units are turned off in a timely manner. For the first aspect, it is better to understand, we can start from the choice of MCU, power supply voltage selection, crystal frequency, etc. For the second aspect, most engineers may not have tried. A timely shutdown of the functional unit is to achieve sleep when the function is idle, and can wake up in time when needed. For example, when the vehicle speed exceeds 30Km/H, the parking sensor can be completely turned off. In fact, the CAN transceiver can work in deep sleep mode (see ISO11898-6), and the transceiver will wake up the MCU only after receiving a specific CAN message.

Figure 5 message selective wake-up

The TJA1145 is a high-speed CAN transceiver designed for automotive electronics that provides differential transmit and receive capabilities. The main features of TJA1145 are low power consumption and sleep mode, supporting ISO11898-6:2013 selective wake-up.

Figure 6 TJA1145

V. Disadvantages and solutions

The CAN node (or ECU) can work in an active or deep sleep state, so the entire network working state must present in various forms. 10 devices = 1 024 system states; 20 devices = 1 048 576 system states. Frequent state switching must be hard to the real-time nature of the CAN bus, so grouping of devices is necessary. The so-called grouping is to bind the CAN node (or ECU) that the function wants to associate to a block, while being in a dormant or active state.

Figure 7 group association settings

Today's CAN energy-saving topics are temporarily talked about here, what do you know about the development of CAN bus? Share your thoughts in the message area.