What should I looking for... single chip dc to ac inverter or split power IC? - Page 1
Forum section: electronics / general

author: beaker353
author_rank: Unknown
timestamp: August 27, 2011, 01:24:46 am
content: I need to build a circuit that either takes +30Vdc in and spits out -12Vdc'ish and +12Vdc'ish, or inverts the +30Vdc into an ac wave form large enough that I could bridge it down to -12Vdc'ish and +12Vdc'ish. (Gotta power an op-amps circuit that simply will not play nice with biasing the inputs. But works like a dream with a split voltage ps.) I would prefer the former, but either way would work. Only need about 150mA-200mA max of the split voltages, can go as low as 9Vdc, and as space and efficiency is not an issue I have no problem filtering the mess out of a nasty ac waveform if needed. What should I be looking for? (I know just enough about electronics that I know I don't know enough, I can only take so many electronics engineering classes at a time and work a 40 hour regular work week...)- EM

author: Psi
author_rank: Super Contributor
timestamp: August 27, 2011, 01:45:39 am
content: I'd probably use a TL494 to drive a transformer that has two 12v outputs.However the TL494 can only handle 200mA max on it's internal drivers so you'd probably need external drivers.There is probably a better chip for this that could do the switching itself, i just cant think of any right now.The TL494 is a very common chip though, with lots of information about.You'll probably spend more time building it than the $30 it would cost for a prebuilt 9-36V -> +/- 12v module.http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=102-1319-ND&x=13&y=20Not that it matters if your building it to learn stuff.You'll probably want to take SMPS ripple into considerations if this is for audio.EDIT: If you have plenty of current at 30V and don't mine producing some heat you could look at a 15V zener and resistor on the 30V. This would give you a 15V center which you could use as ground with a 7812 and 7912 to get +/- 12V

author: beaker353
author_rank: Unknown
timestamp: August 27, 2011, 02:10:05 am
content: That Digikey part is exactly what I was looking for. I'm finding that just figuring out what you need is called is half of the battle. Thanks Psi!

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2011, 01:38:08 pm
content: Could you be over-engineering this?Have you considered using a half bridge and AC coupling the output?That should work well even if you're using a virtual earth for the signal path.

author: ciccio
author_rank: Frequent Contributor
timestamp: August 28, 2011, 06:56:36 am
content: The simplest and cheapest solution (about 2 USD) is to use a virtual ground, such as the TLE2426.See the attached data sheet.It will give a real low impedance point, that you can use as a ground, at exactly half the supply voltage.You can also emulate it with some paralleled op-amps, one electrolytic and some resistors, but it will cost the same or more and give lower performances.Regards

author: ejeffrey
author_rank: Super Contributor
timestamp: August 28, 2011, 08:33:47 am
content: A rail splitter will only work if the power supply is floating or the input and output signals can be AC coupled.

author: Zero999
author_rank: Super Contributor
timestamp: August 28, 2011, 04:36:25 pm
content: Quote from: ciccio on August 28, 2011, 06:56:36 amThe op-amp works pretty well as long as the output is bypassed to the positive and negative rails with capacitors. The current output capacity can be increased by putting some transistors in the feedback loop.