Inductor arrangement for boosting low-voltage piezo drive

I've developed an MSP430 (TI low-power 3V uP) device that drives a
small piezo in push-pull from two pins at 2KHz, and it's not loud
enough. The device has a requirement of very low quiescent power,
and although it flashes an LED at the same time, should be audible
to an older person by the side of a noisy road, so far as possible.
I realise that frequency range is a problem, hence the LED :-).
I haven't finalised selection of the piezo, but I see different
ones with capacitances ranging around 0.02uF. I don't want to
produce a higher drive voltage all the time, as they don't beep
very often and at present the thing idles with the RTC running at
under 1uA.

I was thinking of trying the following arrangement:

Connect each end of the piezo by a series L (SMT inductor?) to +3V,
and each end also to the collector of an NPN BJT in common emitter
mode. Drive the base of each transistor in push-pull, and let the
inductors ring the voltage, hopefully up to 6V or so, as in a
boost-mode power supply.

It doesn't seem crucial to me to get the thing running at resonance,
but if possible, I guess I'd calculate the frequency using half the
piezo's capacitance and the L, aiming for the natural resonance of
the piezo - does that sound right?

Anyhow, I'm confident that this drive arrangement will work, but
is there a better way? Am I missing something? is it sensible and
possible to get SMT inductors in a suitable size?

Clifford Heath.
.

Relevant Pages

  • Re: Inductor arrangement for boosting low-voltage piezo drive
    ... small piezo in push-pull from two pins at 2KHz, ... I haven't finalised selection of the piezo, but I see different ones with capacitances ranging around 0.02uF. ... Drive the base of each transistor in push-pull, and let the inductors ring the voltage, hopefully up to 6V or so, as in a ...
    (sci.electronics.design)
  • Re: Inductor arrangement for boosting low-voltage piezo drive
    ... >> small piezo in push-pull from two pins at 2KHz, ... Drive the base of each transistor in push-pull, ... >> Clifford Heath. ... loud enough, there are a couple at corners near me, that can be heard ...
    (sci.electronics.design)
  • Re: Inductor arrangement for boosting low-voltage piezo drive
    ... > small piezo in push-pull from two pins at 2KHz, ... The device has a requirement of very low quiescent power, ... Drive the base of each transistor in push-pull, ... resonator performs acoustic impedance matching. ...
    (sci.electronics.design)
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