Negative power supply , high current

karas

Joined Sep 8, 2011
209
i need to get -12vdc , 1A and my input is 36vdc+-10% , i do not need to use the module , because it is expensive, and i am trying to use buck-boost and i need suggestions about IC to control my circuit

bushrat

Joined Nov 29, 2014
209
7912 ? That would be the easiest method..

dl324

Joined Mar 30, 2015
10,072
There is a wide variety of switching regulators that will do it.

What is the current capacity of the power source?

bertus

Joined Apr 5, 2008
20,329
Hello,

Perhaps the attached PDF might give you some ideas.

Bertus

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karas

Joined Sep 8, 2011
209
There is a wide variety of switching regulators that will do it.

What is the current capacity of the power source?
the input is 36Vdc and it is very high power(500W) and the output current of -12VDC is 1A

karas

Joined Sep 8, 2011
209
Hello,

Perhaps the attached PDF might give you some ideas.

Bertus
Thanks so much.

karas

Joined Sep 8, 2011
209
7912 ? That would be the easiest method..
my input is positive not negative , so u can not use it

dl324

Joined Mar 30, 2015
10,072
the input is 36Vdc and it is very high power(500W) and the output current of -12VDC is 1A
How much of that 13.9A is being used?

karas

Joined Sep 8, 2011
209

dl324

Joined Mar 30, 2015
10,072
for another circuits
Do you have 1+A to spare for the negative converter?

karas

Joined Sep 8, 2011
209
Do you have 1+A to spare for the negative converter?
yes, forget all the issues about the source, you have vin=36vdc and what ever current do you need

dl324

Joined Mar 30, 2015
10,072
yes, forget all the issues about the source, you have vin=36vdc and what ever current do you need
Had to ask because an unbelievable number of people think they can get something for nothing...

bushrat

Joined Nov 29, 2014
209
my input is positive not negative , so u can not use it
Is it possible to use 7812 and reverse connections? Output from 7812 to be used as 0V and the ground to be used as -12V? Similar to measuring positive voltage with multimeter leads reversed..

MrChips

Joined Oct 2, 2009
20,289
Is it possible to use 7812 and reverse connections? Output from 7812 to be used as 0V and the ground to be used as -12V? Similar to measuring positive voltage with multimeter leads reversed..
Not if the positive source power supply is referenced to 0V.

@karas One solution is to use a buck converter to supply the -12V directly.
Another solution is to build an oscillator, rectify and convert to about -15VDC and then use a 7912 three-terminal regulator.

MrChips

Joined Oct 2, 2009
20,289
The circuit you refer to works because the positive 12V regulator is galvanically isolated from the power source through a transformer.

Yes, if you can create a floating power supply then you can turn it into a positive or negative supply simply by choosing which node you determine to be your 0V reference.

karas

Joined Sep 8, 2011
209
Not if the positive source power supply is referenced to 0V.

@karas One solution is to use a buck converter to supply the -12V directly.
Another solution is to build an oscillator, rectify and convert to about -15VDC and then use a 7912 three-terminal regulator.
You mean buck boost converter and for the oscillator you have to use transformer and this a lot

AnalogKid

Joined Aug 1, 2013
8,310
Is it possible to use 7812 and reverse connections? Output from 7812 to be used as 0V and the ground to be used as -12V? .
No. Sketch it out, keeping in mind that there is no energy storage in a linear regulator. What pushes the ground pin down to -12 V? Also, with the input at +36 V, that'w 48 V between the regulator's input and GND pins, way outside it's spec.

ak