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I found an interesting e-bay listing: LM317 DC-DC 1.5A Adjustable Step-up Boost Voltage Converter Module 1.2-37V

Now I am a beginner, but I know the LM317 is a step-down regulator, and I couldn't find any reference on it being used in a voltage boost circuit. This forum even talks about it's impossibility. The picture on ebay also "smells like" a standard step-down circuit. Considering these I am 95% confident that the module for sell is actually step-down circuit, but I would like to ask your opinion anyway:

Is it possible to make a reasonably simple voltage boost circuit based on the LM317 voltage regulator?

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  • \$\begingroup\$ No. 11 more characters. \$\endgroup\$
    – winny
    Commented Jul 29, 2016 at 22:21
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    \$\begingroup\$ You can make a buck converter out of one, so it may be possible to make a boost converter. But the image lacks the very obvious inductor that would be required. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jul 29, 2016 at 22:37
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    \$\begingroup\$ "... but I know the LM317 is a step-down regulator ..." - Be aware that you're mixing terminologies here. We distinguish linear regulators (the category a LM317 belongs to) from step-down converters (or buck converters). The two categories vary in operation principle, efficiency, and properties such as output ripple. \$\endgroup\$
    – marcelm
    Commented Jul 29, 2016 at 22:47
  • \$\begingroup\$ With an eingangspannung of 4 to 40v, and an ausgangspannung of 1.2 to 37 volts, it's clearly a step down regulator, and clearly matches an LM317 linear regulator specifications. At least the numbers translate unambiguously, and allow the emptor to caveat. \$\endgroup\$
    – Neil_UK
    Commented Jul 30, 2016 at 6:21

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No. It's clearly an LM317 standard linear voltage regulator circuit.

enter image description here

Bear in mind that it's advertised in English on eBay.de so there may be some noise in the translation.

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    \$\begingroup\$ The German text is just as messy as the parts that leaked through in English. Given that the seller is based in China somewhere, this is not surprising. Nor is it surprising that it is being sold as something it isn't. \$\endgroup\$
    – JRE
    Commented Jul 29, 2016 at 22:25
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    \$\begingroup\$ And eBay has 2 magic words: caveat emptor. \$\endgroup\$
    – WhatRoughBeast
    Commented Jul 29, 2016 at 23:12

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