DC-DC converter

DC-DC converter – definition

A DC-DC converter is a power-electronic circuit that converts a direct-current input voltage into another regulated DC voltage. In mobile robotics, it supplies subsystems that require voltage levels different from the main battery bus. Typical loads include an onboard computer, LiDAR, depth camera, GNSS receiver, Ethernet switch, motor-controller logic, USB peripherals, and sensor hubs.

A converter is not only a voltage reducer. It controls voltage regulation, current capability, efficiency, thermal dissipation, output ripple, electromagnetic compatibility, and protection behavior. These properties affect the reliability of an unmanned ground vehicle (UGV), especially when drive motors introduce supply transients or when compute and perception sensors operate from the same battery.

On a Leo Rover or Raph Rover, a DC-DC converter is normally part of the payload power architecture. It can provide a regulated rail for an additional computer, a LiDAR, an Intel RealSense camera, a GPS/RTK receiver, or networking equipment. The converter must be selected according to the electrical requirements of the added hardware and the available battery voltage range. Leo Rover uses a Raspberry Pi as its default onboard compute unit and supports ROS 2. Its differential-drive, four-wheel configuration requires an autonomy stack and additional sensors for autonomous navigation. Source: Leo Rover technical documentation.

Converter topologies used on UGVs

The topology determines whether a converter can reduce, increase, invert, or isolate voltage. For mobile robotics, the required topology depends on the battery bus and the voltage tolerance of the payload.

Buck converter: steps a higher input voltage down to a lower output voltage. It is commonly used for regulated 12 V, 5 V, or 3.3 V payload rails.
Boost converter: steps an input voltage up. It is used when a payload requires a voltage above the battery voltage available at the converter input.
Buck-boost converter: regulates an output when the input may be both above and below the target voltage. This is useful where battery voltage changes significantly during discharge.
Isolated converter: uses galvanic isolation between input and output. It may be required for electrically noisy systems, separate sensor domains, or interfaces exposed to external equipment.

For an ideal buck converter, the duty cycle approximately follows the equation below. Real converters deviate from this relationship because of switching losses, conduction losses, dead time, and control-loop behavior.

D ≈ Vout / Vin

Converter efficiency can be expressed as:

η = Pout / Pin = (Vout × Iout) / (Vin × Iin)

The difference between input and output power is dissipated as heat. Thermal design must therefore consider continuous load, peak load, enclosure temperature, airflow, mounting surface, and derating curves published by the converter manufacturer.

Key electrical parameters

A converter should be specified from measured or documented load requirements rather than nominal voltage alone. The following parameters are relevant when integrating payload hardware on a UGV.

Parameter	Why it matters in mobile robotics
Input-voltage range	Must cover the battery voltage across charging, normal operation, and low-voltage conditions.
Output-voltage accuracy	Must remain within the supply tolerance stated in the payload device specification.
Continuous and peak output current	Must support startup, inrush, compute-load spikes, and sensor operating current without triggering protection.
Output ripple and noise	Can affect cameras, GNSS/RTK receivers, IMUs, analogue interfaces, and communication reliability.
Efficiency and thermal resistance	Determine battery runtime and converter temperature under sustained payload load.
Protection functions	Depending on the model, functions may include input undervoltage lockout, overcurrent protection, short-circuit protection, overtemperature protection, and reverse-polarity protection.
EMC performance	Switching noise can interfere with radios, GNSS reception, camera links, and sensor data acquisition.

Current capacity should not be selected only from average consumption. A computer running ROS 2 nodes, visual perception, Docker containers, or GPU-accelerated workloads can produce transient demand that differs from idle consumption. The applicable peak-current and startup-current values must be taken from the hardware manufacturer’s datasheet.

DC-DC converters in ROS 2 payload integration

ROS 2 does not control a DC-DC converter directly unless the converter provides a programmable interface such as CAN, UART, Ethernet, or GPIO-controlled enable input. However, power state is relevant to system observability. A robotics application can publish battery and power data, detect undervoltage events, and place compute-intensive nodes into a safe state before a power failure.

The standard ROS message for battery status is sensor_msgs/msg/BatteryState. It includes fields for voltage, current, charge, capacity, percentage, power-supply status, health, and technology. Source: ROS 2 sensor_msgs BatteryState interface.

ros2 topic echo /battery_state
ros2 topic hz /battery_state

The update rate of /battery_state is implementation-specific. It depends on the battery-management system, motor controller, converter telemetry interface, and ROS 2 driver configuration. It should be documented in the robot integration package rather than assumed from the message definition.

Integration considerations for Leo Rover and Raph Rover

Leo Rover is suitable for laboratory, educational, and field experiments where additional perception or compute hardware must be integrated with the existing mobile platform. Raph Rover is a larger platform intended for applications that require higher payload capacity. In both cases, the payload power design should separate motor-noise considerations from sensitive electronics requirements.

Verify the payload input-voltage range and connector polarity before connecting it to a regulated rail.
Use a fuse or electronic protection device sized according to the converter and cable specification.
Keep high-current motor wiring physically separated from GNSS, camera, Ethernet, and low-level sensor wiring where possible.
Use manufacturer-specified input and output capacitors. Their equivalent series resistance can affect converter stability.
Measure voltage at the payload connector under drive acceleration and compute load, not only with the robot stationary.
Document the power architecture, wire gauge, fuse rating, connector type, and converter part number in the robot repository.

Standards and technical references

DC-DC converter integration is commonly assessed through electrical safety, electromagnetic compatibility, and environmental requirements. The exact standards depend on the final product, operating region, enclosure, and intended environment.

IEC 61000 series: electromagnetic compatibility requirements and test methods, including electrostatic discharge and conducted or radiated immunity. Source: International Electrotechnical Commission.
IEC 62368-1: safety requirements for audio/video, information, and communication technology equipment. Applicability must be evaluated for the complete system. Source: IEC Webstore.