Controllable power supply units for plant engineering, research and development
Programmable - high-precision - very fast - EMI-immune - bipolar & unipolar


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Controllable DC- & AC- Power supply units
For plant engineering, research and development programmable

high-precision / extremely fast / EMI-free / bipolar & unipolar / 10W to 12kW

SERVOWATT power supply units are completely different !

Installing power supply units for plant and systems. These power supply units are mainly installed in control units for machines, plant and systems; unlike Laboratory power supply units, they do not need a costly protective housing, extensive displays or switches and controllers.

Controllable power supply units. They are precisely the opposite of a "constant" unit with a big capacitor at the output which just permanently supplies the same current or the same constant voltage. With up to four control inputs, they offer a maximum of convenience for ideally fulfilling all possible control engineering tasks, for adding or subtracting control signals or for working as an independent servo system. Extremely fast and precise control systems for power, acceleration, speed, temperature and generally all physical parameters and their processes can be stabilised and independently controlled in this simple manner.

Linear output stages make our power supply units extremely fast and highly precise. We do precisely the opposite of a "normal", slow power supply unit. They work internally with large amplification and bandwidth to achieve speed and precision simultaneously. In standard devices with 500 watts it is possible to alter the output voltage by up to 5 volt per microsecond, which corresponds to frequencies up to 30 kiloherz. Linear output stages don't produce any interferences. These output stages work flexibly and basically produce no interference in the power supply unit. Adjacent systems are not disrupted by external signal components, pulse needles, harmonics or noise.

Choosing the right power supply unit:
Choice of polarity. Depending on the polarity of the output voltage in relation to the main ground, we differentiate with all our power supply units between three device categories: positive, negative and bipolar versions equivalent to 1 and 4 quadrants. Unipolar power supply units can only supply energy in one direction. Bipolar power supply units, on the other hand, can take back energy and therefore very quickly dissipate currents and voltages! This is especially important for loads with capacitances and inductors because these loads have an energy-storing effect.

Tailor-made power supply units - This is our standard

Choosing the right power supply-unit:
1.) Selecting the polarity

Depending on the polarity of the output voltage in relation to the main ground, we distinguish with our power supply units between three device categories: positive, negative and bipolar versions.

Positive unipolar 1-quadrant operation: This is the most frequently used DC power supply unit with a positive output voltage in relation to the ground. Our circuit design even allows external control of the voltage right down to zero, even with full current.

Negative unipolar 1-quadrant operation: There are also applications which require negative voltage in relation to the main ground. These DC power supply units can also be controlled by any potentials from above or below zero volts/main ground.

Bipolar power supply unit or 4-quadrant operation: For applications which require both a positive and a negative output voltage, we offer a third version: controllable AC/DC power supply unit with limit frequencies up to 100 kHz.

Our power supply units can be controlled externally: With up to four control inputs, they offer a maximum of convenience for ideally fulfilling all possible control engineering tasks: The E1, E2, E3 and E4 control inputs can be used as set/nominal or actual value inputs. It is important, to know that the control signals may have a positive or negative potential regardless of the output polarity voltage, in relation to the main ground. Any voltages or currents (e.g. 0-20 mA or 4-20 mA) can be used as control signals.

The analogue controller at the control input ensures speed and precision.

Convincing technical data:
- Small input bias currents, typically 3,0 nA
- Very high internal amplification, better than 20.000.000V/V
- Small offset temperature drift, typically < +- 0,2µV/K
- Offset adjustment, extremely precise: Typical range +- 1,0mV
- High power bandwidth, typically 25kHz, versions up to 100kHz also available
- High slew-rate, typically 5V/µs, versions up to 40V/µs also available
- Very high input impedance, typically 100M Ohms (differential)
- High common mode rejection voltage, typically 135dB at 10Hz
- Excellent linearity
- Zero Ohm impedance at output
- Continuous short-circuit, operation permissible
- Linear power output 25 W to 2 kW, (PWM from 300 W to 12 kW)

2.) Function selection on controllable power supply units
We distinguish between control types: Voltage control is the default. We offer our customers two further externally controllable functions: Current control and servo control.
Voltage controller: As a voltage controller with an output impedance of zero Ohms, the output voltage is always constant and independent of the load so that the current adapts to the load.
Current controller: As a power source, it is precisely the reverse, the output impedance is infinite, the impressed current always remains constant and the voltage adapts to the load.
Servo controller: As a servo controller, the control voltage is compared to the signal supplied by a sensor of the parameter to be stabilised, e.g. a speed.

Contrary to a normal control signal in relation to the zero potential of the main ground, the power supply unit can also be controlled as a differential amplifier by two potentials which are not related to the main ground. We then define your desired power supply unit function by means of a programming PCB between the control inputs and the E+ and E- differential inputs.

For instance it is possible to compensate the voltage drop in long control cables to the load by means of additional sense-cables. Furthermore, the control signals can be integrated and differentiated to achieve specific properties such as high-pass and low-pass filtering. All these special control options turn these power supply units into real supply all-rounders.

Three device versions are available which all basically offer the same functionality.
The chassis versions are designed for higher power ratings, whilst the 19-inch PCBs and the VM series are intended for smaller power ratings.
Chassis versions: DCP-Series: 120 - 4.000 W / +-10V to +-70V / Complete AC-DC power supply unit
Ready for connection with integrated power supply, fan and heat sink
19 inch euroboards: 10 - 800 W / +-10V to +-70V / 19" power supply unit for / connection to a separate
power supply
Mini power supply units / VM-Series : 10 - 400 W / +-10V to +-70V / Value-for-money power supply units / with/without heat sink and power supply as flange version

Power supply units with a linear output stage offer many advantages
Linear output stages do not offer the highest degree of efficiency. This clean solution does, however, offer many advantages which cannot be achieved otherwise. In today's measuring technology alone, such small signals are processed that all sources of interference are generally completely unwanted.

Extremely fast control - Virtually time lag-free reaction in control circuits. Highly dynamic controls demand a time lag-free reaction from voltage and current controllers. In this highly dynamic servo system, the moving coil DC motor accelerates precisely from zero to 2000 rpm with 40 A in just 2.7ms!

Linear control - Infinite resolution without residual ripple. Figure A: Filtered PWM signal. Dynamic control processes demand output stages without a retarding filter at the output. Figure B: Only a linear output stage can supply infinite resolution and high precision to the load.

High power bandwidth - Standard devices typically with 25 kHz Special devices up to 500 kHz: Real-time controllers demand a high power bandwidth equivalent to a high output stage voltage slew rate. Photo: Frequency 55 kHz, slew rate +-- 20V/µs, output +-30V / 4A

EMC immunity - No impulse interference, harmonics or noise in the system. These linear output stages work continuously and basically produce no interference. Adjacent systems are not disrupted by external signal components, pulse needles, harmonics or noise.

Distortion-free bipolar control through zero and therefore the highest dynamic precision. The precise management of current and voltage demands control through zero without dead zones and dead time. In the illustration, current and voltage constantly go through zero. The load therefore remains actively managed in the zero range.

Short-circuit-proof output stages - Exemplary reliability for Demanding applications: Transistors with up to an 8-fold (!) total dissipation loss value guarantee the high reliability of the output stages. Our 4-quadrant operation includes continuous short-circuit operation.

SERVOWATT quality Turn your ideas into reality - Create values

Quality without compromises: The characteristic tracer gives the most reliable indication of the semi-conductors' inner workings. The output stages are tested according to a number of criteria: Maximum voltage, saturation voltage, current amplification, leakage current and insulation voltage.

Realising projects with SERVOWATT power sources

ESO project successfully completed! International research project at the VLT giant telescope in North Chile: success is also the sum total of many correct decisions and developments in a chain of suppliers. Customer-orientation and zero defect quality in this chain are absolutely imperative for SERVOWATT.

SERVOWATT Leistungselektronik GmbH
Fritz-von-Graevenitz-Str. 1-5
70839 Gerlingen (near Stuttgart) - Germany
Tel: 0049 - (0)7156 - 24041 Fax: - 29944 Mail:

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SERVOWATT Leistungselektronik GmbH, 70839 Gerlingen near Stuttgart / Germany
Phone +49 (0) 7156 - 24041, Fax +49 (0) 7156 - 29944, Email info [at]