DC/DC Converters for Transportation Applications

Among the trends that are driving the electrification of these types of vehicles are:

• Increasingly stringent global emissions regulations
• The push towards increased energy efficiency
• Downward cost pressures
• Noise reduction
• The rise of autonomous machines such as AGVs and robots

As shown in Figure 1, off-highway EVs typically use high-voltage (HV) battery packs for the main motive power. An on-board or off-board AC/DC converter provides charging power for these battery packs that supply the traction motor inverter and other high-voltage subsystems with a DC voltage that can be as high as 800V but also 96V or less.

Each type of equipment can employ different voltages based on size. A few examples include:


In addition to the HV supply, the power delivery system must also accommodate numerous low-voltage modules. Depending on the vehicle, these could include instrumentation panels; low-power valves, motors, and actuators; accessory power outlets; door locks; wipers; horns; and interior lighting. Off-highway EVs typically also include a secondary battery that supplies low-voltage devices with 12V–24V; a DC/DC converter module is required to convert the HV voltage to a lower level to charge the on-board 12V or 24V batteries.

RECOM manufactures a wide range of AC/DC and DC/DC converters that meet the power conversion needs of many e-mobility applications.

The RMOD series of regulated DC/DC converters (Figure 2) are specifically designed for use with off-highway electric vehicles to supply the low voltage network from the HV traction battery. The RMOD products are exceptionally rugged, compact, sealed units. They offer a range of solutions from 300W up to 600W, which can be chassis-mounted to avoid the need for cooling fans. The extra-wide input voltage range up to 120VDC makes the RMOD series ideal for electric vehicles with nominal 24V - 96V battery-powered systems.

One characteristic of many off-highway EV is a lack of protection from the elements for electronic modules. Thanks to their waterproof and dustproof housing construction, the RMOD series does not need protective enclosures and can be connected mechanically and thermally directly to the chassis, i.e., at any point on the vehicle, and will therefore operate reliably even under the most adverse conditions.

The RMOD series of DC/DCs includes 300W, 400W, and two 600W versions. The RMOD600-W features a 33.6V to 96V input range (125V/5 mins) with a 24V output; the RMOD600-EW features a 13V output and a wide continuous input range of 33.6V to 125V. Both versions will operate down to 24V for 5 mins maximum. The RMOD family is isolated to 2.5kVDC and hold certifications to IEC/EN/UL/CSA 62368-1. It is intended for baseplate cooled operation up to an ambient of 85°C without derating.

All products in the RMOD series are sealed to IP67 and RMOD400/600 even to IP69K against dust and water ingress and are certified to EN 60068 for resistance to temperature cycling, shock and endurance, humidity/heat cycling, vibration, mechanical shock, and salt spray. Along with comprehensive electrical protection, these certifications make the RMOD series ideal for mounting in exposed areas in tough applications such as off-highway EVs, but also find a home in industrial materials handling equipment.