Electronic operation and control of high-intensity gas-discharge lamps

The ever increasing amount of global energy consumption based on the application of fossil fuels is threatening the earth’s natural resources and environment. Worldwide, grid-based electric lighting consumes 19 % of total global electricity production. For this reason the transition towards energy efficient lighting plays an important environmental role. One of the key technologies in this transition is High-Intensity Discharge (HID) lighting. The technical revolution in gas-discharge lamps has resulted in the highlyefficient lamps that are available nowadays. As with most energy efficient light solutions, all HID lighting systems require a ballast to operate. Traditionally, magnetic ballast designs were the only choice available for HID lighting systems. Today, electronic lampdrivers can offer additional power saving, flicker free operation, and miniaturisation. Electronic lamp operation enables additional degrees of freedom in lamp-current control over the conventional electro-magnetic (EM) ballasts. The lamp-driver system performance depends on both the dynamics of the lamp and the driver. This thesis focuses on the optimisation of electronically operated HID systems, in terms of highly-efficient lamp-driver topologies and, more specifically, lamp-driver interaction control. First, highly-efficient power topologies to operate compact HID lamps on low-frequency-square-wave (LFSW) current are explored. The proposed two-stage electronic lamp-driver consists of a Power Factor Corrector (PFC) stage that meets the power utility standards. This converter is coupled to a stacked buck converter that controls the lamp-current. Both stages are operated in Zero Voltage Switching (ZVS) mode in order to reduce the switching losses. The resulting two-stage lamp-drivers feature flexible controllability, high efficiency, and high power density, and are suitable for power sandwich packaging. Secondly, lamp-driver interaction (LDI) has been studied in the simulation domain and control algorithms have been explored that improve the stability, and enable system optimisation. Two HID lamp models were developed. The first model describes the HID lamp’s small-signal electrical behaviour and its purpose is to aid to study the interaction stability. The second HID lamp model has been developed based on physics equations for the arc column and the electrode behaviour, and is intended for lampdriver simulations and control applications. Verification measurements have shown that the lamp terminal characteristics are present over a wide power and frequency range. Three LDI control algorithms were explored, using the proposed lampmodels. The first control principle optimises the LDI for a broad range of HID lamps operated at normal or reduced power. This approach consists of two control loops integrated into a fuzzy-logic controller that stabilises the lamp-current and optimises the commutation process. The second control problem concerns the application of ultra high performance (UHP) HID lamps in projection applications that typically set stringent requirements on the quality of the light generated by these lamps, and therefore the lampcurrent. These systems are subject to periodic disturbances synchronous with the LFSW commutation period. Iterative learning control (ILC) has been examined. It was experimentally verified that this algorithm compensates for repetitive disturbances. Third, Electronic HID operation also opens the door for continuous HID lamp dimming that can provide additional savings. To enable stable dimming, an observer-based HID lamp controller has been developed. This controller sets a stable minimum dim-level and monitors the gas-discharge throughout lamp life. The HID lamp observer derives physical lamp state signals from the HID arc discharge physics and the related photometric properties. Finally, practical measurements proved the proposed HID lamp observer-based control principle works satisfactorily

Electronic operation and control of high-intensity gas-discharge lamps

The ever increasing amount of global energy consumption based on the application of fossil fuels is threatening the earth’s natural resources and environment. Worldwide, grid-based electric lighting consumes 19 % of total global electricity production. For this reason the transition towards energy efficient lighting plays an important environmental role. One of the key technologies in this transition is High-Intensity Discharge (HID) lighting. The technical revolution in gas-discharge lamps has resulted in the highlyefficient lamps that are available nowadays. As with most energy efficient light solutions, all HID lighting systems require a ballast to operate. Traditionally, magnetic ballast designs were the only choice available for HID lighting systems. Today, electronic lampdrivers can offer additional power saving, flicker free operation, and miniaturisation. Electronic lamp operation enables additional degrees of freedom in lamp-current control over the conventional electro-magnetic (EM) ballasts. The lamp-driver system performance depends on both the dynamics of the lamp and the driver. This thesis focuses on the optimisation of electronically operated HID systems, in terms of highly-efficient lamp-driver topologies and, more specifically, lamp-driver interaction control. First, highly-efficient power topologies to operate compact HID lamps on low-frequency-square-wave (LFSW) current are explored. The proposed two-stage electronic lamp-driver consists of a Power Factor Corrector (PFC) stage that meets the power utility standards. This converter is coupled to a stacked buck converter that controls the lamp-current. Both stages are operated in Zero Voltage Switching (ZVS) mode in order to reduce the switching losses. The resulting two-stage lamp-drivers feature flexible controllability, high efficiency, and high power density, and are suitable for power sandwich packaging. Secondly, lamp-driver interaction (LDI) has been studied in the simulation domain and control algorithms have been explored that improve the stability, and enable system optimisation. Two HID lamp models were developed. The first model describes the HID lamp’s small-signal electrical behaviour and its purpose is to aid to study the interaction stability. The second HID lamp model has been developed based on physics equations for the arc column and the electrode behaviour, and is intended for lampdriver simulations and control applications. Verification measurements have shown that the lamp terminal characteristics are present over a wide power and frequency range. Three LDI control algorithms were explored, using the proposed lampmodels. The first control principle optimises the LDI for a broad range of HID lamps operated at normal or reduced power. This approach consists of two control loops integrated into a fuzzy-logic controller that stabilises the lamp-current and optimises the commutation process. The second control problem concerns the application of ultra high performance (UHP) HID lamps in projection applications that typically set stringent requirements on the quality of the light generated by these lamps, and therefore the lampcurrent. These systems are subject to periodic disturbances synchronous with the LFSW commutation period. Iterative learning control (ILC) has been examined. It was experimentally verified that this algorithm compensates for repetitive disturbances. Third, Electronic HID operation also opens the door for continuous HID lamp dimming that can provide additional savings. To enable stable dimming, an observer-based HID lamp controller has been developed. This controller sets a stable minimum dim-level and monitors the gas-discharge throughout lamp life. The HID lamp observer derives physical lamp state signals from the HID arc discharge physics and the related photometric properties. Finally, practical measurements proved the proposed HID lamp observer-based control principle works satisfactorily

Transition mode stacked buck converter for HID lamps

Abstract—This paper presents a cost-effective electronic lamp driver design for high-intensity discharge (HID) burners based on a stacked buck converter topology. The circuit is operated in zerovoltage switching mode to improve the efficiency, and thereby, enable miniaturization. Among the several possible low-frequencysquare- wave topologies, the proposed synchronous stacked buck converter, combined with a boost converter stage operating as power factor corrector, provides a two-stage HID lamp driver with excellent performance

Observer based ceramic HID lamp control

High intensity discharge (HID) lamps are typically operated at low frequency to avoid damage from acoustic resonance. Accordingly, an electronic ballast normally comprises a buck converter to control the lamp current magnitude, and a bridge to commutate the lamp current at a low frequency. These functions can be combined in a stacked buck converter [1]. The resulting system performance depends on the dynamics of the lamp as well as the ballast, the so-called lamp-ballast interaction [2]. Competitor lamps, production spread, reduced power operation and lifetime effects lead to a wide spread in lamp parameters. Some lamp-ballast combinations tend to be poorly damped, resulting in oscillatory lamp current. In such a system, the negative incremental lamp impedance may interact with the power electronic driver. Furthermore, lamp ageing and reduced power mode operation both tend to increase re-ignition voltage overshoot, which in turn may lead to reduced lifetime, or prematurely extinguishing lamps. Because of considerable nonlinearities, feedback control based on the gas discharge electrical terminal quantities can improve the lamp-ballast performance only to a limited extent. Therefore, to bring the electronic HID lamp-ballast system performance a step further, feedback of the physical lamp states is proposed in this paper. However, direct feedback of the physical lamp states is not practical due to either economic or physical constraints. For this reason, to construct unmeasured system states using a known set of system states and parameters, a ceramic metal halide lamp observer is proposed. The HID lamp observer directly enhances system performance because it allows more sophisticated control schemes that make use of physical quantities like the electrode sheath voltage and cold spot temperature, which heretofore were not accessible. The ceramic metal halide observer is based on energy balance equations that include plasma and arc tube wall dynamics. Finally, simulations and practical measurements are included to validate the observer based ceramic metal halide lamp control

Physics based MATLAB model for ceramic metal halide lamps

Based on physical laws, a phase resolved model of the terminal voltage / current (V-I) characteristic of a metal halide lamp has been developed. Besides the plasma arc discharge characteristic, the energy balance equations include the arc tube wall dynamics and electrode voltage drop. The proposed MATLAB model also provides for physical lamp parameters that enable optimization of the lamp ballast interaction. Practical measurement results support the behaviour predicted by the model very wel

Controlled HID lamp-ballast interaction for low frequency square-wave drivers

High intensity discharge lamps are typically operated at low frequency to avoid damage from acoustic resonance. Accordingly, an electronic ballast normally comprises a buck converter to control the lamp current magnitude and a full-bridge to commutate the lamp current at a low frequency. In such a system, the negative dynamic lamp characteristic may interact with the power electronic driver may give a poorly damped response, sometimes resulting in an oscillatory lamp current. Furthermore, lamp aging and reduced power mode operation both tend to increase re-ignition voltage overshoot, which in turn may lead to reduced lifetime, or prematurely extinguishing lamps. In the present paper, a procedure for obtaining the small-signal dynamic characteristics of metal halide lamps is proposed. Using this dynamic model, the lamp-ballast interaction is simulated and analyzed. A fuzzy-logic control method is presented to cope with nonlinear behavior and improve the lamp-ballast performance. The simulation results are verified with practical measurements on a laboratory prototyp