J. Garcia-Garcia

Evaluation of a low-cost permanent emergency lighting system based on high-efficiency LEDs

Nowadays, Permanent Emergency Lighting Systems (PELSs) are widely used in many applications, including emergency exit indication and lighting in critical or strategic points. Limitation in operation hours in classical lamps (10 000-20 000 h for fluorescent lamps) implies short lamp replacement times and, therefore, high maintenance costs. This paper shows an alternative solution based on high-efficiency LEDs. The long operation life (above 100 000 h) of high-efficiency LEDs with a very simple electronics circuitry implies an interesting solution for these types of applications. A 30-lm and 1-h PELS has been built and tested. A low-cost power supply has been built and used as a battery charger and LED driver.

Small-Signal Modeling of Discharge Lamps Through Step Response and Its Application to Low-Frequency Square-Waveform Electronic Ballasts

In this paper, a simple method to obtain the small-signal model of discharge lamps, and particularly metal halide (MH) lamps, is proposed. A dc voltage source with a series resistor is used to supply the lamp at the required power level. Then, the lamp response against an input voltage step transient is analyzed. From this analysis, the parameters of the equivalent lamp model can be calculated. The proposed method allows obtaining the lamp model in a straight manner from a single test. With this technique, a 35-W MH lamp is modeled at two different power levels. A validation circuit, which includes a resistive ballast and a capacitance, is analyzed to evaluate the possibilities of the proposed modeling technique. The obtained experimental results are in good agreement with the theoretical analysis. The derivation of a time domain lamp model for SPICE-based computer simulators is also introduced. Finally, an example of application in low-frequency square-waveform electronic ballasts is presented

Acoustic-Resonance Characterization of Low-Wattage Metal–Halide Lamps

In this paper, a detailed study and experimentation on acoustic-resonances (AR) in low-wattage metal-halide lamps is presented. In order to excite the AR without extinguishing the electric arc, the lamps were supplied by means of a dc current with a superposed variable-frequency ac signal. By using this methodology, theoretical and experimental resonances were compared in terms of frequency, amplitude, and threshold-power level for their excitation. The experiments were carried out on four 35-W samples from each manufacturer (Osram and Philips), each of them with burning times of 100, 2500, and 5000 h, in order to cope with the full life of this type of lamps. AR maps for each lamp were obtained. These maps show not only the frequencies at which AR appear but also the amplitude of the resonances. The obtained AR maps are intended to be used by designers in order to know if a particular instantaneous lamp power waveform would be suitable to supply the lamp without generating AR. An application example on how to use these maps is also presented

LED Permanent Emergency Lighting System Based on a Single Magnetic Component

The use of high-efficiency LEDs in low-power lighting applications is growing continuously due to new advances in LED features. The lifetime of a low-power fluorescent lamp is around 5000 h. This implies short lamp-replacement times and high maintenance costs. The use of high-efficiency LEDs reduces drastically the maintenance costs due to the long lifetime (>50 000 h). One of the applications where using LED is very interesting is permanent emergency light systems. Generally, these circuits are based on a two-stage design, using two magnetic cores. This paper presents offline power LED driver and battery charger integrated in one magnetic core topology. Besides, the converter allows driving the LEDs in case of a line failure and it complies with the IEC 61000-3-2 Class C Standard.

Complete low cost two-stage electronic ballast for 70 W high pressure sodium vapor lamp based on current-mode-controlled buck-boost inverter

In this paper, a low-cost electronic ballast for high-pressure sodium vapor lamps is presented. The proposed ballast is a two-stage circuit that requires only one switch and one inductor for each stage. The power-factor-correction stage is a buck dc-to-dc converter operating in discontinuous conduction mode to meet the IEC-61000-3-2 Class C requirements. The inverter stage is a low-cost nonresonant topology, based on a buck-boost inverter controlled by means of a specific current-mode control implementation. In addition, a novel and simple circuit, compatible with the presented inverter, is proposed to ignite the lamp. Furthermore, this circuit implementation provides protection against broken lamps.

New control strategy in square-wave inverters for low wattage metal halide lamps supply to avoid acoustic resonances

High intensity of discharge (HID) lamps is the most suitable lamps when it comes to get both high light power levels and good colour rendering. In HID lamps, a lot of theoretical advantages are obtained if they are supplied with high frequencies electronic ballasts: higher efficiency, optimisation of system cost, weight and size, control and remote operation capability, etc. Nevertheless, at these frequencies, acoustic resonances appear in this kind of lamps. In low wattage metal halide lamps, the risk of appearing acoustic resonances is the highest among all HID lamps. To obtain a lack of acoustic resonances in HID lamps, lamp power frequency harmonics must have low amplitude, lower than a certain threshold value, related to activation energy. A supply system can be designed in order to guarantee, at nominal operation, this low power harmonics levels. Nevertheless, in HID lamps, the equivalent resistance of the lamp varies highly in starting and warm-up stages, as well as in the ageing process. So, the system must be designed to adequate the supplying conditions to this load variations. In this paper a new control strategy for high frequency (HF) square-wave inverters is presented, in order to keep this lamp power harmonics in low levels, regardless of the lamp equivalent load. The proposed ballast is presented, as well as the built prototypes and experimental results carried out.

Analysis and design of the LCC-parallel series inverter with resonant current control as HPS lamp ballast

The clamped mode LCC-PS resonant inverter working with resonant current control is analysed. With this control method, the inverter is forced to operate with optimum commutations and without handling reactive energy, minimising both switching and conduction losses. A design abacus is generated and a graphic design method based on that abacus is presented and illustrated with a design example.

Complete low-cost two-stage electronic ballast for 70-W high-pressure sodium vapor lamp based on current-mode-controlled buck-boost inverter

In this paper, a low-cost electronic ballast for high-pressure sodium vapor lamps is presented. The proposed ballast is a two-stage circuit that requires only one switch and one inductor for each stage. The power-factor-correction stage is a buck dc-to-dc converter operating in discontinuous conduction mode to meet the IEC-61000-3-2 Class C requirements. The inverter stage is a low-cost nonresonant topology, based on a buck-boost inverter controlled by means of a specific current-mode control implementation. In addition, a novel and simple circuit, compatible with the presented inverter, is proposed to ignite the lamp. Furthermore, this circuit implementation provides protection against broken lamps.

Small-signal modeling of discharge lamps through step response and its application to low-frequency square-waveform electronic ballasts

In this paper, a simple method to obtain the small-signal model of discharge lamps, and particularly metal halide lamps, is proposed. A DC voltage source with a series resistor is used to supply the lamp at the required power level. Then, the lamp response against an input voltage step transient is analyzed. From this analysis, the parameters of the equivalent lamp model can be calculated. The proposed method allows obtaining the lamp model in a straight manner from a single test. With this technique, a 35W metal halide lamp is modeled at two different power levels. A validation circuit, which includes a resistive ballast and a capacitance, is analyzed to evaluate the possibilities of the proposed modeling technique. The obtained experimental results are in good agreement with the theoretical analysis. The derivation of a time domain lamp model for SPICE-based computer simulators is also introduced. Finally, an example of application in low-frequency square-waveform electronic ballasts is presented.

Analysis of lamp-ballast interaction using the multi-frequency-averaging technique

In recent literature, several small-signal dynamic models for fluorescent lamps have been presented. These models have been used to analyze the lamp-ballast interaction for linear high frequency electronic ballasts. In the present paper, a new analysis method based on the generalized multi-frequency averaging technique is proposed. This method allows obtaining the small-signal dynamic model of an inverter in a straightforward way, even when the inverter behavior is not fully linear. The proposed analysis procedure is illustrated using an example. The frequency response of the small-signal transfer functions obtained with this method are compared with those experimentally measured using a laboratory prototype.