Pontifical Catholic University of Rio Grande do Sul - PUCRS

1. Pontifical Catholic University of Rio Grande do Sul - PUCRS A SINGLE STAGE ELECTRONIC BALLAST FAMILY FOR HIGH PRESSURE SODIUM LAMPS R. Tonkoski Jr., G. B. Ceccon, A. Bombardieri, G. B. Maizonave, R. W. Dos Reis, J. C. M. Lima and F. Dos Reis Microcontrolled Full Bridge Electronic Ballast Prototype. Half Bridge topology. Abstract — In the recent years many authors are working to obtain single stage HPF electronic ballast for fluorescent and HID lamps to achieve cost reduction and to comply with international standard requirements. Usually to obtain HPF in electronic ballast for high pressure sodium lamps a Power Factor Corrector (PFC) is used between the mains and the electronic ballast. In this paper will be reported the study and implementation of two single stage high power factor (HPF) electronic ballasts for high pressure sodium (HPS) lamps using a LCC filter, one using a half-bridge inverter (HB) and the second one using a full-bridge inverter (FB). The main idea in this work is to present two simple electronic ballasts topologies with HPF for HPS lamps working with a 220 VRMS mains voltage. Design criteria and experimental results will be also presented. These topologies present some drawbacks like moderate THD, lamp power limitation once the converter works as a Buck inverter and it is not an ideal PFC. PF around 0.95 are easily obtained. This paper intends to warn other researchers about these structures limitation, but may be an interesting option for some applications. The lamp turns on and off in each semi cycle Voltage and Current in the output of the Bridge Rectifier. Voltage and Current in the mains. Current Harmonic Content Injected into the Mains. Voltage and Current in the HPS lamp in a high frequency period. Utility Grid Voltage Harmonic Content. INTRODUCTION The purpose of this paper is to report the development of two low cost single stage HPF electronic ballasts for HPS lamps for a 220 VRMS mains voltage developed for utilization with a smart public illumination system. Each ballast was implemented using a different converter topology. The design criteria are presented in the paper for the proposed circuits. In order to achieve low cost electronic ballast for HPS lamps with HPF a single stage converter was conceived. The idea is very simple: Once, in high frequency, the HPS lamps have a resistive behavior, why the electronic ballast (inverter and LCC filter) can not be connected directly to the full bridge rectifier? This idea is discussed in this work. It was studied the possibility of using this concept applied to a half bridge (HB) inverter. Unfortunately, in this arrangement the half bridge inverter reduces the available RMS lamp voltage and therefore, restricts the maximum output power. The full bridge-inverter was also explored in order to increase the available RMS lamp voltage. EXPERIMENTAL RESULTS Two prototypes, one using the HB topology and another using the FB topology for 70 W and 250 W HPS lamps respectively were built. A conventional SMPS power line filter with differential and common mode mitigation paths was used. The EMI Filter topology used is presented below. Usually a capacitor between the line and the filter is used, in this project the input capacitor was suppressed once it will block the PLC communications between the other units. The experimental results are presented for the FB topology, since for the half bridge topology the results obtained are similar. Voltage (above) and Current in the lamp. CONCLUSIONS In this paper it was presented two ballast topologies for HPS lamps. It was described two single stage high power factor electronic ballast for high pressure sodium lamps using a half and a full bridge inverter. These ballasts presents a very low cost because it avoids an external PFP. It was observed that using the Half Bridge topology the necessary voltage to achieve the lamp full rated power (250 W) with a 220 VRMS mains will never be achieved, this problem impossibilities the design of this ballast for 250 W HPS lamps. The half bridge topology is suitable for lamps less than 250 W once the main restriction is the available RMS voltage. A prototype for a 70 W HPS lamp with this topology and a second prototype with the full bridge structure for a 250 W HPS lamp were presented. The behavior of the full bridge topology and the half bridge topology achieved was similar. The lamp turns on and off in each semi cycle. These re-ignition periods are attributed to the nonlinear characteristic of the lamp and to DC bus voltage, which drops to zero every semi cycle. The phenomenon of the acoustic resonance was not observed, however it was not the objective of this study to analyze the impact in acoustic resonance. The crest factor found was not good enough considering fluorescent lamps, however for HPS lamps this crest factor is not considered critical. A simple design criteria is proposed, which permits to determine easily the LCC parameters, using an abacus. The assumed resistive lamp behavior is not entirely accurate, but is enough to allow a proper lamp ballast design. In our laboratory, the mains voltage total harmonic distortion was 2.49%, during the measurements. For this situation, the obtained power factor and total harmonic distortion were PF=0.98 and THD=19.93% respectively. EMI Filter Topology.