how to generate +5V\2ma from a -90V\1A floating dc\dc ...?

[bulerias]

hi,
as wrriten on the subject,i have a dc\dc that supplies -90V,and i need to
supply also +5V\2mA,on the same ground.
i thought on linear regulator,to save space & money...but how should i connect the ground between the -90 and the +5V...? (THEY MUST BE ON THE SAME GROUND !!!)...?
THANKS
Bull

 

[techie]

2ma is not hard to get. Use a simple shunt regulator to get -12v from -90v. then put a 4069 IC on that rail. make an oscillator. then use clamp diode circuit to invert the voltage to get something like +9v. regulate it to get +5v and enjoy

 

[jzaghal]

Re:5V dc at 2ma

Hi,

I would wind a length of insulated thin wire on the ferrite transformer or
coil , rectify using a 1n4148 , filter with say a 1 uF cap, obtain a dc
voltage and regulate using 5.1V zener. Don't forget to use a resistor
depending on the dc voltage you get across the 1 uF.

Hope I've been of help.

 

[bulerias]

Re: how to generate +5V\2ma from a -90V\1A floating dc\dc ..

hi,
as wrriten on the subject,i have a dc\dc that supplies -90V,and i need to
supply also +5V\2mA,on the same ground.
i thought on linear regulator,to save space & money...but how should i connect the ground between the -90 and the +5V...? (THEY MUST BE ON THE SAME GROUND !!!)...?
THANKS
Bull

can someone send me pls..a basic circuit...?
(i know its a big request...)
Thanks
Bull

 

[bunalmis]

Re: how to generate +5V\2ma from a -90V\1A floating dc\dc ..

You say this power supply must be floating and you want same ground.

Floating Supply's inputs and outputs has galvanic izolation.

Sory second sch. for +90v