Hey!
I came across this circuit (see attached picture) which is used to create a -15V from a 15V rail then used as an input for a negative voltage regulator.
I couldn't understand quite how the circuit works! Can someone explain this for me please?

PS: the 2 diodes are in the same die, and i am not sure of the orientation of diodes.
But GND is connected on the top pin, -Vin on left pin, and VDD on right pin of the SOT-323 package.



Thanks,

 

I came across this circuit (see attached picture) which is used to create a -15V from a 15V rail

If the +15V input is DC then no, that circuit won't generate a negative voltage.

Where did you "come across" that circuit?

 

There are many things wrong with this circuit.

The bottom half of the dual diode shorts out the 15V supply.
The top diode had Vdd on both ends.

 

If you add another capacitor and an oscillator.

Build Your Own Negative Voltage Generator - Projects (allaboutcircuits.com)

But you're not going to get much current.

You can use a switching regulator to generate a negative voltage.

 

If the +15V input is DC then no, that circuit won't generate a negative voltage.

Where did you "come across" that circuit?

it's not a schematic It's an IGBT gate driver that I am trying to fix. I think this negative voltage regulator is used to generate a -15V rail for fast turn-off of IGBTs and to prevent miller injection phenomena.
The diodes are a SOT-323 package and might be in a different configuration. I thought it could be a BAV99 but I guess I was wrong.

 

I think this negative voltage regulator is used to generate a -15V

That circuit won't work.