Author Topic: DC driver for piezo disc actuator  (Read 1663 times)

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Offline ganzuul

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DC driver for piezo disc actuator
« on: August 03, 2014, 12:10:42 am »
Hello! I'm looking for feedback. =)

This is supposed to be a high-voltage DC driver for a piezo disc sounder turned actuator. It's my first ever electronic circuit design. I'm sure there are entire fields of knowledge missing from it... It is very much a work in progress but it is probably time I showed my work to somebody.

A piezo disc should not tolerate more than 180V input, but at DC levels their impedance is very high, and since they can also return knocks as high voltage into the circuit I've chosen to base this amplifier on TV horizontal deflection output transistors, NPN BJTs with a Vmax of 1500V or more.
The power supply I'm looking at right now is a CCFL driver from a laptop, Royer oscillator, which gives out 1000V square wave at 50kHz, which I intend to rectify to ±1000VDC.  I have not yet started looking into how I might obtain less voltage from these things. All driver boards I have looked at as of yet are controlled by a 5001C PWM generator, so I can get at the pins if needed. I'd prefer to make this part of the circuit modular and uninteresting, so that others who emulate it need not fiddle with it. I hope to simply limit current to 5mA as early as I can in the HV side, and this current limit is very important to the environment the circuit is intended for.


In my breadboard test of this circuit, it really does appear to work as an amplifier. The author seems to refer to it as a push-pull Class A. I think it is just elegant in its simplicity and believe that for my HV, mA application thermal dissipation should be a non-issue. Can you confirm?


I hope to obtain 16 bits of dynamic range out of this thing, and probably on a logarithmic scale, actuator position to voltage. The piezo disks I have to test with are the cheapest pre-soldered ones I could find on Aliexpress, and for their quality I don't mind testing them to destruction at all. I intend to operate six of these actuators total, 3 in parallel, to position two mirrors for a laser.  If successful these designs will become open hardware and licensed according to the art.

The actuators probably don't need such a huge stroke, so a DIY op-amp will suffice.  The circuit I theorized about in this thread won't be developed into anything functional. I'll be looking at components like the ones referenced here instead, if I actually need a really high-voltage op-amp:
« Last Edit: August 07, 2014, 09:50:17 pm by ganzuul »

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