How to choose a DC-DC converter the right way

How do I set input and output voltage?

The first step is defining the input voltage range and the required output voltage. Vehicle power nets vary widely: a nominal 12 V net actually ranges from about 9 V during cranking to over 15 V with the alternator running, and a 24 V net from roughly 18 V to 32 V.

Choose a wide-range input that covers the full span, for example 9‑36 V for mixed 12/24 V applications. The output voltage follows the load, commonly 5 V, 12 V, 24 V or 48 V. A converter can step the voltage down (buck) or up (boost).

Isolated or non-isolated - which fits?

An isolated converter galvanically separates the input and output circuits through a transformer. A non-isolated converter shares a common ground, is more compact, often cheaper and slightly more efficient.

• Choose isolated when ground potentials must stay separate to avoid ground loops and hum.
• Choose isolated for safety needs and protection against fault voltages from the power net.
• Non-isolated is enough when input and output already share the same ground, for example a simple voltage adaptation.
• Typical isolation strength is 1.5 kV, 2.25 kV or 3 kV between input and output.

Why do efficiency and ripple matter?

Efficiency states how much input power actually reaches the output. Good switching converters exceed 90 %, and the difference is released as heat. High efficiency reduces power loss, cooling effort and drain on the vehicle battery.

The output ripple is the remaining AC component of the output voltage, given in mV peak-to-peak or as a percentage. Sensitive sensors, audio and radio equipment demand a low value, often below 1 % or a few tens of mV. For non-critical loads like lighting the value matters less.

Frequently asked questions