Snubbers implementation for magnetron sputtering systems switched mode power supplies

Аuthors

Oskirko V. O.^*, Semenov V. D.^**, Pavlov A. P.^***

Tomsk State University of Control Systems and Radioelectronics, 40, Lenin str., Tomsk, 634050, Russia

*e-mail: oskirkovo@gmail.com
**e-mail: svd@ie.tusur.ru
***e-mail: apeltom@yandex.ru

Abstract

As a rule, high frequency switched mode power supplies (SMPS) are used for reactive magnetron sputtering [1 3]. The point is that such pulse powering allows reducing the probability of electric arcs occurrence and increases stability of reactive magnetron sputtering process. One of the main parts of SMPS for magnetron sputtering systems (MSS) is a transistor former of output pulses. It determines the power source type (unipolar, bipolar, HIPIMS) and its operating efficiency.

As is well known, in contrast to continuous input current mode, switching losses, peculiar to switched mode limit maximum switching frequency, and subject transistors to pulse overloads decreasing the reliability of a pulse former. If soft commutation of transistors is provided, zero-voltage or zero-current switching will allow reduce dynamic losses in transistors and increase reliability of a pulse former.

Reference [4] presents modular SMPSm based on bipolar pulse former (BPF), where soft switching was provided by using snubbers, limiting the current or voltage growth rate during transistors switching.

However, to ensure correct operation of snubbers as a part of BPF their adjustment is necessary, with allowance for real parameters of components in use and BPF operating algorithm. The present work is devoted to solving this problem.

In the course of this work, we developed a computer model of BPF in Swicher CAD/LTspice, based on standard SPICE models of power electronic components. With the help of BPF model, we calculated parameters of snubber elements, necessary to ensure soft switching conditions and energy recovery stored in snubber elements.

In addition, the energy efficiency of BPF with snubbers at the maximum frequency of the output pulses forming of 75 kHz was calculated. The calculation results showed that the use of the snubbers allows reduce significantly switching losses of transistors. Due to energy recovery, stored in snubber components, we managed to reduce the total power losses of BPF by 25 % and increase pulse former efficiency by 0.6 %.

Switching losses reduction of transistors provides increased ВPF reliability, which together with higher efficiency offers a prospect of a further increase of the output pulses frequency and improved stability of reactive magnetron sputtering process.

Keywords:

switched mode power supply, magnetron sputtering system, snubbering curcuits

References

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