how to get a bi-polar dc outputs from a single Battery!

[SOSx]

Hi All,

I am working on a project that is looking to use Lifepo batteries to power
Hypex OEM amplifier modules which have bipolar (+- outputs).

I have found a few very small dc-dc step up convertors with dual bi-polar outputs
but they are all in the 1- 40w range and i really want something that is either capable of 120-200w at +-15-20v or 200-300w +-30-40.

There is the option of using 2 battery packs with the positive on one tied to the negative on the other. Leaving the possitive from one pack and negative from the other. But I am unhappy with this solution as it it leaves the possibility of one rail loosing power completely if (as) the the batteries reach full discharge un-evenly.

Any suggestions/links?

Cheers

[cliffforrest]

Originally Posted by SOSx

Hi All,

...................

There is the option of using 2 battery packs with the positive on one tied to the negative on the other. Leaving the possitive from one pack and negative from the other. But I am unhappy with this solution as it it leaves the possibility of one rail loosing power completely if (as) the the batteries reach full discharge un-evenly.

Any suggestions/links?

Cheers

High power inverters are not easy to do at that power.

Dual batteries are ideal.

If your amp cannot survive loss of one rail it needs redesigning.

It is not difficult to construct an op-amp/comparator that monitors the rails to be within (say) 0.5V of each other and only connects them when they are.

[Andy5112405]

At low voltages like these it is easy to design and build an SMPS that will supply the +/- rails with no danger of the loss of one rail.

Try looking at the TL494 datasheet for ideas.

[Andy5112405]

If you want a simple circuit.

Regulate the battery down to 5V for a simple NE555 oscillator running at 100kHz.

Feed the 100kHz into a D type Flip Flop and use the anti-phase outputs Q and Q(bar) to drive a pair of High Current MosFETs.

Using a Ferrite Core. Make a simple centre tapped (Primary and Secondary) so that the MosFETs can drive the primary in Push Pull.

You can then have one or two secondaries to produce the voltages that you require.

At low voltage the designing is not complicated.

The TL494 would allow for SMPS regulation at source but this may not be necessary in your application.

There are other SMPS chips out there. Use the DIY spirit to see what you can do.