In many applications, the system's input voltage can be unstable or vary over a wide range. Often times, the 2:1 input range seen in many industry standard isolated dc-dc converters is not wide enough to address a fluctuating line voltage. The VHK series and the VFK400W series offer an ultra-wide 4:1 input range, making them ideal for applications where the dc voltage rail is variable such as battery-fed equipment. As the battery loses its charge, the voltage will drop accordingly. To continue to feed a stable output voltage to the load, the dc-dc converter’s input range must be able to accommodate the voltage drop during discharging conditions and voltage rise during recharging conditions.