the 7555 as inverter, and regulating the result

[duck_arse]

seeing as I only ever do things the hard way, and seeing as I do have 7555's and diodes, but don't have any of those charge pump things, I have a question on regulating inverters.




I have built (bredbord) the core circuit above previously, but using a diode/cap multiplier to replace the inductor/mosfet/rect section. the voltage regulation seemed effective, although I'm not sure it's the right way to do with the diode multiplier.

anyway, I'm now wanting to do 7555 as inverter, so the diodes and caps are facing the opposite way, generating -17V or so. if I want to regulate this down to -10V, can I simply swap the NPN for a PNP, emitter to ground, or is this method a bust for negative regulating? maybe series pass transistor instead?

I'm confused by pnp's at the best of times.

[frequencycentral]

Between 2nd and 3rd diode would be -17V approx from 12V input.

Forget the tranny regulator. As you are using the 7555 as a charge pump there's no need for it. It would serve no function.

[duck_arse]

thanks rick. I've hadda nuther look today. I was using a 4 diode (quadrupler?) on 9V and getting -8V2 and -15V with no regulation transistor. seems that because I'm trying to transistor-regulate the voltage right back down to just above doubler, the pulse width gets too skinny and the output current ends up about nothing.

I thort I'd out-thort it tonight, and ran the circuit on a 5V pre-regulator instead. didn't work, not enuff multiplying. I'll try a 6V8 zener reg tomorrow, and/or the voltage tripler circuit, otherwise it'll have to be an inductor or a switch to a hex inverter thing.