Power
Making the right choice: choosing between isolated and non-isolated DC-DC converters
By Giulio Bocciolini, product marketing manager modular & configurable products EMEA, TDK-Lambda P
owering modern electronic systems requires careful selection of the right DC-DC conversion approach. One of the key design decisions that engineers face is whether to use an isolated or non-isolated converter. Each option brings distinct advantages and trade-offs in areas such as safety, efficiency, system complexity, and overall design flexibility. Understanding when and why isolation matters can significantly influence system architecture and performance. This article explores the factors engineers should consider when choosing between isolated and non-isolated DC-DC converters. Modern electronics are increasingly complex. Product engineers are tasked with powering discrete loads with unique voltage and current characteristics, while facing pressure to improve efficiency and cost-effectiveness. Selecting a DC-DC power converter is a foundational design choice that determines whether isolation is required, with consequences that permeate the entire system design, impacting everything from safety and noise performance to size, weight, and cost. The difference between isolated and non-isolated converters lies in the concept of galvanic isolation, which physically and electrically separates two parts of a circuit. An isolated DC-DC converter uses a transformer to transfer power between its input and output stages. There is no electrical conduction path between the two sides; instead, energy is transferred across an insulation barrier via a magnetic field. This creates two galvanically separate circuits, each with its own electrical reference. This barrier is the key to an isolated converter’s most valuable features: safety, electrical noise mitigation, and design flexibility.
A non-isolated DC-DC converter, by contrast, has a direct electrical path and a shared common electrical reference between its input and output. While this direct
36 September 2026
In medical applications governed by IEC 60601-1, isolation requirements are especially stringent, with higher protection levels required where patient safety is involved. Meanwhile, in high-precision instrumentation, audio systems, and test and measurement equipment, electrical noise can corrupt sensitive signals and degrade performance. A common source of this noise is a ground loop, which occurs when interconnected pieces of equipment have different ground potentials, driving a noise current through the ground connection. An isolated converter is a powerful tool for breaking these ground loops. By powering a subsystem through an isolated converter, the DC ground connection between circuits is eliminated, silencing this noise source.
Figure 1: Isolated versus non-isolated DC-DC converter. Source: TDK-Lambda
connection precludes the safety and noise benefits of isolation, it allows for a simpler, more compact, and often significantly more efficient design. The magnetic components that enable isolation are bulky, heavy, and costly. They also contribute to various energy-loss mechanisms in a power- conversion system.
This difference creates the central trade- off. The isolation barrier provides unparalleled safety and noise immunity, but comes at the cost of increased size, weight, complexity, and price. Conversely, a non-isolated converter offers superior performance in terms of efficiency, power density, and cost, but can only be used when the system architecture does not demand isolation.
Components in Electronics
Making the case for isolation Isolated DC-DC converter selection is typically driven by requirements for safety, electrical noise immunity, or functional flexibility that a non-isolated converter simply cannot meet. The most compelling reason to select an isolated converter is safety. In any system where the power converter is connected to a hazardous voltage, such as the AC mains or a high-voltage DC bus, an isolation barrier is generally a non-negotiable requirement to protect operators, users, and downstream electronics from potentially hazardous energy levels. If a fault occurs on the high-voltage primary side, the dangerous voltage cannot pass through to the accessible low-voltage secondary side.
In complex systems such as industrial process controllers, different subsystems often operate with their own local ground references. Powering these from a common, non-isolated source can create unintended current paths. In systems with high transient loads, such as pumps and motors, temporary ground potential differences can also arise when current flows through ground impedances. Isolated converters allow each subsystem to maintain its own ground reference while receiving power from a central source.
Finally, the floating nature of an isolated converter’s output offers valuable design flexibility. A key application is generating a negative output voltage from a positive input. By connecting the positive output terminal of an isolated converter to the system’s primary ground, the negative output terminal will present a negative potential relative to that ground. This technique is commonly used to generate the -48 V supply required in many telecommunications systems, eliminating the need for a dedicated negative-output converter.
www.cieonline.co.uk
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