Resonant driver circuit for piezo buzzer

[cupoftea]

Hi,
We are working for a burglar alarm company in Scotland and wish to have the alarm (Piezo buzzer) as loud as possible.
LTspice and .PNG as attached.
We wish to use a resonant driver circuit as it appears most efficient for our Piezo Buzzer.
Our Vin is 20 to 40V.

We are doing it like in Fig 4....

An Overview of Driver Circuits for Piezo Transducer Buzzers - Industry Articles

This article covers the advantages and disadvantages of several common driver circuit design techniques for piezo transducer buzzers.

www.allaboutcircuits.com

We are not using the blocking diode.
For the LTspice mock-up, would you sim the Piezo buzzer as a capacitor in parallel with a 1k resistor as shown?

KPEG169 Piezo buzzer

https://www.farnell.com/datasheets/97531.pdf?_gl=1*1pko9a*_gcl_au*MTI5OTAzODk1Mi4xNzQxMDMzNjAz

 

[dick_freebird]

Believe some piezo elements have a second
electrode for feedback, for self-oscillation on
the cheap.

A piezo tweeter could be driven with any
tone you like, those are broadband.

 

[FvM]

A piezo tweeter could be driven with any
tone you like, those are broadband.

Discussed type is formed by a resonant disc (about 4 kHz f0). It won't work well for 1.3 kHz.

I don't think that the sketched 5.6 mH/2.7 uF resonator is an appropriate solution.

 

[cupoftea]

Thanks the attached 5m6/283n is 4khz resonant and should be better. Any nice simple circuits to "tell" a micro supplied by 3v3 that the piezo is buzzing or not? Also, what about the PWM'ing transistor suffering its collector going down to -5V...surely a blocking diode is needed in the net to the collector?
What about the attached to tell as simply as possible if the piezo is buzzing or not? Any simpler?

 

[D.A.(Tony)Stewart]

Where are your Specs for Piezo capacitance and max power?

What is your criteria for the loudest using Fletcher Munson curves? Mic verification? or phase resonance?

I agree with Dick.

1 kHz is loudest, those with good hearing 3 kHz is more sensitive, but most alarms sweep f for better response.

I recommend you drive with 12V and just use a step-up auto-transfomer coil. Adjust impedance for MPT.

We produced personal alarms in the late 90's with a motion sensor using a ball bearing in the piezo to trigger the alarm with a 9V battery and autoT. Very loud with 2cm disc.

--- Updated Mar 18, 2025 ---

A girl screaming from a voice chip might be even more effective or a police siren.

 

[dick_freebird]

Curious why you don't just want a piezo alarm
with all that baked in, that runs off 3-18VDC.
Tons of those out there in little plastic cases.
Varying power levels. You could deal with or
change the supply.

Why are you in love with a specific piezo bare
element, that you don't have a driver for, to
the point that you'd rather wallow in "make"
than just go buy in quantity off the shelf?

 

[BradtheRad]

An opamp in a strategic location detects the correct moment to change state. The opamp reads voltage across a low-ohm resistance (rather than the reactive component). You can make the resistance from a few inches of wire.

The simulation displays waveforms showing severe spikes. Some kind of soft switching might improve performance.

 

[betwixt]

...and we haven't even touched the acoustic resonance chamber topic yet. That probably makes as much difference as the electrical drive level and has no running cost.

Brian.

 

[D.A.(Tony)Stewart]

The simulation displays waveforms showing severe spikes. Some kind of soft switching might improve performance.



View attachment 198183

Switching over 600W like this will be rather high in power density in the SOA's.

I think the conjugate impedance matching of a transformer to the piezo C that also boosts voltage is still a better approach.

 

[FvM]

600 W? Piezo disc will most likely break at some 100 mW real power input.

 

[D.A.(Tony)Stewart]

yes 600W is seems a tad high.

Real Piezo alarms like PUI Audio Inc are ;

Buzzers Indicator, Internally Driven Piezo 12Vdc 200 mA 3kHz 125dB @ 12V, 10cm Bracket Mount Wire Leads $10