Unsymmetrical Dual Rail power supply

[Llamarama]

Hello everyone, I want to make a dual rail power supply, but with unsymmetrical outputs. I need +13v and -10v. I will need to supply around 100mA, so that rules out a voltage divider. I found a circuit in the Datasheet for an L165 Power op amp that looks like it would be ideal, but i'm having trouble sourcing these, so I'd rather avoid them. Does anyone have other circuits I could try? Thanks, Mike

 

[Les Jones]

Use a 15 = 0 - 15 vollt secondary transformer with a bridge rectifier and capacitors. Regulate the positive rail using an LM317 and regulate the negative rail using an LM7910 (Or an LM337) 15 - 0 - 15 is a little on the high side for voltage but the next standard one down (12 - 0 - 12)would be too low.

Les.

 

[ronsimpson]

1000 words:

 

[Llamarama]

Thanks for the quick replies, I forgot to mention, this has to run off a DC supply! Sorry guys!

 

[audioguru]

You did not say why you need a negative supply. I would use a 23V supply and bias the opamps or transistors at +10V and use input and output coupling capacitors.

 

[Les Jones]

You have now forgotten to give us information on the DC power supply.

Les.

 

[tomizett]

Yep. How many volts is the DC supply? Also, do you need any particular relationship between the incoming DC supply and your +13V, -10V outputs - for instance:
is (+supply in) connected to (+13V out) or
is (-supply in) connected to (-10V out) or even
is (-supply in) connected to (ground out).

I wonder if the L165 is discontinued? It used to be pretty standard. A quick look on RS turns up the LT1010, which is in the same category, but there might be cheaper options.

 

[Llamarama]

Sorry for the lack of details, the perils of writing a post in between jobs

I need +13v and -10v so I can run a Fluke 8050A I got with a dead mains transformer off batteries, which would also be more useful for me rather than to replace the transformer.

I have a stash of step up DC-DC modules I can use to step whatever battery voltage I have up to 23v rail to rail.

I think the L165 is long out of production, but leafing through the datasheet for the LT1010, there's a very similar circuit so I think i'll order one of them and breadboard it. Thanks

 

[Les Jones]

Here is a link to a good range of isolated DC to DC converters. I think you should fine something here when you decide on your primary power source.

Les.

 

[ronsimpson]

I have a stash of step up DC-DC modules

isolated DC to DC converters

12V battery step up to +13 and a isolated converter to make -10V.
The isolated output(+) goes to ground and output(-) is -10V

 

[tomizett]

It might be advisable to go with a linear post-regulator or some extra LC filtering, to keep switching noise out of the meter. I don't know how sensitive it would be to this - maybe others can comment?

 

[Colin]

Just put 4 or 5 diodes in the -10v line to reduce the voltage.
Then go out and buy the CRAY computer to scrounge the diodes.