Complex for both designers and manufacturers and, ultimately, relevant to end consumers, who expect their products to be not only functional but also safe.
Circuit protection is an everyday routine.
Imagine the following scenario: morning, jogging, damp weather... running shoes, socks, and a nylon t-shirt. All together, these can briefly generate an electrostatic discharge (ESD) of 30,000 V—a potential cardiac arrest for your smartphone or any other portable device playing your favorite music.
Imagine you approach your computer and—bam!—suddenly everything resets. Your first thought: malware or a virus, the computer is too old, or the hardware has failed. It wouldn't occur to you that the simple contact between your costume and the computer triggered a brief but powerful electrical incident.
Circuit protection is routine, yet the problems associated with overvoltage and overcurrent remain an afterthought for most engineers. Why? Because with the expansion of their tasks and the reduction of design cycles, most engineers relegate circuit protection to the bottom of their to-do list. “Faster” is the mantra of the day! Today, engineers must design the core functionality of their devices as quickly as possible. They must create the form, develop the software, build the prototype, and test the concept. Only then, if at all, will they have time to think about circuit protection.
Saving valuable development time:
This approach is creating more problems than ever for product designers. Mobile phones, computers, and music players are getting smaller and smaller. Moreover, they operate at minuscule voltages that are more susceptible to ESD, distant lightning strikes, motor ignitions, and leakage currents from process machinery. This is typically 10,000 or 15,000 volts, but experience is showing that it can reach as high as 30,000 volts.
The unfortunate consequence of leaving such tasks until the last minute is that the functionality of the design suffers. With devices becoming increasingly smaller and requiring the assembly of so many parts, engineers can no longer find space for circuit protection devices on their printed circuit boards. The result: they end up redesigning the boards and losing valuable development time—time that could have been saved if they had considered circuit protection from the outset. To make matters worse, in many cases, engineers don't think about circuit protection at all, but instead rush to choose any readily available solution and an unsuitable protection device, resulting in functional failures, poor reliability, safety issues, electric shock, or even fire.
To help guide the design engineering community in preventing such grim scenarios, we include here some expert recommendations from engineers whose professional lives revolve around the topics of overcurrent protection and shock immunity:
Thinking about circuit protection from the chip stage itself:
Considering circuit protection too late in the project can certainly have serious repercussions for any design engineer. Such a scenario could result in a situation where there is no space available for the ESD device. Or worse, settling for a suboptimal position where the device does not function as intended.
To avoid these problems, the best time to start thinking about these issues is precisely when the chipset is selected and the circuit board layout begins. By proceeding this way, ESD values are available, and designers know how robust and sensitive the chips are. Some of these chips operate at 1.5 volts, and it doesn't take much to disturb them. Experience teaches us that circuit engineering is more complex and delicate than we sometimes realize.
Understanding the Threats:
Fuses are simple, everyone understands them, but overvoltage may not be so obvious, and its consequences may go unnoticed. However, these consequences do exist, even if they are not as catastrophic as those of overcurrent.
Did you know, for example, that power surges have even disabled the Hubble Telescope, shut down refineries, destroyed smartphones, and stopped roller coasters mid-motion? In some portable medical devices, power surges can even be life-threatening. There are numerous potential sources of excessive current and voltage, starting with common lightning, ESD, motors, arc welders, as well as the aforementioned running shoes and socks. Consider lightning, for example: people understand the phenomenon of lightning, but they may not know that it travels through the ground, potentially creating enormous wave distortions in high-voltage power lines a mile away. And this is just one example of the importance of knowing and understanding potential hazards.
Defining the Needs:
To accurately predict a product's circuit protection needs, the design engineer must first be able to envision how it will be used. In other words, it's essential to know where it might end up, understand its environment, and what might be adjacent to it. A device will be more vulnerable in an industrial setting than in an office.
Once the designer understands the environment, they can begin making adjustments. This should start with the connection points. The surge protector should be as close as possible to the connector, not five centimeters away. Understanding the product's target environment and the potential hazards associated with that placement will be crucial in selecting the appropriate circuit protection solution.
Understanding Standards
: Standards determine the design of every product, including circuit protection. Moreover, the list of standards that designers must consider seems endless. And they also differ internationally, regionally, and even locally. Regarding circuit protection, standards include those from Underwriters Labs, Energy Star, NEMA, ATCA, CSA Group, IEEE, and standards bodies in Canada, South America, Japan, Korea, and Europe, among others.
Standards are a crucial part of any project or industry. Design engineers have an obligation to be aware of all relevant standards even before starting a project. Just like components, knowledge and understanding of the regulations governing certain products, both locally and internationally, must also be part of the initial design phase. In other words, you can't create the product and then start looking for the standards that would allow it to function in a particular market.
Staying Informed:
Since circuit protection is not taught at universities, most engineers are more versed in the intricacies of product design than in the topics of overcurrent and shock immunity. This problem is compounded by the fact that most design engineers must juggle numerous projects and have too little time to research the subject. Industry white papers, product specifications, and case studies are always useful as a source of information and education, but also as examples of what worked in certain situations, possibly similar to the present one.
In general terms, even though it's not officially taught in schools, circuit protection is a relevant topic for the everyday lives of end consumers, manufacturers whose brand reputation relies on the perfect functionality and safety of their products, and design engineers whose success is measured by development time and quality. It's something that must undoubtedly be learned through experience and knowledge sharing within the industry. Littelfuse, for example, offers its website speed2design, which is geared towards helping engineers facing time constraints find circuit protection solutions.
Author:
By Bharat Shenoy, Director of Technical Marketing, Electronics Business Unit
Author
Brief Biography: Bharat Shenoy, Technical Marketing Director, Electronics Business Unit, is responsible for market segment analysis, sales channel support, and application engineering for the Electronics Business Unit. Bharat Shenoy joined Littelfuse as Local Sales Director for the Western US region from 2008 to 2011. He began his career as a US naval officer on a nuclear submarine and has held various positions at Tyco Electronics Circuit Protection, including Application Engineer, Local Sales Director, and Commercial Director.
