Simple PS Voltage Splitters Using Audio Amplifiers

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mediatechnology
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Simple PS Voltage Splitters Using Audio Amplifiers

Post by mediatechnology » Mon Aug 11, 2014 2:44 pm

"Simple PS Voltage Splitters Using Audio Amplifiers," Petre Petrov, EDN, February 11, 2014.

Note that the EDN website is often very slow to load...

https://www.edn.com/design/consumer/442 ... amplifiers

Part 2: https://www.edn.com/design/consumer/442 ... s--Part-2-
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Re: Simple PS Voltage Splitters Using Audio Amplifiers

Post by emrr » Tue Aug 12, 2014 10:16 am

Thanks, that's helpful to see.
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Re: Simple PS Voltage Splitters Using Audio Amplifiers

Post by JR. » Wed Aug 13, 2014 1:03 pm

This article is literally what the title says, reconfiguring audio amps to make PS splitters but not IMO an optimal solution. I have done this before much more simply.

#1 why connect the input power to ground? If it is floating like from a battery or floating transformer winding, why not float the input ground and connect V/2 to the outside world ground which will simplify grounding audio circuitry, chassis, et al.

#2 what needs to be clean and lowZ and what can be sloppy? IMO the PS rails can be sloppier than the ground, expecially if regulation is used on the rails.

If you have enough PS headroom, and if you know one side of the V/2 will draw more power than the other you can usually get away with half the active shunt circuitry. I did one design with +/-8V regulated rails for the audio path and a single +5V rail for the digital content. Since I knew the + rail would always draw more current than the negative side, I only needed one active shunt across the negative side to balance it out for the digital circuit draw.

Further if the final rails are regulated the unregulated split does not need to be precision. I think I got away with a single medium power transistor as the active shunt. The base of this power transistor was driven by a simple voltage divider across the input power rail (note the divider had an offset for the shunt transistor Vbe).

So my power splitter was all of one $0.40 transistor, and a few resistors... and my output ground was the actual real world ground.

JR

PS: is it just me or does anybody remember the old dedicated V/2 integrated circuits? I think one of the major IC makers tooled this up in the 70s(?) but had trouble selling them because it was easier and cheaper to just roll your own.
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Re: Simple PS Voltage Splitters Using Audio Amplifiers

Post by mediatechnology » Sat Aug 16, 2014 9:01 am

I thought that the article was over-thought and the solutions over-complicated but decided to post it anyway.

TI does have a simple rail splitter, the TLE2646, but it IMHO is a little noisy: http://www.ti.com/lit/ds/symlink/tle2426.pdf

I have used the LM317 and LM337 as active shunts, not for a rail splitter but a tracking supply "x" volts below the rail: viewtopic.php?f=6&t=600&p=6893
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