STMicroelectronics’ TwisterSIM electrothermal simulator: the patron saint of next-generation automotive safety
作者： Giusy Gambino, Alessio Brighina, Francesco Giuffre', Filippo Scrimizzi
STMicroelectronics Catania Italy
When designing and deploying advanced solutions for harsh automotive environments, designers need interactive simulation tools that are user-friendly, fast, and require low hardware requirements. The use of distributed intelligence can unleash system performance, but requires system resilience and real-time feedback capabilities.
In the automotive industry, designers need to address, reduce and prevent serious issues that can cause damage to critical components such as engine control modules (ECMs) or other electronic control units (ECUs). Failures in these systems may cause accidents or other safety hazards.
To combat these hazards, automakers employ a variety of protective measures such as fuses, circuit breakers and overvoltage protection devices, as well as thermal management technology to prevent critical components from overheating.
Accurate simulation tools can help identify potential problems in advance, allowing engineers to make necessary modifications or adjustments to the design to prevent these problems from occurring in the first place.
In addition, simulation experiments can also optimize the design of electrical systems to ensure that they can handle the maximum current and voltage that may be encountered, making automotive systems safer and more reliable.
Comprehensive simulation capabilities are critical
In the development of next-generation vehicles, engineers face many challenges in power distribution and require a distributed intelligence approach to simultaneously solve several key factors:
• Vehicle toughness;
The ability to withstand unforeseen circumstances such as accidents, severe weather, equipment failure, etc. is critical to vehicle resilience. Energy efficiency plays a key role in reducing power consumption, carbon emissions and maintenance costs, while helping to improve overall vehicle performance and reliability. Sustainability is a key factor in reducing the environmental impact of vehicles and promoting low carbon emissions.
To achieve these goals, engineers must use innovative solutions and concepts proven through comprehensive simulation experiments to develop advanced automotive systems that meet industry needs and provide a safer, more reliable, more sustainable, and more enjoyable driving experience. Intelligent power switch tubes used in power distribution systems are complex electronic components that require electrothermal simulation experiments to ensure optimal performance.
Analyzing the electrical behavior of power switches, including the switching tube's high-voltage current handling capability, response time, and ability to detect and isolate faults, is inseparable from electrical simulation experiments. On the other hand, analyzing the heat generated by a switch during operation requires thermal simulation experiments because heat can affect the performance and reliability of the switch. By conducting electrothermal simulation experiments, engineers can optimize the design of smart switches to ensure that they meet the design performance requirements while maintaining safe operating temperatures. The use of simulation verification methods can improve the energy efficiency, reliability and safety of the power distribution system, while ensuring that the system implements reasonable and effective protection mechanisms and diagnostic functions.
1. Understand product information
To ensure the best choice is made, simulation experiments must be conducted in a user-friendly, customizable and interactive environment so that the behavior of the smart switch can be quickly understood. The first step is to determine which products meet the electrical requirements.
STMicroelectronics' TwisterSIM electrothermal simulator is the ideal tool for this purpose and is designed specifically for selected VIPower products, including smart high- and low-side drivers, as well as full-bridge topologies for motor control. The simulation tool accurately selects candidate devices from a list and provides basic product information. As a result, designers can quickly and easily evaluate the performance of different smart switches and select the one best suited for a specific purpose, as shown in Figure 1.
Figure 1: VIPower Smart Drive Preselection
Based on various input data such as supply voltage, device topology, number of channels, load type and characteristics, power supply type, ambient temperature and PCB power dissipation area, the simulator can provide valuable information about the expected maximum junction temperature (TJMAX). Fast and efficient product pre-selection.
This information is critical in selecting the appropriate on-state resistance (RON) for each channel and ensuring that the operating thermal budget meets the absolute maximum ratings of the device.
2. Get a deeper understanding of performance
To study the electrothermal behavior of the driver, the simulator generates a schematic circuit containing preselected components and input/output circuits connected to the battery and load respectively (Figure 2).
Figure 2: Circuit diagram of VIPower driver simulation experiment
VBATTis the battery voltage;
VIN is the input voltage of the microcontroller;
RLINE_IN and RLINE_OUT are the wire parasitic resistances at the driver input and output.
Before starting the simulation, you need to perform the definition step and customize the project parameters. At this stage, the designer determines parameter values and simulation settings for the components in the circuit diagram.
The parameter values of the components in the circuit diagram are critical in determining the behavior of the circuit and must be carefully selected to ensure that the circuit meets the performance specifications.
A simulation setup defines which operating conditions the designer wants to reproduce and analyze through simulation experiments. For example, the designer may want to examine voltage and current waveforms in a circuit, determine power consumption, or evaluate the thermal behavior of a circuit.
By customizing project parameters and setting simulation variables, designers can ensure that simulation results accurately reflect the behavior of the circuit and provide the information needed to optimize the design (Figure 3).
Figure 3: Simulation definition process
One of the great benefits of using TwisterSIM for simulation experiments is that the simulation results can be displayed in real time during the simulation process. This feature allows designers to monitor the operating behavior of a circuit during simulation and quickly identify problems or areas for improvement.
The real-time display of simulation results can help designers improve the efficiency and effect of design optimization. For example, when the simulation results show that the circuit consumes too much current or the temperature rises too fast, the designer can quickly adjust the circuit parameters and immediately see the impact of parameter changes on the simulation. impact on results.
This feature saves time and resources because designers don't have to wait for the simulation to end and can quickly identify and resolve issues. TwisterSIM's real-time display of simulation results can improve the efficiency and effectiveness of design optimization, thereby improving the energy efficiency, reliability and safety of power distribution systems.
3. Customize simulation results on demand
Figure 4: Customized curves and charts based on data visualization
Engineers can modify simulation parameters, data, and visualizations to meet their specific needs, make informed decisions, and achieve optimal results. The simulator provides a variety of tools for analyzing and optimizing VIPower circuits, such as heat maps, current and voltage waveforms, and power consumption analysis, as shown in Figure 4.
Designers can use TwisterSIM to design and develop efficient and resilient drives with effective diagnostic and protection functions by optimizing the performance and reliability of the design, reducing the risk of failure caused by thermal or electrical stress, and integrating error reproduction and limit parameter recording and other functions. Additionally, this design approach reduces the size and weight of the wiring harness, thereby reducing the vehicle’s carbon footprint.
In harsh automotive ecosystems, especially where repeated short circuit events can lead to thermal shutdown (TSD), it is critical to consider implementing thermal protection mechanisms.
In this case, the drive attempts to restart the system through power limiting protection measures (maximum current and thermal hysteresis cycling) and remains in TSD mode until the overheating problem is eliminated.
TwisterSim also has this specific control function. Taking the high-side driver VND9012AJ (a smart power switch developed with VIPower M0-9 technology) as an example, TwisterSim can accurately reproduce the working conditions of the switch, and then compare the simulation results with experimental data, As shown in Figure 5.
Figure 5: Comparison of simulation results and experimental data for VND9012AJ under repeated short circuit events
IOUTis the output current of the driver;
Dt refers to the time difference between the simulation results and the TSD events in the measured data.
Simulation results show that TwisterSIM is an efficient tool to accurately model and emulate the current limiting and thermal shutdown (TSD) triggering situations of thermal protection mechanisms.
The analog data error of the output current value is less than 2%, and the TSD occurrence time error is about 0.8 ms. This proves that TwisterSIM has a high accuracy in predicting system behavior under realistic conditions.
As the next generation of cars approaches, engineers are challenged to develop advanced solutions where deploying distributed intelligence can unlock powerful performance from systems. To achieve this, new designs must prioritize energy efficiency and resilience, and comprehensive simulation tools are critical to ensure accuracy and effectiveness.
By taking full advantage of TwisterSIM's capabilities, developers can optimize new VIPower drive designs to achieve the highest performance and reliability while minimizing the risk of failure caused by thermal or electrical stress, paving the way for green, low-carbon and sustainable development. the way.
 “TwisterSIM: Dynamic electro-thermal simulator for VIPower products”, Databrief on https://www.st.com/resource/en/data_brief/twistersim.pdf, Sep. 2023.
 M. Bonarrigo, G. Gambino, F. Scrimizzi, "Intelligent power switches augment vehicle performance and comfort", Power Electronics News, Oct. 10, 2023.
 A. Brighina, F. Giuffrè, “Interactive analog/digital mixed signal modeling via HDL simulator and foreign VHDL/Verilog C interface”, Electronicsforyou, Electronics & Technology Portal, 2011.
 D. Maksimovic, A. M. Stankovic, V. J. Thottuvelil, G. C. Verghese, “Modeling and simulation of power electronic converters”, Proc. of IEEE, vol. 89, no. 6, Jun. 2001.
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