How to build a 100 volt power supply?

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coppils7

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Hello,
I need a power supply which outputs 100 volt DC, and at least about 10-50mA. Preferably it would be variable from 0-100 volts (in steps of 5 or 10 volts is totally ok, and if it is quite simple I don't need it to be variable, I can build a few with different output). I have 230v AC mains, should it be done with a transformer and rectifier and something more, or would it be easier to step-up for example 12 or 24 volt DC? Is it possible to use an op-amp to step up voltage to 100 VDC? I would maybe prefer to step-up a lower DC voltage, but anything is okay.
 

Dear Coppils
Hi
As i understood , you wanna build a 0-100v variable power supply with 50ma current. so you can use a series ceramic capacitor with the power line and then you can rectify it and ...... BTW , i think if this supply be not isolated , it will be harmful and dangerous , and if you are beginner , i suggest you , don't try to do it , because it is dangerous . but you can do it with switching systems , or a simple low current transformer ( 230/110).
Best Wishes
Goldsmith
 

Get a variac with a 1:1 transformer for protection and a fullwave rectifier to make DC.
 

Dear klystron
Hi
AS i know , the variacs are based on auto transformers , what are not isolated.
Respectfully
Goldsmith
 

I agree with Goldsmith, that is why I sugested a 1:1 isolation transformer for protection (see my post) The 1:1 transformer is on the output of the variac.
 

Having no mains isolation in supplies is QUITE DANGEROUS. The best safe method is use as Isolated Transformer and a Rectifier. For making it variable a controlled Thyristor circuit can be used in the Primary Side.
 

Would it work to use a regular "house lamp dimmer" for 230VAC and then rectify it's output? That would be simple, but would it work? And is it possible to use a 230v -> 110V conversion transformer instead of an isolation transformer, as they are quite expensive? I mean a transformer that is used for using 110V devices from 230V..

If I don't need it to be variable, would there be some easy way to build it?
 

Again HI
Yes it is possible . but you should filter it correctly and you should use EMI before that to prevent from harmonics interference . and again it will has hazard for your health ( because it is not insulated)
Best Lucks
Goldsmith
 

Mains AC can be dropped to a lower voltage by inserting a capacitor. It's useful when you only need small current, as with lighting an led.

Example, this link:

Marc's Technical Pages: Mains LED

A diode bridge will convert to DC output.

It may be hard to get exactly 100V. If you have a particular load then you must experiment to find the particular value of capacitor to give 100 V.

Or you can use a zener diode, or several in series, to regulate to 100V.

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If you don't wish to use mains power, then a DC supply can be stepped up using a switch mode DC-to-DC converter, containing an inductor.
 

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