Question: Please I really need suggestions on this.
I want to generate a -/+50V dual-rail at >=100mA supply for a circuit I am working on.

I bought 2 copies of this boost converter module from Amazon and it converts 9V to 50V no problem.
<https://support.envistiamall.com/kb/xl6009-dc-dc-5v-to-48v-boost-step-up-converter-power-supply-module/> However, when I tried to get the negative rail by connecting the positive Vout+ of one board to the negative Vout- of the other to create a ground so as to have a +50V, a -50V, and a ground, I got sparks. I later thought that the board might be built in such a way that the negative output Vout- is connected to the input voltage ground for safety, and when I connected Vout+ to the other Vout-, I short circuited the supply….which makes sense. (May be that is also because I was testing it with the same desktop power supply instead of 2 separate 9V batteries)

But now it is the weekend, the lab is closed and I am out of solutions. I saw this IC on AD ([LT8471](https://www.analog.com/media/en/technical-documentation/data-sheets/8471fd.pdf)) that can do what I need but it has an incredibly long lead time which I cannot afford.

I also contemplated using a NE555 timer to do what I want, but that chip has a maximum current output of around 50mA (I need 100mA). The LTspice simulation produced an output voltage of 50V, current 800mA. But I doubt it will handle what I want.

Please I would appreciate any suggestions. Thanks in advance!!!!

Answer: 
Your explanation about why you got sparks is probably right: most DC-DC converters (and all really cheap ones I've used so far) have a common ground between input and output.

I don't think it's for safety (I would even say that isolated output is safer), but it is cheaper and simpler, and OK for 98% of hobbyist projects (+ it avoids the begginer's mistake to forget to connect grounds together).

So if you want to generate a -50V as you suggested, then you need either isolated DC-DC converters (it is usually written explicitly), or you need to use independent supplies (without connecting their grounds): two 9V batteries are a good solution for this (if you use main connected supplies, make 100% sure they are fully isolated).

WARNING: most DC-DC converters can not handle to sink current on the Vout+ pin, not to source current on the Vout- pin: if you want to go this way, make sure you don't have any current going "the wrong way" (if need be, post you schematics for other people to check).

Otherwise, the "normal" solution would be to buy either a symetric supply, or a negative voltage supply.

I would also suggest you do some readings about electrical safety if you are not familiar with it: 100V DC starts to be dangerous (48V DC is the maximum considered "safe by default").
> 
> I want to generate a -/+50V dual-rail at >=100mA supply for a circuit I am working on.
> 
> 
> 

Here is an inverter that supplies the 2 voltages simultaneously.  

Just use PWM for driving, with some "protection" to be provided.  

Transformer should not be too hard to find or make.
Note that 2 A (or more at starting) are needed for generating the outputs voltages. (around 2 \* 7 W ... for 2 \* 50 V - 100 mA outputs).

[![enter image description here](https://i.stack.imgur.com/UN75e.png)](https://i.stack.imgur.com/UN75e.png)