12
\$\begingroup\$

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?

\$\endgroup\$
14
\$\begingroup\$

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.

\$\endgroup\$
3
  • 2
    \$\begingroup\$ Does this imply there's galvanic separation thanks to the opto-coupler? \$\endgroup\$ – sharptooth Jun 6 '11 at 14:43
  • 4
    \$\begingroup\$ @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). \$\endgroup\$ – stevenvh Jun 6 '11 at 14:52
  • 1
    \$\begingroup\$ Schematic showing opto-isolation block diagram showing isolation in feedback \$\endgroup\$ – endolith Jun 7 '11 at 18:47
1
\$\begingroup\$

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.

\$\endgroup\$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.