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For my application, I need three voltages +5V, +15V, -15V

Initially, I was using wall socket plugs to connect two 15 volt adaptors, in which I connected the + and - together and considered it as ground, and used that common ground connected to another wall adapter (5V)'s negative to get a common ground, and all my voltages +5V, +15V and -15V.

Since this is cumbersome, I wanted to streamline my power supply, I got a USB-C PD adaptor (capable of giving 20V), and three off the shelf module of LM2596 from amazon, along with a USB-C PD power negotiation chip (zy12pdn). However, wiring it up as mentioned above leads to a short.

Below is the circuit diagram that I am using, previously it was wall adaptors, now its buck converters, now this leads to a complete short and stops USB-C PD from working.

  • Can adding diodes help the situation?
  • Is there something wrong with this approach?
  • How can I fix it?

Here is my rough circuit diagram

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  • \$\begingroup\$ That's simply not fixable with these converters. But there are switching converters which can generate a negative output from a positive supply. Better yet just buy a mains supply with the outputs you need. \$\endgroup\$ Oct 8, 2020 at 13:34
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    \$\begingroup\$ Ground on input and output are linked, so hard to see how you can achieve. You need a buck-boost for negative. \$\endgroup\$ Oct 8, 2020 at 13:39
  • \$\begingroup\$ I got a module off amazon amazon.com/dp/B07NTXSJHB based on XL6009, unfortunately, this too has a common ground. @StainlessSteelRat do you have any suggestions on how to work this out? \$\endgroup\$
    – sandeepzgk
    Oct 13, 2020 at 18:28
  • \$\begingroup\$ That shouldn't be a problem, if it set up for negative voltages. Your problem was common ground, while trying to use buck as a negative source. \$\endgroup\$ Oct 13, 2020 at 18:31
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    \$\begingroup\$ This will give you +15V and -15V. KNACRO 20W Micro Boost Step-Down Voltage Converter DC 5-40V to DC ±15V No idea on power needs. \$\endgroup\$ Oct 13, 2020 at 22:05

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This cannot work as on this type of buck converters, the - and the input and the - at the output are shorted. Let me draw those connections into your drawing:

enter image description here

Note how your "-15 V has a direct connection to ground.

You're also shorting (to ground) the + output of the most left converter.

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  • \$\begingroup\$ Can you point out what kind of buck conveter would work in such a situation ? \$\endgroup\$
    – sandeepzgk
    Oct 8, 2020 at 21:08

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