IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 3, MAY/JUNE 2014 2197 Dielectric Barrier Discharge Ozonizer Using the Transformerless Single-Switch Resonant Converter for Portable Applications Zainal Salam, Member, IEEE, Mochammad Facta, and Muhammad Amjad Abstract—This paper describes the analysis, design, and con- struction of an ozonizer based on a single-switch resonant con- verter (SSRC). The main contribution of the work is the removal of the transformer from the SSRC, resulting in much smaller footprint and higher efficiency. High voltage (up to 4.0 kV p-p ) is achieved using a resonant tank, which comprises of an LC circuit combined with the chamber’s equivalent circuit components. De- spite the absence of the transformer, the topology is able to gener- ate sufficiently high voltage to initiate and sustain the formation of micro-discharges. Geometrically, the chamber is constructed as a planar type, using muscovite mica as dielectric. The main advan- tage of using mica is its availability in thin sheet (less than 1 mm), which then allows for the lowering of the initiation voltage. To validate the analysis and design, an experimental prototype of the ozonizer is build. It is found that the ozonizer draws very little power, i.e., less than 8 W with very high ozone yield (over 120 g/kWh at 1.0 L/min). The maximum measured efficiency is 75%. The proposed ozonizer is fed from a low voltage power source (up to 40 V dc) and hence its suitability for a wide range of portable applications. Index Terms—Ozone, ozonizer, power supply, resonance, single-switch converter, transformerless. I. I NTRODUCTION O ZONE gas is increasingly used in industrial applications— particularly for bleaching, sanitizing, and cleaning purposes. Unlike other conventional chemical-based oxidizing agents (such as chlorine), it leaves no harmful residues to the environment. Furthermore, ozone is easily soluble in water and is therefore very suitable for water-related applications, for example water purification, waste-water oxidization, and sterilization [1]. To date, the most cost-effective and popular ozonizer (ozone generator) is based on the dielectric barrier discharge (DBD) concept. Primarily, it comprises of an ozone chamber that fed by a high voltage ac power supply. The chamber is constructed using two parallel plates (electrodes), at least one of which is covered with dielectric sheet. Air Manuscript received May 29, 2013; accepted August 26, 2013. Date of publication September 18, 2013; date of current version May 15, 2014. Paper 2013-EPC-403, presented at the 2013 IEEE Applied Power Electronics Con- ference and Exposition, Long Beach, CA, USA, March 17–21, and approved for publication in the IEEE TRANSACTIONS ON I NDUSTRY APPLICATIONS by the Electrostatic Processes Committee of the IEEE Industry Applications Society. The authors are with the Center of Electrical Energy Systems, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia (e-mail: zainals@fke.utm.my; mochfacta@gmail.com; Muhammad. Amjad@iub.edu.pk). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2013.2282493 or oxygen gas is forced to flow in-between a space between the electrodes—known as the discharge gap—while a high ac voltage is applied between the electrodes. If the potential across the electrodes is sufficiently high, it forms an electric field, which in turn generates microdischarges that break the oxygen molecules into two single oxygen atoms. Each oxygen atom combines with O 2 to form ozone gas (O 3 ). One of the main advantages of DBD ozonizer is that it can be easily operated at ambient pressure and temperature [2]–[4]. However, at room temperature, ozone is a highly unstable gas; storing or transporting ozone is not feasible and hence it must be generated and consumed on site [5], [6]. There is a demand for mobile ozonizers that is fed from portable sources such as battery or photovoltaic (PV) cells; the market for them can be envisaged in instant food sanitizers, water purifiers, odour reducers and disinfectors for medical equipments. In addition, there is a large need for low-cost and effective water purification facilities in the less developed world, in which electrical grid is inaccessible. To increase the output of the ozonizer, the chamber is fed by a high frequency power supply. Normally, resonant inverters with step-up transformer are employed. In [7]–[11] a voltage-fed full bridge resonant inverter with high frequency transformer and inductor is proposed. The inductor is placed at the secondary [10], [11] or primary [7] side of the transformer to stabilize the flow of microdischarge in the chamber. In [12], a current- fed full bridge inverter which employs a parallel inductor between the secondary and the ozone chamber is implemented. In several other works, push-pull inverters that utilize two inductors (used as chokes) are proposed [13]–[17]. However, in each of the aforementioned topologies, the number of power (semiconductor) switches is more than one; for example full bridge and push–pull topologies are based on four and two switches, respectively. Furthermore, each power switch requires a gate driver and its associated protection circuit. Additionally, the sizes of the step-up transformer and inductors add to the volume and cost of the power supply [18]. For a portable ozonizer, the main objective is to reduce the component count and to increase the converter’s efficiency. Accordingly, it is desirable to remove the transformer due to several reasons: first, the overall size of the power supply size can be reduced significantly. Second, with the absence of the transformer, the converter efficiency can be increased as the losses due to winding resistances are no longer present. In addition, it will eliminate the spikes due to the leakage induc- tance; hence, the protection/clamping circuit for the switch is 0093-9994 © 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.