Eliminate Arcing in 48 V Boardnet Systems With a New eFuse Design

Benefits of The e-Fuse Design in Automotive Applications

With the arrival of 48V boardnet systems, a new method for safely connecting and disconnecting high current loads—electric power steering, electric turbocharger, etc.—to the battery is required due to arcing problems associated with using mechanical relays. An electronic fuse (eFuse) on a compact, double-sided FR4 PCB with passive cooling has been designed to switch loads up to 200A at 48V to address this issue. This design also features a pre-charge function to limit potential inrush current to an acceptable level and continuous current measurement for use by the vehicle’s body control module to monitor battery health. This presentation by Vishay will demonstrate the benefits of this innovative design.  

Overcurrent and Overvoltage Protection

In most inverter drive designs, each motor phase's current must be monitored for control purposes or overload protection. Several commonly used methods for measuring current in a motor drive, resistive shunt, and hall effect sensors are among the most popular.  A hall effect sensor is easier to implement as a turn-key solution than a resistive current shunt, requiring additional circuitry. However, hall effect sensors have certain limitations. Firstly, they have low linearity over a wide current range and offset error at high temperatures. There can also be excessive measurement latency and bandwidth limitations depending on the switching frequencies being used. Also, a hall effect sensor requires a separate power supply for operation and the overall system cost tends to be somewhat higher. And finally, customization of a hall effect sensor is not possible, whereas a current shunt from the Vishay Dale division can be configured to meet mechanical constraints of the system, either in one of the many standard packages from 0603 to 5931 or a custom version of the larger 8518 shunt.  

With a wide range of e-Fuse solutions for overcurrent and overvoltage protection in automotive systems, Vishay meets clients’ needs across the globe with zero defects, zero incidents, and zero failures. For example, Vishay’s WSLP 3921 offers the lowest resistance values of the surface-mount Power Metal Strip series, down to 100µΩ and the highest power rating at 15W. This performance envelope is often required in battery management systems, high-power traction inverters, and motor control in 48V automotive applications and electric vehicles. 

Vishay D2TO20 resistor is an AEC-Q200 qualified SMT power resistor for automotive systems featuring Vishay’s Thick Film Technology. For overvoltage protection, XMC7K24CA is snap-back type TVS with an extremely low clamping voltage ratio for suppressing transient voltage to lower clamping voltages than conventional TVS. Vishay NTCS0805 negative temperature coefficient (NTC) thermistors provide temperature-dependent current-limiting capabilities in automobiles. The product comes in the standard 0805 footprint and is AEC-Q200 qualified. Other offerings can be found in Vishay’s application matrix. 

Power Conversion

As dual board net systems, i.e., vehicles with both a 12V bus and a 48V bus, are becoming more popular, a high-power bi-directional 48V to 12V DC/DC converter is a key building block in the vehicle’s architecture. To optimize the vehicle's overall efficiency, energy must be transferred in either direction between the 12V battery and the 48V battery, depending on the electrical demands of the vehicle and the state of health of the batteries. 

The 12V bus supports the vehicle's lower power loads, such as interior and exterior lighting, powertrain control modules, infotainment systems, and other basic control modules or functions. The 48V bus was created for the new higher power loads to reduce current levels and lower the cost of wiring and other related components. These loads would include electric power steering, air conditioning, engine cooling, electric turbos, and add-on parallel hybrid inverters. Vishay’s SQJA84E TrenchFET® power MOSFETs are AEC-Q101 qualified for high performance in automotive DC/DC converter operations.