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Bench Talk for Design Engineers | The Official Blog of Mouser Electronics


Circuit Protection – Why Bother?? Kelly Casey

Let’s face it - circuit protection can be a tough sell. Here’s why: 

1) Circuit protection isn’t sexy. It doesn’t add any “wow factor to the product." 

2) In fact, it doesn’t add any functionality to the product at all. 

3) Any effect circuit protection has on the function of a device is likely negative. Adding capacitance, resistance or potential non-linearity to an I/O port is rarely useful in promoting high data rates. 

4) It adds cost and can increase complexity. 

What circuit protection does do is provide some measure of reliability. It gives the end product the ability to sustain and likely survive potentially damaging electrical surges or contact with unexpectedly high voltages without exposing the user to electrical shock or becoming a fire hazard. 

 

However, protection against rather vague threats is always a challenge. Mothers Against Drunk Driving (madd®) has undoubtedly had a positive effect on the safety of our roads, but the identities of the people whose lives their campaigns have saved cannot be determined. 

Circuit protection has become the norm in many types of equipment and electrical equipment is more reliable today than ever before, so when the boss tells you he doesn’t want to pay for circuit protection, it’s a bit like saying that seat belts aren’t useful anymore because no one is dying in traffic accidents! I would point out that circuit protection has drastically improved the safety and reliability of all kinds of electrical equipment and its very presence is the reason for the increased safety and reliability. But that’s hard to prove, and better circuit protection may hard to justify on a tight budget. 

So what is the motivation for designing circuit protection into your products? In my view, there are three kinds of circuit protection customers: 

1) The Elite: These are companies who simply want to be the best in their markets. They are the household names – the premium brands. These companies and their customers value the enhanced reliability and longer life their designs enjoy when equipped with robust circuit protection. In a sense, they are primarily protecting their brand – their reputation. Their customers are selecting to buy their products in part due to this enhanced reputation, which allows them to price their products at a premium, thereby preserving their profit margins. 

2) The Astute: These are companies that can justify the higher costs of designs equipped with circuit protection. Equipment that is leased or rented must have sufficient reliability to stay functional in the hands of someone that doesn’t own it. Also, equipment sold with long warranty periods (like commercial/industrial LED lighting) must remain in service or the selling company, and not the purchaser, may be on the hook for repairs or replacement. These companies can calculate the payback on circuit protection. If the MTBF (mean time before failure) can be extended sufficiently to reduce the probability of failure “X” amount across all equipment sold, then they will save “Y” dollars in repair/replacement costs that can be used to fund the circuit protection. As a side benefit, these companies enjoy an improved reputation as well – without affecting their bottom line. 

3) The Slackers: Let’s face it – this is a big group. They only use sufficient circuit protection to satisfy regulatory requirements. Essentially, they only use CP components because they can’t be in their market without it. They will search for the cheapest protection scheme that will allow them to just sneak by the regulatory tests. They aren’t going to spend one penny more to extend the life of their products because they compete solely on price and failed product is someone else’s problem… 

Into which group does your company fall? I can assure you that, as a designer, it’s a lot more fun working in the Elite bunch!



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Kelly Casey is VP of Engineering for FM Technical Consulting, and holds a Bachelor of Science Degree in Electrical Engineering from the University of Nebraska, as well as a Master of Science Degree in Electrical Engineering from the Georgia Institute of Technology. Previously, Mr. Casey has held various roles at Bourns, Littelfuse, and Teccor Electronics.  

 

Kelly Casey is VP of Engineering for FM Technical Consulting, and holds a Bachelor of Science Degree in Electrical Engineering from the University of Nebraska, as well as a Master of Science Degree in Electrical Engineering from the Georgia Institute of Technology. Previously, Mr. Casey has held various roles at Bourns, Littelfuse, and Teccor Electronics. 
Kelly Casey is VP of Engineering for FM Technical Consulting, and holds a Bachelor of Science Degree in Electrical Engineering from the University of Nebraska, as well as a Master of Science Degree in Electrical Engineering from the Georgia Institute of Technology. Previously, Mr. Casey has held various roles at Bourns, Littelfuse, and Teccor Electronics. 

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