Beyond the limitations of traditional fuses

Vehicle power protection is becoming increasingly electronic. The circuit protection role that traditional mechanical fuses and relays played is now being replaced by semiconductor-based smart protection devices. At the center of this change is Infineon Technologies’ PROFET™ Wire Guard solution. This product is a smart high-side switch that performs current sensing and overcurrent protection simultaneously, and is designed to overcome the various limitations of conventional mechanical fuses.

The existing vehicle fuse method has a fundamental limitation in that it is a mechanical device. Even if a circuit malfunction occurs and the fuse blows, it cannot be detected or recorded in advance, and the operating error is also large. Therefore, manufacturers have been overly conservative in designing the wire thickness and component capacity in preparation for overcurrent situations. This has resulted in increased weight and cost of vehicle systems.

“Mechanical fuses cannot sense or diagnose the status of the wire or load, so a large safety margin had to be built into the wire during design,” explains Infineon’s manager Jong-Min Lee. “Smart protection devices can diagnose the system status in real time and precisely sense the current to optimize the wire thickness,” he emphasized.

Design flexibility and industrial scalability of smart fuses

PROFET™ Wire Guard is a clear technological advancement compared to the existing PROFET series. The most notable difference is the support of the I²t protection characteristic. This technology allows setting the overcurrent cut-off conditions by taking into account both the current size and the time it has flowed. This allows for electronic implementation of a protection curve similar to the melting characteristics of existing fuses, and can be flexibly applied to various wire specifications.

Wire Guard's 6 I²t Protection Curve Graphs

In addition, this product provides an ultra-low power Idle mode, consuming only the minimum amount of current even when the system is in standby, and can transmit various information such as overcurrent status (OCT), I²t setting value, and current sensing accuracy to the ECU through the diagnostic pin, which is also advantageous for functional safety response.

“The idle mode pin and diagnostic pin can transmit the status to the system in real time, and various diagnostic functions are built in, which is very advantageous for securing functional safety during design,” said the manager.

In fact, Wire Guard has been applied to electric vehicle OEM projects in Germany and China. In the premium electric vehicle market, the movement to reduce or eliminate mechanical fuses is already accelerating, and in response to this trend, the demand for semiconductor-based protection devices is also rapidly increasing.

Design tools are also available for developers. Infineon offers a dedicated tool that simulates the various operating conditions of the Wire Guard family, allowing developers to import their own load profiles and wire specifications, compare them directly with the product specifications, and set up protection curves. This allows developers to design products more quickly and accurately.

Capacitive Load Switching feature

In this way, Wire Guard is emerging as a core technology that goes beyond simple circuit protection and changes the power distribution structure of the automotive electrical system itself. Electronic fuses integrate fuses and relays into a single semiconductor, and are superior to existing methods in various aspects such as precise protection, system diagnosis, design flexibility, and maintenance efficiency. As vehicle electrification and electrification are in full swing, semiconductor-based smart protection solutions are expected to become the new standard.