PDUS210 - 210 Watt Ultrasonic Driver
The PDUS210 is a complete solution for driving precision and high-power ultrasonic actuators. The amplifier includes high-speed resonance tracking of a series or parallel resonance modes, vibration amplitude control, and analysis functions such as impedance and frequency response measurement. The PDUS210 is well suited to both OEM product integration and laboratory use for research and development. Applications include ultrasonic drilling and cutting, medical devices, dental devices, ultrasonic testing, liquid cavitation, and vaporization.
The PDUS210 is controlled via USB and the included software package. An RS485 interface also provides a straight-forward method to control and monitor the amplifier for automatic test and OEM applications.
The PDUS210 generates a pure sine-wave output which avoids the excitation of secondary resonance modes by the drive harmonics. This makes it ideal for operating at the electrical parallel resonance, or “anti-resonance”. This operating point is close to the mechanical resonance frequency but is less sensitive to changes in load dissipation, which is useful in precision machining applications where constant vibration amplitude is desired.
The PDUS210 is available with standard output voltage ranges from 17 Vrms to 282 Vrms, and current ranges from 0.7 Arms to 11 Arms. These ranges are optimized for load impedances ranging from 1.5 Ohms to 400 Ohms at resonance. For research and development applications, a reconfigurable version is available (PDUS210-FLEX) which uses external output matching transformers that are purchased separately. A transformer kit (TX210-Kit1) is also available, which includes all six standard output voltage ranges at a discounted price.
Ultrasonic Drive Methods
For an introduction to driving ultrasonic transducers, refer to Introduction to Ultrasonic Drivers
Resonance Tracking and Amplitude Control
The following figure plots the mechanical and electrical frequency response of an ultrasonic transducer. The impedance minima at is known as the series resonance, which is approximately equal to the mechanical resonance frequency. At this frequency, the phase response has a high slope and value of zero degrees. Resonance tracking is achieved by varying the drive frequency to regulate the phase to zero. Alternatively, the phase set point can be selected to operate above or below resonance, which may provide higher immunity to load variations. Systems with low quality factor may have phase responses that are non-zero at resonance. In such cases, an impedance response should be performed to identify the desired operating phase.
Electrical and mechanical response of an ultrasonic transducer.
The resonance tracking system of the PDUS210 is described in the diagram below. A phase detector (M) measures the impedance phase angle between the primary voltage and current. The phase controller Cθ(s)varies the drive frequency to maintain a constant phase set point θref.
Phase control loop in the PDUS210 driver.
When operating at the series resonance, the vibration amplitude is approximately proportional to the actuator current. Therefore, to minimize sensitivity to load variations, the RMS current should be held constant. To achieve this, the PDUS210 can be operated with either voltage or current set points.
The electrical response also exhibits an impedance maxima, known as the parallel resonance. At this frequency the applied voltage is approximately proportional to the vibration amplitude, so constant voltage excitation is most commonly used. Phase tracking at the parallel resonance is identical to the series resonance, except for the opposite slope of the phase curve, which requires a negative controller gain. Any positive phase controller gain will track a series resonance mode, while any negative controller gain will track a parallel resonance mode.
Choosing the Voltage Range
The PDUS210 is available in voltage ranges from 17 Vrms to 282 Vrms, which correspond to impedances ranging from 1.5 Ω to 400 Ω. The optimal choice is determined by the transducer impedance at resonance, and the choice of series or parallel resonance.
The first step is to measure the impedance of the transducer at the series and parallel resonance. This can be performed with an impedance analyser or simply a signal generator and oscilloscope. If possible, these tests should be performed at moderate power with both minimum and maximum load conditions. Fill out the values in the table below:
Table of operating impedance at resonance.
For operation at the series resonance, the most suitable amplifier has an optimal impedance which is close to, or slightly greater than the fully loaded impedance. Since transducer impedance tends to increase with applied power, an amplifier with a higher optimal impedance is recommended. If the amplifier has a higher optimal impedance than the load, the current limit will be reached before the voltage limit, and the maximum achievable output power is:
where Irms is the maximum driver current.
For operation at the parallel resonance, the most suitable amplifier has an optimal impedance which is close to, or slightly less than the fully loaded impedance. Since transducer impedance tends to reduce with applied power, an amplifier with a lower optimal impedance is recommended. If the amplifier has a lower optimal impedance than the load, the voltage limit will be reached before the current limit, and the maximum achievable output power is:
where Vrms is the maximum driver voltage.
Custom Voltage Range
Custom voltage ranges and optimal impedances are available to provide maximum power for a specific transducers.
|Output Voltage||0 - 800 Vp-p||See standard voltage ranges|
|Output Current Max||0 - 32 Ap-p||See standard voltage ranges|
|Optimal Load Impedance||1.5 - 400 Ohms||See standard voltage ranges|
|Output Waveform||Sine wave|
|DC Output Voltage||Zero||DC Offset Possible|
|Output Isolation||Isolated or Grounded|
|Max Output Power||210 W||With optimal load impedance|
|Internal Power Dissapation||130 W||Maximum|
|Frequency||20 - 200 kHz||6 kHz to 500 kHz possible|
|Power Supply||48 V, 280 Watt|
|Controller||Phase tracking, current control, power control||2 ms frequency update rate Resonance or anti-resonance|
|Interface||USB, RS485||RS232 possible|
|Digital IO||4 DIO||
For manual control
|Enclosure Dimensions||227 x 168 x 54 mm (L x W x H)|
|Temperature Range||0C - 50C|
Standard Voltage Range
|Output Voltage Range|
|Order Code||Max Voltage||Max Current||Optimal|
Note: The output voltage resolution and tolerance is 8 bits, or 256 levels. Therefore, the smallest possible change in voltage is FSR / 256, where FSR is the full scale range in any units. The minimum output voltage is also limited by resolution. When the amplifier is enabled and the output voltage is set to zero volts, the actual output voltage may be up to 1% of FSR.
The relationship between maximum achievable power and the load impedance is plotted in the following figure. In this plot, the impedance is normalized to the optimal impedance. For example, the optimal impedance of the PDUS210-400 is 100 Ohms. From the plot, it can observed that greater than 100 W can be achieved with a normalized impedance from 0.65 to 2.1, which for the PDUS210-400, is 65 Ohms to 210 Ohms.
Maximum output power versus normalized impedance
The impedance ranges for other common power levels are listed in the following table. For example, all amplifiers will supply more than 150W with a normalized load impedance between 0.71 and 1.4. For the the PDUS210-400, this is equivalent to 71 Ohms and 140 Ohms.
|Minimum Power||Z Low||Z High|
Range of normalized load impedance versus output power
|OVL||Indicates an overload or shutdown state, see overload protection|
|USB||USB 2.0 Type-B device connector|
|L1||Uncommitted LED indicator|
|L2||USB Activity indicator|
|RS485||Isolated RS485 interface, GND is the remote ground|
|Test||+/-4V Input produces full-range output voltage. Test use only|
|Aux||Connected to ADC converter, not presently used|
|Current Monitor||Output current monitor, AC Coupled. The gain is 0.00264 x Vpp V/A|
|Voltage Monitor||Output voltge monitor, AC Coupled. The gain is 5.06/Vpp V/V|
|Lemo HV Output||Suits LEMO 0B.302 Connector (E.g. FGG.0B.302.CLAD42)|
|Screw HV Output||Suits Anphenol TJ0331530000G Connector|
The sensitivity of the current and voltage monitors are determined by the peak-to-peak output voltage range. For example, the peak-to-peak output voltage range of the PDUS210-400 is 400, so the current gain is 1.056 V/A, and the voltage gain is 0.01265 V/V.
|Remote Control||Digital Input-Output (D-SUB9 Connector) The Pinout is:|
|1. 3.3V Supply|
|2. In1 (3.3V to 24Vlogic, max 30V)|
|3. In2 (3.3V to 24V logic, max 30V)|
|4. Out1 3.3V logic (24V output optional)|
|5. Out2 3.3V logic|
|Power 1||Suits Amphenol TJ0331530000G Connector|
|Power 2||Suits 6-Pin power connector for Meanwell GST280A48-C6P|
|RS232||Isolated RS232 serial port. Uses same isolated supply as RS485, do not use both simultaneously (D-SUB9 Connector) The pinout is:|
|1. Not Connected|
|2. Receive In|
|3. Transmit Out|
|4. Not Connected|
|5. Isolated Ground|
There are four types of overload protection:
This overload is triggered when the current to the power amplifier exceeds 5.7 Amps average. When triggered, the power amplifier is shutdown, causing the “Overload” front panel LED to illuminate. To restart the amplifier, an enable command is required.
At power-on, the power amplifier is shutdown by default and requires an enable command to start.
Load Power Dissipation Overload
This overload is triggered when the real power dissipated by the load exceeds the threshold defined in the user interface. An enable command is required to clear this overload.
Amplifier Power Dissipation Overload
This overload is triggered when the real power dissipated by the power amplifier exceeds 100 Watts. An enable command is required to clear this overload. Triggering this overload usually means that the load impedance is poorly matched to the output voltage and current range of the amplifier.
This overload is triggered when the heatsink temperature exceeds 70C. An enable command is required to clear this overload. Check the fan and heatsink for blockages.
Frequency Sweep Overview
To Track a Resonance
RS485 is a two-wire communication standard, commonly used for industrial machine-to-machine, and computer-to-machine communications (Introduction to RS485).
The PDUS210 responds to the commands described in https://github.com/PiezoDrive/RS485-API
An example script for Python (example.py) can be found at https://github.com/PiezoDrive/RS485-API.
For testing purposes or to control the amplifier from a PC, an RS485 USB cable is required, for example, FTDI USB-RS485-WE-1800-BT. The connection diagram below is recommended. A text based application such as Putty can be used to send or receive commands.
Standard Delivery Contents
- PDUS210 amplifier with chosen configuration e.g.PDUS210-800
- Power supply, 280W 48V, Meanwell GST280A48-C6P
- IEC C13 Mains power cable suitable for the shipping destination
- USB Cable, Type A to Type B, 3 foot.
- 2 x Three-way Plug-in screw terminal connectors (Amphenol TJ0331530000G, or similar)
- 1 x Four-way Plug-in screw terminal connectors (Amphenol TJ0431530000G, or similar)
Warranty and Service