Galvanic isolation: what it is, how it works and when it is needed

February 27, 2024

Introduction

Galvanic isolation (G.I.) is a fundamental technique in the field of electronics and electrical engineering. It consists of electrically separating two circuits in order to prevent current flow between them.

In this article we will analyze in detail what G.I. is, how it works and when it is needed. We will explore the various existing methods of galvanic isolation and the most common applications of this technique.

What is galvanic isolation

In electronics, galvanic isolation (also called electrical isolation) indicates the electrical separation of two circuits through the insertion of an insulator between them.

This prevents current flow between the circuits and makes them electrically independent. The two circuits always share the ground reference, but have no conductive connection between them.

G.I. is used mainly for two purposes:

  • Protect people from electric shocks
  • Protect electronic circuits from damage and malfunction

By electrically separating two circuits, the risk that dangerous voltages and currents in one circuit can affect the other is eliminated. G.I. is therefore fundamental for safety in the electrical and electronic field.

galvanic isolation
Electrician working

How galvanic isolation works

There are various techniques for achieving galvanic isolation between two electrical circuits. The most common methods are:

  • Isolation transformer: uses the principle of electromagnetic induction to transfer signals from one circuit to another without conductive connection.
  • Optoisolators: use optical components (LEDs and phototransistors) to transmit light signals instead of electrical ones.
  • Capacitive couplers: take advantage of a capacitor’s ability to transmit high frequency signals from one circuit to another.
  • Digital isolators: integrated circuits designed to receive a digital signal on one side and regenerate it identically on the other galvanically isolated side.

Each of these methods exploits different physical principles to transfer signals without creating a conductive connection between the circuits, thus ensuring perfect G.I.

When is galvanic isolation required

G.I. is required in many electronics and electrical engineering applications. Here are the most common situations where it is necessary to electrically isolate two circuits:

  • Interfacing between high and low voltage circuits: for example between the power grid (230V) and low voltage electronic circuits.
  • Protection against interference and discharges: isolation prevents malfunctions due to dangerous voltages/currents from other circuits.
  • Reduction of ground loops: ground loops that can cause interference and hum in electronic circuits.
  • User safety: mandatory for medical, domestic and industrial equipment to protect people from electric shock.
  • Measurement of floating signals: when measuring voltages that are not referred to ground.

In summary, whenever there is a potential difference between electrical circuits, it is good to use G.I. to ensure safety and proper functioning of the system.

Conclusions

G. I. is a fundamental technique for electrically separating two circuits operating at different potentials. It guarantees safety for humans and prevents malfunctions and interference in electronic circuits.

There are various methods to achieve galvanic isolation by exploiting different physical principles. It is required wherever there is a potential difference between electrical circuits, in particular to interface high and low voltage systems.

References

Galvanic isolation – Wikipedia

Principles of operation of galvanic isolation

Galvanic Isolation: What It Is And Why It’s Necessary

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