Power Converters – To Isolate or Not To Isolate, That Is The Question

Power converters are among the most critical pieces of electronic equipment, with a host of both everyday devices and industrial equipment depending on them to function. You can run into converters in both isolated and non-isolated versions. Let's subject both to closer inspection in this article.

Isolation in Power Converters Summarised

In isolated converters, the input and outputs are physically separated by dividing the circuit into different sections. This prevents direct current from flowing between them. Usually, a transformer serves as the barrier between those two sections. In this configuration, each of the circuit parts has its own independent ground (If you're unsure what ground is, read this). However, the transformer or a similar device of this kind still manages to transfer some power between the circuits – otherwise you would have two completely independent circuits with no connection to each other.

In non-isolated converters, there is no such separation present and the current flows between the input and output directly, with a single common ground. That being said, let's go into further details in each individual case.

When Is Isolation Beneficial?

• Ground loop breaking
This is especially important in circuits that can't handle noise very well. Isolated converters can be used to protect these sensitive circuits from noisy ones that might cause unnecessary interference or even damage to them.
• Floating outputs
In isolated power converters, the isolated outputs have a stable voltage between output terminals, but they are not referenced to a different output – they are "floating" (for further explanation of floating, watch this video). Connecting the floating output terminal to a different circuit node fixes it to a different voltage and makes it possible to change the floating output voltage according to the particular need.
• Safety
Isolated power converters offer a high degree of protection from dangerous input voltage, which is mediated before reaching the output. There are varying degrees of protection in isolated power converters though, with some being much safer than the others.

What Are the Upsides to Non-Isolated Converters?

• Price
Money talks and sometimes using a non-isolated converter is more practical for pure financial purposes – provided safety is not compromised. The price of isolated converters is almost always higher due to the costs of building a transformer and providing additional levels of insulation. Other parts such as optocouplers also drive the prices of isolated converters up. This is not the case with non-isolated converters, which are cheap to build and its costliest part is just an inductor.
• Dimensions
Naturally, with less parts usually come the smaller sizes. Inductor-based converters are much more compact and, as a result, are even capable of working on higher switching frequencies.
• Performance
One of the biggest upsides of non-isolated converters in this regard is the ability to directly – and therefore better – control the output, which results in an increased performance. Their size plays an important role here as well, since they can be placed in the close vicinity of the output, which eliminates some of the transmission line noise that could hamper the performance.

Which of these two converters would you prefer in your project? Isolated or non-isolated? You can discuss their pros and cons below!

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