“Across the globe, whether helping automakers offload the internal combustion engine or transitioning to fully electric vehicles, we all need to work together to reimagine the automotive industry and reduce emissions. Electrification has proven to be a more suitable tool for reducing emissions, but as the voltage inside the vehicle increases, as shown in Figure 1, monitoring and maintenance of the subsystems becomes even more important.
Across the globe, whether helping automakers offload the internal combustion engine or transitioning to fully electric vehicles, we all need to work together to reimagine the automotive industry and reduce emissions. Electrification has proven to be a more suitable tool for reducing emissions, but as the voltage inside the vehicle increases, as shown in Figure 1, monitoring and maintenance of the subsystems becomes even more important.
Figure 1: Roadmap from Hybrid to Electric Vehicles
It is based on continued innovative development of monitoring and maintenance subsystems that time-to-market for hybrid/electric vehicles (HEV/EV) is accelerating while maximizing driving time and ensuring passenger safety. But at the same time, there are still some technical difficulties regarding the monitoring and maintenance in the battery management system and the traction inverter system. Below are the eight most common questions and TI’s recommendations.
1. How to increase energy density and system efficiency to improve the range of hybrid/electric vehicles?
Doubling the power output for the same size provides significant cost savings and also facilitates fast charging. This can be achieved by operating the power converter (PFC stage and DCDC in an OBC or fast DC charger) at high switching frequencies, reducing the size of the magnetic components and thus contributing to high power density. For a given application, higher system efficiency leads to lower losses and smaller heat sink solutions. It also reduces thermal stress on the device and helps extend lifetime.
2. How can a hybrid/electric vehicle provide the same user experience as a gasoline vehicle?
The driving experience is improved by increasing the available range per charge while reducing charging time. Achieving these goals requires advanced battery management systems and efficient power electronics on both the vehicle and grid infrastructure (charging piles) side.
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3. How to improve the reliability of HEV/EV battery management system?
The BQ79606A-Q1 is designed to improve reliability through the following features:
The voltage monitor, temperature monitor and communication functions are ASIL-D rated for automotive safety integrity.
The optional daisy-chain ring architecture ensures stack communication even when the communication cable is disconnected (limp-home mode).
Designs that achieve robust hot-swap performance without the need for external Zener diodes.
4. How to solve the poor discharge performance of lithium-ion battery pack in low temperature environment?
Hybrid/electric vehicle battery packs operate within a controlled temperature range to optimize charge-discharge performance at low temperatures and ensure the battery remains within a safe operating area at high temperatures. To apply a proper thermal management strategy, accurate voltage and temperature sensing at the cell/pack (as shown in the BQ79606A-Q1) is necessary. These may require preheating at cold start conditions and cooling at higher temperatures.
5. How to monitor the BMS system?
Scalable Automotive HEV/EV 6s to 96s Li-Ion Battery Monitoring Demonstrator Reference Design in Daisy-Chain Configuration Implements the BQ79606A-Q1 to Create Highly Accurate and Reliable System Designs for 3 to 300 Series, 12V to 1.2 kV Li-Ion Battery Packs . The design scales between 6 to 96 series battery monitoring circuits and communicates battery voltage and temperature to help meet ASIL-D requirements.
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6. What are the advantages of using silicon carbide (SiC) or gallium nitride (GaN) in-vehicle equipment in a traction inverter?
New advances in SiC power circuits can help designers develop more efficient, lighter and smarter EV powertrains such as traction inverters, on-board chargers and fast DC charging stations. Devices such as the new UCC21710-Q1 and UCC21732-Q1 are TI’s first isolated gate drivers to integrate sensing capabilities of insulated gate bipolar transistors (IGBTs) and SiC FETs, improving system reliability and providing fast Detection time to prevent overcurrent events while ensuring safe system shutdown.
7. How to prevent the traction inverter from overheating?
The TMP235-Q1 helps traction inverter systems react to temperature fluctuations and apply appropriate thermal management techniques with low power consumption, small package size and high accuracy.
8. Why is a temperature sensor required to ensure the reliability of a traction inverter system?
Temperature detection is a key parameter to ensure EV performance as well as passenger safety. And automotive OEMs are also prioritizing temperature detection to reassure consumers that these novel modes of transportation are safer than internal combustion engines.
By applying appropriate temperature detection techniques, the higher the accuracy, the greater the chance that the system will respond quickly to temperature fluctuations.
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According to the International Energy Agency, the number of electric vehicles on the road will triple by 2021. Hence the need for more advanced monitoring and maintenance. Texas Instruments continues to help electrify the car and help the cars of the future achieve even higher expectations.