Galvanic isolation in MEAN WELL power supplies


Ensuring electrical safety when using electrical and electronic devices is a key requirement that must be met without fail, without exceptions. There are a number of measures that ensure electrical safety in various parts of the network and load connection circuits. One of the effective ways to protect against electric shock, implemented directly in the power source (AC/DC converter), is galvanic isolation.

Galvanic isolation or galvanic isolation is the general principle of electrical isolation of the considered electrical circuit in relation to other electrical circuits. Due to galvanic isolation, the transmission of energy (or signal) from one electrical circuit to another is carried out without direct electrical contact between these circuits. To ensure galvanic isolation, MEAN WELL uses two main technical solutions:

  • inductive (transformer) galvanic isolation, which is used in most topologies of pulse-type power supplies.
  • optical isolation by means of an optocoupler (optocoupler) or optorele, for signal circuits.

In the documentation, MEAN WELL in most cases provides an enlarged block diagram of the power supply, without disclosing the actual topology, which indicates, among other things, the type of galvanic insulation and the place of its installation. Transformer galvanic isolation is used in the channel of the main conversion (the use of additional transformer windings is also allowed) – designated as number 1, and optocouplers in feedback circuits – number 2 (for example, the HDR-100 series):

Структурная схема AC/DC преобразователей на DIN рейку серии HDR-100Block diagram of AC/DC converters on DIN rail of the HDR-100 series

Low-power power supplies, like the presented HDR–100 series, can have an electric shock protection class II - often found in network adapters, for example, the GST18E series, as well as low-power modules designed for installation on a printed circuit board, for example, the IRM series. In this case, complete isolation is provided between the input and output of the power supply. However, the vast majority of MEAN WELL power supplies have an electric shock protection class I (for example, the SDR-960 series).

Структурная схема AC/DC преобразователей серии SDR-960Block diagram of AC/DC converters of the SDR-960 series

A feature of power supplies with this class of protection is the mandatory connection of protective grounding (FG), which is connected through decoupling capacitors to both the input and output of the power source, including the device housing. In this case, the power supply also has a galvanic isolation between the input and output, however, for power supplies with electric shock protection class I, it is important to comply with the installation and operation requirements.

For DC/DC converters, galvanic isolation is not a mandatory requirement for electrical safety, however, in most switch-type power supply topologies, the use of a separation transformer is necessary, therefore, galvanic isolation is also provided in power supplies of this type. For example, galvanic isolation is available in DC/DC converters of the case type of the SD, RSD series.

As a rule, the flowchart and technical features are presented in the Specification for the power supply, but if you have any questions, as well as questions related to the selection and use of MEAN WELL products, you should contact the email address .