Application-Specific Capacitors for Laser Power Supply Units

Power supply units for high-power laser diodes in research systems require special capacitors: They must ensure fast discharge of the energy that is needed for the generation of high-current pulses. Mersen delivers custom solutions that are successfully used in the power supply units of Schumacher Elektromechanik GmbH

Back in 1949 Schumacher Elektromechanik GmbH started manufacturing transformers and industrial electronic components, as well as power supply units. Among other achievements, the company made a major contribution to the development and production of the first model wireless remote control. In the 90s Schumacher produced the first special power supply units for lights, and later also for industrial and laser applications – the latter including the necessary software controllers. Today Schumacher Elektromechanik GmbH specializes in the development of laser power supply units, as well as integrated cooling units and their controllers. This is achieved by means state-of-the-art production systems, which can also be used for the manufacture of externally developed products.

 

Figure 1: Mersen FTCAP capacitors are the right choice for special applications in small and medium quantities

 

Application-specific capacitors for laser power units

“We are very active particularly in the areas of laser power supply units and controllers”, explains R. Winkler, Head of Purchasing at Schumacher Elektromechanik GmbH. “The fact is that the various laser types require custom solutions.” The Schumacher product spectrum ranges from CW power supplies for argon lasers and highvoltage power supplies for CO2 lasers through CW and pulse power supplies for light-pulsed and diode-pumped lasers, all the way to integrated cooling elements, Pockels cell drivers, TEC controllers, Peltier power supplies and controller supplies for excimer lasers. Of course, it is also possible to combine different supply types. The power supply units cover power ranges from a few watts to 20 KW.

Buffering of the voltage in the power supply units requires capacitors, which Schumacher has been purchasing from Mersen for many years. The main demand is for aluminium electrolytic capacitors of the SIH and GW series. The latter are used for example in the power supply units for high-power laser diodes in research systems: Such systems require fast discharge of the energy for generation of highcurrent pulses of about 100-500µs. “The capacitors are integrated in the capacitor bank of a laser power unit, where they buffer the supply voltage”, explains R. Winkler. “The aluminium electrolytic capacitors are very reliable in this application and fulfil the requirements of our specifications.”

 

Figure 2: Schumacher also purchases aluminium electrolytic capacitors of the SIH series from Mersen

 

Thermally optimized for high ripple currents

The GW series are threaded FTCAP capacitors that are insensitive to high ripple currents. As a side effect, however, the high currents also cause increased temperatures in the capacitors. Special winding constructions therefore ensure optimal heat dissipation at the capacitor base. In addition, the GW series is optionally equipped with base cooling by means of a Sil-Pad that dissipates the heat.

 

Figure 3: The GW series capacitors are used by Schumacher for example in the power supply units for high-power laser diodes in research systems

 

A special feature of the GW series is the patented stepped base: This design ensures that the base of the capacitor is flat despite the adjacent heat shrink tube. Air inclusions are therefore reduced, which would hinder dissipation of heat from the capacitor to the heat sink. Thermal resistance is substantially lower, for processing of high loads despite the compact design. In addition, the cup features an outer bead, which allows seamless mounting of the capacitor to a heat sink by means of a ring clamp manufactured in-house by Mersen. A positive side effect is that the pad and the use of a ring clamp for mounting electrically insulate the capacitor from the heat sink. This provides a large leakage distance that prevents the flow of residual earth-fault currents.

GW series aluminium electrolytic capacitors are designed for high performance despite their compact size. Their optimised internal construction achieves a high CV (capacity-voltage) product. The advantage is minimal power loss as soon as an electrical load is applied. Since the special design not only saves space but also improves cooling performance, this also reduces costs to the user.

 

Custom developed capacitors for successful applications

R. Winkler is very satisfied with the GW series capacitors: “Like all Mersen components, they function with absolute reliability.” Another advantage for the head of purchasing is that the Mersen location based in the North of Germany can also implement custom requirements if needed: “Mersen produces custom-tailored capacitors for several of our applications.” This versatility is a unique selling proposition in the industry – FTCAP capacitors are the right choice for special applications in small and medium quantities. The special field is customized special solutions.

In addition, the company offers a range of high-quality standard products, but always with the option of adapting them – for example, if a customer needs a normal form with requirements for adaptation of other factors, such as voltage, current, dimension, pulse resistance, and oil resistance. “The cooperation – from development through to large-scale production – is very well structured and the subsequent production process is streamlined and well organized. We are satisfied and look forward to future challenges”, concludes R. Winkler.

 

About the Author

Jens Heitmann holds a Master's and Bachelor's Degree in International Management Studies at European University Flensburg and a Master's and Bachelor's Degree in International Business, Language, and Culture at the University of Southern Denmark. He currently works as the account manager/marketing manager at FTCAP GmbH since January of 2016. He is particularly skilled in marketing, employer branding, and brand development.

 

This article originally appeared in the Bodo’s Power Systems magazine.