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I am trying search something which I can use to convert 220V-DC to about 30-50V DC. I don't want it to be a transformer. I found some voltage regulators providing required output but not having the required input, so all useless, but there may be some available which escaped me. You can also suggest something, which I can make at home but not too advanced for a Senior High School student. Thanks.

Edit (Thanks to @Transistor, @Asmyldof) I am trying to make a air cleaner, so trying to power an electric motor having the given range requirement, ie, 30-50V DC. I am converting the 220v AC mains supply to 220v DC(slightly lower) using 'bridge rectifier', which I had already made and tested. I will also use 'filter capacitor' in the circuit (parallel) before the regulator.

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    \$\begingroup\$ "I don't want" is not a technical reason. "I only need 2 mA and a 50g transformer would be too heavy" is. So, give us the problem you're actually trying to solve. \$\endgroup\$
    – Marcus Müller
    Commented Dec 10, 2017 at 9:57
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    \$\begingroup\$ Also be aware that you seem to be designing a non-isolated power supply so that the low voltage side will be at mains potential and, for that reason, rather dangerous. What do you want to power with this circuit? Put all the information into the question and not in the comments. \$\endgroup\$
    – Transistor
    Commented Dec 10, 2017 at 10:20
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    \$\begingroup\$ And also include in that description of what it is you actually want to do and why, where does the 220VDC come from. \$\endgroup\$
    – Asmyldof
    Commented Dec 10, 2017 at 10:22
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    \$\begingroup\$ You can't design a regulator for anything without knowing how much power it requires. \$\endgroup\$
    – Finbarr
    Commented Dec 10, 2017 at 11:10
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    \$\begingroup\$ @user171450 That will produce 310V DC without the motor connected but with a capactitor on the output of the rectifier. Once you connect a load (the motor) it will drop. What it will drop to depends on the motor and the capacitor. \$\endgroup\$
    – Simon B
    Commented Dec 10, 2017 at 11:11

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Producing 220V unregulated DC is actually making life harder for yourself. Buck regulators aren't normally specified to take that high an input voltage.

If you are certain that nobody will be able to touch any live parts, then a simple capacitive dropper circuit may work. But it's difficult to design properly without knowing the current that will be drawn by the motor. If it's too high, then the thing may end up more bulky than just using a transformer.

In particular, you'd need to know the starting current of the motor, which is normally a lot higher than the running current.

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