-VE Voltage Regulator

Hi Pratish,

         Can you elaborate a little bit more about the application you have in mind? It seems very interesting that you have the need of both a positive and negative very high voltage rails.

             Victor.

Hi Pratish,

i see that Victor has responded before me.  So I will only say that of course you could use the TL783 by referencing the circuit to the negative rail and the input voltage to ground.  The resistor divider circuit will need to be recalculated to account for fact that the negative output is now referenced to the negative rail instead of to ground.

Bill 

When i called TI technical Support this after noon, i was told that the design was not possible by swapping the ground and the input. That is why i posted my question here in the forum to see if the community had any idea on how this can be achieved. I will give it a try.

This power supply for a ultrasound unit. It will provide high voltage to a pair of MOSFET which will generate a bipolar pulses of +-120V, Which will be used to detect vibration using some transducers. 

Thank you Very much for your suggestions!

Hello Pratish,

If the negitive input voltage is floating then the output (using standard +120V design) can be grounded and the return lead can be used as a -120V output.
Floating means no connection to ground; for example a isolated transformer tap.

Regards,
Ron Michallick

The Negative voltage is coming from a transformer, and a bridge rectifier, and some smoothing capacitors!

Pratish,

That qualifies as floating; so it can be used with a TL783.

Be sure the input to output differential on the TL783 is never greater than 125V including start up, power down, and load faults.
The TL783 has a high drop out voltage, si Vi-Vo can't be too small either.

Regards,
Ron Michallick

Does anyone have any reference on how this can be attained? i tried a couple of different approach in getting the the negative voltage from TL783 but i failed.

Any reference or a schematic available?

Will this work?

Pratish,

You would have less ripple with a full wave bridge rectifier. The series 100k resistors need to be removed.

The feed back resistors try to set the output voltage at 1.25V * (114k/120ohm+1) = 1,089V
Try replacing 114k with 10.44k

Please be very careful, the voltages in this circuit are dangerous.

Regards,
Ron Michallick

Hi!

After a successful simulation of the circuit attached, i built the circuit just to be disappointed. The simulation gave me +- 100V on each end, but when i built the circuit on a PCB, i ended up getting an unregulated +-183.3V. The regulation circuit didn't do a thing.  

5126.End_of_Semester_Presentation.pdf

On the design, i was using the center from the center tap transformer as ground to all the other ground. but now that i attached the  input from the center to the input of the regulator, my circuit doesn't have a ground anymore. Could this be the reason for not getting the right voltage? If so, how do i find a ground in my circuit?

Anyone has any other solutions?

I finally got it to work. Thanks alot for all your  help...