Intelligent Power Switches, or IPS, are tiny devices with enormous consequences when it comes to power conversion, protection, and overall electrification of vehicles. According to Persistence Market Research, they represent a 2-billion market today and will be twice as big by 2032. On their end, engineers are seeing firsthand how smart fuses and new protection devices are drastically transforming vehicles and user interactions. Even mainstream vehicles are now featuring fuse boxes that rely solely on electronic devices, and zonal architectures are even gaining new ground in affordable electric models. IPS devices are everywhere, from lighting systems to seat heating, body control modules, advanced driver assistance systems (ADAS), and more. But are engineers ready for them?
Looking beyond IPS devices
It’s more than just the component
Choosing the right IPS is a complex proposition. In fact, too often, teams underestimate the challenges that come from designing a system that requires IPS devices. This usually takes the form of overlooking where they come from, what they do, or even if they are part of a larger ecosystem. Paradoxically, while IPS devices take less and less space on a PCB, their impact is growing, and the consequences of choosing an inappropriate device are having an increasingly negative impact on consumers and their vehicles. Some engineering teams are also having a harder time transitioning to new paradigms.
For instance, I2t curves are highly customizable in eFuses with the ability to program shut-off overloads per channel and benefit from response times below 100 µs. In essence, the I2t curve defines the relation between the spike in current over time before the fuse “melts”, meaning that it disconnects the circuit from the load. Thanks to electronic fuses and their faster performance and more customizable curves, engineers can create more efficient designs, smaller PCBs, and demonstrably higher reliability. Yet, many teams still rely on a more expensive and less efficient microcontroller for the I2t curves, simply because that’s how it’s “always been done”.
This latter issue highlights the engineering complexities behind the selection of IPS devices and the new trends designers must adopt to stay relevant. In addition to this, teams must also contend with finding the right load characteristics, thermal management, and switching behavior, while also dealing with electromagnetic interference, grounding, and other challenges. And while going into detail for each of these technical considerations is not possible in a single blog post, this list demonstrates that looking at data sheets is just not enough. It’s one thing to have specifications. It’s another thing to know, in advance, how everything will behave once installed on a PCB and confronted with over-currents.
Obtaining a global picture
It’s for this reason that ST offers eDesignSuite, a design and simulation tool that reduces friction during development by making circuit design more intuitive. We stand apart from the competition because our journey into IPS devices in automotive doesn’t start with one product, but a look at a whole module, with simulation to anticipate its behavior and catch issues before printing the first layout. TwisterSIM is another simulator for VIPower technology that covers use cases outside of eDesignSuite to help designers choose the right devices. It even offers wire harness and load type selection to replicate real-world applications.
Looking at ST’s IPS devices
VIPower high-side drivers
Besides offering tools that help look at the overall design, ST also has a unique portfolio thanks to a combination of high-side drivers and smart fuses. When it comes to the former, many are familiar with our VIPower family of devices. Avid readers of the ST Blog will remember that we covered the VIPower M0-7 a couple of years ago. A version of this IPS even comes with a fully integrated motor driver to help create small PCBs and more efficient systems. In a car, these savings can add up to a total weight loss of 50 kg per vehicle. And there are many more VIPower series, from the M0-1 to the M0-9.
VIPower M0-9
Indeed, the VIPower M0-9 is the first high-side driver family to include an SPI interface. ST provides quad- or six-channel variants featuring digital current sensing for automotive applications, thanks to a 10-bit analog-to-digital converter. At their core, we find a 40 V trench vertical MOSFET with digital logic and analog circuits, hosted in a 6 mm x 6 mm QFN package. Inside the devices, advanced digital on-chip diagnostic and protection features improve the monitoring capabilities of body electronic control units. Additionally, thanks to the advanced levels of integration, the M09 SPI family enables engineers to simplify their board design and reduce their overall footprint, thus shrinking development times and costs.
Smart fuses
The other big category of IPS devices for automotive is smart fuses, or STi2Fuse, which are intelligent switches that embed the fuse curve protection for both loads and cables. Thanks to logic that enables developers to configure their levels of protection, smart fuses are more than a simple mechanical fuse replacement. Under typical operation, smart fuses can switch the loads. At the same time, in case of hazardous failures, they can isolate the fault with a fast trigger of a few microseconds (comparatively, mechanical fuses would require 50 ms). The high level of configurability allows car manufacturers to optimize the wire harness and PCB dimensions to lower the total weight by up to 20%.
The logic embedded in STi2Fuse also enables our smart fuses to provide information on the circuit’s electrical behavior, facilitating system health monitoring and predictive maintenance. It’s an entirely new set of monitoring tools that offers new data for developers and users. For instance, smart fuses can detect when a cable is about to fail, thus offering users the ability to replace them before a catastrophic failure. Or, if the battery is running low, the system of smart fuses could turn specific circuits off, like those going to the seat warmers, to conserve battery without user involvement. Electronic fuses are also resettable and improve reliability and safety in line with the latest carmaker requirements for new zonal vehicle architectures.
As the weight of cars becomes a concern for cities and overall infrastructure, and as electrification is transforming vehicles and moving them toward a zonal architecture, engineers are increasingly in need of solutions that help adopt these latest trends and create innovations with significant implications for the environment and the lives of their customers. But just looking at one device is not enough. That’s why ST offers design tools and a diverse range of IPS devices. Because a comprehensive challenge demands a holistic approach.
Learn more about ST’s Intelligent Power Switches (IPS) for automotive
