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I have been seeing a video about how boost converters works. I was wondering why one would choose a boost converter system over a transformer to step up voltage (except the fact that boost converter is for DC and transformers are for AC->as I understood it).

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    \$\begingroup\$ That last fact is so significant... \$\endgroup\$
    – user76844
    Jul 19, 2017 at 3:11
  • \$\begingroup\$ Unlike booster, transformer also provides isolation between input and output. \$\endgroup\$ Jul 19, 2017 at 5:00
  • \$\begingroup\$ The boost converter actually generates AC (by switching the DC) to step up, the coil providing the transforming. \$\endgroup\$
    – Transistor
    Jul 19, 2017 at 6:20

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That is it exactly. Transformers only work on AC. Put DC into a transformer, it will basically act as a short circuit.

A boost converter (actually any switching regulator) is actually just a way to use DC in a transformer by converting it to AC. In a simplified view, a boost converter consists of three parts: an inverter to turn DC into AC (square wave, not sine wave); a transformer; and a rectifier/filter to turn it back into DC.

The additional stuff I'm ignoring include a feedback system to vary the duty cycle of the square wave to regulate the output voltage and the fact that because the square wave is much higher frequency than the mains, the transformer can be much smaller.

Edit: it was pointed out that I was describing a flyback converter, not a boost converter. A boost converter instead uses an inductor to store and release energy as switched current (effectively AC) is fed to it. However, my point stands: in order to increase voltage from DC, you must turn it into AC first to allow something to transform it into a higher voltage.

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  • \$\begingroup\$ "... a boost converter consists of three parts: ...; a transformer; ..." - A boost converters is a specific topology that uses an inductor for the energy storage, not a transformer! Maybe you mean a flyback converter, which does use a transformer? \$\endgroup\$
    – marcelm
    Jul 19, 2017 at 8:20
  • \$\begingroup\$ @marcelm Yes, you are correct. My bad. \$\endgroup\$
    – DoxyLover
    Jul 19, 2017 at 15:27
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Transformers work on the Mutual Induction principle, which is not possible in DC

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  • \$\begingroup\$ It would be great if you could expand the explanation you give in your (correct) answer \$\endgroup\$
    – clabacchio
    Jul 19, 2017 at 15:14

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