Power boost fed from a voltage doubler

[yeeshkul]

Guys can you see any troubles in feeding a Power Boost with 18V coming from a simple 555 based 9->18V DC voltage doubler?

[antonis]

Troubles in Voltage feeding, no..!!

Troubles in Current feeding, perhaps...

(I don't know about your Power Boost current demands but you can overcome it via a bypass power transistor..)

[yeeshkul]

The Power Booster current draw is about 4mA, so i suppose that should be ok. I am maybe a bit afraid of a crosstalk between the doubler and the audio paths.

[antonis]

I can't see any reason for this...

(but wait for someone who - maybe - have involved with such case..)

edit: Maybe you'll have a small problem with ripple voltage but you can overcome it with a bigger capacitor and - perhaps - with a simple RC filter..

[bool]

A simple CRC (pi-filter) at the doubler output using good low-ESR caps and a well designed ground return path should do it. Imho a 47 Ohm resistor should be good enough for the filter.

Also, a good low-ESR lytic should be placed between the 555's supply pins (8 and 1 iirc).

[yeeshkul]

Thanks. Do you mean i shall put the PI filter instead of the 22u output cap?

[antonis]

The 22μF cap is for "smoothing" output voltage...

bool means to place the filter after the cap (first filter's cap in parallel with the output cap..)

[yeeshkul]

That is what i mean, do i have to have there two separate parallel caps or just one with capacity of those two caps in parallel (the smoothing cap || the first filter cap)?

[bool]

Oh my ... just add a RC network to the existing output cap to form a CRC "pi-filter" (f.e. a 47 Ohm and another 22uF). That shouldn't be too complicated or what?

[yeeshkul]

that is exactly what i mean - to add it to the existing output cap. Thanks for the advice.

[Mark Hammer]

What frequency is it running at?

[yeeshkul]

I think it shall be about 2kHz ...

[antonis]

edited...

[samhay]

It is generally best practive to run these at frequencies above ~ 20 kHz so that any bleadthrough into the audio is not audible.