reliable dual voltage schematic

[Renegadrian]

Hi, it's a couple of days I try to google for a reliable dual voltage splitter...I want a (almost) ripple-free ckt that is gonna give -9v from 9v I got one with 555 working but diodes on the output take out some voltage, is it possible to have a full 9v 0v -9v supply out of your regular wall wart input?! thank you guys!

[armdnrdy]

For a single effect onboard supply look up LT1054CN charge pump.

[italianguy63]

Or TC1044SPCA.  Search the archive for "Charge Pump"-- we had an in depth discussion about it with schematics a couple months ago.  MC

[Renegadrian]

right thanx guys - I was looking back at the schem I posted looooooong time ago in the voltage multiplier thread...it can give also a negative voltage - I mean the one with just 4 trannies.

[Renegadrian]

I should have a 7660 around or maybe a 1044...In the meantime, I tried that ckt I mentioned with 3 bc547 and 1 bc557, it works but it has a 2v voltage drop, I guess the 1n4002 are to blame...do those other ckts with 1044 or 7660 have that drop on the negative side?!

[italianguy63]

Working from memory here.. When I used the 1N400x I was experiencing about a .8V drop.  I stopping putting the diode in series for reverse protection, and instead used it as a path to ground for reverse polarity protection.  On the output of the charge pump, I used a 1N5817 (in series) instead to stop back-flow back into the charge pump; it has far less of a drop.  I think like .4V.  I assume you are using the 1N400x in a rectifier type situation-- so not much getting around it.  In my charge pump experience.  I am getting right at -9V out.  I lose about a 1/2 a volt.  MC

[garcho]

Rectify an AC wall wart. 12VAC + regulation = +9VDC/-9VDC

EDIT: corrected my math

[samhay]

You can get +/- V(in) if you use the basic charge pump (7660S, 1054 etc) voltage inverter circuit.

However, if you want a really quiet regulated supply, you could try the 'bipolar supply doubler' shown in the 1054 data sheet. It works with other charge pumps too, and you can then use voltage regulators to give you +/- 9,12 or 15V.

http://cds.linear.com/docs/en/datasheet/1054lfg.pdf

Edit - it's not a great solution if you need signficant current draw. What do you want to power?

[Renegadrian]

it should power a simple tl074 so not much current I s'ppose...have to check its datasheet...

[Renegadrian]

Yep, I can do the same with that layout too...
http://www.sm0vpo.com/power/vconv_01.htm
but I guess it's overkill, I read somewhere it's not so important to have the same voltage and different values will work the same.

[SISKO]

I made myself a 555 charge pump/inverter to power the negative rail on my XP100 whammy. Works fine excepet for a low level whine when certain leds are tunrned on on the display. Cant find why it happens, but i can live with it

[italianguy63]

I've had LED noise before too.  Fixed easily with a cap/resistor filter on the LED leg.

[SISKO]

I've had LED noise before too.  Fixed easily with a cap/resistor filter on the LED leg.

Was a continous whine or a pop when the led turned on/off?

[samhay]

it should power a simple tl074 so not much current I s'ppose...have to check its datasheet...

A charge pump should happily do this.

[duck_arse]

sisko, do you mean a single led, or one of the led digits?

[italianguy63]

Yes.  I was able to isolate that it was LED noise (background hissy whine)  and not the charge pump by disconnecting the LED.  So, the LED was "noisey" and I filtered it.  (Just one of my experiences).

[SISKO]

sisko, do you mean a single led, or one of the led digits?

One of the led digits. I tought it was some kind of heterodying, but varying the frecuency of the 555 inverter did not "move" the frecuency of the whine.

[duck_arse]

the seven segment display is possibly multiplexed. big # like 88 load up the supply, and also add lots of hash. you can sometimes hear multiplexing hash increase with counting displays.

[SISKO]

the seven segment display is possibly multiplexed. big # like 88 load up the supply, and also add lots of hash. you can sometimes hear multiplexing hash increase with counting displays.

Yes, that probably is the problem. Any known solution? Maybe what  italianguy63 said..

[duck_arse]

probably powerline filters, and seperating all the digital supplies. although, even if you could hack some into yr box, you might still end up with hash in earth returns and stuff.