![]() Lamp current-waveform comparison.ĭC offset is another waveform that must be considered when using CCFLs. This means that the electrical power-in to light-out efficiency is greatly reduced in a system operating with a high-crest-factor waveform.įigure 4. Although the high-crest-factor waveform has the same RMS current as the sinusoidal waveform, its current excursions beyond the sinusoidal waveform's 150% peak level do not generate additional light, only heat. Figure 4 shows two current waveforms with approximately the same RMS current. Conversely, nonsinusoidal waveforms with large crest factors are not efficient CCFL drivers. ![]() ![]() Sinusoidal waveforms provide the greatest efficiency. Lamp CurrentĬCFL efficiency is greatly affected by the current waveform driving the lamp. Lamp self-heating brightness characteristic. Strike voltage-temperature dependence.įigure 3. Lamp-brightness temperature dependence.įigure 2. As illustrated in Figure 3, the lamp exhibits a self-heating characteristic, which directly affects the lamp brightness after the lamp is struck.įigure 1. At cold temperatures, lamp brightness drops significantly (see Figure 1) and the voltage required to initially strike (i.e., turn on) the lamps rises significantly (see Figure 2). The operating characteristics of CCFLs are strongly influenced by temperature, as shown in Figures 1, 2, and 3. The general trends described here, however, apply to all CCFLs. Note that the data shown here was collected on a particular CCFL, and that the specific data will change based on the CCFL model used in an application. This application note describes some of these CCFL characteristics. High efficiency (electrical power in, to light out)ĬCFLs have some unique characteristics that must be considered for maximizing their efficiency, life span, and usefulness.CCFLs have many desirable features, including: The UV light, in turn, excites an inner coating of phosphor, creating visible light. When a high voltage is placed across the tube, the gases ionize creating ultraviolet (UV) light. This application note describes some of these unique CCFL characteristics.Ĭold Cathode Fluorescent Lamps (CCFLs) are sealed glass tubes filled with inert gases. CCFLs offer many desirable features, but they also have unique characteristics that must be considered to maximize their usefulness. Cold Cathode Fluorescent Lamps (CCFL) are used as white-light sources to backlight liquid crystal displays (LCDs).
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