28.12.2012 Views

Piezomechanik

Piezomechanik

Piezomechanik

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

<strong>Piezomechanik</strong> · Dr. Lutz Pickelmann GmbH<br />

Amplifiers<br />

D/A Converters<br />

Electronic HV-Switches<br />

for Piezoactuators


Table of Contents<br />

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3<br />

Electro-Mechanical relations of piezoelectric actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4<br />

Practical aspects of dynamically operated piezoactuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7<br />

Selection guide for amplifiers/supply electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9<br />

Special features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11<br />

Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11<br />

Useful formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12<br />

Data of amplifiers<br />

SQV analog amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13<br />

Low voltage analog power amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16<br />

High voltage power amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19<br />

Bimorph amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24<br />

D/A Converters, Computer-Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26<br />

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28<br />

2 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


Amplifiers, D/A Converters, Electronic HV-Switches for piezoactuators<br />

1. Introduction<br />

Piezoelectrical actuators are innovative driving systems,<br />

which show increasing application potential for highly sophisticated<br />

driving/positioning tasks in a great variety of technological<br />

fields. The main areas of interest include<br />

• the extreme positioning sensitivity, enabling such<br />

systems to handle dimensions in the atomic scale<br />

• extreme force generation resulting for example in high<br />

acceleration rates during dynamic operation.<br />

For some applications no practicable alternative to piezoactuators<br />

exist<br />

• Piezoelectric actuators are used for the ultraprecise positioning<br />

of components and mechanical setups ranging<br />

from low weight optical elements, up to heavy loads such<br />

as tooling machines. The newest scanning microscope<br />

General considerations for electronic supplies for piezoactuators:<br />

In the simplest case a piezoactuator should move according<br />

to an external signal i.e. from a sinewave generator, or other<br />

source. In most cases, this original signal cannot be applied<br />

directly to the piezoactuator because voltage and power<br />

usually do not match the actuator’s requirements. An amplifier<br />

has to be used to convert the signal to result in sufficient<br />

travel and dynamics of the actuator.<br />

This is an important aspect of actuator’s application:<br />

The adaptation of a piezoelement to a distinct task is determined<br />

only in part by its mechanical properties and geometrical<br />

size. Equally important for the system’s performance<br />

are the properties of the driving electronics.<br />

The same actuator can be used for completely different<br />

operating profiles depending only on the choice of the supply<br />

electronics:<br />

signal<br />

generator<br />

elec. signal<br />

function generator<br />

feedback control electronic<br />

computer<br />

amplifier<br />

pulser<br />

Fig. 1:<br />

Schematic representation of an actuator system<br />

When designing a piezoactuated system the designer<br />

has to deal simultaneously with actuator and supply to<br />

get the optimum matching. A step-by-step definition<br />

whereby the actuator is first-chosen and then a sub-<br />

matching<br />

electronics<br />

technologies such as STMs, AFMs etc. require precise<br />

handling of probe tips with sub-nanometer precision,<br />

which can only done in a reasonable way by using piezomechanical<br />

elements.<br />

• The high acceleration rates/short reaction times predestinate<br />

piezoelements for the control of fast processes in<br />

valve technology, fuel injection application, mechanical<br />

shaking excitation for test purposes with time periods/risetimes<br />

in the microseconds range.<br />

• Piezoactuators are very attractive candidates for active<br />

vibration control and cancellation even in heavy and extended<br />

mechanical structures such as vehicles, airplanes,<br />

helicopters, ships. A special feature is the dual effect of<br />

piezoelectricity, which can be used both for sensing and<br />

actuating. Single element can therefore be used as smart<br />

transducers acting simultaneously as sensor and actuator.<br />

Slow cycling of an actuator requires only a small low power<br />

supply, whereas pulsed operation i.e. generating mechanical<br />

shocks, needs supplies with peakpowers in the kilowatt<br />

range.<br />

Computer control of actuators comprises an additional step:<br />

the computer data has to be converted by a D/A converter of<br />

sufficient speed and resolution, and the low voltage signal is<br />

than amplified to the actuator’s requirements.<br />

piezo<br />

actuator<br />

mechan.<br />

reaction<br />

sequent selection of the supply may lead to costly and<br />

ineffective approaches.<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators<br />

3


2. Electro-Mechanical relations of<br />

piezoelectric actuators<br />

2.1. Principle structures of piezoactuators<br />

Generally, all piezoelectric devices/transducers such as<br />

stacks, bimorphs, tubes can be described as a kind of capacitor<br />

with an electromechanically active dielectric medium:<br />

the PZT ceramic. Therefore, the electrical capacitance of<br />

such devices is an important operating parameter, especially<br />

when adapting the supply electronics for dynamic operation.<br />

The electrical capacitance of piezoactuators is shown in the<br />

data sheet.<br />

The strain within the PZT-medium is related to the internal<br />

electrical field strength when a voltage is applied to the element.<br />

An important consequence for practical consideration<br />

is, that the thinner the PZT-layers are, the lower can be the<br />

driving voltage. Furthermore the degree of lamination determines<br />

the electrical capacitance of piezoactuators.<br />

ceramic endfaces<br />

piezoceramic<br />

layers<br />

electrical<br />

connection<br />

Fig. 2a:<br />

Schematic representation of the capacitive layer structure of a<br />

piezostack<br />

Fig. 2b:<br />

Discretely built-up piezoelectric stack (high voltage type), external<br />

contact electrodes visible<br />

Low voltage actuator types are operated with maximum<br />

voltages ranging from 50 V to 150 V, whereas the high<br />

voltage elements require hundreds of volts up to 1000 V (and<br />

more). For standard stacks the achieved maximum strain is<br />

about 1–1.5‰ of the stack length. There exist highstrain<br />

stacks based on optimized PZT-materials showing a strain of<br />

2‰ and more at fieldstrength of 3 kV/mm.<br />

2.2. Polarity of piezoelectrical elements<br />

For piezoelectrical components an electrical polarity is<br />

usually defined. Piezoelectrical actuators e.g. stacks can only<br />

achieve their maximum response by applying the maximum<br />

voltage with correct polarity. Operation with counterpolarity<br />

voltage although possible is limited to remarkably lower<br />

ratings. A stack actuator shrinks under these conditions,<br />

increasing thereby to some extent the total moving range of<br />

the stack (see brochure “piezomechanical stackactuators”).<br />

Bare piezostacks without casing are usually electrically insulated<br />

at the mechanical mounting points. They are supplied<br />

with pigtails showing the polarity by red(+) and black(–) insulation.<br />

Such elements can be combined therefore with positive<br />

or negative voltage supplies without difficulty. The situation<br />

changes, when actuators with casing are used. Here, the<br />

ground is defined by the coax-cable and therefore the polarity<br />

of the supply voltage is fixed.<br />

Piezoactuators with casing and the supply electronics from<br />

PIEZOMECHANIK are designed for positive polarity both for<br />

low voltage and high voltage actuators. This supports the<br />

easy combination of higher voltage actuators with lower<br />

voltage supplies, which is an important aspect for dynamic<br />

operation of actuators (see section 2.5.).<br />

2.3. Operating characteristics of piezoactuators<br />

The expansion of piezoelectric actuators is illustrated by<br />

voltage/expansion diagrams showing the well-known<br />

hysteresis (fig.3).<br />

rel.<br />

expansion<br />

rel. voltage<br />

Fig. 3:<br />

Relative voltage/expansion diagram of a free running piezoactuator for<br />

different voltage reversal points<br />

4 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


Actuators are normally classified by the maximum applicable<br />

voltage for maximum stroke, and characterised as low<br />

voltage and high voltage types. For newcomers in piezotechnology,<br />

this sometimes gives the impression, that the voltage<br />

rating of an actuator is the sole criterion for selecting a<br />

proper electronic supply. This is however not correct.<br />

For any application of piezoactuators the electrical power/<br />

current balance for charging and discharging the piezoactuator’s<br />

capacitance has to be kept in mind. The variety of<br />

electrical supplies on offer is due mainly to the different<br />

power/current ratings of these devices.<br />

The charge/current balance during operation is related to<br />

the capacitive nature of actuators as shown below:<br />

Basic capacitor equation<br />

Q(t) = C U(t) C actuator’s capacitance<br />

Q actual electrical charge<br />

U applied voltage<br />

Obviously the expansion of an actuator is also related to<br />

the quantity Q of electrical charge stored in the actuator’s<br />

capacitance C, when a voltage U is applied.<br />

From this charge balance, the kinetic parameters of motion<br />

like speed and acceleration can be derived. These relations<br />

are the base for specifying the necessary current/power for<br />

distinct driving conditions.<br />

Actuator’s position l ~ charge = Q(t)<br />

.<br />

Speed v ~ current I = dQ/dt = Q(t)<br />

..<br />

Acceleration b ~ variation of current = dI/dt = Q(t)<br />

The generation for example of a sine-wave oscillation by<br />

a piezoactuator requires a defined supply current depending<br />

on actuator’s capacitance and moving amplitude.<br />

Therefore an amplifier has to be selected for both criteria:<br />

voltage and current.<br />

Another consequence of the above is that, during a<br />

steady state of the actuator (constant position, constant<br />

force) no current is flowing, therefore no power is required.<br />

When a charged actuator is disconnected from<br />

the supply, it holds its position. This is an important<br />

difference to electromagnetic systems, where a constant<br />

position requires constant electrical power due to the<br />

sustaining current.<br />

The speed of an actuator cannot be increased infinitely even<br />

by very high currents, but is limited by the elastic properties<br />

of the stack. The maximum speed of stacked elements is in<br />

the range of a few m/sec.<br />

Because of the very limited moving range of piezoactuators<br />

the generation of above speeds requires high acceleration<br />

rates up to 10 4 –10 5 g.<br />

During operation of a piezodriven mechanical setup for highly<br />

dynamic application, it has to be verified that the mechanics<br />

coupled to the actuator shows a sufficiently high stiffness/<br />

resonant frequency, otherwise the mechanics cannot follow<br />

actuator’s motion and it is fruitless to optimize the drive for<br />

high speed/acceleration.<br />

2.4. Peak current, average current<br />

Piezoactuators require electrical power/current only during<br />

dynamic operation. Expansion and contraction are characterized<br />

by charging/discharging currents.<br />

The short term available maximum peak current of a supply<br />

determines the minimum risetime/maximum speed of an<br />

actuator. Amplifiers of the series LE provide a special booster<br />

stage for high peak currents to get minimum risetimes.<br />

The average current of a supply determines the longterm<br />

cw-repetition rate of charging/discharging an actuator.<br />

For cw sine oscillation of an actuator, the required peak and<br />

average currents show a fixed ratio of approx. 3:1. Therefore,<br />

the selection of a supply to obtain a distinct cw-actuator frequency<br />

has to consider both, peak and average current data.<br />

2.5. Power efficiency<br />

This section will lead on the first glance to the (surprising)<br />

result, that it is sometimes very reasonable and necessary to<br />

combine a high voltage actuator with a low voltage supply,<br />

where only a fraction of the actuator’s maximum amplitude<br />

can be achieved.<br />

The reason for this strategy are twofold:<br />

• optimizing power efficiency of a dynamically operated<br />

actuator system<br />

• minimizing selfheating of a dynamically operated actuator.<br />

The basic idea is easily demonstrated with the following<br />

example, where the task requires the generation e.g. of a<br />

+/–2,5 µm sine oscillation with a distinct frequency:<br />

The first example uses an actuator type PSt 500/5/5, where<br />

500 V has to be applied to get the full stroke of 5 µm.<br />

A second example is to use the longer stack PSt 500/5/15<br />

capable for a 15 µm motion at 500 V, showing an actuator’s<br />

capacitance 3 times larger than in the 1st case.<br />

The important fact is, that with the longer stack only 150 V<br />

are needed to get the desired 5 µm stroke.<br />

Comparing the actuators’ energy content 1/2 CU 2 respectively,<br />

despite its larger capacitance the longer stack is<br />

favoured regarding power efficiency as only 1/3 of the power<br />

necessary to drive the shorter PSt 500/5/5 with full strain is<br />

required. It is obvious, that a 150 V system’s total power efficiency<br />

is further improved by using a 150 V supply showing<br />

higher current output compared to a 500 V supply operated<br />

at reduced voltage rating.<br />

In the above described strategy, the problem of selfwarming<br />

under dynamic operating conditions is minimized by the<br />

reduced power input and by distribution of the dissipated<br />

energy over a larger volume/surface of the longer actuator.<br />

This is a powerful method to extend the application range of<br />

piezoactuators to high frequency cw-operation without the<br />

risk of overheating.<br />

This strategy of dynamic operation of actuators with reduced<br />

strain shows restrictions in other operating parameters: A<br />

longer stack has a lower stiffness and resonance, and it has<br />

to be determined, whether this is acceptable for a distinct<br />

application.<br />

Finally, an important contribution to the overall power<br />

efficiency of an actuator system is the use of recharger<br />

amplifiers (switched amplifiers).<br />

In most applications, piezoactuators display mainly a reactive<br />

load, where the energy content of a charged actuator flows<br />

back to the amplifier during the discharging cycle. Switched<br />

amplifiers RCV are able to recycle this energy with high efficiency,<br />

so that the needed linepower for a dynamically operated<br />

system has only to cover the (much smaller) active part<br />

of the power balance.<br />

This active power is drawn from the system as mechanical<br />

power or dissipated by the selfheating of the actuators.<br />

This technique shows the optimum of systems’s overall<br />

power efficiency, and favours actuator applications, where<br />

high power levels are required e.g. for active vibration cancellation<br />

in heavy mechanical structures (vehicles, airplanes<br />

etc.) or anywhere, where the power consumption from the<br />

power supply is restricted i.e. battery operated systems.<br />

Power efficiency � is defined as<br />

� = (P r–P al) Pr = reactive power output from amplifier<br />

� = (P r) Pal = active power consumption from line<br />

An ideal amplifier without internal losses shows an efficiency<br />

1.<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators<br />

5


2.6. Frequency response<br />

The performance of an amplifier is characterized by its frequency<br />

response, describing what cw-frequency/amplitude<br />

relations that can be achieved for a defined capacitive load.<br />

The achievable maximum frequencies of an actuator/supplysystem<br />

depend both on the output power of the supply, the<br />

capacitance of the driven actuator and the oscillation amplitude.<br />

To make the selection of an amplifier/actuator combination<br />

with respect to frequency response easier, some response<br />

curves for different capacitive loads are shown in the<br />

data sheet for distinct amplitudes. The response for intermediate<br />

capacitances are achieved by simple interpolation.<br />

An additional figure for an amplifier’s performance is the<br />

achievable minimum risetime, which is tabulated for some<br />

load capacitances (see section 2.4.).<br />

2.7. Voltage stability, noise<br />

One of the most striking features of piezoactuators is their<br />

unlimited positioning sensitivity, which explains the sub-nanometer<br />

resolution for example scanning tunnel microscopes:<br />

A infinitely small voltage step Æ U is transformed into infinitely<br />

small mechanical shift Æ l.<br />

Æ l = l Æ U/U l = actuator’s shift for signal voltage U<br />

Neglecting external influences, the positioning sensitivity of<br />

an actuating system is limited only by the stability of the<br />

electronic supply (noise).<br />

Example:<br />

The amplifiers SQV 150 show a noise of approx. 1 mV equivalent<br />

to a S/N ratio of about 10 5 . A 100 µm actuator such as<br />

the PSt 150/7/100 VS 12 operated with the SQV 150 shows a<br />

variation in position of only 1 nm.<br />

2.8. Pulsed operation of piezoactuators<br />

An important feature of piezoactuators is their capability to<br />

produce extreme forces and acceleration rates, which can be<br />

used for fast switching of valves or to produce mechanical<br />

shocks. In such cases, the actuator should switch in as short<br />

time as possible between 2 distinct levels, whereas the exact<br />

motion profile between these levels is not important.<br />

The minimum risetime of an actuator can derived from its<br />

elastic properties:<br />

A short electrical pulse excites the resonant oscillation of the<br />

actuator and the minimum risetime Tp can be estimated by<br />

Tp Å Tr/3 Tr = period time of actuator’s resonance<br />

Tp = minimum risetime in pulsed operation<br />

Example:<br />

A systems’s resonant frequency of 3 kHz results in a minimum<br />

mechanical risetime of about 100 µsec.<br />

A simple calculation shows, that above shown pulse generation<br />

requires peak powers up to the kilowatts range with currents<br />

of 10 to 100 Amperes. In these cases it is reasonable<br />

not to use analogue amplifiers but electronic pulse switches.<br />

The common design of a HV-pulse generator consists of a<br />

high voltage supply, which continuously charges at a defined<br />

low power (i.e. 50 Watt) a large internal charge storing<br />

capacitor.<br />

This capacitor delivers short term the very high currents to<br />

the external piezoactuator capacitance, when it is switched<br />

by transistors via a load resistor R. The load resistor R acts<br />

as current limiter to avoid electrical overpowering and<br />

defines the time constant RC of the pulser (rise/fall-time)<br />

according the well-known relation<br />

Ua = U o (1-e -t/RC )<br />

R = internal load resistor of switch<br />

C = capacitance of external load (piezoactuator)<br />

Ua = voltage level at actuator<br />

Uo = supply voltage from internal charge storing capacitor<br />

For the operation of the HVP’s 3 time constants have to be<br />

distinguished:<br />

• Switching time of output transistors:<br />

order of magnitude: 1 µsec<br />

defines the minimum electrical pulsewidth<br />

• Time constant RC:<br />

Defines the signal/voltage risetime at the actuator.<br />

Pulsewidths shorter RC lead to a partial charging of the<br />

actuator and thereby to intermediate positions between<br />

“low” and “high”<br />

• Period time of actuator/actuated system (fig. 4.):<br />

This time constant defines the minimum mechanical<br />

rise/fall-time of the system.<br />

To excite the minimum mechanical risetime Tp of an actuator,<br />

the RC time constants of the pulsersystem has to be<br />

shorter than Tp.<br />

voltage step<br />

Fig. 4:<br />

Excitation of a mechanical pulse by a voltage step 0V/Uo; lo final static<br />

position of actuator<br />

2.9. Feedback controlled systems<br />

Piezoelectric actuators are well-suited for setting up electronically<br />

controlled systems for fast and precise handling of<br />

mechanical parameters such as position, speed and force.<br />

Because of the hysteretic and slightly nonlinear behaviour of<br />

piezoactuators, and nonpredictable external influences, this<br />

has to be done by feedback control. A sufficiently fast and<br />

sensitive transducer picks up the actual position or other<br />

parameter of interest and the signal is evaluated by feedback<br />

control electronics, producing the control signal for the<br />

actuator.<br />

The overall efficiency e.g. precision of such a system is<br />

determined by the transducer and electronics and not by the<br />

actuator. The high performance of feedback controlled<br />

systems is demonstrated by the atomic resolution of the<br />

scanning tunnel microscopes (STMs).<br />

6 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


A further application is the active stabilization of mechanical<br />

arrangements e.g. laser resonators against misalignment due<br />

to thermal drifts or mechanical shocks (see “feedback controlled<br />

stabilization PiStab 2”).<br />

3. Practical aspects of dynamically operated<br />

piezoactuators<br />

3.1. Preloading, reset mechanisms<br />

Piezoceramic is sensitive to tensile stress, it shows a damage<br />

strain of only 1‰.<br />

Note, that this tensile stress can be created externally and<br />

also internally by dynamic operation. This fact is easily seen<br />

in Fig 4/sec. 2.8., where the application of an electric pulse<br />

leads to overshooting of the actuator relative to the steady<br />

state position. This overshooting can cause tensile stress<br />

and thereby damage to the actuator when the relevant forces<br />

are not compensated by other means.<br />

To prevent damage by tensile forces the following strategies<br />

are commonly applied:<br />

• passive preloading/reset of actuators<br />

This technique is mostly applied to stack actuators:<br />

An elastic spring compresses the piezostack with a defined<br />

force shown in fig. 5a, b. A preloaded stack is less sensitive<br />

to externally applied tensile stress for several reasons, i.e. a<br />

reduction in stacklength is achieved by the preload force. A<br />

Fig. 5a:<br />

Mirror tilter with passive prestress/reset<br />

Fig. 5b:<br />

Linear stackactuator with passive prestress/reset<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators<br />

piezostack<br />

tilting<br />

prestress spring<br />

piezostack<br />

mirror surface<br />

prestress/reset<br />

spring<br />

7


eal tensile stress is acting on the ceramic only, when the<br />

external force lengthens the stack beyond the original (loadfree)<br />

state.<br />

Furthermore, the elastic counterforce slows down the moving<br />

mass in the overshoot phase during dynamic operation.<br />

So, the applied preload force can be chosen according the<br />

tilting<br />

Fig. 6a:<br />

Mirror tilter with active (push-pull) reset<br />

piezostack piezostack<br />

Fig. 6b:<br />

Linear push-pull arrangement of piezostacks for active reset<br />

simple mass acceleration law to accommodate the accelerated<br />

masses within the desired short rise/fall-times.<br />

The standard preloading VS of PIEZOMECHANIK actuators<br />

cover a wide range of applications. It is possible to apply<br />

higher preload forces, which can be supplied on request or<br />

can be applied externally (see brochure “piezomechanical<br />

stackactuators”).<br />

• active reset<br />

(push-pull mode, antagonistic configuration)<br />

mirror surface<br />

A more sophisticated reset mechanism for compensating<br />

dynamic forces is the arrangement with two complementary<br />

working actuators shown in fig. 6a, b. The advantages<br />

include a symmetric force balance for both directions of<br />

motion, and higher resonance frequencies compared with<br />

passive preloading.<br />

3.2. Selfheating<br />

Another aspect of dynamically operating piezoactuators is<br />

their selfheating. Due to the ferroelectric nature of PZT ceramics,<br />

the electrical operating power transferred to the actuator<br />

is partially dissipated as heat. For example an actuator<br />

PSt 150/5/15 with full amplitude operation heats up to the<br />

operating temperature limit at about 600 Hz. Higher temperatures<br />

will shorten an actuators lifetime. A further increase of<br />

frequency therefore requires cooling or an equivalent reduction<br />

of amplitude (see sec. 2.5).<br />

Simple surface cooling results in limited success for large<br />

volume actuators, because PZT ceramics have poor thermal<br />

conductivity. Furthermore measuring the actuator’s temperature<br />

on its surface does not reflect the internal conditions. A<br />

good parameter for checking the volume temperature is the<br />

temperature dependence of the electrical capacitance of the<br />

actuator leading to a shift of the current balance.<br />

Fig. 7:<br />

Temperature dependence of the electrical capacitance of a typical<br />

piezoactuator (relative to capacitance at roomtemperature)<br />

8 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


3.3. Vibration control, acoustical noise<br />

Every dynamic excitation of a piezoactuator attached to a<br />

mechanical structure acts back on this structure. Pulsed or<br />

oscillating actuators generate vibrations in the mechanical<br />

structure. In case of a resonance a large amplitude response<br />

can emerge even for small excitation levels, which can interfere<br />

with the regular function of the structure. Therefore,<br />

dynamically operated structure have to be designed for sufficiently<br />

large resonant frequencies, and include sufficient<br />

damping to avoid these unwanted side effects at the driving<br />

frequency.<br />

Vibration suppression can be done in passive or active ways.<br />

An example for active pulse compensation is shown in fig. 8,<br />

where a counteracting piezostack compensates for the<br />

repulse of the original stack, e.g. shifting a mirror.<br />

Generally, piezoelements are powerful tools for vibration<br />

control, both for generating vibrations (shakers) and for cancellation<br />

(active vibration isolation and damping). Active com-<br />

static suspension<br />

mirror compensating<br />

mass<br />

piezostack piezostack<br />

impulse 0<br />

Fig. 8:<br />

Mechanical impulse compensation<br />

pensation can be done in feedback controlled systems,<br />

where a transducer detects an incoming vibration, and<br />

excites an antivibration with proper amplitude and phase<br />

relation via an actuator.<br />

From ergonomic aspects, it must be kept in mind, that<br />

actuator vibrations can produce acoustical noise which may<br />

be very uncomfortable for the operator.<br />

4. Selection guide for amplifiers/supply electronics<br />

PIEZOMECHANIK offers a wide range of supply electronics<br />

to obtain the optimum solution for different applications<br />

of piezoactuated systems.<br />

For specifying dynamically operated actuator/amplifier<br />

systems the power/current requirements are determined<br />

by the actuator’s capacitance. Note that the actuator’s<br />

capacitance can vary up to 50% (e.g. see section 3.2.)<br />

leading to correspondingly elevated power/current<br />

ratings.<br />

The supply electronics and actuators from PIEZO-<br />

MECHANIK are set to positive polarity for both high<br />

voltage and low voltage components, so that widest<br />

compatibility is achieved e.g. for power efficient<br />

arrangements according sec. 2.5.<br />

On request PIEZOMECHANIK supplies piezocomponents<br />

for negative operating polarity.<br />

4.1. SQV amplifiers<br />

The range of SQV amplifiers comprises the 3 main voltage<br />

ranges, where piezoactuators are offered namely 150 V<br />

(+200 V), 500 V and 1000 V. The output power is a few watts,<br />

which is sufficient for most applications. Smaller volume<br />

actuators can be operated even with higher dynamic/frequencies.<br />

SQV amplifiers show low noise and are therefore<br />

best suited for positioning tasks with highest positioning sensitivity.<br />

SQV amplifiers are available as 3-channel versions e.g. for<br />

optomechanical xyz adjusters.<br />

4.2. LE amplifiers<br />

LE amplifiers are used, when the power/current requirements<br />

cannot be covered by the SQV amplifiers. The LE series<br />

includes current boosters for optimum system power efficiency,<br />

when e.g. a high frequency sinoidal oscillation has to<br />

be excited, or to get short rise/fall-times for a rectangular<br />

signal.<br />

The LE amplifiers are available for power levels up to hundreds<br />

of watts.<br />

Due to these elevated power levels, selfheating of actuators<br />

according sec. 3.2. should be considered.<br />

4.3. RCV recharging amplifiers<br />

The RCV switched amplifiers are designed for driving<br />

large volume/large capacitance piezoactuators with high<br />

currents and powers up to the kilowatt range beyond the<br />

levels of the LE analog amplifiers. This situation occurs for<br />

example with the active excitation and cancellation of<br />

vibrations in heavy mechanical structures e.g. vehicles,<br />

airplanes etc.<br />

Because the design of RCV amplifiers has to be adapted to<br />

some extent to the operated load, there are no standardized<br />

devices. In principle, RCV amplifiers can also be designed for<br />

lower power ratings. Please contact us for details.<br />

4.4. Bipolar amplifiers<br />

Usually piezoactuators such as stacks are operated unipolar<br />

or asymmetrically bipolar to get maximum displacement.<br />

Some applications exist, where piezoelements are operated<br />

symmetrically bipolar, but to avoid depolarization of the PZT<br />

ceramic, the electrical field strength and thereby actuator’s<br />

efficiency has to be held sufficiently low.<br />

Reasons for bipolar operation include simple electrical driving<br />

conditions e.g. of piezobenders (bimorphs), shearmode<br />

actuators or enhancement of stack actuators lifetime e.g.<br />

within feedback control loops for position stabilization. In this<br />

case, the middle position is defined by 0 V, no offset is required<br />

for symmetric positioning range. This leads to long-<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators<br />

9


term low electrical fields preventing materials degradation by<br />

charge carrier diffusion.<br />

Nevertheless, bipolar amplifiers can also generate unipolar or<br />

asymmetric output by applying a proper signal.<br />

4.5. BMT, AGV antagonistic amplifiers<br />

The AGV/BMT amplifiers are designed to drive push-pull<br />

(antagonistic) stack arrangements or piezobenders (“Bimorphs”)<br />

described in section 3.1. By electrical preloading,<br />

the full operating range of the ceramics can be used without<br />

the risk of depolarization which may happen during simple<br />

bipolar operation. The modulation of the antagonistic piezoelements<br />

is done by a single driving signal, complementary<br />

action is achieved by different static offsets shown in fig. 9a,<br />

b, c. This strategy ensures forced synchronization of motion<br />

of the 2 elements even under high dynamic driving conditions.<br />

For an antagonistic setup, the actuators have to show potential<br />

free design, meaning that the operating ground of the<br />

AGV/BMT<br />

Fig. 9a: Push-pull-stack arrangement with schematic electronic supply<br />

configuration<br />

Fig. 9b:<br />

Operation of a parallel-bimorph with electrical preloading<br />

AGV/BMT amplifier<br />

Fig. 9c:<br />

Equivalent circuit to piezoactuator arrangements 9a, 9b<br />

AGV/BMT<br />

amplifier<br />

piezoelements has to be separated from general ground of<br />

the arrangement.<br />

4.6. HVP high voltage switches for pulse operation<br />

HV-pulse generators are used when currents beyond the<br />

level of common amplifiers are necessary and where a<br />

steady movement of an actuator is not required, but only<br />

defined levels should be set within short times or where<br />

mechanical shocks have to be produced.<br />

The HVP high voltage pulse generators from PIEZOMECHA-<br />

NIK show some interesting features enabling the user to<br />

drive piezoactuators in a more sophisticated way than the<br />

simple “high”, “low” procedure with common switches.<br />

Beside the levels “charging = high”, “discharging = low”<br />

there exist a third level “neutral”, where the output is set to<br />

high resistance, so that the charge content (= position) of the<br />

actuator is kept constant. Thus the system can be set and<br />

held in intermediate positions. This is achieved by applying<br />

signal pulses with width less the time constant RC of the<br />

system, leading to only a partial charging of the actuator’s<br />

capacitance corresponding an intermediate position.<br />

A general approach for pulsed actuator operation is not to<br />

oversize current specs for a distinct application, because too<br />

powerful pulses may cause unnecessary mechanical and<br />

electrical stress to the system. On the other hand the<br />

mechanical reaction time cannot be infinitely improved by<br />

increasing the pulsepower (see sec. 2.8.).<br />

4.7. Computer interfaces<br />

For computer control of piezoactuators a lot of designs and<br />

arrangements for interfacing exist. The selection of the<br />

proper interface for a distinct application depends on the<br />

basic hardware/software the user can provide, and the<br />

flexibility he wants to achieve with his setup.<br />

• Computer with internal D/A converter: computer output is<br />

an analog signal<br />

The supplies low voltage analog signal output (e.g. 0 V to<br />

+10 V) is applied directly to the analog amplifiers etc. from<br />

PIEZOMECHANIK.<br />

• HV-PC-card: The computer output is an analog signal. This<br />

card is inserted in the computer and produces immediately<br />

an analog-HV-signal for voltages up to +150 V or +500 V<br />

also in multichannel configuration. The power range is<br />

similar to the SQV or lower power LE amplifiers. This signal<br />

is directly applicable to the piezoactuator. Space saving<br />

configuration.<br />

• External D/A Converters: The computer output is digital<br />

data.<br />

In this case, the digital data has to be transferred via a<br />

serial or parallel interface similar to any other peripheric<br />

device for a computer e.g. a printer.<br />

The data is then converted by a D/A stage into an analog<br />

signal with subsequent amplification by usual analog<br />

amplifiers.<br />

The low voltage D/A converting unit can be a stand-alone<br />

device, or can be integrated to the amplifiers cabinet. In all<br />

these cases, the analog functions of the amplifiers remain<br />

active e.g. a manual setting of an “offset” voltage is possible,<br />

which is useful for adjusting setups before starting<br />

computer control. Multichannel systems are available.<br />

10 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


5. Special features<br />

Analog amplifiers from PIEZOMECHANIK show some special<br />

features, which are very useful for the operation of piezoactuators:<br />

“Offset”<br />

The amplifiers are provided with a potentiometer where a<br />

DC-output voltage can be manually set over the full operating<br />

range. In this mode, the amplifier can be used as an<br />

adjustable voltage supply without the application of an<br />

external signal.<br />

When an external signal is amplified, the “Offset” voltage is<br />

superimposed automatically. This is useful, when the signal<br />

generator produces only bipolar signals which have to be<br />

shifted to get the unipolar signal required to drive piezoelements<br />

effectively.<br />

“Amplitude”<br />

Using this potentiometer, the input signal can be adapted to<br />

the working range of the amplifier. It is possible to use signal<br />

levels 5 V as well as 10 V (e.g. from standard D/A converting<br />

units).<br />

Current booster<br />

Higher power amplifiers such as the LE types are provided<br />

with a current booster, which enable the amplifier to produce<br />

a much higher current (for a limited time) than the long term<br />

average current. In this mode, the amplifier is optimized for<br />

high power efficiency when a capacitive load such as a<br />

piezoactuator is operated.<br />

The current booster reduces further the risetime, when<br />

rectangular signals are applied.<br />

For these amplifiers the risetimes for a variety of loads are<br />

tabulated in the datasheet.<br />

Monitor output<br />

The average output voltage is shown on the front display of<br />

the amplifiers.<br />

Realtime signal monitoring is done by the “Monitor”-output,<br />

which represents the actual power output status by a 1:100<br />

ratio low power signal. The monitor-output is used for realtime<br />

representation via an oscilloscope. Further it can be<br />

used as a signal source for any control arrangement (feedback<br />

control, voltage limitation), where information about the<br />

current status of the actuator is needed.<br />

6. Safety Instructions<br />

• During operation of piezoactuators voltages and electrical<br />

currents are present which may be harmful to the<br />

operator<br />

• Installation and operation of actuators and electronics<br />

supplies must be carried out by authorized personal<br />

only<br />

• All electrical installation of electric supplies, cables and<br />

connectors must be carried out according to standard<br />

safety regulations<br />

• Piezoactuators can show large electrical capacitances,<br />

and charged actuators can store electrical charge at<br />

high voltage levels, even for long times after being disconnected<br />

from the power supply.<br />

When large volume actuators are not in use, discharge<br />

them carefully, and hold them shortcircuited.<br />

• Piezoactuators can generate electrical charge at high<br />

voltage levels, when varying load or temperature is<br />

acting on actuators with open leads.<br />

When large volume actuators are not in use, discharge<br />

them carefully, and hold them shortcircuited.<br />

• Take care when opening amplifiers and pulsegenerators.<br />

High voltage levels can be held for a long time<br />

after disconnecting the devices from line due to large<br />

capacitance internal capacitors. If these devices must<br />

be opened, wait at least 15 minutes after disconnecting<br />

them from line. Complete discharge of the internal<br />

capacitors has to be ensured by shortcircuiting via a<br />

proper resistor.<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 11


7. Useful formulas<br />

Notice: the following relations are dealing with ideal capacitors, where the capacitance is invariable under the driving conditions.<br />

But piezoactuators show to some extent deviations from this ideal behaviour due to their ferroelectric nature. Their<br />

capacitances depend on electrical fieldstrength (voltage level), temperature and other parameters and may exceed the nominal<br />

values by 50%, which are stated in the data sheet.<br />

General:<br />

capacitor relation C = Q/U<br />

charging/discharging current<br />

I(t) = C dU/dt<br />

Average current l, t repetition rate, U o maximum voltage<br />

Sinuoidal excitation<br />

Unipolar signal<br />

Current<br />

U o max. supply voltage<br />

f frequency<br />

C actuators capacitance<br />

Peak current<br />

Average current<br />

I a = U oC/t<br />

U(t) = U o/2 (1-cos 2 p ft)<br />

I(t) = U o C p f sin (2 p ft)<br />

I p = p U max C f<br />

I a = U max C f<br />

Peak current exceeds average current by factor p.<br />

Current booster needed for optimum power efficiency.<br />

Symmetric triangular signal<br />

Peak current<br />

Average current<br />

I p = U maxCf<br />

I a = U maxCf<br />

No current booster necessary.<br />

Pulse excitation<br />

Operating voltage Ua(t) of actuator:<br />

Charging current Ic(t)<br />

Ua(t) = U o (1-e –t/RC )<br />

Ic(t) = (U o-Ua(t))/R<br />

R load resistor of pulse generator (see sec.2.8.)<br />

Peak current at pulse onset:<br />

Average current<br />

Ic max = U o/R<br />

I a = U oCw<br />

w repetition rate, U o supply voltage<br />

Power balance<br />

Energy content E of a charged capacitance<br />

E = 1/2 CU o 2<br />

Average power consumption P A during cycling with repetition<br />

rate w<br />

P A = 1/2 CU o 2 w<br />

Dissipated power (selfheating problem)<br />

During the charging/discharging cycles, the transferred<br />

power is partially dissipated into heat according<br />

P dis = tand CU o 2 w<br />

tand dissipation factor<br />

5–10% of total power with common PZT actuator ceramics<br />

12 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


SQV analog amplifiers (low voltage/high voltage types)<br />

SQV 1/150 single channel amplifier<br />

+150 V output<br />

Special features: see chapter 5.<br />

Potentiometer “Offset”<br />

Potentiometer “Amplitude”<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: –10 V thru +150 V<br />

Max. peak current/average current: approx. 60 mA<br />

Gain: 30<br />

Noise: approx. 1 mVpp with capacitive load (actuator)<br />

Connector: BNC<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 165x210x70 mm<br />

Weight: approx. 1.7 kg<br />

SQV 3/150 triple channel device<br />

3 independent channels<br />

Performance data /channel equiv. SQV 1/150<br />

LC-voltage display, channel selection by dial<br />

Dimensions: WxDxH 215x210x70<br />

Weight: 2.4 kg<br />

Option:<br />

Amplifier for 200 V output: on request<br />

open<br />

output:<br />

U max/2 >20 kHz<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 100 V/150 V<br />

22 µF 40 msec /80 msec<br />

4.2 µF 8 msec /18 msec<br />

1.2 µF 2 msec / 5 msec<br />

330 nF 0.5 msec /1.2 msec<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 13


SQV 1/500 single channel amplifier<br />

+500 V output<br />

Special features: see chapter 5.<br />

Potentiometer “Offset”<br />

Potentiometer “Amplitude”<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +500 V<br />

Max. peak current/average current: approx. 20 mA<br />

Gain: 100<br />

Noise: approx. 1 mVpp with capacitive load (actuator)<br />

Connector: BNC<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 165x210x70 mm<br />

Weight: approx. 1.7 kg<br />

SQV 3/500 triple channel device<br />

3 independent channels<br />

Performance data /channel equiv. SQV 1/500<br />

LC-voltage display, channel selection by dial<br />

Dimensions: WxDxH 215x210x70<br />

Weight: 2.4 kg<br />

open<br />

output:<br />

U max/2 >20 kHz<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 300 V/500 V<br />

1.2 µF 20 msec / 42 msec<br />

660 nF 10 msec / 22 msec<br />

330 nF 5 msec / 11 msec<br />

100 nF 1.5 msec / 3.5 msec<br />

30 nF 0.5 msec / 1.2 msec<br />

14 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


SQV 1/1000 single channel amplifier<br />

+1000 V output<br />

Special features: see chapter 5.<br />

Potentiometer “Offset”<br />

Potentiometer “Amplitude”<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +1000 V<br />

Max. peak current/average current: approx. 10 mA<br />

Gain: 200<br />

Connector: LEMOSA OS.250 (BNC adaptor available)<br />

Noise: approx. 5 mVpp with capacitive load (actuator)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 165x210x70 mm<br />

Weight: approx. 1.7 kg<br />

SQV 3/1000 triple channel device<br />

3 independent channels<br />

Performance data /channel equiv. SQV 1/1000<br />

LC-voltage display, channel selection by dial<br />

Dimensions: WxDxH 255x290x115<br />

Weight: 3.5 kg<br />

open output<br />

U max/2 >20 kHz<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 700 V/1000 V<br />

1.2 µF 70 msec /140 msec<br />

330 nF 20 msec /35 msec<br />

100 nF 6 msec /10 msec<br />

30 nF 1.8 msec / 3 msec<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 15


Low voltage analog power amplifiers<br />

LE 150/025 single channel amplifier<br />

+150 V output<br />

Special features: see chapter 5.<br />

Potentiometer “Offset”, “Amplitude”, Current Booster,<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: –10 V thru +150 V<br />

Max. peak current: approx. 250 mA<br />

Max. average current: approx. 70 mA<br />

Gain: 30<br />

Noise: approx. 15 mVpp<br />

Connector: BNC<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 185x330x150 mm<br />

Weight: approx. 4 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

Amplifier for 200 V output: on request<br />

Computer interfaces:<br />

Optionally, the amplifier LE 150/025 can be equipped by a serial or parallel (CENTRONIX) computer interface (designation as<br />

LE 150/025-S or/-P respectively) for digital control by a fast data transfer and D/A conversion. Up to 3 channels can be operated<br />

simultaneously.<br />

All analog functions of the amplifier remain active. By using ”offset” the amplified signal can be superimposed by a DC-voltage<br />

and the operating voltage range can be varied by ”amplitude” for easy adaption to a distinct application. The resolution is<br />

12 bit.<br />

Order code<br />

LE 150/025 analog amplifier<br />

LE 150/025-S with additional serial interface<br />

LE 150/025-P with additional parallel interface<br />

open<br />

output:<br />

U max/2 >20 kHz<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 100 V/150 V<br />

22 µF 10 msec/50 msec<br />

4 µF 2 msec/ 3 msec<br />

1.2 µF 0.5 msec/ 0.8 msec<br />

330 nF 120 µsec/180 µsec<br />

16 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


LE 150/100 single channel power amplifier<br />

+150 V output<br />

Special features: see chapter 5<br />

Potentiometer “Offset”, “Amplitude”, Current Booster,<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +150 V<br />

Max. peak current: approx. 1200 mA<br />

Max. average current: approx. 350 mA<br />

Gain: 30<br />

Connector: BNC<br />

Noise: approx. 15 mVpp<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 330x260xl55<br />

Weight: approx. 7 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

amplifier for 200 V output: on request<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 100 V/150 V<br />

47 µF 3 msec/7 msec<br />

22 µF 1.8 msec/4 msec<br />

4 µF 330 µsec/500 µsec<br />

1.2 µF 90 µsec/130 µsec<br />

330 nF 20 µsec/35 µsec<br />

Computer interfaces:<br />

Optionally, the amplifier LE 150/100 can be equipped by a serial or parallel (CENTRONIX) computer interface (designation as<br />

LE 150/100-S or/-P respectively) for digital control by a fast data transfer and D/A conversion. Up to 3 channels can be operated<br />

simultaneously.<br />

All analog functions of the amplifier remain active. By using “offset” the amplified signal can be superimposed by a DC-voltage<br />

and the operating voltage range can be varied by “amplitude” for easy adaption to a distinct application. The resolution is<br />

12 bit.<br />

Order code<br />

LE 150/100 analog amplifier<br />

LE 150/100-S with additional serial interface<br />

LE 150/100-P with additional parallel interface<br />

open<br />

output:<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 17


Amplifier system LE 150/200<br />

(formerly LE 150/2)<br />

Modular arrangement of up to 3 independent channels.<br />

For operation of large volume/high capacitance piezoactuators.<br />

The technical data are similar to the LE 150/100 amplifier<br />

except for higher peak current.<br />

Technical data valid per channel.<br />

Special features: see chapter 5<br />

Potentiometer “Offset”, “Amplitude”, Current Booster<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: –10 V thru +150 V<br />

Max. peak current: 2000 mA<br />

Max. average current: approx. 400 mA<br />

Gain: 30<br />

Connector: BNC<br />

Noise: approx. 50 mVpp<br />

Display: LCD, 3 digits<br />

Dimensions: Single channel version LE 150/200-1<br />

BxWxD 340x350x180<br />

Weight: 10 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

Amplifier for 200 V output: on request<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 100 V/150 V<br />

47 µF 2.4 msec/4 msec<br />

22 µF 1.2 msec/2 msec<br />

4 µF 240 µsec/400 µsec<br />

1.2 µF 60 µsec/150 µsec<br />

330 µF 15 µsec/40 µsec<br />

Computer interface:<br />

The amplifier system LE 150/200 is available with a computer interface module for both types of data transfer serial and parallel<br />

(CENTRONIX). Up to 3 channels can be operated simultaneously. All analog functions of the amplifier modules remain<br />

active. By “offset” the amplified digital signal can be superimposed by a DC-voltage and the operating voltage range can be<br />

varied by “amplitude” for easy adaption to a distinct application. The resolution is 12 bit.<br />

Order code: D/A-LE<br />

Analog amplifier LE 150/300<br />

Single channel power amplifier<br />

Output: Voltage range –10 V thru +150 V<br />

Max. peak current: 3 A<br />

Max. average current: 1 A<br />

open<br />

output:<br />

Analog amplifier LE 150/100 bp<br />

Bipolar amplifier system with +/–150 V output.<br />

Voltage range: –150 V thru +150 V<br />

Max. peak current: 1000 mA<br />

Max. average current: 200 mA<br />

18 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


High voltage power amplifiers<br />

LE 430/015 single channel amplifier<br />

+430 V output<br />

Special features: see chapter 5<br />

Potentiometer “Offset”, “Amplitude”, Current Booster,<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +430 V<br />

Max. peak current: 150 mA<br />

Max. average current: approx. 35 mA<br />

Gain: 85<br />

Noise: approx. 50 mVpp<br />

Connector: LEMOSA 0S.250 (BNC adaptor available)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 185x330x150 mm<br />

Weight: approx. 4 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 300 V/430 V<br />

1.2 uF 2 msec/3 msec<br />

660 nF 1 msec/1.4 msec<br />

330 nF 0.5 msec/0.7 msec<br />

100 nF 180 µsec/250 µsec<br />

30 nF 70 µsec/l00 µsec<br />

Computer interfaces:<br />

Optionally, the amplifier LE 430/015 can be equipped by a serial or parallel (CENTRONIX) computer interface (designation as<br />

LE 430/015-S or/-P respectively) for digital control by a fast data transfer and D/A conversion. Up to 3 channels can be<br />

operated simultaneously.<br />

All analog functions of the amplifier remain active. By “offset” the amplified signal can be superimposed by a DC-voltage and<br />

the operating voltage range can be varied by “amplitude” for easy adaption to a distinct application. The resolution is 12 bit.<br />

Order code:<br />

LE 430/015 analog amplifier<br />

LE 430/015-S with additional serial interface<br />

LE 430/015-P with additional parallel interface<br />

open<br />

output:<br />

U max/2 >20 kHz<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 19


LE 1000/035 single channel amplifier<br />

+1000 V output<br />

Special features: see chapter 5<br />

Potentiometer “Offset”, “Amplitude”, Current Booster,<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +1000 V<br />

Max. peak current: 350 mA<br />

Max. average current: approx. 100 mA<br />

Gain: 200<br />

Noise: approx. 50 mVpp<br />

Connector: LEMOSA 0S.250 (BNC adaptor available)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 260x340x160 mm<br />

Weight: approx. 4.5 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

open<br />

output:<br />

Unipolar amplifier LE 500/070<br />

Output voltage 0 V thru +500 V, peak current appr. 700 mA, mean current approx. 250 mA<br />

Bipolar amplifier LE 500/035 bip<br />

Output voltage +/–500 V, peak current approx. 350 mA, mean current approx. 100 mA<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 1000 V<br />

200 nF approx. 0.5 msec<br />

1 µF 3 msec<br />

5 µF 15 msec<br />

20 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


LE 1000/100 single channel amplifier<br />

+1000 V output<br />

Special features: see chapter 5<br />

Potentiometer “Offset”, “Amplitude”, Current Booster,<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5.)<br />

Input resistance: 10 kOhm<br />

Input connector: BNC<br />

Output:<br />

Voltage range: 0 V thru +1000 V<br />

Max. peak current: 1000 mA<br />

Max. average current: approx. 300 mA<br />

Gain: 200<br />

Noise: approx. 50 mVpp<br />

Connector: LEMOSA 0S.250 (BNC adaptor available)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 160x380x210 mm<br />

Weight: approx. 5.5 kg<br />

Options:<br />

Multichannel arrangements: on request<br />

open output:<br />

Unipolar amplifier LE 500/200<br />

Output voltage 0 V thru +500 V, peak current appr. 2000 mA, mean current approx. 700 mA<br />

Bipolar amplifier LE 500/100 bip<br />

Output voltage +/–500 V, peak current approx. 1000 mA, mean current approx. 300 mA<br />

Frequency response<br />

Risetimes:<br />

(for square wave input signal)<br />

Load risetime<br />

capacitance to 1000 V<br />

200 nF approx. 0.2 msec<br />

1 µF 1 msec<br />

5 µF 5 msec<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 21


High efficiency power recharger amplifiers<br />

RCV<br />

The basic philosophy of switches recharging amplifiers is<br />

described in sec. 4.3.<br />

PIEZOMECHANIK offers recharging amplifiers for average<br />

powers of 500 Watts up to the kWatt range.<br />

Because recharging amplifiers have to be adapted to some<br />

extent to the capacitance of the actuator and the desired<br />

driving conditions, a detailed offer is made after receipt of<br />

specifications and requirements.<br />

Generally, the device can be matched to an application<br />

within the below stated limits:<br />

Example:<br />

E.g. RCV amplifiers have been developed for active vibration<br />

cancellation showing following data<br />

Load capacitance: approx. 20 µF<br />

Operating frequency: up to 400 Hz<br />

Voltage range: +/–200 V<br />

Max. peak current: 10 A<br />

Risetime for a 200 V voltage step at 5 µF load: 100 µsec.<br />

If you are thinking about recharging amplifiers for your<br />

application, contact us.<br />

Voltage range: –600 V to +600 V<br />

Peak currents: up to 10 A<br />

Peak power: 2 kW<br />

Average power: 500 W<br />

Ripple/noise by switching mode: approx. 200 mV<br />

Power efficiency with loss-free capacitive load: > 95 %<br />

(definition see sec. 2.5.)<br />

22 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


Power pulsers HVP<br />

(see sec. 2.8.)<br />

The HVP switches/pulsers show 3 operational levels<br />

positive square wave = charging of actuator<br />

negative square wave = discharging of actuator<br />

zero level = output neutral: no charge transfer = steady state<br />

of actuator.<br />

The internal supply (source) voltage of the HV pulser can be<br />

set by a potentiometer and is shown on the front panel LC<br />

display. The specified peak currents are achieved for max.<br />

supply voltage setting.<br />

General data<br />

Input:<br />

signal “high” = charging of actuator: > +3 V<br />

signal “low” = discharging of actuator: < –3 V<br />

signal “neutral” no charge transfer: 0 V<br />

Connector: BNC<br />

Output:<br />

Voltage/currents see listing<br />

Average power: 50 Watts<br />

Minimum pulse width: approx. 3 µsec<br />

Repetition rate: up to 50 kHz<br />

Connectors: LEMOSA 0S.250 and 2 banana pin plugs<br />

Types max. voltage peak Load time constant RC/<br />

currents resistors for load capacitance<br />

V A Ohms<br />

HVP 200/50 +200 50 4 40 µsec / 10 µF<br />

HVP 200/100 +200 100 2 20 µsec / 10 µF<br />

HVP 500/20 +500 20 25 25 µsec / 1 µF<br />

HVP 500/50 +500 50 10 10 µsec / 1 µF<br />

HVP 500/100 +500 100 5 5 µsec / 1 µF<br />

HVP 1000/10 +1000 10 100 50 µsec /0.5 µF<br />

HVP 1000/20 +1000 20 50 25 µsec /0.5 µF<br />

HVP 1000/50 +1000 50 20 10 µsec /0.5 µF<br />

Options: HVP can be supplied for altered source voltages<br />

altered current ratings<br />

higher average powers<br />

Power resistor box PRB:<br />

The peak current of a HVP switch can be reduced by using the external resistor box PRB e.g. for adaption to a lower capacitance<br />

actuator. It contains 3 power resistors of different ratings and is connected between HV-switch and actuator.<br />

The resulting peak current is determined by the total resistance of the arrangement:<br />

internal resistor of switch (see listing) + the external resistor.<br />

The box is equipped with one input coax cable/LEMOSA 0S.250 plug. Each resistor has its individual output connector and is<br />

selected thereby.<br />

PRB I: 1 resistor 2 Ohms<br />

1 resistor 5 Ohms<br />

1 resistor 10 Ohms<br />

PRB II: 1 resistor 10 Ohms<br />

1 resistor 20 Ohms<br />

1 resistor 50 Ohms<br />

Input/output connectors: LEMOSA 0S.250 (BNC adaptors<br />

available).<br />

Display: 3 1 /2 digit LCD<br />

Dimensions: WxDxH 260x340x160<br />

Weight: 4.5 kg<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 23


Amplifiers for push-pull actuator configuration<br />

Bimorph amplifiers<br />

(see sec. 3.1./4.5)<br />

BMT 60 bimorph amplifier<br />

For the philosophy of driving multilayer bimorph actuators<br />

under electrically preloaded conditions check brochure<br />

“piezoelectric bending elements”. In this case, the ceramic is<br />

operated with permanently forward polarized voltage and<br />

thereby prevented from depolarization, so the maximum<br />

mechanical performance is achieved.<br />

The bimorph amplifier BMT 60 has been designed to drive<br />

multilayer-benders elements in the above described optimum<br />

way with high dynamics.<br />

Because of the analogy of the electrical operation of antagonistic<br />

piezostacks configuration and bimorphs, the BMT 60<br />

can also drive complementary acting push-pull stack<br />

arrangements (sec. 3.1.)<br />

Special features:<br />

Potentiometer “Offset”<br />

Potentiometer “Amplitude”<br />

Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 100 kOhm<br />

Input connector: BNC<br />

Output:<br />

3 pole connector for ground 0 V,<br />

fix voltage U F +60 V<br />

Signal voltage U S 0 V thru +60 V<br />

Max. peak current: 280 mA in each branch<br />

Gain: 12<br />

Noise: approx. 20 mVpp<br />

Connector: 3 pole connector LEMOSA<br />

(1 m cable with suitable plug is included)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 165x210x70 mm<br />

Weight: approx. 1.4 kg<br />

output<br />

connector<br />

24 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com


AGV 150/013 amplifier<br />

This amplifier has been designed to operate low voltage<br />

stack push-pull configurations in the electrically preloaded<br />

mode (see sec. 4.5.). Because of the analogy in the electrical<br />

driving scheme, also bimorph elements can be operated by<br />

this amplifier with high efficiency.<br />

Special features: Potentiometer “Offset”, “Amplitude”,<br />

Current Booster, Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 100 kOhm<br />

Input connector: BNC<br />

Output:<br />

3 pole connector for ground 0 V,<br />

fix voltage U F +150 V<br />

Signal voltage U S 0 V thru +150 V<br />

Max. peak current: 130 mA in each branch<br />

Max. average current: 70 mA in each branch<br />

Gain: 30<br />

Connector: 3 pole connector LEMOSA<br />

(1 m cable with suitable plug is included)<br />

Noise: approx. 20 mVpp<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 185x330x150 mm<br />

Weight: approx. 4 kg<br />

AGV 430/08 amplifier<br />

This amplifier has been designed to operate high voltage<br />

stack push-pull configurations in the electrically preloaded<br />

mode (see sec. 4.5.). Because of the analogy in the electrical<br />

driving scheme, also bimorph elements can be operated by<br />

this amplifier with high efficiency.<br />

Special features: Potentiometer “Offset”, “Amplitude”,<br />

Current Booster, Monitor output<br />

Input<br />

Input: +/–5 V (+/–10 V see chapter 5)<br />

Input resistance: 100 kOhm<br />

Input connector: BNC<br />

Output:<br />

3 pole connector for ground 0 V,<br />

fix voltage U F +430 V<br />

Signal voltage U S 0 V thru +430 V<br />

Max. peak current: 80 mA in each branch<br />

Max. average current: 35 mA in each branch<br />

Gain: 85<br />

Noise: approx. 50 mVpp<br />

Connector: 3 pole connector LEMOSA<br />

(1 m cable with suitable plug included)<br />

Display: LCD, 3 digits<br />

Dimensions: WxDxH 185x330x150 mm<br />

Weight: 4.5 kg<br />

output<br />

connector<br />

output<br />

connector<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 25


The optionally available interfaces which are integrated to<br />

amplifiers are described in the corresponding data sheet for<br />

the amplifiers e.g. LE 150/025-S.<br />

This basic range of interfaces is completed by the units<br />

described in the following section<br />

1. Stand alone D/A converter DAI-3:<br />

The DAI-3 unit corresponds to the interface option D/A-LE of<br />

the LE 150/200 amplifier system. It shows both serial and<br />

parallel (CENTRONIX) data input for handling up to 3 channels<br />

independently. The analog output is 0 V thru +10 V and<br />

can be plugged directly to the analog amplifiers described in<br />

this catalog. It is obvious, that the DAI-3 unit can be used to<br />

control any other system, requiring an analog input control<br />

signal.<br />

front<br />

D/A converters, Computer-Interfaces<br />

2. PC-plug in cards with analog HV-output<br />

The PC plug in-cards generate the analog HV-signal for<br />

immediate operation of piezoactuators or other loads.<br />

The advantages of the PC-AHV cards are the spacesaving<br />

arrangement within the computer cabinet, where no external<br />

additional amplifiers are needed and the speed and reliability<br />

of data handling. The cards show current boosters for<br />

elevated driving dynamics.<br />

They are available in single and triple channel versions.<br />

General data<br />

• PCI-Bus<br />

• 8 bit data bus<br />

• Setting of port address by a DIL switch<br />

• Voltage resolution 14 bit for unipolar output<br />

13 bit for bipolar output<br />

• Width 1 slot<br />

• PC board dimensions<br />

Interfaces: serial RS 232<br />

parallel (CENTRONIX)<br />

Resolution: 12 Bit<br />

Output signal: 0 V thru +10 V (other settings e.g. bipolar: on<br />

request)<br />

High modulation rate of output: up to kHz with parallel data<br />

transfer e.g. for fast feedback control systems.<br />

Line operation<br />

3 analog independent outputs<br />

26 Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators http://www.piezomechanik.com<br />

rear


PC-AHV +150/1 single channel<br />

Output voltage: 0 V thru +150 V<br />

Max. peak current: 75 mA<br />

Max. average current: 25 mA<br />

Resolution: 14 bit<br />

Noise: approx. 5 mV<br />

Output connector: LEMOSA 00.250 (BNC adaptors available)<br />

PC-AHV +150/3 triple channel<br />

Output voltage: 0 V thru +150 V<br />

Max. peak current: 75 mA/channel<br />

Max. average current: 25 mA (total for 3 channels)<br />

Resolution: 14 bit<br />

Noise: 5 mV<br />

Output connector: LEMOSA 00.250 (BNC adaptors available)<br />

PC-AHV 150bp/1 single channel<br />

Bipolar output voltage: –150 V thru +150 V<br />

Max. peak current: 50 mA/channel<br />

Max. average current: 15 mA<br />

Resolution: 13 bit<br />

Noise: approx. 5 mV<br />

Output connector: LEMOSA 00.250 (BNC adaptors available)<br />

Optionen: geänderte Leistungsdaten, Ausgangsbuchsen etc. auf Anfrage<br />

Feedback Control Stabilization PiStab-2<br />

Modern HiTechnologies often use physical effects, which are<br />

extremely sensitive in magnitude to any small deviation from<br />

the correct position of the mechanical components of the<br />

device. Any misalignment e.g. by thermal drifts can diminish<br />

the device performance e.g. the optical output power of a<br />

discretely setup laser resonator). Other examples are the<br />

coupling efficiency of freely coupled optical fibers, interferometers,<br />

sensor/transducer arrangements in microsystems,<br />

biological systems etc.<br />

To ensure a stable optimum operation the task is to detect<br />

the onset of mechanical misalignment and to readjust the<br />

Mirror mount with 2 piezocontrolled degrees of freedom and a PiStab-2<br />

feedback controlled electronics/supply<br />

PC-AHV 150bp/3 triple channel<br />

Bipolar output voltage: –150 V thru +150 V<br />

Max. peak current: 50 mA/channel<br />

Max. average current: 15 mA (total for 3 channels)<br />

Resolution: 13 bit<br />

Noise: approx. 5 mV<br />

Output connector: LEMOSA 00.250 (BNC adaptors available)<br />

PC-AHV +500/1 single channel<br />

Output voltage: 0 V thru +500 V<br />

Max. peak current: 15 mA<br />

Max. average current: 5 mA<br />

Resolution: l4 bit<br />

Noise: approx. 5 mV<br />

Output connector: LEMOSA 0S.250 (BNC adaptors available)<br />

PC-AHV +500/3 triple channel<br />

Output voltage: 0 V thru +500 V<br />

Max. peak current: 15 mA/channel<br />

Max. average current: 5 mA (total for 3 channels)<br />

Resolution: 14 bit<br />

Noise: approx. 5 mV<br />

Output connector: LEMOSA 0S.250 (BNC adaptors available)<br />

components actively. For micro- and nanopositioning purposes,<br />

the first choice include all kinds of piezoactuated<br />

systems such as stacks, bimorphs, hybrid systems etc.<br />

The stabilization electronics PiStab-2 controls up to<br />

2 degrees of freedom for mechanical longterm stabilization of<br />

position sensitive effects.<br />

For more details please ask for brochure “PiStab-2”.<br />

Example: Stabilization of a laser resonator<br />

piezoelectric actuators x, y<br />

controlled end mirrow<br />

operating<br />

+ modulation input<br />

PiStab-2<br />

photodiode<br />

signal with<br />

modulation<br />

Arrangement for stabilizing an Ar laser for maximum output power<br />

against misalignment by tilting one of the resonator mirrors for<br />

2 degrees of freedom by 2 low voltage actuators in a mirror mount<br />

http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators 27


Accessories:<br />

PIEZOMECHANIK supplies a wide range of connecting<br />

systems, adaptors, extension cable to make the installation<br />

and compatibility of components as easy as possible.<br />

When a complete actuator/amplifier system is ordered, the<br />

actuators will be equipped with the plugs corresponding the<br />

amplifier’s connector.<br />

Further adaptors are available for the combination different of<br />

connector systems.<br />

Adaptors:<br />

Plug coupler<br />

BNC LEMOSA 00.250 (low voltage systems)<br />

BNC LEMOSA 0S.250 (high voltage systems)<br />

LEMOSA 00.250 BNC<br />

LEMOSA 0S.250 BNC<br />

Coaxial cable RG 178 with plug – one end free, length 1.5 m standard, other lengths on request<br />

LEMOSA plug 00.250<br />

LEMOSA plug 0S.250<br />

BNC<br />

Extension cables with plug and coupling end, length standard 2 m, other lengths on request<br />

LEMOSA 00.250 system<br />

LEMOSA 0S.250 system<br />

Extension cables combining different connector systems e.g. BNC-LEMOSA on request.<br />

Custom designed amplifiers<br />

If you cannot find the proper electronic supply to solve your actuating problem, please contact us. PIEZOMECHANIK can<br />

adapt the available standard devices to your needs (e.g. for 12 V, 24 V or other line voltages).<br />

On request custom designed electronics can be used.<br />

INNOTICS INC.<br />

#Rm1016, Sam-Poong B/D, 310-68, Eul-Gi-4Ga, Joon-Gu,<br />

100-849, Seoul, Republic of KOREA<br />

Tel. :+82-2-2276-1013<br />

Fax. :+82-2-2274-0469<br />

¤É¤Ñ¤Website : www.innotics.com<br />

E-mail : sales@innotics.com<br />

<strong>Piezomechanik</strong> · Dr. Lutz Pickelmann GmbH<br />

Berg-am-Laim-Str. 64 · D-81673 München · Tel. XX 49/ 89 / 4 3155 83 · Fax XX 49/89/4 31 6412<br />

¡¤§¤¤¿<br />

e-mail: info@piezomechanik.com · http://www.piezomechanik.com Stand: November 1998

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!