Amplifier for Piezo Stack Actuators
Dear gentlemen,
I am new to this Forum and like to get some advice. I am currently working with piezo stack actuators, "Motors" with small travel and extremely high Forces.
The operating voltage of these motors is from 0-120V. Electrically, they are a capacitive load with 10-40µF. Dedicated amps for these devices are extremly expensive, usually in the range of thousands of Dollars.
I am looking for an alternative, and think that Audio chip amps might be a good solution. I have already seen the devices of Apex, however, I want to try it with Audio amps.
I have a bunch of questions:
I hope you can help me out here!
Best regards,
Stefan
Dear gentlemen,
I am new to this Forum and like to get some advice. I am currently working with piezo stack actuators, "Motors" with small travel and extremely high Forces.
The operating voltage of these motors is from 0-120V. Electrically, they are a capacitive load with 10-40µF. Dedicated amps for these devices are extremly expensive, usually in the range of thousands of Dollars.
I am looking for an alternative, and think that Audio chip amps might be a good solution. I have already seen the devices of Apex, however, I want to try it with Audio amps.
I have a bunch of questions:
- I think that a class A/B amp will be the "safest" way to start. Do you recommend a chipamp with that voltage?
- Negative voltages will break the actuator. Can I supply a chipamp asymetrically? -Vcc = 0V +Vcc = 120V? Do I have to decouple the inputs then?
- Piezo actuators are large capacitances. Do audio amps manage this different load case or will they go nuts? Do I need some adaption circuit?
- Do you think that even a class D chipamp might work for these actuators?
I hope you can help me out here!
Best regards,
Stefan
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Amacron, (Crown Audio) produced the DC 500 many years ago that was an excellent class B solid state amplifier with a frequency response of DC to 25kHZ. These were used not only for PA use but motor controllers. Class D would be the way to go I think. Not sure there is much to choose from ready made, possibly an IRS2095 driving some tasty FETS on a 120V rail?
how fast slew, frequency needed for peak current calc
many chip amps won't like the Cload or the power factor - for narrow band work people often put a inductor in series with the piezo
transformers can be custom wound work to adapt common audio power amps to piezo load but like AC symmetric output
the highest V cheap linear chip amps would be the TDA7293, but the power factor and current requirement would likely want a custom multiply paralleled design, possibly bridged too for high Vswing
a bit of series R in the output stabilizes against the pure C load, needed anyway if paralleling chip amps to share the current
input common mode V limits may make some level shifting or virtual ground arrangement necessary but with DC coupling you can hold the output at any V within the chip amp's spec, offset supply or load "ground"
many chip amps won't like the Cload or the power factor - for narrow band work people often put a inductor in series with the piezo
transformers can be custom wound work to adapt common audio power amps to piezo load but like AC symmetric output
the highest V cheap linear chip amps would be the TDA7293, but the power factor and current requirement would likely want a custom multiply paralleled design, possibly bridged too for high Vswing
a bit of series R in the output stabilizes against the pure C load, needed anyway if paralleling chip amps to share the current
input common mode V limits may make some level shifting or virtual ground arrangement necessary but with DC coupling you can hold the output at any V within the chip amp's spec, offset supply or load "ground"
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