buck boost/step up ? battery to constant 18v

[rompelstilchen]

Hi,

I want to power an lm386 that can receive up to 18v supply
I use a 9v battery,(I could put two in serie), but I dont want the power of the amplifier to depend on battery voltage that will go down as time goes by

but I am not sure what ic/circuit I should use, I been looking a couple of days on google about this but I could not find any relevant info/tutorial

thanks

 

[larry_walker]

Hi,

As far as I understood your problem, I think you need a voltage regulator.
If so, you should take a look to an LM78XX (LM7805 for example).

Cheers.

 

[Warpspeed]

The simplest circuit would probably be a buck/boost converter.

https://en.wikipedia.org/wiki/Buck–boost_converter

With this, a negative input voltage is converted to a positive output voltage (or the other way around).

This has a couple of advantages apart from its simplicity.
Voltages can be converted either up or down (or both) if required.
And its pretty safe, in that if it blows up, it just stops working without the possibility of damaging whatever is on the output.

 

[rompelstilchen]

Hi,

As far as I understood your problem, I think you need a voltage regulator.
If so, you should take a look to an LM78XX (LM7805 for example).

Cheers.

well I dont think that a lmxxx would do step up
when the battery is 3v low, an lm cant go abeve that input voltage
otherwise we would not have invented boosters

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I know but I was wondering if anyone knew an IC that does 18v constant output

 

[rompelstilchen]

https://www.pololu.com/product/799

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besides, voltage regulators, when bucking input voltage, convert unecessary voltage to heat, wich can lead to use heatsinks and waste a lot of energy

 

[treez]

so you have to convert a voltage that is 3v to 18v input, to 9v output?

What is the power level?

If I were you, I would use a mini-boost converter to boost the 3v situation up to a decent bias voltage for the main converter ic, which would be a sepic controller, which could give you your 9v output from 3 to 18v input.
When vin rises above 3v, the boost converter would just get swamped and shut down, which is fine as it can do that...just put a diode from vin to vout of the boost. It is called "swamping"