Does switched-mode power supply feature galvanic separation?

Question

I've carefully read Wikipedia article and can't get one important thing - is there galvanic separation in such supply?

The diagram in that article goes like this:

SMPS block diagram

What I see here is that the transformer is only on one path and there's the "output->chopper controller" path that bypasses the transformer. Usually the transformer is the unit that performs galvanic separation.

Does this mean a switched-mode power supply doesn't feature galvanic separation between the input and the output? Is it possible for unlimited current to flow through the power supply?

stevenvh · Accepted Answer · 2011-06-06T15:03:23.823

14

Not all SMPSs provide galvanic separation. DC/DC converters transforming between two low voltages in a circuit often don't. The block diagram, however, shows a mains connected SMPS, and most of those do have galvanic separation.

The feedback often goes via an opto-coupler, which indeed is missing in the article's block diagram. The signal is PWM, so a normal (digital output) opto-coupler can be used.

edited Jun 06 '11 at 15:03

answered Jun 06 '11 at 14:40

stevenvh

145,832
21
457
668

2

Does this imply there's galvanic separation thanks to the opto-coupler? – sharptooth Jun 06 '11 at 14:43
4

@Sharptooth - Yes. In the forward path it's the transformer, in the feedback it's the opto-coupler (between the chopper controller and the inverter chopper). – stevenvh Jun 06 '11 at 14:52
1

Schematic showing opto-isolation block diagram showing isolation in feedback – endolith Jun 07 '11 at 18:47

Leon Heller · Answer 2 · 2011-06-06T15:25:09.720

1

It depends on the supply. The ones used for laptops and mobile phone chargers have an isolated output which is achieved with a transformer. The high frequency used means that it can be very small.

edited Jun 06 '11 at 15:25

answered Jun 06 '11 at 14:35

Leon Heller

38,983
2
62
96

Does switched-mode power supply feature galvanic separation?

2 Answers2

Linked