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I was wondering if I could put two DC-DC boost converters in series.

Each of these converters is fed from a DC source which is basically a USB charger of 230VAC to 5VDC/1A.

The voltage output of these converters should have some fixed ratio (i.e. 2.)

enter image description here

enter image description here

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    \$\begingroup\$ Your title say series but your text body describes a parallel arrangement. Please draw a block diagram of what you are proposing. \$\endgroup\$
    – winny
    Dec 3, 2021 at 11:02
  • \$\begingroup\$ Picture added as requested. I'd add that I am using two MT3608 boost converters \$\endgroup\$
    – settimed
    Dec 3, 2021 at 11:45
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    \$\begingroup\$ Oh! Now it’s clear. Add a bypass diode across each and you should be good to go as long as the DC input sources are floating towards each other. \$\endgroup\$
    – winny
    Dec 3, 2021 at 11:52
  • \$\begingroup\$ That’s correct on the diodes. You should be good to go. \$\endgroup\$
    – winny
    Dec 3, 2021 at 14:19

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Yes. As long as the 5Vdc supply is electrically isolated from the mains and the dc supplies do not share a common ground, this should work without a problem.

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  • \$\begingroup\$ So I can do that without bypass diodes as recommended by @winny \$\endgroup\$
    – settimed
    Dec 3, 2021 at 12:05
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    \$\begingroup\$ You only really need a bypass diode in parallel with each capacitor if one of the boost converters fails. Then the bypass diode will activate under this fault condition. Keep in mind that in your picture, the connection of the bypass diode is incorrect. You need two diodes if you want to have this optional protection. \$\endgroup\$
    – mr_js
    Dec 3, 2021 at 13:00
  • \$\begingroup\$ I updated the figure to include your recommendation. I suppose that the added bypass diodes have the same electrical requirements as for the converters' diodes (current handling, reverse voltage blocking and switching speed). Please correct me if I am mistaken. \$\endgroup\$
    – settimed
    Dec 3, 2021 at 13:20
  • \$\begingroup\$ Boost or 5 V goes into OCP or similar. Cheap protection against that edge case. \$\endgroup\$
    – winny
    Dec 3, 2021 at 14:20

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