A High Voltage Zero Current Switching- Series Resonant Converter Using DSP Rakshita Dhar, Bindu S, Sincy George Dept. Of Electrical Engineering F.C.R.I.T, Vashi Navi Mumbai, India P C Saroj, Archana Sharma Accelerator And Pulse Power Division B.A.R.C Trombay, India Abstract – High voltage DC sources are widely used in power industries. The conventional dc sources have been replaced by solid state DC sources due to its large size and heavy weight. This paper deals with the implementation of high voltage DC source for Marx generator which is used to generate high voltage impulses for various application such as testing of insulation of electrical apparatus, insulators used for supporting power lines etc. The DC sources implemented here achieves zero current switching using series resonant principle so that switching losses can be reduced compared to other DC- DC converters. A complete design of 1 kV (open circuit voltage) zero current switching series resonant DC source is done. A prototype of the converter 410 V, 5 W (open circuit voltage) is implemented using DSP TMS320F28069. Satisfactory results are obtained and presented in the paper. Also effect of increasing the switching frequency of converter on output voltage and output voltage ripple is analyzed. Keywords – high frequency transformer, series resonance, voltage multiplier circuit, zero current switching. I. INTRODUCTION High voltage DC sources are used for various applications such as generation of high voltage impulses for testing power transformers, lighting simulators, microwave generation etc. They are also used as input dc source to the Marx generator. Traditionally, DC sources used for Marx generator consists of linear power circuit, electrostatic generator, voltage multiplier circuit etc [1, 2]. These conventional methods for DC sources have large size and heavy weight. Also, the disadvantage in voltage multiplier circuit is that as number of stages increases its output voltage decreases [2]. By using solid state devices it is possible to have high voltage DC sources with compact size and light weight. The solid state high voltage DC source using resonant principle is designed and implemented. Resonant converters can be operated in zero current switching or zero voltage switching (ZCS/ZVS) technique. The turning on and turning off of the converter switches in ZCS/ZVS technique is either at the switch current zero or at switch voltage zero respectively [3]. The different types of converter topologies considered for literature survey are - buck-type current-fed push-pull converter giving 5-30 kV output voltage [4], zero current switching-pulse width modulation (ZCS-PWM) converter [5] and fifth order resonant converter for high voltage dc power supplies with 10 kV, 1.1 kW output [6]. Yen Chen et al designed buck-type current-fed push-pull converter giving 5-30 kV output voltage. This kind of configuration has disadvantage of high peak voltage stress upon primary switches during off-state. This voltage is greater than two times the input voltage. Also it doesn’t use any soft switching techniques, hence converter losses increases [4]. Chris Iannello et al designed zero current switching pulse width modulation (ZCS-PWM) converter. This has advantages of reducing switching losses but it has no scope for varying the output voltage. If one of the stages of Marx generator fails then the output voltage of its source can be increased to obtain the required output of Marx generator [5]. Navid Shafiei et al designed a 10 kV, 1.1 kW fifth order resonant converter for high voltage DC power supply. This topology uses ZVS technique thereby reducing switching losses. But due to increased complexity of resonant circuit these multi-element resonant converters exhibit complex dynamic behavior [6]. Sze Sing Lee et al designed a 5.6 kV high voltage DC source for X- ray power supply application using zero current switching - series resonant (ZCS-SR) technology [7]. The authors used analog devices for generation of switching pulses whereas in this paper DSP TMS320F28069 is used for generation of switching pulses for application of source to Marx generator. A 410 V (open circuit voltage) ZCS-SR source is designed and analyzed. In section II, working principle of ZCS-SR converter is explained. Section III explains design of power circuit and control circuit. Section IV gives hardware results. Effect of increasing switching frequency of converter on output voltage and output voltage ripple is presented in section V. Conclusion is given in section VI. II. WORKING OF ZCS-SR CONVERTER Fig. 1 shows the schematic diagram of a zero current switching- series resonant converter. The converter has two main parts- power circuit and control circuit [7]. Fig. 1 shows the power circuit in detail. Power circuit consists of input voltage , single phase inverter, resonant capacitor , leakage inductance of high frequency transformer , high International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Published by, www.ijert.org ICNTE-2015 Conference Proceedings Volume 3, Issue 01 Special Issue - 2015